Turtles With Jobs

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Close your eyes and imagine a turtle working as an engineer, a custodian, or a postal worker. Now, that may be a slight exaggeration, but what if I told you that turtles play many essential roles in your everyday life? 

Capitalizing on Nature

The term “ecosystem services” is used to describe the positive impacts that a species contributes to society. These may pop up in many unexpected ways: vector control, climate stability, crop pollination (Ceballos et al., 2020), the list is virtually endless. Ecosystem services are beneficial to humankind, and they are important to our health and economic wellbeing (Weiskopf et al., 2020). Without us humans even thinking about it, nature is improving our water quality, providing us with recreational opportunities (Turner and Daily, 2008), and flood/storm protection (Cardinale et al., 2012)...on the condition that we take care of it in return.

Nature is here for us to enjoy and protect

Ecosystem services provide humankind with great financial benefits. As of 2011, the economic value of the total global ecosystem services was USD $125 trillion/year (Costanza et al., 2014). That is almost double the global gross domestic product (USD $73 trillion/year). This is money that we are saving by allowing nature to do the work for us. 

Turtles on the Job

Turtles are exceptional workers when it comes to providing us with ecosystem services. This is largely because turtles have a high biomass. Biomass is a fancy word for how much ‘turtle’ there actually is in a certain area. Pond sliders can have a biomass of 877 kilograms per hectare (Congdon et al., 1986)…that's whole lotta turtle! In fact, turtles actually exceed the biomass of all other reptiles and herds of large herbivores on the African plains (Lovich et al., 2018). The energy that's stored in all these turtles is used for transferring nutrients between aquatic and terrestrial habitats, seed dispersal, bioturbation (disturbing soil in a way that allows for proper drainage and plant growth), water purification, and even cleaning up pollution that is produced by humans (Lovich et al., 2018). 

Without these builders and gardeners, the world would look a lot different.

The Downfall of Turtles

Turtles are in trouble; more than 61% of turtle species are at risk of extinction, and they are becoming increasingly threatened. In Ontario, all 8 of our native turtle species are listed as at risk on the provincial or federal level. Remember how I said that biomass is a way to quantify the amount of ecosystem services taking place? Well, when populations decline, so does biomass. When there are less turtles available, we experience not only their absence, but also the absence of the benefits they give to us. Extinction is a permanent outcome, so when we lose a species, we also lose the ecosystem services that they offered to us and we are left to fill their role. This can be expensive and time consuming!

Turtles are experts at ecosystem engineering

 

Turtles are threatened by a number of factors, including habitat loss and degradation, collection for pet trade and medicinal use, climate change, road mortality, and disease (Stanford et al., 2020). Fortunately, you don’t need to be a turtle expert to contribute to saving these species: you can learn how you can help and start making a difference by signing up to be a Turtle Guardian here!

So, the idea of turtle engineers and custodians isn’t an exaggeration. In fact, it might even be an understatement. 

Written By: Michaela S. Bouffard, Biologist and Road Ecologist, The Land Between and Turtle Guardians

 

References

Cardinale, B. J., Duffy, J. E., Gonzalez, A., Hooper, D. U., Perrings, C., Venail, P., ... & Naeem, S. (2012). Biodiversity loss and its impact on humanity. Nature, 486(7401), 59-67.

Ceballos, G., Ehrlich, P. R., & Raven, P. H. (2020). Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction. Proceedings of the National Academy of Sciences, 117(24), 13596-13602.

Congdon, J. D., Greene, J. L., & Gibbons, J. W. (1986). Biomass of freshwater turtles: a geographic comparison. American Midland Naturalist, 165-173.

Costanza, R., De Groot, R., Sutton, P., Van der Ploeg, S., Anderson, S. J., Kubiszewski, I., ... & Turner, R. K. (2014). Changes in the global value of ecosystem services. Global environmental change, 26, 152-158.

Lovich, J. E., Ennen, J. R., Agha, M., & Gibbons, J. W. (2018). Where have all the turtles gone, and why does it matter?. BioScience, 68(10), 771-781.

Stanford, C. B., Iverson, J. B., Rhodin, A. G., van Dijk, P. P., Mittermeier, R. A., Kuchling, G., ... & Walde, A. D. (2020). Turtles and tortoises are in trouble. Current Biology, 30(12), R721-R735.

Turner, R. K., & Daily, G. C. (2008). The ecosystem services framework and natural capital conservation. Environmental and resource economics, 39, 25-35.

Weiskopf, S. R., Rubenstein, M. A., Crozier, L. G., Gaichas, S., Griffis, R., Halofsky, J. E., ... & Whyte, K. P. (2020). Climate change effects on biodiversity, ecosystems, ecosystem services, and natural resource management in the United States. Science of the Total Environment, 733, 137782.

Butt-Breathers and Frogsicles: Overwintering Herpetofauna at their Northern Range Limit

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How do you survive the cold of winter? Do you bundle up in your warmest jacket and mittens? Maybe you stay cozy in your toasty house. I bet you don’t rely on making antifreeze in your blood or exchanging oxygen using your…umm…butt!

Assuming you are a human reading this, you are an endotherm. That means that you control your own body temperature using your metabolism. This is opposed to being an ectotherm, which is when the temperature of the environment dictates body temperature. This is the case with reptiles and amphibians: cold seasonality equals cold body temperature. But what happens when the environmental temperature drops below zero?

To Freeze or Not to Freeze

Generally, letting your body temperature drop below 0℃ is lethal. This is because when tissue freezes, ice crystals form by taking water from the cells and causing them to dehydrate, resulting in cell death (Karow and Webb, 1965). This is not the case in some frog species, such as Wood Frogs, who can not only tolerate freezing, but can actually do it for 7 months of the year (Larson et al., 2014)! They do this by forming a glucose-based antifreeze, and dispersing it throughout their body. This allows the cells themselves to remain liquid, but the extracellular matrix to freeze (Duman, 2015), essentially creating a living frogsicle.

Wood Frogs can remain frozen solid for up to 7 months (Photo: Janet M. Storey)

Frogs aren’t the only herptiles that can stand the cold. Hatchling Painted Turtles also have adaptations to survive below zero. Rather than freezing solid, their body fluids stay liquid even when faced with freezing environmental temperatures. This is called ‘supercooling.’ This extraordinary phenomenon is possible because hatchling Painted Turtles lack ice nucleating agents (INAs), which are responsible for triggering the formation of ice crystals (Costanzo et al., 1998). No INAs, no ice formation. Painted Turtles often lay their eggs above the frost line at the end of the summer, and the hatchlings overwinter in their natal nest until spring. The body fluids of these hatchlings are capable of remaining liquid in environmental temperatures as low as -20℃ (Lee and Costanzo, 1998). 


Hatchling Painted Turtles have a unique freeze avoidance mechanism called ‘supercooling’ (Frozen Planet II, BBC).

No Oxygen, No Problem

But what if freezing or supercooling isn’t an option? Well, you need to avoid the extreme cold. This is the case for the adult turtles of Ontario. They overwinter under the ice of ponds, where the temperature of the water remains stable and above the freezing point. However, there isn’t very much oxygen under the ice, so they need to lower their metabolic rate in order to reduce their oxygen requirements (Storey, 2007). When the water conditions under the ice become anoxic (deprived of oxygen), the turtles of Ontario differ in how they cope with this limiting factor based on whether they are anoxia tolerant or intolerant. The anoxia intolerant turtles (Wood, Map, Musk, and Spiny Softshell Turtles) navigate this obstacle by aggregating in high oxygen sites, and relying on breaks in the ice to come up for air (Robichaud et al., 2023). 

It is the anoxia tolerant species (Blanding’s, Spotted, Snapping, and Painted Turtles) who really shine when it comes to mind-boggling adaptations. Specifically, it is the Painted Turtle who stands out in the crowd. Painted Turtles are known to use their cloaca (an organ used for waste excretion and reproduction) to uptake oxygen from the environment; a process called cloacal respiration. That's right, they use their butt! This is because the inside of the cloaca is full of blood vessels that make the perfect surface for gas exchange (you can read more about these butt-breathing antics here). 

Ontario’s turtle species spend the winter under the ice of frozen water bodies (Wisconsin DNR).

The overwintering wizardry of Painted Turtles does not end there, however. In order for them to survive in oxygen depleted water, they need to switch to a type of metabolism that does not require it, called anaerobic respiration. This comes with a catch: anaerobic respiration creates a toxic byproduct called lactic acid (Jackson, 2000). This is the same byproduct that causes muscle cramps when we exert ourselves during exercise. In order to neutralize this build up of acid, they use carbonate from their shells (Jackson et al., 2007). This is comparable to how we take a Tums when we have too much acid in our stomachs, also known as heartburn. 

Left in the Cold

Without these precious overwintering sites to meet the needs of our shelled friends living in the harsh northern winters, they would not survive (Freeman, 2022). Habitat destruction, specifically in the form of wetland filling and loss, results in turtles no longer having access to the overwintering site that they have relied on for years, causing them to succumb to the cold. Turtles create a spatial map of their home range at a very early age, becoming highly devoted to that area and unable to find their way through new environments (Roth and Krochmal, 2015). This is why turtles who are relocated to a new habitat are often unable to find a suitable overwintering site and are left defenseless in the face of predators and seasonal extremes. 

Being committed to the protection of overwintering habitats is a big step toward keeping these butt-breathers and frogsicles safe at their northern range limit. To help, sign up to become a Citizen Scientist with Turtle Guardians!

