Archive for the ‘Uncategorized’ Category

After a long absence…   Leave a comment

I’ve been pretty slow to post here for a while – and this is because after a crazy winter, it’s now field season. But my 2013 turtle team and I are blogging about our work and about turtles in general for Wildlife Preservation Canada (, a wildlife conservation NGO that supports my research as well as work on a wide variety of threatened Canadian species. Read about our current work at

Enjoy the rest of the spring… summer is right around the corner!

— Christina Davy




Posted May 27, 2013 by thinkingturtles in Uncategorized

A turtle by any other name…   Leave a comment

Did you know that the common snapping turtle has another name? It is also known as the mossy back turtle. The reason for this is that algae sometimes grows on the snapping turtle’s shell, so it looks like it has a soft and silky “mossy” back.


Thick green algae growing on the shell of some snapping turtles led to the name “mossy back”. The algae looks particularly bright and “furry” when seen underwater. (Photo: Christina Davy)

“Mossy back turtle” seems a much nicer (and less scary) name than snapping turtle. I think if this turtle had been introduced to me this way at our first meeting, I would have noticed amazing details that I didn’t notice until later. The “snap” is distracting, in name and in person. A lot of people don’t like the snapping turtle as much as other turtles, but I wonder if that would be different if people were introduced to it by its other name.

Snapping turtles got their name because they can “snap” at you a lot. But generally they only do this in defense when they are on land. They are just trying to scare us away so they can safely continue their journeys to lay eggs or get back to the water.

painted-snapper plastra

Lower shell or “plastron” of a Painted Turtle (left) and a Snapping Turtle (right). Notice that the Painted Turtle can pull so tightly into its shell that no part of its legs, head or tail are visible, while the Snapping Turtle is not protected at all by its plastron. (Photo: Christina Davy)

Unlike other turtles, snapping turtles do not have a shell that covers their entire tummy. This shell on the tummy of a turtle is called the plastron. So if a coyote or a racoon were to flip a snapping turtle upside down, the turtle would not be able to protect itself by hiding under its plastron. Its best defense is to appear very ferocious and scare away predators (including we humans) so they do not try to flip it upside down.

Even as long ago as 1784, a doctor named John Ferdinand Smyth Stuart demonstrated typical prejudice against the snapping turtle in North America. He noted that they “bite very fiercely” when angered and that they do not let go easily when they do bite. Stuart contrasted the snapping turtle with other turtles of North America, which he judged to be“extremely beautiful,” “adorned with all the elegance of the brightest colouring , and the most fanciful engravings, or lines in regular and exact uniformity: this kind [of turtle] is perfectly inoffensive and harmless.”

Speaking from my experience working in the field, I can tell you that a beautifully marked painted turtle, even a cute little baby one, may bite you (hard) if given the chance. Being handled is a stressful experience for wild animals, and biting is a defense mechanism that many animals have – even the “cute” ones. When conservationists work with wild turtles, they are always very gentle and careful. But turtles can feel threatened when they are caught and handled. Try to imagine what it would feel like if you were a turtle and a kind stranger twenty-times your size lifted you up out of your home! If that was me, I’d be scared!

Just because we find something beautiful does not mean it is harmless. Likewise, just because we think something is scary or fierce does not mean it can’t also be beautiful and amazing. Nature can (and usually does) do more than two things at once!

I would like to have had the chance to ask John Stuart in person why he separated the snapping turtle from all the other turtles that he thinks are “extremely beautiful.” But I think many people today think similarly. Unlike the pretty patterns of the painted turtle or the cute spots of the spotted turtle, the snapping turtle is often covered in algae. Even when the shell is clean, it is not decorated with the same brilliant colours and patterns that we find on some other turtles. The snapping turtle also grows a lot bigger than the turtles that John Stuart liked. And the snapping turtle does demonstrate its “snap” much more often than other turtles, particularly because it does not have the ability to hide in its shell like many other turtles.


Adult male Snapping Turtle (Chelydra serpentina),otherwise known as the “mossy back”, encountered on the shore of Lake Erie. (Photo: Leif Einarson)

But pay close attention to the details the next time you are at a zoo and get a chance to see a snapping turtle up close with some safety glass between you to help you both feel more safe and comfortable. Take a close look at its eyes! Snapping turtles have BEAUTIFUL eyes with very complex, unique patterns in them. No other turtles have eyes quite like the eyes of a snapping turtle. Maybe beauty is in the eye of the beheld!

