Your Pond or Mine?

Abstract

Eggs of the gray tree frog. During amplexus, the male deposits sperm on the eggs as the female lays them. Hours later, the protective jelly firms, shielding the developing embryos until they hatch as tadpoles. I t's a warm Saturday night in July, and things are literally hopping down at the pond. Hordes of male gray tree frogs have gathered at the water's edge, belting out guttural trills that fill the air with songs of frog love. Seduced by the dulcet tones, female frogs their eggs ripe for fertilization descend from the trees around midnight for their once-yearly night of romance. Each selects a male and pulls him onto her back in a mating clasp called amplexus. But instead of lingering to luxuriate in the embrace and release her eggs, she immediately hops away with her lover still clinging in search of a more perfect pond for pairing. Why, after being dragged around season after season for millennia, haven't the species' males evolved to call from sites that better suit the females? Ecologists who study the gray tree frog, Hyla chrysoscelis, have long been stumped by this odd gender gap. Although the phenomenon remains unresolved, new research shows that males and females of this nonterritorial species have somewhat different criteria for what constitutes the ultimate love puddle. William J. Resetarits Jr. and Henry M. Wilbur of Duke University in Durham, N.C., began studying the species' disjointed breeding behavior in 1985. As population ecologists, they sought to discover whether opposing natural forces kept the males and females out of sync. We want to understand how ecology affects the behavior of organisms, says Resetarits, now at the University of Missouri-St. Louis. We're really interested not only in the behavior of individual species, but what effect their behavior may have on the community In the June ECOLOGY, Wilbur, now at the University of Virginia in Charlottesville, and Resetarits report the results of 52 long, sweaty summer nights spent in the woods of North Carolina, monitoring the frogs' mating quirks at 45 pseudo-ponds.