Biologists wade through ponds to tally frog eggs
PROVO, » Biologists with the Utah Division of Wildlife Resources spent Monday afternoon wading through ponds near Diamond Fork Canyon with one goal in mind: to find frog eggs.
More specifically, the DWR wildlife biologists were looking for eggs belonging to the Columbia spotted frog, a native species threatened by habitat loss and a variety of predators, in order to monitor the species’ population levels.
Finding adult spotted frogs, which normally grow up to the length of a credit card, can be difficult this time of year, according to Keith Lawrence, a native aquatics projects leader for DWR, “so we count the eggs as a surrogate to counting the adults directly.”
Every year during the Columbia spotted frogs’ mating season, which Lawrence said typically lasts from early March to midapril, DWR wildlife specialists monitor population levels by tallying egg masses — large, viscous globs consisting of between 200 and 500 eggs — in various natural and human-made ponds throughout the state.
Lawrence located about 30 egg masses in a halfdozen ponds in the Diamond Fork area Monday afternoon. He said they typically find between 60 and 70 masses in the 20 or so ponds in the region.
Though not an endangered species, Columbia spotted frogs are included on the Utah Sensitive Species List, one of four amphibian species on the list.
The others are the western toad, Arizona toad and the Great Plains toad.
One indicator of how well the frog species is doing is the amount of rain or snowfall the state gets, Lawrence said. Some populations make it through years of droughts, and others don’t.
“We have populations where we’ve seen that,” he said. “Years of drought, they go down too close to zero. And even when we have a wet year on the heels of that, they don’t come back.”
Among the factors affecting the frog populations is a loss of wetland habitat in central Utah and throughout the state, Lawrence said.
“Probably the largest threat that they face, and it’s certainly a big factor here (in Diamond Fork), is how much habitat they have,” he said. “But there are other threats.”
One threat is chytridiomycosis, an infectious disease that can lead to death in amphibian species, according to Amphibiaweb.
“Our native frogs are virtually all affected by it,” Lawrence said.
Invasive species such as bullfrogs, which the U.S. Department of Agriculture says were introduced to Western states during the early 1900s, are yet another threat facing Utah’s Columbia spotted frogs.
“They can outcompete them for food. But mostly, they’ll eat them. So wherever we have bullfrogs with spotted frogs, we have a problem,” Lawrence said.
The DWR biologist added that sandhill cranes are another predator of Columbia spotted frogs.
In the early 2000s, the Utah Reclamation Mitigation and Conservation Commission and partners created ponds throughout Diamond Fork Canyon to help the spotted frog populations rebound, Lawrence said.
“Ensuring that there’s enough of this kind of wetland habitat for them is certainly a key aspect of trying to conserve them, and there’s just been a lot of loss of wetlands almost wherever you go,” he said. “And that’s the reason for the restoration effort that’s been done here.”