Written by: Michaela S. Bouffard, Biologist, Road Ecologist, The Land Between and Turtle Guardians

 

Literature Cited

Costanzo, J. P., Litzgus, J. D., Iverson, J. B., & Lee JR, R. E. (1998). Soil hydric characteristics and environmental ice nuclei influence supercooling capacity of hatchling painted turtles Chrysemys picta. Journal of Experimental Biology, 201(22), 3105-3112.

Duman, J. G. (2015). Animal ice-binding (antifreeze) proteins and glycolipids: an overview with emphasis on physiological function. The Journal of experimental biology, 218(12), 1846-1855.

Freeman, H. C. (2022). Identifying Suitable Turtle Overwintering Habitat Through the Integration of Thermal, Chemical and Physical Wetland Properties.

Jackson, D. C. (2000). Living without oxygen: lessons from the freshwater turtle. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 125(3), 299-315.

Jackson, D. C., Taylor, S. E., Asare, V. S., Villarnovo, D., Gall, J. M., & Reese, S. A. (2007). Comparative shell buffering properties correlate with anoxia tolerance in freshwater turtles. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 292(2), R1008-R1015.

Karow Jr, A. M., & Webb, W. R. (1965). Tissue freezing: A theory for injury and survival. Cryobiology, 2(3), 99-108.

Larson, D. J., Middle, L., Vu, H., Zhang, W., Serianni, A. S., Duman, J., & Barnes, B. M. (2014). Wood frog adaptations to overwintering in Alaska: new limits to freezing tolerance. Journal of Experimental Biology, 217(12), 2193-2200.

Lee Jr, R. E., & Costanzo, J. P. (1998). Biological ice nucleation and ice distribution in cold-hardy ectothermic animals. Annual Review of Physiology, 60(1), 55-72.

Robichaud, J. A., Bulté, G., MacMillan, H. A., & Cooke, S. J. (2022). Five months under ice: biologging reveals behaviour patterns of overwintering freshwater turtles. Canadian Journal of Zoology, 101(3), 152-162.

Storey, K. B. (2007). Anoxia tolerance in turtles: metabolic regulation and gene expression. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 147(2), 263-276.

Pheromones & Juvenile Turtles – Scent Trailing

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What is ‘Scent Trailing’?

In the animal world there are many forms of communication and sensations which we, as humans, commonly overlook. One such sense is called scent trailing, a form of chemical communication (Butler & Graham, 1995). Scent trailing is the ability of an individual to follow a conspecific (an individual of the same species) based on a pheromonal (secreted chemical scent) trail they leave behind (Brown & MacLean, 1983). Similar to the trail of breadcrumbs used in Hansel and Gretel. This behavior has been widely studied and confirmed in snake species, typically allowing the pursuit of mates or hibernacula (overwintering areas) (LeMaster et al., 2001; Mason & Parker, 2010). Male Box Turtles, which native to the USA, are believed to use scent trailing during mating season to find a mate (Huff, 2005). A similar observation was found in Desert Tortoises, where males would sniff the ground to track females for courtship (behavior or communication used to attract a mate) (Berry, 1986). These findings suggest the possibility that scent trailing could also be used by turtles in Ontario.

Photo: Desert Tortoise by Joshua Tree Provincial Park - Flickr (1) Flickr (2)

What animals display this behavior?

As previously mentioned, animals such as reptiles are known to use scent trailing. An animal that has had lots of attention in this field of research are snakes (Mason & Parker, 2010). Snakes and other squamates use a characteristic tongue movement which allows them to sample the chemosensory (scent and taste) cues in the environment. The tongue delivers the cues near an organ in the mouth or nose called the vomeronasal or Jacobson’s organ (Mason & Parker, 2010). The Jacobson’s organ is located in the nasal cavity and uses specialized skin to detect stimuli (scents or taste cues) left in the environment (Gillingham & Clark, 1981; Negus, 1956). Various papers have confirmed that adult and juvenile snakes use chemicals left in their environment by other individuals of the same species to find mates and hibernacula (Brown & MacLean, 1983; Burger & Zappalorti, 2011; Mason, 2009; Brown & MacLean, 1983; Martin, 2019). Male snakes will use these scent trails to track females during mating season, whereas females are much less likely to scent trail other turtles of the same species (Mason, 1992). In a study by Joanna Burger (1979) Pine Snake snakelets were seen switching courses to follow adult trails to winter hibernacula. This behavior is highly advantageous in regions with harsh winters as locating hibernation dens significantly increases juvenile snake survival (Martin, 2019).

Photo: Pine Snake from iNaturalist by Springhunter - https://www.inaturalist.org/observations/105231115

Another reptile species that is known to use scent trailing are Spotted Salamanders. Juvenile Spotted Salamanders metamorphosize in ponds and wetlands before coming ashore to find hideaways (Greene et al., 2016). Exploring their new habitat comes with high risks and it is believed that these efts (baby salamanders) scent trail other individuals of the same species to suitable habitats. In a study by Kathryn Greene and colleagues (2016), efts were frequently found to choose hideaways with adult salamanders when introduced to two hideaways (one with adults and one without). These observations suggest that efts use chemical cues to locate appropriate and safe habitats to increase their chance of survival.

Photo: Spotted Salamader by U.S. Geological Survey - Flickr

A gap in knowledge exists in the present literature on how turtle hatchlings make their way to a suitable overwintering site as they are given no parental assistance (Pappas et al., 2009). Scientists speculate that many environmental or innate traits may be involved in orienting hatchlings to their critical first overwintering site, but they are generally not well understood (Warner & Mitchell, 2013).

Could scent trailing adults in the area assist hatchlings on this critical journey?

Do hatchlings use scent trailing to find overwintering sites? Why is this a concern?

Since various reptiles have been known to use scent trails to discover important areas in their habitat, it may be possible that hatchling turtles also possess this ability. Once eggs are laid, they receive no further parental care. Therefore, upon hatching from eggs, freshwater turtles need to use innate abilities and environmental cues to find their way to inhabitable areas (Pappas et al., 2009). The current literature contains very little information on turtle hatchlings as they are difficult to detect and track at their small size (Paterson et al., 2012). Various cues have been implicated in hatchling navigation including; solar, visual, olfactory (smell), and social facilitation (following other hatchlings or turtles) (Mason & Parker, 2010; Pappas et al., 2009; Butler & Graham, 1995).

Photo: Snapping Turtle Hatchlings - The Land Between

In a study conducted by Amelia Whitear and colleagues (2017), the chemical cue preference in Spiny Softshell hatchlings, a highly aquatic turtle species, was investigated. Scientists found that hatchlings preferred water scented by individuals of the same species (conspecifics) over unscented water. Potentially indicating that hatchlings use scent cues to move towards conspecifics and increase chances of survival by leading them toward areas with high quality resources or hibernacula. The scientists also investigated this phenomenon in Blanding’s and Snapping Turtles but no preference was found. These findings may have been due to the fact that these two species are semi-aquatic and thus may have reduced abilities to detect chemical cues in the water, compared to Spiny Softshell Turtles. It is possible that semi-aquatic turtle species instead rely on terrestrial chemical cues left on materials in the area (i.e. grasses, vegetation, rocks, etc.) (Whitear et al., 2017). In the future, further investigations should focus on this possibility to assist in determining recovery activities and assess aspects of turtle population stability.

Why is this important & directions for future studies:

Staff at The Land Between are excited to see whether future studies can confirm if turtle hatchlings in Ontario use scent trailing to navigate their new environment to find overwintering sites. Understanding this phenomenon is a huge conservation priority because as adult turtles are lost, it is expected that fewer scent trails are available for hatchlings to follow. As these paths disappear, we anticipate that recruitment of juveniles into the adult population will also experience a serious decline should this be the main means of locating hibernacula. One of the greatest challenges a turtle will face is surviving the first year of life, which scent trailing may facilitate (Berman; Brown & MacLean, 1983). Should this be the case, then by protecting adult turtles, mitigation strategies will also support hatchling survival.

