The Science Behind Algonquin's Animals - Painted Turtle Research in Algonquin Provincial Park
  Research Projects Painted Turtle Research in Algonquin Provincial Park
   
 

 
Common Name Painted Turtle
Scientific Name Chrysemys picta
Other Names Midland Painted Turtle

General Appearance: Painted Turtles have a 12 to 17 centimetre shell that is olive-brown in colour. The orange, red and yellow markings on the edge and side of the shell, and on the head and legs, are characteristic of Painted Turtles. Each foot has five claws and are longer on males than females. The reason for the elongated claws on male turtles is for stroking the female's chin during courtship. If threatened, Painted Turtles can fully withdraw their head, limbs and tail into their shell for protection.

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Weight: Female Painted Turtles weigh up to 500 grams and males are typically lighter, weighing about 300 grams.

Migration: Painted Turtles do not migrate, however, female Painted Turtles will sometimes move long distances to seek suitable nesting sites. This movement takes place in the month of June when female turtles will deposit between four and 16 oval eggs in a shallow nest dug in a sandy area such as a beach or roadside embankment.

Food Sources: Painted Turtles are omnivores, consuming both plants and meat. Typical food may include aquatic plants, aquatic and terrestrial insects, insect larvae, snails, amphibians, crayfish, leeches, fish eggs, and small fish (alive or dead).

Did you know?

  • Painted Turtles, like all other reptiles, are exothermic (cold blooded), meaning that they do not generate their own body heat like mammals. Instead, Painted Turtles depend upon the surrounding environment to regulate their temperature. That is why in the spring of the year, many people first see Painted Turtles sunning themselves on logs or bog mats, increasing their internal temperatures. The increase in body temperature allows for body functions, such as digestion of food, and egg development to occur at a faster rate.

Major Predators: The shell of adult Painted Turtles provides them with significant protection from predators and makes them almost invulnerable to predation.

Conversely, eggs and hatchling turtles are extremely vulnerable to a wide variety of predators. Nest predators include raccoons, foxes and skunks. Hatchling Painted Turtles have many predators which include raccoons, foxes, skunks, gulls, crows, ravens, herons, weasels and snapping turtles.

Breeding: Mating of Painted Turtles occurs throughout the spring and into the early summer and typically begins as soon as turtles emerge from hibernation. Male Painted Turtles are considerably smaller than the females and subsequently can not overpower them for mating as other turtle species do such as Snapping and Wood turtles. Instead, courtship begins with the male slowly pursuing the female. When he has caught up to her he swims in front of her to face her. The male then stroked the face and neck and the female with his elongated foreclaws. If the female is receptive she will return the gesture by stroking the male's forelimbs. During periods of mutual stroking the male will frequently swim away from the female. After repeating this behavior several times the female will sink to the bottom and the male will follow and copulation will start.

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Research Procedures: Since 1978, Wolf Howl Pond and West Rose Lake, on Algonquin Park's Mizzy Lake Trail, has been the site of a long-term Painted Turtle research program started by Dr. Ron Brooks of the University of Guelph.

Since the start of the study, approximately 500 turtles have been marked in the two water bodies. The purpose of the research is to obtain a better understanding of the natural history and ecology of Painted Turtles.

It has been learned that 99 out of every 100 adult turtles survive from one year to the next. This is an extremely high survival rate. Despite this very high survival rate amongst adults, the survival rate among hatchling Painted Turtles is very low. This is because eggs and hatchlings are very susceptible to predation from a variety of animals. During a lifetime a female Painted Turtle may only have two offspring that survive to adulthood. This balance in survival rates is necessary or Algonquin Park would be overrun with turtles.

Sexual maturity in Painted Turtles is very slow; 7-9 years for males, 11-16 years or more for females. One aspect of Dr. Brook's research on Painted Turtles in Algonquin Park looks specifically at how sex of hatchling turtles is determined. For most vertebrates sex of the offspring is determined by one sex chromosome provided by each parent. In humans a male has XY chromosomes and females have XX. In some species of turtles, such as the Painted Turtle, there are no sex chromosomes. This means that at fertilization the turtle embryo has no sex. What has been discovered in other turtle research is that sex is determined by temperature, and the temperature determines which sex hormones will be produced. This occurs during the middle third of incubation. For Painted Turtles this falls during weeks seven to ten of incubation. In laboratory conditions it has been demonstrated that Painted Turtle eggs incubated at differing constant temperatures will produce a constant sex. Painted Turtles have two threshold temperatures, a point where above a certain temperature one sex will be produced and below the other sex will be produced. For Painted Turtles these are above 27șC and below 23șC. Above and below these temperatures females will be produced, in between, 23-27șC, males will be produced. In nature, turtle nests are exposed to continually fluctuating temperatures during this critical period of sex determination. What Dr. Brooks wanted to determine was if a mean temperature of nests in the wild could be used to determine the sex of Painted Turtles.

