Biologist's Research Shows How
Peepers' Chorus is Linked to Survival
By John Wray
nless we have a lot of rain soon, this will be a difficult year for frogs, according to Kentwood Wells, professor of ecology and evolutionary biology. Because of the drought, he says, many of the smaller temporary ponds where they breed are either already dry or well below normal levels.
Wells says his graduate students have found that many of the local ponds they used for their research last year are totally dry or will dry up as soon as the trees begin to leaf out and drain what little water there is for their foliage. So chances are the tadpoles in some of the area's temporary ponds won't be able metamorphose into little froglets in time to make it out and will die.
Still, Wells doesn't think there is too much cause for concern as yet: "The frog population explodes in wet years, so a year or two of drought doesn't represent a real threat to the overall frog population."
Wells explains that frogs, unless they are eaten by snapping turtles, or snakes, or birds, typically live from three years (which is about the maximum for spring peepers) up to 10 years, which is the maximum life span of bullfrogs. Five years is the typical lifespan for green frogs.
"The population dynamics of frogs are such that the population tends to go up and down with wet and dry years and usually sustains itself unless there are many years of continuous drought," Wells says. Two years ago, the Northeast had an unusually wet spring and summer.
Contrary to popular belief, the frog population in Connecticut hasn't declined, but remains as robust as ever. While some areas of the nation have experienced mysterious declines in frog populations, particularly in the national parks in the western United States, the populations of frogs who call Connecticut home have not declined, he says, except where development has reduced their habitat.
But although the overall numbers haven't gone down, the state has a relatively small number of frog species - just 10 - whereas the U.S. as a whole has some 100 different species of frogs and toads. The reason, says Wells, is that this region was covered with ice only 10,000 or so years ago.
"Sometimes I can't believe that I am paid to work at what I have loved best since childhood," he says.
But Wells' work is a serious pursuit. He is just finishing up a major book, The Ecology and Behavior of Amphibians, which will be published by the University of Chicago Press. It's a book he's been working on for much of his career.
Wells did his undergraduate work in zoology at Duke University, completed his doctorate in vertebrate zoology at Cornell, then did a year's post-doctoral work at the Smithsonian Tropical Research Institute in Panama, before joining UConn as an assistant professor in 1977. Since then he's been teaching courses in herpetology, vertebrate social behavior, and vertebrate biology.
The group's studies have revealed some interesting insights into the relationship between the physiology of frogs and their need to communicate at mating time.
For example, the metabolism of some frog species rises 25-fold when the frog is trying to attract females or scare off rivals with a series of calls, whereas its metabolism when jumping rises only about three times the resting rate.
This tremendous expenditure of energy, Wells says, results from basic differences in the muscle tissue in the male frog's trunk, which has evolved in order to provide the force required to produce its mating calls. This specialized muscle tissue in the trunk is heavily laced with blood vessels and the muscle cells themselves are heavily laced with mitochondria (where metabolism occurs) and lipids (fats), which supply the energy needed for the high rate of metabolism.
The chorus of spring peepers, a welcome herald of the changing season, is a sign that these creatures are expending a prodigious amount of energy not just for the entertainment of the human species but, more importantly, to ensure the survival of their own.