By: Andrea O’Halloran - March 2022

Edited by: Sabrina Hasselfelt

 

Sources:

  • Berman, Leora. Interview 2020. 
  • Brown, W. S., & MacLean, F. M. (1983). Conspecific scent-trailing by newborn timber rattlesnakes, Crotalus horridus. Herpetologica, 430-436.
  • Burger, J. (1989). Following of conspecific and avoidance of predator chemical cues by pine snakes (Pituophis melanoleucus). Journal of Chemical Ecology, 15(3), 799-806.
  • Burger, J., & Zappalorti, R. T. (2011). The Northern Pine Snake (Pituophis melanoleucus) in New Jersey: its life history, behavior and conservation. Nova Science Publishers, USA, 1-56.
  • Butler, B. O., & Graham, T. E. (1995). Early post-emergent behavior and habitat selection in hatchling Blanding’s turtles, Emydoidea blandingii. Massachusetts. Chelonian Conserv. Biol, 1(3), 187-196.
  • Cooper, W.E., and Vitt, L.J. (1986). Interspecific odour discriminations among syntopic congeners in scincid lizards (Genus Eumeces). Behaviour 97:1-9. 
  • Gillingham, J. C., & Clark, D. L. (1981). Snake tongue-flicking: transfer mechanics to Jacobson's organ. Canadian Journal of Zoology, 59(9), 1651-1657.
  • Greene, K. M., Pittman, S. E., & Dorcas, M. E. (2016). The effects of conspecifics on burrow selection in juvenile spotted salamanders (Ambystoma maculatum). Journal of Ethology, 34(3), 309-314.
  • Huff, J. (2005). Box turtles: The elusive history of the box turtles of Woodend. Audubon Naturalist News, 4-6.
  • LeMaster, M. P., Moore, I. T., & Mason, R. T. (2001). Conspecific trailing behaviour of red-sided garter snakes, Thamnophis sirtalis parietalis, in the natural environment. Animal Behaviour, 61(4), 827-833.
  • Martin, C. E. (2019). Behavioral Aspects Of Chemoreception In Juvenile Cottonmouths (Agkistrodon Piscivorus).
  • Mason, R. T. (1992). Reptilian pheromones. Biology of the Reptilia, 18, 114-228.
  • Mason, R. T., & Parker, M. R. (2010). Social behavior and pheromonal communication in reptiles. Journal of Comparative Physiology A, 196(10), 729-749.
  • Negus, V. E. (1956). The organ of Jacobson. Journal of Anatomy, 90 (Pt 4), 515
  • Pappas, M. J., Congdon, J. D., Brecke, B. J., & Capps, J. D. (2009). Orientation and dispersal of hatchling Blanding’s turtles (Emydoidea blandingii) from experimental nests. Canadian Journal of Zoology, 87(9), 755-766.
  • Paterson, J. E., Steinberg, B. D., & Litzgus, J. D. (2012). Revealing a cryptic life-history stage: differences in habitat selection and survivorship between hatchlings of two turtle species at risk (Glyptemys insculpta and Emydoidea blandingii). Wildlife Research, 39(5), 408-418.
  • Warner, D. A., & Mitchell, T. S. (2013). Does maternal oviposition site influence offspring dispersal to suitable habitat? Oecologia, 172(3), 679-688.
  • Whitear, A. K., Wang, X., Catling, P., McLennan, D. A., & Davy, C. M. (2017). The scent of a hatchling: intra-species variation in the use of chemosensory cues by neonate freshwater turtles. Biological Journal of the Linnean Society, 120(1), 179-188.

Why I Shouldn’t Relocate This Turtle…

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Having a turtle appear in your yard may be a great opportunity to observe and learn from these incredible species. But for people with dogs or other potential dangers in their yards, this may be a stressful situation. That brings us to the question of the day: can you move a turtle off your property? Can you carry it over to the wooded area down the street, or to the swamp in the nearby park? You’d think that moving the turtle to a ‘better habitat’, somewhere you find more suitable for them, would be the best course of action. However, contrary to our “instinct” this is actually may not be the safest or best thing for the turtle, and while a complex issue, relocation can threaten a turtle’s survival.

As with any wild animal, a turtle found on your property should be left alone as much as possible. Most of Ontario’s turtles have small territories that contain everything they need to survive. For example, a Blanding’s Turtle’s home range typically only extends a few kilometers (Ministry of the Environment, Conservation and Parks, 2021). Turtles learn from a young age where to forage, nest, and hibernate, areas to which many will show fidelity, returning year after year,  for the rest of their lives (Mid-Atlantic Turtle & Tortoise Society, 2022). A study by Aaron R. Krochmal and Timothy Roth in Washington of Western painted turtles at their  research site; a patchwork of old growth woodlands and agricultural fields,found that turtles will follow “long, intricate routes with amazing precision—specific to within a few meters—to far-off, permanent water sources year after year, returning home again when the seasons next change”. 

When relocated to a new area, a turtle is no longer familiar with its surroundings, and can have difficulty navigating the new area to find food or other essentials such as safe and stable hibernation sites (Vanorio, 2021). When relocated to a new area, a turtle will most often attempt to find its way home. Unfortunately, turtles can then die of starvation or will perish due to other hazards (roads, construction, predators) in their attempt to get back home (Vanorio, 2021; Mid-Atlantic Turtle & Tortoise Society, 2022). 

A study to examine effects of relocation on eastern box turtles (Terrapene carolina), in North Carolina compared home ranges and movement patterns of 10 resident and 10 relocated box turtles. The study found that home ranges of relocated turtles were approximately significantly larger than resident turtles and that relocated turtles also moved a greater average distance per day than resident turtles. Additionally, 5 relocated turtles experienced mortality or disappearance compared to no mortality or disappearance of resident turtles (Hester et al). 

Another study of the eastern box turtle was carried out for over thirty years at the Mason Neck National Wildlife Refuge in Virginia showed that relocated did not do as well in the first years, but those that did survive, were on par with resident turtles. Therefore, as a rescue strategy for populations where existing native turtles are resident, relocation may be a recourse however,   individuals may suffer (Orr et al). Instances, however, where there are no significant numbers of resident turtles can be a different story entirely for newcomers’ survival as any existing habitats may not be adequate, available, suitable, and the necessary cues (social or biological such as  pheromone) may also be lacking to assist in relocation success. 

Therefore, while not always a death sentence, often the dangers that turtles face, both after being relocated and when attempting to return home, are a serious threat to their survival (Farnsworth and Seigel, 2013).

Moving Turtles off the Road

Roads often intersect existing turtle territories, resulting in turtles being at risk of mortality from cars, predation by animals who thrive in disturbed areas, and poachers. These threats are especially prevalent during periods of turtle migration in spring when moving from hibernation sites, during nesting season and again in the fall when returning to hibernation areas . Many females use road shoulders to lay their eggs, as the conditions there are usually favorable, and therefore there is often a crescendo of activity on roads during nesting season. 

Roads pose the highest threat to freshwater turtles in North America, and more than 60% of these shelled allies are at risk of extinction because of road mortality and habitat losses. 

Therefore, it is advisable and encouraged to help turtles off the roads when they are crossing the tarmac, and in the direction that they are going- and only if it is safe for you and other drivers on the road. Please note however that any assistance to turtles should be given after observing the situation to ensure that you are doing what is best for the turtle and for your own safety (Pulfer, 2021); If the turtle is nesting (this will look like she is digging with her back legs), please do not move the turtle, but keep an eye on her for safety until she finishes. Watch the female who has just finished nesting to see where she plans to go. Often females will simply make a large U-turn back to the natural area behind her after nesting. However, if she is indeed crossing the road, you can assist the turtle directly or accompany the turtle to reach the other side safely. Turtle Guardians has videos to teach you how to hold and help snapping turtles and other freshwater turtles. 

You can also help save turtle nests in these situations: When the turtle has finished nesting and she is out of harm’s way, place a light object (a hat, cloth, glove) on top of the nest, note the location using your smartphone or by taking a picture with identifying features and call Turtle Guardians at 705-854-2888. Often the organization can send a trained individual to either protect (with a nest cage) or excavate (under permit) the nest so that the eggs can be incubated in a safe location.

As stated above, always move a turtle in the same direction that it was heading, to avoid having it turn around and head back onto the road once again (Pulfer, 2021; Mid-Atlantic Turtle & Tortoise Society, 2022). It's best to place a turtle about 30 feet from the road, so the turtle is away from road dangers and does not turn back if startled. For more information on how to help a turtle cross the road, please visit our website at www.turtleguardians.com/helping-a-turtle-across-the-road/, here you can find helpful resources on how to safely transport turtles!

It may be tempting to move a turtle to a better, or seemingly more suitable, habitat further down the road or to the wetland down the street from your house, but the best thing you can do for the turtle’s survival is to move them the shortest distance possible across the road and leave them be if they are on your property (Mid-Atlantic Turtle & Tortoise Society, 2022).

Written by Kiara Duval. Edited by Leora Berman

Works Cited

Blanding's turtle. (2021, August). Retrieved February 01, 2022, from https://www.ontario.ca/page/blandings-turtle

Effects of Relocation on Movements and Home Ranges of Eastern Box Turtles. April 2008. Journal of Wildlife Management 72(3):772 - 777, JOY M. HESTER, Steven J. Price and Michael E. Dorcas

Long-term comparison of relocated and resident box turtles, Terrapene carolina carolina JOHN M. ORR1*, CARL H. ERNST & TIMOTHY P. BOUCHER2

Mid-Atlantic Turtle & Tortoise Society. (2022). Helping turtles cross roads. Retrieved February 01, 2022, from http://www.matts-turtles.org/helping-turtles-cross-roads.html

Ministry of the Environment, Conservation and Parks. (2021, March). General habitat description for the Blanding’s turtle (Emydoidea blandingii). Retrieved February 1, 2022, from https://files.ontario.ca/mecp-blandings-turtle-general-habitat-description-en-2021-04-20.pdf

Pulfer, T. (2021, August 17). How you can help turtles cross the road. Retrieved February 01, 2022, from https://ontarionature.org/how-you-can-help-turtles-cross-the-road/

Vanorio, A. (2021, October 14). There is no place like home – turtle homing instincts. Retrieved February 01, 2022, from https://www.foxrunenvironmentaleducationcenter.org/new-blog/2019/4/13/there-is-no-place-like-home-turtle-homing-instincts

How a Painted Turtle Finds Its Way, Unlike many species, this common reptile migrates from memory, Scientific American, Timothy Roth, Aaron R. Krochmal January 30, 2019

What Determines the Sex of a Turtle?

