Researchers hunt for clues behind decline of Wyo’s largest turtle

Christine Peterson, via Wyoming News Exchange
Posted 6/25/21

Up close, the spiny softshell turtle looks a little like a leather pancake, but few people get that kind of glimpse.

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Researchers hunt for clues behind decline of Wyo’s largest turtle


Up close, the spiny softshell turtle looks a little like a leather pancake, but few people get that kind of glimpse. 

In most sightings, they likely resemble an alligator, with only a long nose and pair of eyes poking out of the water, waiting for food to wander by. If they see or hear you before you see or hear them, they’re gone. They’re not social creatures, especially not with humans.

But don’t mistake their skittishness for cowardice, said Brian Tornabene, a postdoctoral researcher at the University of Montana who spent years studying the spiny softshell turtle. One of Wyoming’s largest turtles — which can grow to about 19 inches long — is anything but scared. 

“It has an attitude,” Tornabene said. “They are snappy and won’t take anything from you. They will bite and snap and claw, and they’re really, really cool.”

They’re also likely threatened. By what, exactly, researchers are just now beginning to parse. Biologists have theories, most revolving around water levels, but one thing they know for certain is that populations are declining in the Bighorn Basin, and likely have been for decades.

The Wyoming Game and Fish Department just started a two-year research project to figure out why, first by assessing just how many of the odd-looking turtles currently exist in the Bighorn Basin.

“Although it’s anecdotal, there’s a lot of evidence that they have declined,” said Wendy Estes-Zumpf, Wyoming Game and Fish Department’s herpetological coordinator. “People who live in the area used to see them, and when they come to us and say, ‘where have the spiny softshells gone,’ we start to listen. This has been going on for a couple decades.”

The spiny softshell is most commonly known for, well, its soft shell. As the name indicates, this turtle’s shell is like thick, leathery skin that’s flatter and more streamlined than most turtle shells. 

A specialized shell allows the spiny softshell to spend much of its life underwater, said Tornabene. In fact, about six months of the year during winter, the spiny softshell finds a deep hole with slow water current and just stays there. It hibernates, processing oxygen from the water through its skin, mouth and cloaca.

That’s why you aren’t likely to see it wandering around on land like a snapping turtle or crossing a road like a western painted turtle, Estes-Zumpf said. They will perch on a bank or occasionally on a log to bask in the sun, but otherwise spend most of their time underwater. 

“A lot of times, you won’t see their shell sticking out of the water at all,” she said. “You will see their little eye bumps and the tip of their tubular snout.”

That snout is also a defining feature, resembling pig snouts more than a traditional turtle nose. The snout is attached to a thin head and exceptionally long neck. The combination allows spiny softshells to burrow under mud or water with their noses in the air waiting to snatch crayfish, minnows or just about anything else edible that floats by. 

While the spiny softshell lives throughout the central stretch of the U.S., they’re often found in marshy areas near larger lakes. The turtles in Wyoming and Montana, on the other hand, are well adapted to meandering rivers like the Platte, Powder and Bighorn. 

Spiny softshell turtles are, by their nature, elusive, but landowners, anglers and biologists along the Bighorn River between Thermopolis and Bighorn Reservoir and some of its tributaries used to see them with some frequency. That has changed over the last couple decades, Estes-Zumpf said. 

Game and Fish biologists were concerned enough several years ago they briefly surveyed the population. In a summer of trapping, researchers unearthed only nine turtles. Even more concerning, Estes-Zumpf said, is that all nine were adults. 

“It could indicate we have very limited recruitment and successful reproduction in the population,” Estes-Zumpf said. “Most turtles live well over 20 years, and it takes males four to five years to reach sexual maturity and females eight to nine years.”

Troubles with reproduction could be one of the biggest issues threatening the spiny softshell, researchers believe.

The turtles nest immediately after spring runoff on beaches. If water levels rise during that time, as they can below reservoirs, the turtles may not be able to lay eggs, or have to wait until well past their optimal window. And if their nest floods, the eggs won’t survive. 

A female might only lay a few dozen eggs at most in a nest, and fewer than a dozen hatch into baby turtles. Incubation takes months, and eggs cannot survive the first frost, Tornabene said. 

An increase in predators like raccoons and skunks could also be weighing on eggs and baby turtles. Invasive Russian olive trees are encroaching on the beach-like habitat the turtles need for nests. Human presence near nests can also attract predators, so biologists ask people to stay away from nesting areas or nests if they happen to see any in the spring or summer. 

Justin Autz, a Game and Fish herpetologist, will spend this summer and next looking for spiny softshells. He has specialized nets meant to gently capture the turtles without injuring them. The department hopes that four days a week of turtle searching from May until September will yield good data on the current population. 

“People might think turtles aren’t valuable because they don’t get anything from them, but they are critical to functioning ecosystems,” Tornabene said. “Turtles do a lot. They make up a lot of biomass. They eat fish and control native and nonnative species alike, and they’re very, very cool. 

“If we lose them, do we know what will happen? No,” Tornabene said. “But do we want to take that risk? No. Biodiversity is important.”

Report sightings

Wyoming Game and Fish Department biologists ask anyone to report sightings of eastern spiny softshell turtles in the Bighorn Basin. Call or email Justin Autz or 262-337-3027 with the date observed and location.

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