— Leif Einarson


Small female Snapping Turtle (Chelydra serpentina) gazing with her beautiful eyes at the camera and showing off an impressive, emerald-coloured patch of algae (“moss”) on her shell. (Photo: Leif Einarson)

Posted January 14, 2013 by thinkingturtles in Uncategorized

A Desperate Rescue   3 comments

SNTU -105 was the one hundred and fifth turtle, out of six hundred and sixty-five turtles, to be admitted to the Kawartha Turtle Trauma Centre in 2011. It was a memorable case. A large female snapping turtle, she arrived in terrible condition. As is the fate of many female turtles in the spring, she was hit by a car as she migrated from her home in the swamp in search of the perfect spot to lay her eggs.

Snapping turtles are different from other species of turtles in that their plastron (the bottom of their shell) is much smaller than their carapace (the top part of their shell). While many species of turtle are able to pull themselves completely into their shell when confronted with a dangerous situation, snapping turtles do not have this option -their shells are too small! Instead snapping turtles only defence on land is aggression (in the water they will almost always swim away from danger). Often motorists think that they can “straddle” a turtle with their car to avoid hitting it, but a snapping turtle sees this as a threat and will snap at the undercarriage of the car, often leading to severe head injuries, such as broken jaws, crushing wounds to the head and shearing wounds of the carapace. Such was the case with SNTU-105.

When she was admitted, SNTU-105 was in rough shape. She was lethargic and large portions of her carapace had been sheared off. Her head had been hit as well, leaving her with a broken jaw. She had lost a lot of blood and was very quiet and unresponsive. Immediately SNTU-105 was given pain meds, antibiotics and fluids. She began moving around a bit when she was given her needles, as I’m sure you or I would too!

SNTU-105 was left overnight so that her pain medication had time to set in and so that she wasn’t overstressed. The next day she underwent sedation and had her jaw wired and her fractures secured with special brackets and wire. She was then x-rayed and it was discovered that she was a mother-to-be! It was clear that she had been struck while on her way to nest and still had 22 eggs inside of her!

Over the course of the next month SNTU-105 reluctantly laid her eggs one by one. Each egg was carefully collected and placed in an incubation box and kept at an optimum temperature in the turtle nursery in hopes that they would eventually hatch. In the wild, less than 1% of turtles survive to adulthood! This is due to being heavily preyed upon by raccoons, skunks, and other predators as well as many other factors. By incubating SNTU-105’s 22 eggs, we could be making a huge impact on the snapping turtle population!

As SNTU-105’s eggs slowly developed over the course of the next few months, she continued to undergo treatment. The extent of her wounds meant that she had to have bandage changes every day in order to keep infection out. She underwent daily bandage changes for nearly four months! Finally enough scar tissue had formed that she was able to be without the protective covering of the bandages and was finally able to be moved into deeper water where she could hide and feel safe. She was also very hesitant to begin eating on her own as is the case with many of our injured patients. It’s hard to eat when you’re not feeling well! After many weeks of providing her with juicy earthworms and delicious fish, she finally began eating on her own, which was a huge relief and meant that she was beginning to feel better!

Due to the extent of her wounds, SNTU-105 has been kept over the winter to ensure that she is fully recovered and ready to go back into the wild by the time spring comes. When turtles hibernate, their metabolic rate slows down and makes it much more difficult for them to heal themselves. By keeping them over the winter, they do not go into hibernation and therefore continue healing at a normal rate.

One of SNTU-105's fifteen healthy hatchlings

SNTU-105 is now waiting for the weather to warm enough for her release, but she will not be going alone! In August, the first of her eggs began to hatch. A tiny head popped out of one of the eggs and surveyed the world for the first time. It was the first of 15 of the 22 eggs to hatch; a huge success!!  SNTU-105’s babies are now patiently waiting for spring to arrive so that they can be released back into their natural habitat.

– Olivia Vandersanden

Posted April 12, 2012 by thinkingturtles in Uncategorized

Turtles are individuals too!   3 comments

When I was a boy, I thought a deer was a deer, a duck was a duck, and a bug was a bug. I thought all snakes were the same, each coyote was a clone, and every robin was identical. Man, was I wrong!