He also wanted to take a look at how female Painted Turtles selected sites for nesting. Since temperature is important for sex determination, in a cool climate like Algonquin Park, there is the possibility that the sex ratio would favour one sex. In the two study ponds the sex ratio is approximately 4:1 in favour of females, and 85% of hatchlings are female. Temperature is also important for embryo development. If temperatures are too cool the embryos will not develop before the onset of colder temperatures in the fall. By looking at nest sites selected by female Painted Turtles, Dr. Brooks was hoping to determine if they were selected to determine the sex of offspring from year to year or to maximize rapid embryo development and therefore increase offspring survival.

A study was conducted within the current study site at Wolf Howl Pond and West Rose Lake in Algonquin Provincial Park during the summer of 1983 and 1984. Nests were located by observing female Painted Turtles laying eggs or looking for characteristic disturbance patterns in the sand. During the two year period temperatures were monitored in 45 nests, 20 during the first year and 25 during the second. In order to significantly monitor nest temperatures a thermometer was placed at the bottom of each nest cavity. Temperatures were then recorded during the critical period of sex determination, weeks seven to ten, during the morning at 8:00 a.m. and then again in the evening at 8:00 p.m. Hourly testing of the soil over a 48 hour period had shown that these times were representative of the minimum and maximum soil temperatures. After the critical period of embryo development, the nests were excavated, and the eggs taken to the lab to be incubated and finish hatching. Once the eggs were hatched the sex of the hatchlings were then determined.

In order to determine if mean temperature in naturally incubated nests could be used as a measure for determining sex ratio, Painted Turtle eggs were also incubated at constant temperatures in laboratory conditions, and the results compared. Laboratory incubation occurred during the first year of the study (1983). Eggs were removed from the nest when the female was finished laying and taken to the laboratory. In total 19 clutches (146 eggs) were used for laboratory incubation. Individual eggs were placed in jars and incubated at temperatures ranging from 20șC to 32șC at 2șC intervals in seven separate incubators. Eggs remained in the incubators until they hatched at which point the sex of each hatchling was determined.

Selection of nest sites was also studied during the 1983 and 1984 field season at Wolf How Pond. Nest depth, distance to nearest vegetation, slope (i.e. nest on flat or sloping ground) and orientation of slope (south-west or north-east) was recorded in 179 nests over the two year period. Temperatures were also taken in 45 nests and 48 randomly chosen sites for comparison. These were taken at 8:00 a.m. and 8:00 p.m. until the end of the critical period for sex determination.

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Research Habitat: The Painted Turtle is one of North America's most wide spread turtle species. In Canada they range from Nova Scotia to British Columbia, but their northward range is limited by temperature. Painted Turtles can survive in cool temperatures but temperature affects the rate of development in eggs. If there are not enough warm days, turtle eggs will fail to develop and hatch. In the continental United States, Painted Turtles are found as far south as Louisiana. In Algonquin Provincial Park, the Painted Turtle is near the northern edge of its range. One of two common resident turtles (the other being the Snapping Turtle, Chelydra serpentina), most Park visitors quickly learn to recognize the Painted Turtle because it can often be seen sunning its self on logs, rocks, beaver lodges, bog mats and other structures in beaver ponds and shallow sections of lakes. Painted Turtles live in shallow, soft bottomed ponds, lakes, rivers and creeks in Algonquin. To ensure their survival, Painted Turtles also require a suitable, sandy area in which to nest.

Did you know?

  • Even though Painted Turtles hatch from their egg in September, the turtle hatchlings do not emerge from the nest until the following spring. Baby Painted Turtles do not head to the water and spend the winter at the bottom of ponds as other young turtles do. Instead, they "freeze solid" withstanding temperatures as cold as -10°C under the layer of sand and snow. A special protein produced by the turtle's liver allows ice crystal to develop in a uniform manner within the baby turtle's body. They also produce natural antifreeze that prevents the cells from freezing and becoming damaged. Thus, only the water out outside of the cells is actually frozen.

While in this frozen state baby turtles show no sign of muscle movement, no heartbeat, and no blood flow. This ability to tolerate freezing is only possible for the first winter. In all other winters, these young turtles will have to find refuge from the cold winter temperatures with all other Painted Turtles in the mud at the bottom of Algonquin's many ponds. When the warmer temperatures of spring arrive, young turtles head to the surface, unaffected by their previously frozen state, and head to the water.

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Research Questions

1. How long will painted turtles live?

While it is known that the survival rate of Painted Turtles is very high what is unknown is how long they will live. It is theorized that Painted Turtles may live up to 300 years and some of the turtles in the study ponds could be easily a 100 years or more. To date, no reliable method of aging turtles has been developed. The only known method is to mark hatchling turtles as they emerge from the nest.