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Can you tell the sex of the hatchling in the photo above just by looking at it? No! In most species, sex is determined by the genes that are passed down from parents to offspring. But, this is not the case for every animal. Many species of reptiles, like some lizards and turtles, use a different method, called temperature-dependent sex determination (TSD). This is a process where the ambient temperature determines the sex of an offspring without the use of sex chromosomes. TSD is the differentiation of gonads depending on the incubation temperature of the eggs (Tezak et al., 2020). Specific incubation temperatures produce males or females, and intermediate temperatures can result in the development of either one (Spotila et al., 1987). There are also three distinct types of TSD, and they affect hatchlings differently.

For most turtle species, temperature plays a huge role in determining the sex of their hatchlings. There are three patterns of TSD that have been discovered so far (Spotila et al., 1987). In the first pattern, ‘Ia’, females are produced at higher temperatures, and this pattern is the one most often seen in turtles. In pattern ‘Ib’, the opposite happens, and higher temperatures produce males. The final pattern ‘Il’ produces females at both high and low temperatures, meaning males are only found at intermediate temperatures (Hulin et al., 2009). It should be noted that there are a few turtle species that use this latter pattern as well. These patterns are determined as they relate to a “pivotal temperature”; an important value representing the temperature where males and females are produced in equal proportions (Hulin et al., 2009).

Research has been done whereby scientists have tested cooler nests versus warmer nests (McCoy et al., 1983). To date, mostly all turtles are known to use pattern ‘Ia’, where warmer temperatures produce females and colder temperatures produce males (Spotila et al., 1987). However, because pattern ‘II’ occurs in some turtles and lizards, it is thought to possibly be the ancestral form which ‘Ia’ and ‘Ib’ originated from (Santidrián Tomillo et al., 2015). 

Some turtles that display TSD include many sea turtles such as Green, Loggerhead, and Leatherback (Standora and Spotila, 1985), but also in freshwater turtles such as snapping turtles, Map turtles (Spotila et al., 1987), Painted turtles (Hulin et al., 2009), and Red-eared sliders (Ramsey et al., 2007). 

There is a precise period of embryonic development at which this temperature is needed for the development of either ovaries or testis (Hulin et al., 2009). Studies have pinpointed this critical period to the middle-third section of incubation (Spotila et al., 1987). The temperature of incubation needs to be quite precise for this determination. For example, the Red-eared slider needs temperatures of above 31°C to give females, where temperatures under 26°C give males (Ramsey et al., 2007). Any temperature in between gives mixed ratios. 

The nesting location therefore has an influence on temperature and therefore the development of turtle hatchlings. In a study done on Green turtle nests, it was observed that the nests located on open beaches mainly produced females, while the nests shaded under vegetation produced 94% males (Standora and Spotila, 1985). This is because the location of these nests, being either in full sun or in full shade, controlled the ambient temperatures experienced by the eggs. 

Varying temperature conditions are also known to affect the ratio of males to females in a given nest. In nesting Map turtles on the Mississippi river, this variation based on temperature has been observed. In this study, four different sites produced various ratios spanning from mostly females to mostly males (Spotila et al., 1987). Another variation that may have an impact within the nest itself is pivotal temperature. At this pivotal temperature, nests “react” keenly to slight changes and therefore if nests are near the pivotal temperature generally, simply the metabolic heat can effect sex and cause females to hatch from the eggs at the centre where there is more heat, and males will hatch from along the outskirts of the nest (Standora and Spotila, 1985). 

But one cannot determine the sex of hatchlings in their nests easily. There are limited physical or morphological markers and there are considerable ethical issues when sampling nests and hatchlings as well.  And while scientists can now guess-timate ratios based on nest and air temperatures, these methods are not reliably accurate. A recent study by Tezak et al, 2020, has helped uncover a method of testing for hormones in the blood of hatchlings, to accurately determine their sex at early ages and with minimally invasive techniques. Red-eared slider hatchlings were tested for Anti-Müllerian hormone (AMH), and found that only male hatchlings possessed this hormone, as it plays a critical role in male differentiation. AMH was found to be an accurate marker of turtle sex in both the red-eared sliders and loggerhead turtles in the study (Tezak et al., 2020).

Something that cannot be ignored when talking about TSD is the dangers that temperature changes can have on populations, especially during climate change. The predicted rate of temperature change is very high over an unusually short timeframe, and can have disastrous consequences on different species, making it more crucial that researchers understand the effects of climate changes on our wildlife and ecosystems. These new extremes in temperatures that are predicted to result from climate change, may modify some life history traits for TSD species, or result in strong sex ratio biases that skew the population towards female majority. 

In a study performed on painted turtles, sex ratios were directly correlated with air temperatures (Hulin et al., 2009). This would mean that increasing temperatures produced increasing numbers of females. Having more females than males is not inherently bad, as males reach sexual maturity and can reproduce much quicker than females (Santidrián Tomillo et al., 2015). However, climate change could mean an overabundance of females, which would eventually lead towards extinction (Hulin et al., 2009; Tezak et al., 2020). It is also possible that the ratios could be balanced out over time (i.e. one season of mostly females followed by one of mostly males) (Spotila et al., 1987), but there is no guarantee that the warming temperatures would allow this. 

There are a few ways that turtles may adjust to a degree due to increasing temperatures including attempting to choose alternate temperature-specific nesting sites or adjust locations within their territories entirely (phenotypic plasticity; changes made in response to the environment). Other possibilities are microevolution (changes of numbers of genes in a population) (Hulin et al., 2009). However, turtles are generally slow-moving and highly attuned yet also reliant on patterns in the environment, therefore the rate of any adaptations may not be sufficient. 

Turtles that can nest multiple times throughout the year also play an important role in balancing these changes, as they can also nest during cooler months (Spotila et al., 1987), however not all species double-clutch (lay twice during the season). 

Therefore, human-intervention and habitat restoration becomes more essential; Mitigation techniques development could potentially help reduce the effects of climate change on the nesting turtles, some of which may include  nest shading, nest-irrigation, both which could be facilitated through native plantings to extend shade areas and habitat integrity; and also  climate-controlled hatcheries (Santidrián Tomillo et al., 2015).

As we’ve seen through all the examples given above, temperature is one of the most important factors when determining the sex of turtle hatchlings. Things like next placement, ambient air temperatures, and the specific patterns in nest construction can also sway the ratio of males and females in each nest individually. It is important for us to remember that while climate change is a growing reality, we can have an impact on these nests and future populations of turtles; be mindful of this when discovering a nest and alert your local conservation organization, such as Turtle Guardians which may have incubation permits; maintain natural plants and habitats to ensure there is shade, moisture and features that support native wildlife too.

Written and Researched by Kiara Duval, December 2021

Works cited

Hulin, V., Delmas, V., Girondot, M., Godfrey, M. H., & Guillon, J.-M. (2009). Temperature-dependent sex determination and global change: Are some species at greater risk? Oecologia, 160(3), 493–506. https://doi.org/10.1007/s00442-009-1313-1 

McCoy, C. J., Vogt, R. C., & Censky, E. J. (1983). Temperature-controlled sex determination in the sea turtle Lepidochelys olivacea. Journal of Herpetology, 17(4), 404. https://doi.org/10.2307/1563594 

Ramsey, M., Shoemaker, C., & Crews, D. (2007). Gonadal expression of SF1 and aromatase during sex determination in the red-eared slider turtle (Trachemys scripta), a reptile with temperature-dependent sex determination. Differentiation, 75(10), 978–991. https://doi.org/10.1111/j.1432-0436.2007.00182.x 

Santidrián Tomillo, P., Genovart, M., Paladino, F. V., Spotila, J. R., & Oro, D. (2015). Climate change overruns resilience conferred by temperature-dependent sex determination in sea turtles and threatens their survival. Global Change Biology, 21(8), 2980–2988. https://doi.org/10.1111/gcb.12918  

Spotila, J. R., Standora, E. A., Morreale, S. J., & Ruiz, G. J. (1987). Nesting habitat characteristics of green sea turtle (Chelonia mydas) in the Tambelan Archipelago, Indonesia. Herpetologica, 43(1), 74–81. https://doi.org/10.37473/dac/10.1007/s11852-021-00798-4 

Standora, E. A., & Spotila, J. R. (1985). Temperature dependent sex determination in sea turtles. Copeia, 1985(3), 711. https://doi.org/10.2307/1444765 

Tezak, B., Sifuentes-Romero, I., Milton, S., & Wyneken, J. (2020). Identifying sex of neonate turtles with temperature-dependent sex determination via small blood samples. Scientific Reports, 10(1). https://doi.org/10.1038/s41598-020-61984-2 

 

Reproductive Ecology of Freshwater Turtles in Ontario

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Ontario is home to a wide variety of amazing plants and animals, each with unique behavior and life histories (timeline of reproduction and lifespan, essentially, the life cycle). For years, ecologists have been fascinated by diversity all over the world, and here in Ontario is no different! As a global loss of biodiversity continues, scientists are eager to understand each unique behavior and adaptation in an effort to help protect all species. One group of animals of particular concern and fascination is turtles. Turtles are as unique in their life histories and reproductive cycles as they are morphologically (how they are shaped). Though the eight native species found here in Ontario face similar challenges, they have slight differences when it comes to their life cycles. Distinctions exist between species from the time they mate, to the time their hatchlings leave the nest.

In Ontario, the reproductive cycle of turtles pauses during the winter months, as turtles overwinter (or brumate) during periods of cold weather. When they emerge from their state of inactivity in the spring, a season of mating begins which can be ongoing through the fall. The females of some species begin nesting in late spring, while others lay their eggs during the early summer. Most hatchlings emerge from their nests during the fall, but some species are known to overwinter in their nests instead.