One of the biggest blessings of being a biologist for the past decade is the privilege of getting to know intimately each individual within the same population of a single species. I have had the fortune of experiencing this several times, with several taxa (groups of organisms). My understanding of this phenomenon emerged during my graduate studies in conservation biology at Acadia University in Nova Scotia. I was tasked with studying an endangered species, the Blanding’s turtle (Emydoidea blandingii) in a rural area outside of Kejimkujik National Park.

It was my job to find out how many individuals of this species inhabited the rural working landscape surrounding the protected area, what the threats were to the population (if there was a population at all), and engage the community to assist in the recovery of the species.

The first individual Blanding’s turtle I captured pooped in my lap. It was a 13 year old juvenile, and I called him “Turd” – the second one was also a juvenile, which I had trouble catching up to. I called her “Scoot” – and the third was a male, who miraculously disappeared from my canoe when I wasn’t watching – I called him “Houdini”.

That first year I worked with the turtles I captured 26 individuals, including six juveniles, 10 males and 10 females. Because I attached small radio-transmitters to their shells I could follow them around on a daily basis to determine their habitat use and movement patterns – I was able to get to know them all quite well. I saw some individuals over 100 times that spring, summer, and fall, and what struck me was the consistency of their “personalities”, or more scientifically, “behaviour patterns.”

“Scoot” was always hard to catch, because she was so fast. “Houdini” was always disappearing and showing up in new areas. “Shy” was … well, always shy – I never saw her emerge from her shell, she was always tucked in tight.

Before Jane Goodall emerged onto the scene of wildlife biology, it was a huge taboo to name individuals of a study species. Anthropomorphism, as it is called, was a sin. Scientists are objective! Animals are not people! But … people are animals. And her work with chimpanzees in the Gombe reserve revealed to the world that, just like you and I, individual animals are UNIQUE. The turtles of Pleasant River, Nova Scotia unveiled this revelation for me, and for that I am eternally grateful to them.

More recently I have been conducting research for the Toronto Zoo in southern Ontario on, you guessed it, Blanding’s turtles. My career has come full circle! I captured 63 individuals in a wetland complex north of Lake Erie, and photographed the belly shell (plastron) of every individual. Like the turtles of Nova Scotia, each individual impressed upon me their uniqueness – in their behaviours, habitat selection, distances travelled, and overall temperament, among other things. I named these turtles too, mostly after landowners in the surrounding community. I gave every landowner surrounding the swamp a picture of “their turtle” and described to them where it lived, and what it was like. I figured they would be much more likely to become stewards of the wetland and help protect the turtles if they knew their namesake was out there in the swamp somewhere. I think it worked.

One of the coolest things about Blanding’s turtles (besides the permanent smile on their face, bright yellow chin, and beautifully speckled shell) is the pattern on their plastron – every turtle’s is unique, just like our fingerprints. The poster on which I assembled all my photos from the last two years is meant to symbolize that uniqueness, not only in shape and pattern, but also in behaviour and personality.

Biodiversity is phenomenal, and protecting dwindling species like the Blanding’s turtle can help preserve what is so amazing and special about life on earth – its variety. If you want to purchase one of these posters and support the program, contact the Ontario Turtle Tally (

— Brennan Caverhill

Posted March 31, 2012 by thinkingturtles in Uncategorized

Density dependence in the Snapping Turtles of Lake Sasajewun   Leave a comment

Measuring the plastron (lower shell) length of a female Snapping Turtle with callipers. We record several measurements of each captured turtle every year to measure their growth. (Photo: M. Keevil)

I work at a long term research project in Algonquin Provincial Park that has been studying Snapping Turtles in Lake Sasajewun since 1972. Each year turtles are caught by hand or in traps, new ones are marked, and then they are released. The other researchers and I also patrol nesting areas and measure the size and number of eggs that each mother turtle lays. Together this information allows us to keep track of the size of the population, the growth and survival of each individual turtle, and how many eggs the females lay. In three winters in the late 1980s more than half of the Snapping Turtles in Lake Sasajewun were killed by Otters while the turtles were hibernating under the ice. Despite the fact that Otters are not rare in Algonquin Park, this event was unusual; we have never observed this happening there before or since. Although unfortunate for the victims, this event provides a natural experiment that allows us to see how Snapping Turtles in this lake respond to a large decrease in density.

