Climate change could devastate painted turtles, according to new study

March 12, 2019, Iowa State University

Climate change threatens the painted turtle, a species that undergoes temperature-dependent sex determination. Research led by Nicole Valenzuela indicates that warming temperatures, as well as wider fluctuations in temperature, could lead …more

An Iowa State University biologist is sounding the alarm for the painted turtle, one of many reptiles for which climate change could prove particularly threatening.

Fluctuations in temperature driven by climate change could devastate a range of species for which sex is determined by temperature during critical stages of development, according to recently published research led by Nicole Valenzuela, a professor of ecology, evolution and organismal biology. Rising temperatures, along with wider oscillations in temperature, could disrupt the ratio of males to females in painted turtle populations and threaten the survival of the species, Valenzuela said. The study was published in the peer-reviewed journal Scientific Reports.

Painted turtles undergo temperature-dependent sex determination while developing inside the egg. Eggs exposed to warmer temperatures tend to produce females, while cooler temperatures tend to produce males, Valenzuela said. Numerous turtle species – as well as crocodilians, some lizards and the tuatara – undergo temperature-dependent sex determination. And increasing average temperatures combined with stronger thermal fluctuations that result from climate change could lead to drastic shifts in the demographics of those species, she said, eventually leading to population collapse and possibly extinction.

Valenzuela and her coauthors exposed eggs from Iowa to temperatures recorded in nests from three different painted turtle populations in Iowa, Nebraska and Canada from which the proportion of males and females was also recorded. Valenzuela said that allowed the experiments to compare the responses of multiple painted turtle populations, which revealed that not all populations exhibit the same sensitivity to temperature.

Read more at: 

New Jersey Meadowlands -Diamondback Terrapins & other turtles may be falling prey to poacher - via Herp Digest

September 20, 2012, by Brian Anderson, Staff Writer, NewJersey.com, Turtles in the Hackensack River may be falling prey to poachers. The Riverkeeper contends he witnessed poachers attempting to set traps recently. The turtles were saved as the poachers’ boat wouldn’t start. 

But for Captain Bill Sheehan of the Hackensack River, it was a disconcerting sight to see a group of men, armed with turtle traps, looking to trap the diamond terrapins in the Hackensack River a few weeks ago. Sheehan said though this group of men wasn’t able to hunt any turtles that day (their boat broke down while still on shore), they had a permit from the state of New Jersey to hunt and sell turtles, and were looking to sell the turtles for human consumption.

Sheehan said the permit allowed them to trap turtles in three rivers: the Passaic, Hackensack and Rahway.

"That’s what upset me most about these guys—they had a permit," he said.

Sheehan said these turtles live longer than other aquatic life in the Meadowlands, and eat the smaller creatures found in the river. It’s a problem because the Hackensack River has a history of pollution. These turtles likely accumulate contaminants from the river. If the turtles are eaten, Sheehan said, the "bioaccumulation" becomes part of the individual who eats the turtle.

Sheehan said the men told him they were planning on selling the turtles to restaurants in other states, such as New York’s Chinatown.

However, officials from the New Jersey Department of Environmental Protection (NJDEP) say there is no permit for hunting diamondback terrapin turtles, and that selling turtles is illegal in the state.

Bob Considine, a spokesman at the NJDEP, said the agency grants only one type of permit in regards to diamond terrapins. Under a study/collection permit, researchers and scientists can learn about the diamond terrapins found in New Jersey waters. The study must be approved and must show to have a positive effect on the species’ conservation, public welfare or the environment, he said.

"This permit does not allow someone to collect these animals to keep them long term," Considine said. "Catching diamondback terrapins is not permitted in the state, and violators can face a fine."

Diamondback terrapins can often be found in the marshes of the Saw Mill Creek Wildlife Management Area, along the banks of the Hackensack River, and other Meadowlands marshes. Three native species of Meadowlands turtles—the diamondback terrapin, the painted turtle and snapping turtle—regularly sun themselves along the marshy banks.

The New Jersey Meadowlands Commission (NJMC) is currently conducting a study on the diamondback terrapin, said Mike Newhouse, NJMC researcher. A group of researchers have been studying the diamondback terrapin population in the Hackensack River since 2009. Hundreds of turtles have been tagged since the study began, and researchers at the NJMC continue to tag turtles—a sign that the population of the diamondbacks in the Hackensack River is likely growing.

Last year, DEP issued 39 permits for studying these turtles, according to officials. When scientists apply for the permit, they must indicate where they will be working and what the study is about.

Both Sheehan and the DEP say that turtle meat, especially form turtles in the Hackensack River, could contain toxins and contaminates as a result of long-term pollution in the Hackensack River. The blue claw crabs found in the Hackensack River are highly polluted, and along the banks of the river, signs advise against eating the crabs.

Diamondback terrapins and blue claw crabs both feed on similar food—small invertebrates, fish and vegetation on the riverbed. Though there is no official ban or advisory on consumption of turtle meat, Considine advises against it.

"However, one can assume is if there are crabbing or fishing restrictions in that area, other creatures can accumulate contaminants in their system, and caution is urged," Considine said.

Considine confirmed there is no trapping permit for terrapin turtles, but the state does permit the hunting on snapping turtles throughout New Jersey. Residents with a valid fishing license can catch up to three snapping turtles per day, and hunting season for snapping turtles is between Jan. 1 - April 30, and June 16 - Dec. 31.

Whether they are hunted or admired from a distance, Meadowlands area turtle species are a pleasant sight to behold.

Variation in male, female turtle shells provides advantage when facing predators (Via Herp Digest)

Variation in male, female turtle shells provides advantage when facing predators
Released: 11/15/2011 2:00 PM EST
Source: Allen Press Publishing Services
News Release
FOR IMMEDIATE RELEASE

Newswise - Herpetologica - One way to tell a male turtle from a female turtle is a difference in the shape of their shells. While this pattern of sexual dimorphism is common among turtle species, it could have other effects on turtle biology. The differing shell designs may exhibit different strengths in standing up to the attack of a predator, and therefore the survival rate of one sex over the other.

The current issue of the journal Herpetologica reports on the mechanical implications of shell shape differences between two species of male and female turtles. The Painted Turtle (Chrysemys picta) is an aquatic species, and the Wood Turtle (Glyptemys insculpta) is a terrestrial species.

Females turtles tend to have larger, domed shells, which may indicate the ability to hold large clutches of eggs. Males, on the other hand, typically have flatter shells and larger openings for their limbs, allowing them greater movement. This improves their success in courtship and mating.

To test the strength of these varying shells, researchers created digital models of the shells for finite element analysis. This computer model uses simple geometric shapes to create a complex structure-the turtle shell in this case. It then calculates the response of those elemental shapes to create the response of the shell as a whole. Twelve load conditions, representing the bite of a predator at different locations, were applied.

The females of both species fared better than the males, although male and female Wood Turtles were more evenly matched. Female shells showed less stress than male shells. The concave shape of the plastron, or underside, of the male Wood Turtle's shell in particular exhibited significantly increased stress, indicating it would be more easily punctured by a predator.

These differences between sexes may stem from selection based on other factors besides predation. Currently, there are no data showing that females are more likely to encounter predators, for instance, and that therefore their shells have become better able to withstand such attacks. However, these variations can have an effect on turtles' lives and offer important implications for turtle conservation efforts.

Full text of the article "Dimorphism in Shell Shape and Strength in Two Species of Emydid Turtle," Herpetologica, Volume 67, Issue 4, November 2011, is available at: http://www.hljournals.org/