Mating is typically observed throughout the active season (early spring to late fall) (Bulte et al., 2021; COSEWIC, 2004-2018; ECCC, 2016). Peaks in this activity are most common after emergence from overwintering sites in the spring and in the fall before entering brumation (period of inactivity). Fall matings may be completed out of convenience, as turtles may congregate at overwintering grounds, providing ample opportunity to find a mate. These fall matings are possible because females are capable of storing sperm in their bodies for long periods of time for later use, so they can store the sperm over the winter for use the following spring. Male turtles may use different courtship tactics to gain access to females during this time, such as titillation in Painted Turtles; This courtship activity involves the use of his long claws to stroke the female’s head and/or eyes. 

In Ontario, female turtles commonly reach sexual maturity, the stage in their life when egg production begins, around 10 years of age. However, other species may need to wait longer, for example, Blanding’s Turtles reach maturity much later, at 20-25 years of age. Snapping Turtles also take a long time to mature, living 17-19 years before entering this life stage (COSEWIC, 2016a, ECCC 2016).

Once a female has achieved reproductive maturity, she is now able to mate with males to produce offspring. Before nesting, some species, such as Painted Turtles, may spend more time basking to assist with egg development. Basking is a method that turtles use to regulate their body temperature and ultimately fine-tune the rate of physiological processes. This is accomplished through energy acquisition, the energy is then used by the individual to complete processes such as egg development ( Jain‐Schlaepfer et al., 2017; Topping & Valenzuela, 2021, Carrière et al., 2008; Krawchuk & Brooks, 1998). When egg development is complete, females begin the nesting process. Between late May and early July all female turtles carrying fertilized eggs will complete nesting. Certain species, such as the Musk, Northern Map, and Spotted Turtles, do not follow this timeline exactly and are known to wait until June to begin this process (COSEWIC, 2004, 2012a, 2012b). Snapping Turtles, on the other hand, tend to finish depositing their eggs in June, earlier than most other species (ECCC, 2016).

 

Huge variation is observed when studying the average number of eggs found in each respective species’ nest. Each nest produced by an individual female is referred to as a clutch.  Clutch sizes of Ontario turtles typically range from as little as 5 to as many as 20 eggs. Snappers are again an exception to this pattern, with the incredible ability to produce as many as 109 eggs in a single clutch (ECCC 2016)! On the other hand, Musk turtles are known to produce very small numbers of eggs in a clutch, ranging from 3 to 7 eggs total (COSEWIC, 2012a).

 

Egg production takes place once a season for most species of turtle in Ontario, but a few species are physiologically able to produce two clutches of eggs in a given year. These species include Midland & Western Painted, Northern Map, and Spiny Softshell Turtles (COSEWIC, 2006; 2012b; 2016b; 2018b). Unfortunately for declining turtle species, some females are not able to mate and then nest annually. Instead, such as in the case of Blanding’s Turtles, some females may only nest once every three years (COSEWIC, 2016a). This is of concern for species with declining populations, as limited nesting in turn limits the number of offspring introduced to the population. 

Nesting Blanding’s Turtle - The Land Between

Once eggs have been laid, the turtle offspring undergo a period of development in the nest termed incubation. Each species typically requires at least 2 months, and up to 90 days of incubation before the eggs begin to hatch, however, there are some exceptions. Blanding’s Turtles and Wood Turtles have the greatest ranges of incubation time, with 56-133 days and 65-116 days, respectively (COSEWIC, 2016a; Walde et al., 2007). Spotted Turtles require the longest time for development in the nest, with no less than 80 days of incubation before hatching (COSEWIC, 2004).

Most turtle species, including some of Ontario’s turtles display temperature dependent sex determination. This is the process whereby the sex of the offspring inside the egg is determined entirely by the temperature of the nest during the incubation process. There is no genetic designation involved (Crews et al., 1994). These species include; Northern Map, Painted, Snapping, Blanding’s, Spotted, and Musk Turtles (COSEWIC 2004-2018b; ECCC 2016). The sex of Spiny Softshell and Wood turtle hatchlings is determined through genetics (COSEWIC, 2016b; COSEWIC, 2018a). Genetic sex determination is the same process seen in humans, where sex is decided based on parental chromosome inheritance.

The majority of hatchlings begin emerging from their nests early in August, and some stragglers may still be observed leaving the nest as late as October. Interestingly, Painted and Northern Map Turtle hatchlings may overwinter in their nests and instead emerge the following year. These hatchlings still hatch from their eggs in the fall but remain in the nest cavity through the winter and emerge the following spring.

 

As we learn about the differences in reproductive timing between species of Ontario turtles, we are reminded of the immense biodiversity here in Ontario. Reproductive differences can even be seen within individuals of the same species. Understanding these reproductive differences is important to inform best management practices. Intraspecies differences occur throughout species’ ranges and this is why local studies are necessary. 

Management practices for turtle population conservation may include installation of turtle crossing signs with special emphasis on the active season for turtles. These signs remind the public to be aware of turtles on the road, and to reduce mortality to nesting turtles and hatchlings. As scientists begin to uncover the differences between the reproductive behaviors of different species of Ontario turtles, they also begin to understand the impact the loss of one adult turtle can have on a population. This can be detrimental as the loss of one adult causes a cascade of reproductive loss through the population for years to come, as turtles take many years to reach reproductive maturity and as the rate of recruitment (the rate at which turtles replace themselves) is also very low as many eggs and related hatchlings will not reach adulthood).

Research by: Kiara Duval & Andrea O’Halloran

Written by: Andrea O’Halloran (March 2022) Edited by MaryEllen Abberger and Leora Berman

Sources:

Angoh, S. Y. J., Hooton, L. A., & Davy, C. (2018). Can You Tell the Turtle by its Eggshell?

Baker, P. J., Costanzo, J. P., Iverson, J. B., & Lee, R. E. (2003). Adaptations to terrestrial overwintering of hatchling northern map turtles, Graptemys geographica. Journal of Comparative Physiology B, 173(8), 643-651.

 

Bulté, G., Huneault, B., & Blouin‐Demers, G. (2021). Free-ranging male northern map turtles use public information when interacting with potential mates. Ethology, 127(11), 995-1001.

 

Carrière, M. A., Rollinson, N., Suley, A. N., & Brooks, R. J. (2008). Thermoregulation when the growing season is short: sex-biased basking patterns in a northern population of painted turtles (Chrysemys picta). Journal of Herpetology, 42(1), 206-209.

 

COSEWIC (2004). COSEWIC assessment and update status report on the spotted turtle Clemmys guttata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 27 pp.

 

COSEWIC (2006). COSEWIC assessment and status report on the Western Painted Turtle Chrysemys picta bellii (Pacific Coast population, Intermountain-Rocky Mountain population and Prairie/Western Boreal - Canadian Shield population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 40 pp. (www.sararegistry.gc.ca/status/status_e.cfm). 

 

COSEWIC. (2012a). COSEWIC assessment and status report on the Eastern Musk Turtle Sternotherus odoratusin Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 68 pp.(Species at Risk Public Registry).

 

COSEWIC. (2012b). COSEWIC assessment and status report on the Northern Map Turtle Graptemys geographica in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 63 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm).

 

COSEWIC. (2016a). COSEWIC assessment and status report on the Blanding’s Turtle Emydoidea blandingii, Nova Scotia population and Great Lakes/St. Lawrence population, in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xix + 110 pp. (http://www.registrelepsararegistry.gc.ca/default.asp?lang=en&n=24F7211B-1).

 

COSEWIC. (2016b). COSEWIC assessment and status report on the Spiny Softshell Apalone spinifera in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii ;+ ;38 ;pp.

 

COSEWIC. (2018a). COSEWIC assessment and status report on the Wood Turtle Glyptemys insculpta in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 51 pp. (Species at Risk Public Registry).

 

COSEWIC. (2018b). COSEWIC assessment and status report on the Midland Painted Turtle Chrysemys picta marginata and the Eastern Painted Turtle Chrysemys picta picta in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xvi + 107 pp. (http://www.registrelepsararegistry.gc.ca/default.asp?lang=en&n=24F7211B-1).

 

Costanzo, J. P., Dinkelacker, S. A., Iverson, J. B., & Lee, Jr, R. E. (2004). Physiological ecology of overwintering in the hatchling painted turtle: multiple-scale variation in response to environmental stress. Physiological and Biochemical Zoology, 77(1), 74-99.

 

Crews, D., Bergeron, J. M., Bull, J. J., Flores, D., Tousignant, A., Skipper, J. K., & Wibbels, T. (1994). Temperature‐dependent sex determination in reptiles: Proximate mechanisms, ultimate outcomes, and practical applications. Developmental genetics, 15(3), 297-312.

 

Environment and Climate Change Canada. (2016). Management Plan for the Snapping Turtle (Chelydra serpentina) in Canada [Proposed]. Species at Risk Act Management Plan Series. Ottawa, Environment and Climate Change Canada, Ottawa, iv + 39 p

 

Galbraith, D. A., White, B. N., Brooks, R. J., & Boag, P. T. (1993). Multiple paternity in clutches of snapping turtles (Chelydra serpentina) detected using DNA fingerprints. Canadian Journal of Zoology, 71(2), 318-324.