2. Does mean nest temperature predict sex ratio among Painted Turtles?

It is known that temperature is responsible for survivability and sex determination in Painted Turtles. What is not known is how fluctuating temperatures in natural conditions influence sex ratios. By comparing Painted Turtle eggs incubated in a laboratory with eggs incubated under natural conditions, Dr. Brooks investigated if mean nest temperatures could be used to determine survivability and sex ratios in Painted.

With incubation temperatures set at 2 șC intervals between 20 șC and 32 șC only males were produced at 22, 24 and 26 șC. Only females were produced at 30 and 32 șC and both sexes were produced at 20 and 28 șC. The highest percentage of males occurred at 26 șC (100%) and survival rates were highest at 26 șC and the lowest at 20 șC.

In comparison, results from naturally incubated nest in the field showed that, as in incubators, the highest percent of males, and highest survival rates occurred at intermediate temperatures. At lower temperatures though, percentage of males was higher than in laboratory conditions.

Hatchlings that were naturally incubated in nests with mean temperatures of 23, 24 and 25 șC were 100% female. In contrast, hatchlings incubated at these temperatures in the laboratory were 100% male. As well, in natural nests, with mean temperatures of 19.5 to 23.5C which should produce males, most hatchlings were females. Survival was also highest (89%) at a mean temperature of 22 șC, whereas in controlled conditions eggs incubated at this temperature constantly resulted in 75% mortality. Fluctuating temperatures during the critical stage must then have some effect on both survival and sex determination.

The results showed that, while controlled laboratory conditions would produce hatchlings of a certain sex if eggs were incubated at a constant temperature, estimating sex by mean temperatures based on laboratory result did not produce the same sex ratios in naturally incubated nests. Mean temperatures are therefore not reliable enough to predict sex of Painted Turtle hatchlings which are exposed to fluctuating temperatures. Only species of turtles which have deep nests, where there is very little movement in temperature during the critical stage of development, would mean temperature be adequate to predict sex.

3. Do Painted Turtles select nest sites to determine offspring sex ratio or to decrease offspring mortality?

Since Painted Turtles rely on temperatures to determine the sex of offspring, and also for completion of embryo development, Dr. Brooks wanted to examine if there were any similar characteristics that female Painted Turtles used to select nesting sites. If so, were the sites selected to influence sex ratios of hatchlings or to decrease hatchling mortality? To do this, characteristics and temperatures of Painted Turtle nests and randomly chosen sites in the nesting area were compared. Nest temperatures were also compared to one another to determine if they were relatively the same. If nest temperatures were close to one another this would suggest that female Painted Turtles chose nest sites to maximize rapid hatchling development and thus increase offspring survival.

Within the nesting areas, female Painted Turtles selected nest sites that were relatively warm compared to randomly chosen sites. It was concluded that the slope of the site and lack of vegetation were indications to female turtles that the site was warm. The reason that females would choose warm sites over cooler ones is that temperatures in cool sites in the short Algonquin summer growing season are not warm enough to allow for the embryo to fully complete development. Thus, in a northern environment, such as Algonquin Park, nests in cooler locations have a higher mortality. Some females do nest in cooler sites and while these do have a higher mortality than warmer sites, they produce most of the males in a female biased population.

During the study, warm sites produces females and cooler sites produced males or females, or both, depending on the distribution of temperatures of the site. This showed that it is difficult to predict the effect of a particular nest site on sex ratio, especially from year to year where seasonal temperatures may differ. For instance, in 1983 which temperatures were average, the coolest nests produced predominately males, while all other nests produced females. This was because the cooler nests spent enough time at male producing temperatures. Whereas, in 1984, which was a warmer than average year, the nests with the coolest temperatures exhibited the highest mortality. Those cool nests that did survive produced males and females or only females and warmer sites produced only females. "Therefore, although females can consistently select relatively warm nest sites, the effect of ‘relative warmth' on sex ratio depends on the weather in that year, more than on the particular site selected." say Dr. Brooks. "In contrast, the effect of relatively warm nest sites on hatchling survival appears more predictable and concludes that distribution of nest temperatures within the same range indicates selection of nest sites to decrease hatchling mortality rather than to influence offspring sex ratio."

Given that characteristics of a nest-site, the weather from year to year and threshold temperatures are all important factors in determining the sex ratio of Painted Turtles, using nest-sites to estimate sex ratios is limited at best.



Suggested Reading
Educators: Learn more about Algonquin’s habitats, download readings and worksheets from the Educator Resources section of the Web Site, or you may also learn more through the following publications:

The Reptiles and Amphibians of Algonquin Provincial Park
Completely revised, and for the first time using coloured photographs, the new edition of Reptiles and Amphibians of Algonquin Provincial Park does more than merely introduce readers to the 31 species of turtles, snakes, frogs and salamanders that have been recorded in Ontario's most famous provincial park. Numerous sidebars delve into the fascinating biology and life histories of Park reptiles and amphibians, drawing heavily on over 25 years of research conducted in the Park by the book's senior author, Dr. Ron Brooks of the University of Guelph. Perhaps the best small book on these subjects ever written in Canada.


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