 The first question that I set out to answer was whether there had been a population recovery. Because not every turtle is caught every year, and because many factors can cause differences in the number of turtles that are caught in a given year, we cannot just count the number of turtles. Instead we have to create a mathematical model of the population that takes into consideration the chances that a turtle that has not been caught is actually still alive. This model allows us to produce yearly estimates of the size of the population (how many turtles are in the lake), how many new individuals entered the population, and how many died (or travelled to other lakes). These estimates showed that the population of adult females was constant before the Otter event, then dropped by about 60% and then was stable or slightly declining at the new, smaller population size for the next twenty years up until the present day. There was no sign of recovery at all. The fact that there was no recovery, even after two decades, is worrisome for turtle conservation because it suggests that many turtle populations may not recover from declines caused by human activities even after those activities cease.

This is B7 ("B7" is the code on her identification tag that is visible in the photograph) putting the finishing touches on her nest. She is using her back feet to pack soil into the opening of the nest to protect her eggs. She is a female who has been nesting around Lake Sasajewun for at least 39 years (probably a lot longer). In all that time nearly all of her nests that we monitored failed because of predators or weather that was too cool for successful incubation. On average Snapping Turtles require many breeding seasons to successfully produce enough hatchlings that a few of them will survive to adulthood. (Photo: M. Keevil)

If density dependence is important for these turtles, then we would expect a population that is now at a much lower density to survive and reproduce at a greater rate and to begin to increase. Why didn’t this Snapping Turtle population recover? One contributing factor is likely to be the large amount of time that it takes for a baby turtle to grow into an adult, begin laying eggs of her own, and then over many years to lay enough times that some of her hatchlings survive. Perhaps there simply has not been enough time for increases in fertility or a decrease in death rates to translate into more turtles. So I decided to look at growth, fertility, and death rates when density was high as well as after the Otter event, when it was low. Looking for an effect of density on these aspects of the turtles’ biology might reveal that density dependence was occurring and that a slow recovery could be predicted in the future. However, I could not find any indication that the turtles were surviving better, growing faster, or laying more eggs. These findings strongly suggest that these Snapping Turtles will not recover to their former numbers for a long time. To me, it shows how important it is to protect remaining Snapping Turtle populations because we can’t count on them to bounce back once they have been damaged.

— Matt Keevil





This plot shows the estimated population size of female Snapping Turtles at my study site (red lines with solid red dots), and a model of the proportion that survived in each year (blue lines with solid blue dots). During three winters when many turtles were killed by Otters (red circles), survival rates were lower and the population size declined. After that, survival increased back to what it was before, and so the population has stayed nearly stable for the last 20 years. However, it has stayed at a much lower level. If survival rate was density dependent then I predicted that survival rates would increase and that this would cause the population to start to recover. My work has shown that survival has not increased, but the open symbols show a hypothetical scenerio of what the population size would be (red open dots) if survival had increased by 3% (blue open dots).




















A Red Fox digging up a Snapping Turtle nest and eating the eggs. High levels of nest predation is one reason why so few of the eggs laid by turtles ever result in new adults that can contribute to population growth. Mortality rates can be high for young turtles as well. Turtles need to reproduce many times over many years in order to contribute to the next generation. (Photo: M. Keevil)


Posted March 8, 2012 by thinkingturtles in Uncategorized

An introduction to life histories and density dependence   Leave a comment

Biologists and conservationists alike are interested in the life history of the plant or animal species that they study. Life history is the schedule of important events and processes in the life of an organism – when it matures, when and how often it reproduces, and how its likelihood of survival might change throughout its lifespan. Different kinds of plants and animals have evolved different life history strategies that reflect the particular challenges they face in their environments. For example, the plants that we call weeds live in habitats that are frequently disturbed, like gardens or a field that gets tilled every year. The plants that are successful in such an environment grow quickly and reproduce early. They invest so much in reproduction that many garden weed species do not live for more than one summer. On the other hand, trees grow, survive, and reproduce in forests where there is little disturbance, and competing trees are well established. Young trees grow slowly, taking many years to mature, waiting for an opportunity, like a newly formed gap in the canopy, before reaching their full size and investing in reproduction. A tree’s life history strategy is to ensure its survival from one year to the next – maximizing the success of its offspring by spreading reproduction out over many years. A weed’s life history strategy is to invest resources in reproduction, sacrificing a long life for lots of young in the short term.