 

Jain‐Schlaepfer, S. M., Blouin‐Demers, G., Cooke, S. J., & Bulté, G. (2017). Do boating and basking mix? The effect of basking disturbances by motorboats on the body temperature and energy budget of the northern map turtle. Aquatic Conservation: Marine and Freshwater Ecosystems, 27(2), 547-558.

 

Krawchuk, M. A., & Brooks, R. J. (1998). Basking behavior as a measure of reproductive cost and energy allocation in the painted turtle, Chrysemys picta. Herpetologica, 112-121.

 

McGuire, J. M., Congdon, J. D., Kinney, O. M., Osentoski, M., & Scribner, K. T. (2015). Influences on male reproductive success in long-lived Blanding’s Turtles (Emydoidea blandingii). Canadian Journal of Zoology, 93(6), 487-497.

 

Moldowan, P. D. (2015) Secret Love Life of the Painted Turtle.

 

Moldowan, P. D., Brooks, R. J., & Litzgus, J. D. (2020). Sex, shells, and weaponry: coercive reproductive tactics in the painted turtle, Chrysemys picta. Behavioral Ecology and Sociobiology, 74(12), 1-14.

 

Nagle, R. D., Lutz, C. L., & Pyle, A. L. (2004). Overwintering in the nest by hatchling map turtles (Graptemys geographica). Canadian Journal of Zoology, 82(8), 1211-1218.

 

Pearse, D. E., & Avise, J. C. (2001). Turtle mating systems: behavior, sperm storage, and genetic paternity. Journal of Heredity, 92(2), 206-211.

 

Topping, N. E., & Valenzuela, N. (2021). Turtle Nest-Site Choice, Anthropogenic Challenges, and Evolutionary Potential for Adaptation. FRONTIERS IN ECOLOGY AND EVOLUTION, 9.

 

Walde, A. D., Bider, J. R., Masse, D., Saumure, R. A., & Titman, R. D. (2007). Nesting ecology and hatching success of the wood turtle, Glyptemys insculpta, in Quebec. Herpetological Conservation and Biology, 2(1), 49-60.

 

Weisrock, D. W., & Janzen, F. J. (1999). Thermal and fitness‐related consequences of nest location in painted turtles (Chrysemys picta). Functional Ecology, 13(1), 94-101.

Trials and Innovations -Testing Turtle Tunnels in The Land Between

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ecopassage3

We have been hard at work testing some new designs and combinations of materials to find affordable and effective solutions for turtle tunnel systems in Ontario's Highlands. And just like most experiments, there are ups and downs, wins and losses, but we are going to persevere until we find the right mix of products and cost to do the job.

Read about our pilot work here: TT Report (2)

fencing 9

The Loyalty of Turtles to Their Routes

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Researchers have found that turtles are creatures of habit when it comes to seasonal activities. Though it is very species-dependent, the majority of turtles display some sort of fidelity (faithfulness) to their home regions. That is, they return to the same areas for various activities year after year. Studies have shown that some species of turtles have fidelity to nesting, overwintering, and foraging sites (Schofield et al., 2010; Casale et al., 2007). For a specific example, painted turtles have been observed to show fidelity to nesting areas (Roth and Krochmal, 2015). There is also another type of fidelity that turtles exhibit: route fidelity. This is defined as loyalty to migration routes used to travel between various habitat types. However, route fidelity in turtles is not as well-studied as the other types of fidelity. 

Studies focused on migration routes are important for many ecological and conservative reasons. Understanding a population's distribution and habitat requirements allows us to better understand how to protect species and support their conservation (Schofield et al., 2010; Siegwalt et al., 2020). The long-term viability of different species can be directly impacted by environmental processes, human activity, and many other factors (Schofield et al., 2010). Predicting nesting sites, migratory pathways, foraging sites, and over-wintering sites are some of the main priorities when it comes to the turtle conservation effort (Broderick et al., 2007). Knowing when and where turtles spend their time can help us to understand where protection efforts are needed. These efforts can also help us to realize the effects human activities can have on their critical habitats (Casale et al., 2007). Understanding the level of fidelity that turtles have to their migratory routes when traveling between foraging, nesting, and overwintering sites is key to discerning where to focus conservation efforts (Broderick et al., 2007). For example, assessing where painted turtles nest, as it is close to the same area yearly (Rowe et al., 2005), would allow us to protect this nesting area more effectively. However, this is not as easy to assess as it may seem.

Predicting population distribution of turtles has always been difficult due to their elusivity and extensive home ranges (Horton et al., 2017). For example, Snapping Turtles have been observed to follow their migration routes very carefully, although they do periodically change their preferred sites (Keevil et al., 2018). However, there is hope for these studies with the advancements of modern technology, such as satellite tracking, which has made it possible to remotely track an animal's movement (Horton et al., 2017). This allows researchers to analyze trajectories and pinpoint patterns of navigation that different individuals use year after year (Horton et al., 2017). By being able to point out these migratory corridors, researchers can make recommendations for mitigation strategies for these regions. For example, monitoring or controlling fisheries activity during the turtle's migratory season can have a substantial impact on turtle conservation, as shown in a study done by Boderick and colleagues (2007). They showed that Green and Loggerhead sea turtles spent a lot of time resting on the seabed, making them highly susceptible to demersal (groundfish) fishing gear (Broderick et al., 2007). 

The results of turtle route fidelity studies have been somewhat inconsistent. That is, there appears to be a great deal of variability in route fidelity, especially among different species of turtles. To demonstrate this, I will present examples from a few different studies. 

First, for sea turtles: in a study by Schofield and contributors (2010), the movement of male Loggerhead Sea Turtles was tracked. Though these turtles did return to their original foraging sites each year, they did so by using a myriad of different routes. In a different study conducted on female Hawksbill Sea Turtles, Hawkes and contributors (2012) showed there was not always strong fidelity to migratory routes, and that routes varied in some cases by hundreds of kilometers. However, strong nest and foraging site fidelity was still observed (Hawkes et al., 2012). Further, Boderick and her colleagues (2007) were able to demonstrate some route fidelity in female Green Sea Turtles and Loggerhead Sea Turtles when examining post-nesting migration to foraging grounds. These turtles were tracked for many years and used highly similar routes to return to their foraging and over-wintering areas. 

The results are a bit more regular for freshwater turtles where studies demonstrate more definitively that some species may use the same routes to get to their overwintering sites. This appears to be the case for the European Pond Turtle studied by Thienpoint and colleagues (Thienpont et al., 2004). In another study performed on Painted Turtles, a native Ontario species, incredible route precision when returning to sites was observed year after year (Ross and Krochmal, 2015). 

Overall, however, there is still uncertainty in the literature with regards to turtle migratory route fidelity. However, all the information presented here was taken from studies where route fidelity was not the main focus. This highlights the need for future studies to focus specifically on turtle migratory route fidelity. This will further inform the need for conservation efforts focused specifically on turtle migration routes.  

Fidelity patterns in turtles can be very important for their prolonged survival. They can also be highly variable between different species. As you may already know, many turtle species travel incredibly long distances, both by water and over land, between the sites they use for various life activities including hibernation, mating, and feeding (Shimada et al., 2020; Thienpont et al., 2004). You might be wondering: why would they spend so much time and energy going back and forth to the same spots every year? To answer this question, we will look at a few different factors. 

Firstly, maintaining fidelity to specific sites is considered by many to be a low-risk strategy (Schofield et al., 2010). The turtles know that specific sites have provided them with the resources they needed in the past, and this offers them security (Schofield et al., 2010). This means that returning to a site that they’ve used previously can be much more beneficial than searching for a new, unexplored site. Most turtles will return to the same foraging sites every year and only stray if their existing site has suffered degradation and is no longer profitable (Schofield et al., 2010). Studies have also shown that both locally raised and newly released turtles show site fidelity to the area where they were released or born (Attum et al., 2013). The released turtles in particular might choose to remain in the area of their release, as this is the area that becomes familiar to them. Other factors that could impact a turtle’s fidelity to a particular site could also be related to familiarity accompanying easier defense of the territory, or the quality of the site (Broderick et al., 2007). 

Turtles are incredible animals with very interesting, if variable migratory patterns. The ability of some species to pinpoint specific locations over hundreds of kilometers and return to them is a fascinating subject to many researchers. Knowing what sites they favor and when they are likely to return can facilitate our studies and present opportunities  to learn more about them. Being able to study these patterns will not only increase our understanding of their behavior, but will also allow us to better guide conservation efforts to protect native turtle species.

Author: Kiara Duval - November 2021

Edited by: Andrea O’Halloran and Leora Berman

The Overwintering Struggles of Freshwater Turtles in Ontario

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Harsh Ontario winters present unique problems for non-migratory animals. Ectotherms, such as freshwater turtles, need to employ strategies to avoid freezing while living in cold conditions for extended periods of time because the external temperature determines their body temperature. There are two strategies turtles are known to use to survive severe winter conditions: freeze avoidance and freeze tolerance (Cantrell et al., 2014). Freeze avoidance is considered a behavioural strategy. Turtles will spend the winter below the water surface, in areas where temperatures do not dip below freezing, to avoid ice penetration (the entry of ice crystals from the environment into their body) (Costanzo et al., 2008; Valerio et al., 1992). All adult freshwater turtles in Ontario do this. The second strategy, freeze tolerance, is the ability to survive the physical freezing and thawing of one's body without injury or death (Costanzo & Lee, 2013). This strategy is known to be employed by Painted turtle hatchlings (Cantrell et al., 2014).

