PIERRE, S.D. (AP) - Call it a cold case for investigators trying to track down one cold-blooded individual.
Biologists know that one of South Dakota's two known species of salamander was found here decades ago, but they're not sure it's here now. So this summer and probably next winter, University of South Dakota students will probe wetlands in northeastern South Dakota to try to sleuth out the missing amphibian.
"We have a crew right now looking for a particular salamander called the mud puppy that has been seen since the 1920s. Our last museum sample was from 1927," USD associate professor Jake Kerby told the Capital Journal. Kerby is a herpetologist, or a scientist who studies reptiles and amphibians. "We are going to survey Day, Marshall and Roberts counties."
Kerby is optimistic that the species still might be here after all, in part because in addition to those museum specimens from the 1920s and earlier, one of his USD students sorting through a collection up the road at South Dakota State University at Brookings found a mud puppy that had been collected as recently as 1981.
"I feel pretty hopeful that they're still out there, just that they're in low numbers and nobody's looking for them," Kerby said.
Kerby said the only other salamander species in South Dakota, the tiger salamander, is more common. Since South Dakota is at the western edge of the eastern tiger salamander's range and the western tiger salamander's range begins somewhere in eastern South Dakota, there may be quite a lot of diversity within that tiger salamander's population. To make matters more complicated, the tiger salamander and the mud puppy look alike in the larval stages.
The only way to tell them apart at that stage is to count the toes on the back feet. Kerby said the mud puppy has four toes on the back foot; the more common tiger salamander has five.
Kerby added that mud puppies remain aquatic, so the only salamander South Dakotans will ever see on land is the more common tiger salamander.
Kerby and his colleagues have proposed a range for the mud puppy that would include the northeastern corner of South Dakota, the eastern fringe of North Dakota, and western Minnesota. He added that colleagues in Minnesota who catch mud puppies have told him it's actually easier to find mud puppies in winter, since the cold-blooded amphibians remain active under the ice. His students will probably drill through the ice this winter and use traps to try to capture mud puppies in that same northeast part of the state; but they are already searching for mud puppies this summer.
The mystery of the vanished mud puppies also has an element of whodunit. If the salamanders have indeed vanished from the state, or simply if they're less abundant, there are plenty of potential villains.
Kerby said introduced fish species sometimes leave native species of salamander unable to adapt to an aggressive new predator. Pollutants could be a factor. So could disease - especially one called chytrid fungus that preys on amphibians in cold climates, and another called ranavirus. And then there's the biggest villain of all.
"The No. 1 factor is just habitat loss," Kerby said. "That can include drainage of wetlands or modification of lakes."
There are an estimated 15 species of amphibians in South Dakota in all, Kerby said, though the count sometimes varies depending on how scientists count certain species.