Earth Notes: Northern Leopard Frogs

Sep 11, 2019

In recent decades northern leopard frogs have become refugees in their own land.

Northern leopard frog
Credit Diane Hope

These beautiful green frogs with dark spots were once abundant across northern and central Arizona. But extended drought, aggressive invaders like bull frogs, and the deadly chytrid fungus have shrunk populations to only small pockets.

In Arizona, the Game and Fish Department is creating a number of northern leopard frog “refugia”—the term biologists use for safe places where relict populations of previously widespread species can thrive—and as a source population to repatriate to other suitable habitats.

Perfect northern leopard frog habitat means constant year-round water—and a deep hole. The frogs need about eight feet of water and two feet of pond mud to survive freezing winters.

As temperatures drop in fall, the frogs nestle into that mud, where they go into torpor—the amphibian equivalent of hibernation. Their bodily functions grind to an almost complete halt until spring thaw.  

When they emerge, the frogs must hide from predators like herons and western terrestrial garter snakes—so each refugium also needs drier areas of long grass where the frogs can catch insects without being eaten themselves!

Rearing them in captivity isn’t a good idea because young frogs need to learn to fend for themselves once they’re released into the wild.

The most successful refugia so far are in House Rock Valley on the Arizona Strip. The hope is to create more safe places for long-term survival of these little aquatic leopards.