When overwintering in a body of water where the surface freezes over, oxygen availability is limited. To survive in these conditions, turtles need to find a habitat with stable oxygen supply and temperature, to which they show site fidelity (they return to the exact same sites year after year because they have these specific conditions). In addition, they shift to anaerobic metabolism. This is only practical during overwintering because metabolic rates are extremely slowed during this process, and require very little energy. However, anaerobic metabolism causes increased lactic acid production and depletion of glycogen stores, which can threaten the survival of an overwintering turtle (Cantrell et al., 2014). Additionally, oxygen dispersal (availability) is not uniform throughout the water column, so a turtles’ position in the body of water has significant effects on physiological processes such as metabolism and respiration (Cantrell et al., 2014). 

Adult turtles are known to adjust their position in the water, despite choosing the same sites each year (hibernation site fidelity), in order to avoid freezing temperatures (Bodie & Semlitsch, 2000) and to minimize acidosis (excess acid present in body fluids) (Greaves & Litzgus, 2008). Taylor and Nol (1989) observed multiple occasions where three Painted turtles readjusted their positioning after ice formed over their overwintering pond. They also found that an individual moved within the water column to an area of higher oxygen availability when the environment became anoxic (void of sufficient oxygen levels), suggesting that turtles, despite their vulnerability and slowed movements are capable of relocating from a low to high quality area within their dedicated hibernation site, however, scientists did not observe such adjustments (of greater than 1 m) after ice cover developed over the water bodies (Edge et al., 2009). Unfortunately, hatchlings and juveniles tend to occupy shallower overwintering grounds and readjust less often than adults. Because young turtles are less able to adjust to changing conditions, they are sometimes unable to respond accordingly, and do not survive through the winter (Bodie & Semlitsch, 2000). Some hatchlings are able to forgo the dangerous search for an ideal overwintering location and instead wait out the winter in their nest cavity (Ultsch, 2006); Painted turtle hatchlings are known to employ this freeze tolerance strategy (Cantrell et al., 2014), while snapping turtles are not known for this adaptation. Adult turtles also have a bit of an edge over juveniles, as their shells are a source of calcium which act to remove some lactic acid build up during hibernation, while hatchlings don’t have the same advantage (Ultcsh, 2006). 

However, there are other reasons for adult turtle mortality in winter such as anoxia (the loss of oxygen), predation, freezing temperatures (Ultcsh, 2006), and immunosuppression (Refsnider et al., 2015) where, because temperatures determine both metabolic processes and immune system function, turtles may succumb to disease or infections during hibernation. Surprisingly, however, winter turtle mortality rates are lower than mortality rates in spring and summer. 

The ability for a species to survive in an environment with very low oxygen availability is called anoxia-tolerant. Different species of turtles have varying degrees of tolerance/intolerance; some turtles are anoxia-intolerant, while others are anoxia-tolerant. For example, Western Painted turtles are considered the tetrapod with the best anoxia-tolerance, while Map and Wood turtles are considered anoxia-intolerant. For this reason, Map and Wood turtles are known to select hibernation sites where dissolved oxygen is elevated and the water surface does not completely freeze over (such as flowing streams and lakes) (Cantrell et al., 2014); These environments allow them to maintain aerobic respiration while hibernating (Reese et al., 2002). Anoxia-intolerant turtles need to overwinter in an area with a higher partial pressure of oxygen, which would restrict the number of overwintering sites a turtle can occupy.  

Regardless of the level of tolerance a species has to low oxygen conditions, all turtles are immuno-supressed during the winter, and also are unable to use their lungs to acquire oxygen during hibernation, and instead, will use either their cloaca (end of digestive tract) or skin for respiration (Edge et al., 2009).

Hibernation site fidelity (the returning to the same hibernation sites annually) is high for both anoxia tolerant and intolerant turtles, because the site must have very specific conditions for overwintering. Therefore the conversion, contamination, or loss of small wetland habitats and shoreland areas threatens turtle survival and therefore the success of future generations. Without access to crucial habitats, turtles are unable to survive the cold winter months. A lack of information and attention to these areas, and increased land development means that turtles will  have little hope moving forward. 

Another threat to overwintering adults is predation; in a study of intact hibernation sites conducted by Brooks and colleagues (1991), it was found that the majority of turtles that did not survive the winter were casualties of predation. This was deduced because turtle carcasses that were found were mutilated and had wounds indicating that they had been attacked by a predator. Predation is a threat to turtles in the spring as well; when emerging from overwintering grounds, turtles are at an elevated risk of predation because hypoxia (insufficient oxygen available for body tissues) (Newton & Herman, 2009) and related metabolic acidosis which make them sluggish and slow moving. They are therefore less able to avoid predators at this time by fleeing (Greaves & Litzgus, 2007). Again in the late autumn before ice over, turtles are again at an increased risk of predation (Greaves & Litzgus, 2007). During this stage, the water’s temperatures are low and therefore turtles are less able to mobilize; the cold initiates a torpor (inactivity) state (Newton & Herman, 2009). 

Another threat to the health of turtles during hibernation is immune system depression which is exacerbated by low energy reserves. Again, when emerging from overwintering grounds there can be a delay in the immune system “rebooting” as this depends on body temperature. At this time turtles will be more susceptible to infection. In an overwintering study, Brown & Brooks (1994) found that of the four turtles that died after emergence, two of them had succumbed to bacterial infections most likely due to their lowered immune function. 

The vulnerability of turtles due to cold temperatures is an issue of growing concern as climate change affects seasonal temperatures, and where unusual temperature fluctuations are becoming more common. Therefore, the chances of a turtle emerging early (when ambient temperatures are too low to kick-start immune function) are increasing, and especially as the spring migration to return to home ranges elevates a turtle’s exposure to risks of infection. Furthermore, the undulating weather patterns in late autumn also make the onset of freezing temperatures dramatic and erratic. (Refsnider et al., 2015). 

Ontario turtles face many challenges including habitat loss, contamination, and alterations; and anoxia, predation, and immune suppression when overwintering. Identifying and conserving critical hibernation sites is essential for turtle survival. Understanding the effects habitat destruction and climate change on turtle overwintering sites and behaviours, especially here in The Land Between bioregion (the northern range of many species’ habitats) will have important influence on conservation strategies to protect turtle overwintering areas and turtle populations as a whole (Litzgus et al., 1999). 

By: Andrea O’Halloran - December 2021

Sources:

Bodie, J. R., & Semlitsch, R. D. (2000). Size-specific mortality and natural selection in 

freshwater turtles. Copeia, 2000(3), 732-739.

 

Brooks, R. J., Brown, G. P., & Galbraith, D. A. (1991). Effects of a sudden increase in natural 

mortality of adults on a population of the common snapping turtle (Chelydra serpentina). 

Canadian Journal of zoology, 69(5), 1314-1320.

 

Brown, G. P., & Brooks, R. J. (1994). Characteristics of and fidelity to hibernacula in a northern 

population of snapping turtles, Chelydra serpentina. Copeia, 1994(1), 222-226.

 

Cantrell, E. A., Dong, C. M., Hill, C. A., & Warren, D. E. (2014). Buoyancy control in 

cold-submerged painted turtles: implications for overwintering physiology and behavior. Herpetologica, 70(4), 388-394. 

 

Costanzo, J. P., & Lee Jr, R. E. (2013). Avoidance and tolerance of freezing in ectothermic 

vertebrates. Journal of Experimental Biology, 216(11), 1961-1967.

 

Costanzo, J. P., Lee Jr, R. E., & Ultsch, G. R. (2008). Physiological ecology of overwintering in 

hatchling turtles. Journal of Experimental Zoology Part A: Ecological Genetics and 

Physiology, 309(6), 297-379. 

 

Edge, C. B., Steinberg, B. D., Brooks, R. J., & Litzgus, J. D. (2009). Temperature and site 

selection by Blanding’s Turtles (Emydoidea blandingii) during hibernation near the species’ northern range limit. Canadian Journal of Zoology, 87(9), 825-834.

 

Greaves, W. F., & Litzgus, J. D. (2007). Overwintering ecology of wood turtles (Glyptemys insculpta) at the species' northern range limit. Journal of herpetology, 41(1), 32-40.

 

Greaves, W. F., & Litzgus, J. D. (2008). Chemical, thermal, and physical properties of sites 

selected for overwintering by northern wood turtles (Glyptemys insculpta). Canadian 

Journal of Zoology, 86(7), 659-667.

 

Litzgus, J. D., Costanzo, J. P., Brooks, R. J., & Lee, Jr, R. E. (1999). Phenology and ecology of 

hibernation in spotted turtles (Clemmys guttata) near the northern limit of their range. Canadian Journal of Zoology, 77(9), 1348-1357.

 

Newton, E. J., & Herman, T. B. (2009). Habitat, movements, and behaviour of overwintering 

Blanding’s turtles (Emydoidea blandingii) in Nova Scotia. Canadian Journal of Zoology, 

87(4), 299-309.

 

Refsnider, J. M., Palacios, M. G., Reding, D. M., & Bronikowski, A. M. (2015). Effects of a 

novel climate on stress response and immune function in painted turtles (Chrysemys picta). Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 323(3), 160-168.

 

Reese, S. A., Jackson, D. C., & Ultsch, G. R. (2002). The physiology of overwintering in a turtle that occupies multiple habitats, the common snapping turtle (Chelydra serpentina). Physiological and Biochemical Zoology, 75(5), 432-438.

