Last week, the Forum reported on northern leopard frog sightings in the West End. Many landowners have claimed they rarely see the species anymore, but others have said they’re seeing the leopard frog now, this summer, more than in past years.
Based on CPW Wildlife Biologist Tony Bonacquista’s recommendation, the Forum spoke with Dan Cammack, also a CPW Wildlife Biologist, who specializes in amphibians. Cammack told the Forum while he mostly does work with the Boreal toad, an endangered species in Colorado, he knows a bit about northern leopard frogs and “bumps into them pretty frequently.”
He said northern leopard frogs are a species of concern, at Tier 1 on the state’s recently revised wildlife action plan. He said there have been declines on the Front Range and eastern plains. He said he didn’t think, however, the leopard frogs had declined much on the Western Slope. In fact, he said he was surprised that some in the West End are reporting not seeing the frogs much in the last few decades, or that they’re just seeing them appear again.
“I can’t say why that might be,” he said.
Did previous years’ moisture help?
Cammack did say the leopard frogs are a “boom and bust species.” While the region has been in a serious drought, the Western Slope had wet years in 2019 and 2023. He said those could’ve been good breeding years for the frog, and perhaps people in the West End are now seeing adult frogs as a result — and seeing them return to breeding habitats.
He said while he can’t speak to Nucla specifically, as he’s done no formal surveys there, he’s run into many northern leopard frogs in Montrose and Gunnison. He said they’re even more common on the north fork of the Gunnison River, though he finds them in all the different basins.
He said he can’t exactly remember times of finding the frogs in the San Miguel Basin, and usually he’s in the West End sampling for native fish. He said it’s possible there could be a leopard frog resurgence though.
He then listed three primary threats to the species: habitat destruction, drought and bullfrogs.
Bullfrogs are predators
Bullfrogs on the Western Slope are non-native amphibians, considered invasive by the state. They’re native to Mississippi and Missouri drainages, but they made their way out West and are a problem. They’re predators. Cammack said bullfrogs will eat small mammals and small birds, and they will predate on native amphibians and displace them.
“And they’re a vector for disease,” he added. “Chytrid fungus — they can carry that, but it doesn’t seem to impact them. It does impact other, more sensitive amphibians.”
That fungus is a real threat to the Boreal toads in the high county, which have disappeared because of it. He said northern leopard frogs are affected by the Chytrid fungus too. While the disease doesn’t eliminate the frogs as a species, it can reduce their numbers. He said the bullfrogs’ predation and the Chytrid fungus are things CPW is paying attention to.
The current leopard frog study
Cammack said for anyone with large numbers of leopard frogs, he’d be interested to do some field work. He’s helping a graduate student from Colorado State University, with colleagues, study the species. Cammack said the group is looking at genetic samples from various basins and how the leopard frogs’ makeup differs. Anyone with five to 10 leopard frogs on their property in the West End is asked to call Cammack. He and fellow researchers would like to visit and study the frogs.
He said by nature, species have different lineages in different basins. He referenced the cutthroat trout, which have genetic characteristics that differ on the Colorado River, compared to other rivers. He said there’s a unique genetic fingerprint found in species because of geographic isolation, and nobody has studied it in Colorado’s leopard frogs — until now.
The numbers vary
Cammack said historically the leopard frogs have been on the Front Range. He added while numbers have declined in eastern Colorado, there are active conservation efforts going on there, like the establishment of open spaces. He said wildlife biologists are paying attention to habitats and also removing bullfrogs in places where leopard frogs have declined.
He said his opinion is that the leopard frog is at status quo in western Colorado.
“Our consensus is that (the northern leopard frog) is not in decline on the Western Slope,” he said, though he admitted landowners in the Nucla area could very well be noticing a trend. Maybe populations are fluctuating there. In other places on the Western Slope, though, he reiterated he does regularly see the leopard frog.
