The Frog Invasion

by Forrest M. Mims III

When we moved to Geronimo Creek in South-Central Texas in 1985, drought conditions made frogs and toads scarce. When the rains returned, frogs and toads became abundant. Fat bull frogs (Rana Catesbeiana) lounged on logs in the creek. Green tree frogs (Hyla cinerea) perched on our windows to wait for moths and other insects. various toads (Bufo sp.) hung out around the house and office.

Then the frog population plunged for a few years until 2001 brought an invasion of southern leopard frogs (Rana sphenocephala). Ever since there have been plenty of frogs between my country office and the creek, including two kinds of midget frogs and various other species I have not yet identified.

This winter’s weak but wet El Niño has provided perfect weather for frogs. As twilight arrives every evening, loud choruses of trills and chirps can be heard from the ponds and springs.

On a recent spring evening I spotted a green tree frog perched on a dead giant ragweed stalk along a trail. We have often found green tree frogs on our windows and porches, but in all the years we have lived here I have only seen two in the woods. That's the result of their excellent camouflage and the way they remain perfectly still. Green tree frogs may be easy to see when they’re perched on a window or a brick wall. But they are nearly invisible in their natural habitat.

This particular green tree from was either sound asleep or, like the wild rabbits out here, thought itself to be completely invisible. It didn’t seem to notice when I placed a camera a few inches away from him to take his picture.

After six or seven photos, one with a flash, the frog was pretending to be as invisible as when I arrived. So I slowly backed away from him and resumed walking down the trail.

Frog populations are in sharp decline in some regions around the world. Several years ago some scientists became famous by claiming that frogs were disappearing because of the thinning of the ozone layer. The extra ultraviolet rays leaking through the thinner ozone layer were supposedly killing frog eggs.

Recently more reasonable explanations for frog decline have been found, including a dangerous fungal infection. In some cases the infection may have been spread by scientists who didn’t clean their boots and waders between expeditions to visit frog colonies.

Frogs may be in trouble elsewhere, but they seem to be in great shape in the new springs, ponds and the stock tanks along Geronimo Creek in South Central Texas this spring. Let’s hope the tadpoles that hatch from their eggs enjoy dining on the population explosion of mosquito larvae in all the new springs and seeps left behind by the El Niño.

Forrest M. Mims III and his science are featured online at www.forrestmims.org.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.