Snapping turtle nesting on the shoulder of a small highway. (Photo: C. Davy)

Animals show a similar range of life history strategies, and turtles are much more like a mighty oak than a garden weed. Like trees, most of a turtle’s offspring don’t survive very long, but when a few do reach maturity, they can live for a very long time. Because turtles are adapted to spread their reproductive effort out over a long time, it takes many years for the average mother turtle to produce enough nests so that she will be able to replace herself in the next generation. 

Snapping turtle female laying eggs. Turtles dig a nest chamber in the ground using their hind feet, and then deposit the eggs into the nest chamber before scooping earth back on top of the eggs to cover the nest. (Photo: C. Davy)




Density dependence is an important concept in the ecology of plant and animal populations and it is what tends to keep populations stable. Density is the number of individuals of a species for a given unit of area. If there are 200 pike in a 20 hectare lake, then the density is 10 pike per hectare. When the number of individuals in a habitat is very high, there is more competition for less resources, and predators and parasites increase. In this situation there are fewer births and lower survival because each animal has less resources to put into avoiding predators, growth, and reproduction. However, when density is low, each individual can find food more easily because there is less competition and there can also be fewer parasites and predators. The few individuals that are around survive better, grow faster, and produce more offspring so the population increases. In a stable environment these complementary aspects of density dependence act to keep population size fairly constant – if the population gets low, individuals reproduce more and it recovers, but if the population is too high, reproduction goes down, survival is lower, and the number of animals is reduced.

This tiny hatchling was found feeding on mosquito larvae in a small pool. It had had already survived its first harsh Algonquin winter. If it is a female it will take 16-19 more years before it lays its first nest. (Photo: M. Keevil)

All populations are not affected the same way by density dependence. How strongly a population responds to changes in density depends on both the environment and the life history of the species in question. If a new factor – such as an unusually harsh winter or an increase in human hunting – causes a loss in numbers, some animal populations, especially those that are more like weeds in their life histories, return quickly to their former levels. On the other hand, animals such as turtles that take a long time to grow and reproduce take much, much longer to recover. Even if competition is reduced and survival is high once more, it still takes a long time for a young turtle to reach maturity and contribute to population recovery.
 — Matt Keevil

Posted February 22, 2012 by thinkingturtles in Uncategorized

Secret lives of baby turtles   1 comment

As people, we are very lucky to have our parents to take care of us early on in life. Can you imagine what would happen if we were left to fend for ourselves just after being born? Well, that sort of life is reality for turtles!

Comparing the size of a one-year-old Blanding’s turtle in my hand with an adult. These two were found sharing a small pool for hibernation. (Photo: J. Paterson)


After laying their eggs, mother turtles leave their youngsters to fend for themselves. As baby turtles come out of their nest in late summer, they must learn quickly to find somewhere safe or they could be in trouble! Big turtles have hard shells to protect themselves from scary animals like racoons, foxes, and coyotes, but the shells of baby turtles are too soft to be of any use.


I spent two years following the lives of baby Blanding’s turtles in Algonquin Provincial Park using special transmitters glued to the turtles’ shells.

A cute baby Blanding’s turtle with a transmitter glued to the top of its shell. These turtles are only 3 - 4 cm long when they come out of their egg but they can move more than 100 m in one day! (Photo: J. Paterson)

Despite being so young, these baby turtles are sneaky! One day, after spending hours digging through rotting leaves on the shore of a swamp, I was almost ready to give up on ever finding the two hatchling turtles hidden there. My assistant, ready to quit for the day, then punched a tree root in the hole we had dug. She accidentally punched a hole in the root, and neither of us was ready for what was INSIDE the root. There they were, not just the two turtles with transmitters, but also three other baby turtles. It was late fall, and all of the turtles were inside the hollow root ready to enter hibernation for their first winter.

Here are five hatchling Blanding’s turtles that were hiding inside a root underground. They were found using the transmitter seen on the shell of two turtles. (Photo: J. Paterson)

Against all odds, some hatchling turtles successfully make it to sites to hibernate safely. But, one way to make this journey easier for tiny turtles is to protect the habitat that these turtles live in. Forests may be dangerous for little turtles but roads and big buildings are even worse. By following baby turtles I hope that we can protect habitat for the babies and adults of this beautiful turtle!

— James Paterson

Posted February 11, 2012 by thinkingturtles in Uncategorized