 

Taylor, G. M., & Nol, E. (1989). Movements and hibernation sites of overwintering painted 

turtles in southern Ontario. Canadian Journal of Zoology, 67(8), 1877-1881.

 

Ultsch, G. R. (2006). The ecology of overwintering among turtles: where turtles overwinter and  its consequences. Biological reviews, 81(3), 339-367.

 

Valerio, P. F., Kao, M. H., & Fletcher, G. L. (1992). Fish skin: an effective barrier to ice crystal 

propagation. Journal of Experimental Biology, 164(1), 135-151.

How Hibernation Wetlands Stabilize Turtle Populations.

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Hibernation is commonly observed in many species of animals, especially those inhabiting Northern regions where there are significant drops in temperature during the winter months. In Ontario, freshwater turtles are ectotherms (their internal temperatures mimic the external temperatures) which make them “unequipped” to directly face the ruthlessness of winter conditions. For this reason, they stow away in the winter to avoid the unfavourable conditions of the colder months. Scientists have found that some turtles overwinter close together in groups, and this practice is called communal hibernation (Edge et al., 2009; Litzgus et al., 1999; Brown & Brooks, 1994).

Communal hibernation is thought to have many benefits, but not in the way you’re used to hearing about. As ectotherms (where their temperature is determined by their environment), huddling together does not provide individuals with a rise in body heat like it does for endotherms such as humans and even penguins who may gather together for warmth (Duncan, 2016). Rather, the benefits of gathering together present themselves in less obvious ways. Some of these benefits include using group “signals” which would increases the chance of leaving hibernation sites at the same time (Litzgus et al., 1999), or as signifiers for a safe place to go when available hibernation sites become a limited resource (Greaves & Litzgus, 2007). Group hibernation may however, simply be a result of a group of individuals having overlapping home ranges (Edge et al., 2009). But there are some indications that there is more to this story: 

Interestingly, aggregations at overwintering sites are more common in Northern ranges. This observation indicates that overwintering areas may, in fact, be a limiting resource to turtle survival there and that may be why turtles overwinter in groups (Newton & Herman, 2009). 

Additionally, increased mating opportunities are thought to result in congregations of turtles. People may think that turtles mate in the early spring before nesting season begins. While this can be the case, turtles also perform courtship and mating at overwintering sites late into the fall before stowing away from the cold. This is possible for most turtle species (Pearse & Avise, 2001) because most females can physically store sperm in their bodies for future use (Environment Canada, 2015). In turtles, tubules in the oviduct that are specialized to store sperm are generally observed, indicating that this may be a common component of their reproductive behaviour (Pearse & Avise, 2001). Repeated paternity was commonly found in a study on Blanding’s turtles, displaying that females could use stored sperm over subsequent years from the same male to produce her eggs (Henning & Hinz, 2016).  Amazingly, there have been instances where female turtles in care (captive turtles) have been isolated from males, and yet, astonishingly, the females continue to produce offspring (Pearse & Avise, 2001). Therefore, hibernating where other turtles are found has advantages; the increased likelihood of finding a mate! Should a female be unable to find a mate in the spring, she can find a mate in the winter, and still successfully lay eggs during the nesting season using stored sperm (Carrière et al., 2009). 

Another benefit: males generally move great distances during the typical spring mating season to seek out females (Buchanan, 2017). However, if males mate at overwintering sites, they are less motivated to seek out mates and thus, able to spare energy during this active season, because, at times, female mates may be hard to find. Therefore, communal overwintering also allows a male turtle to save energy and yet increase success, by mating at the same site he overwinters (Carrière et al., 2009).

In a study investigating hibernation site selection of Blanding’s turtles, Christopher Edge and collaborators (2009) discovered multiple Blanding’s turtles copulating and hibernating together (≥ 5m) in Algonquin park. At these sites, groups of turtles ranged from two to seven individuals, with both sexes present in all scenarios. This could suggest that communal areas are promoted by the mating opportunities related to grouping together, or it may simply be because habitat destruction has limited the number of overwintering sites available for the population (Edge et al., 2009).

In a study conducted to investigate courtship and mating behaviours of Northern Map turtles, results suggested that communal hibernation was widely displayed in this population. In Lake Opinicon, 75% of studied males ventured near two popular turtle overwintering sites throughout the course of the study. The scientists were able to track the movement of these individuals using radio-telemetry. This tool uses radio signals and transmitters attached to animals (in the case of turtles it is typically attached at the rear-end of their shell) (Litzgus et al., 1999)) to observe their movement while off site. The data did not indicate what percent of males successfully completed overwintering at these sites. However, the results suggest that the majority of males in the area do travel close to communal sites to reap the benefits of group mating (Bulté et al., 2021).

Alternatively, in a study on Wood turtles conducted in Sudbury, Greaves and Litzgus (2007) did not find any evidence to support the idea that turtles overwinter in groups. This places some doubt on the general view that all turtles have a tendency to behave this way. The study was run using visual observation and tracker data. Although the general consensus was that turtles did not overwinter in groups, a pair was documented mating at the overwintering sites before separating for the winter. This supports the idea that turtles may use opportunistic fall mating interactions to increase their fitness (Greaves & Litzgus, 2007).

In Georgian Bay Ontario, a four-year hibernation study on Spotted turtles noted that communal hibernation was commonly found. The researchers again employed the use of radio-telemetry to track the locations of Spotted turtles over the years as well as visual observations to supplement this data. The primary purpose of this study was to assess the ecology and typical hibernation behaviours of Northern Spotted turtles. In the process the scientists also made other remarks. Of the eleven hibernation sites monitored, seven were found to be used for communal hibernation of turtles (≤ 9). This region is, however, considered to be the northern range of a Spotted turtles territory suggesting that this observation could be due to limited hibernation site availability, as previously discussed (Litzgus et al., 1999).

While hibernating in groups seems to have many upsides, this behaviour can nevertheless be dangerous for vulnerable subpopulations of freshwater turtles because grouping together can increase the risk of extirpation (a subpopulation being completely wiped out in an area). In cases where large groups of turtles come together, the increased activity can attract predators (Litzgus et al., 1999). Related is that during the winter, turtles are in a state of inactivity under the water because the low temperature causes metabolic depression and physiologically, metabolic depression limits an individual's ability to move (Newton & Herman, 2009; Edge et al., 2009). Therefore turtles cannot escape attacks by predators at this stage. These situations can be particularly detrimental to unstable subpopulations as it can result in a huge loss of reproductive adults, and potentially result in extirpation (Litzgus et al., 1999).

But also, habitat destruction or alteration can affect overwintering populations; The viability of typical overwintering sites can be changed and make that area unsuitable for overwintering (Litzgus et al., 1999). Examples include when wetlands and shorelands are “filled in '' or drained, or water levels are changed, most often, artificially. Typically, turtles select a pond or water body for overwintering, where there is the potential for a barrier to form between the turtle and the ambient air temperature. The barrier produces a comparatively warmer environment (Ross and Anderson, 1990). Some wetlands may be quite small with stable water levels, a thick warm substrate, also where a layer of ice may become the needed boundary between the water and the air. Without this stable underwater refuge, a turtle’s risk of desiccation and encountering freezing temperatures is significantly elevated (Markle et al., 2020). Unexpected changes in habitat conditions often result in indirect changes to the hydrological condition and water temperatures of the area (Bodie & Semlitsch, 2000) which then can result in many unintended deaths. Therefore, turtles grouping together for the winter, means that more individuals are vulnerable to negative events, and which may increase the chance of local extirpations. In other words, many adults can be killed off because of human alterations to habitats or during a particularly difficult winter (White, 2013). 

It is accepted that communal hibernation is exercised by freshwater turtles, however, researchers have not concluded that it is employed in every turtle species. Future studies may aim to determine whether this phenomena exists reliably in all turtle populations, and should also aim to assess the patterns of this behaviour based on the spatial ecology of areas. Doing so, will help to inform attuned policies and improved conservation measures. 

Generally, conservation of all hibernation areas (chiefly wetland habitats) is of the utmost importance because death of adult breeding turtles individually will destabilize local populations, but also where there may be communal groups, local extirpations of turtle populations is an immediate concern.  As habitat areas and their quality are compromised by human activity, and as temperatures become more inconsistent due to climate change, the threat to turtle populations is an increasing reality for Ontario freshwater turtles. Human development with subsequent habitat loss may also increase communal hibernation, and then in addition to the vulnerabilities from more destruction or climate change, increased threat from predation events is added to the mix. For all these reasons, continued efforts to preserve wetlands and surrounding areas are vital to the protection and longevity of freshwater turtles in Ontario.

Written by Andrea O'Halloran, edited by Leora Berman and Kiara Duval

Sources:

  • Bodie, J. R., & Semlitsch, R. D. (2000). Spatial and temporal use of floodplain habitats by lentic and lotic species of aquatic turtles. Oecologia, 122(1), 138-146.
  • Brown, G. P., & Brooks, R. J. (1994). Characteristics of and fidelity to hibernacula in a northern population of snapping turtles, Chelydra serpentina. Copeia, 1994(1), 222-226.
  • Buchanan, S. W. (2017). The influence of altered habitat: landscape ecology of freshwater turtles in Rhode Island (Doctoral dissertation, University of Rhode Island).
  • Bulté, G., Huneault, B., & Blouin‐Demers, G. (2021). Free‐ranging male northern map turtles use public information when interacting with potential mates. Ethology, 127(11), 995-1001.