Question

In Panama, male Tungara frogs call females to ponds using a two-part mating vocalization that goes something like "Beeeewww-Chuck", in which the "Beeeewww" part is a high pitched whine and the "chuck" part is a low-frequency call that is is deeper in larger frogs. Once females arrive at a pond, males fight each other for access to females, and often threaten each other by swallowing air to make their bodies appear bigger. As a result, the pond is often filled with puffed-up males giving their Beeeeww-Chuck calls and pushing each other around. If females are interested in large males with good genes for the local environment, what cue should they use to assess male quality in choosing a mate, and why?

Answer 1

The túngara frog (Engystomops pustulosus) is a species of frog in the family Leptodactylidae.Its natural habitats are subtropical or tropical dry forest, dry savanna, moist savanna, subtropical or tropical dry lowland grassland, subtropical or tropical seasonally wet or flooded lowland grassland, freshwater marshes, intermittent freshwater marshes, pastureland, heavily degraded former forest, ponds, and canals and ditches.

Coming to the question proper, the selection of a male partner by a female Tungara frog is a complex process. The females always prefer to mate with bigger males, as larger the size of the male, more is the rate of fertilization. In the mating season, usually the ponds will be filled with multiple species of frogs, but the females usually prefer to mate with the same species. One of the top criteria in selecting a male partner from its own species is the coplexity of the males call.

Males produce a call that consists of a whine, and can also add up to seven short chuck sounds to their mating call. A call consisting of both a whine and a chuck is considered a complex call.

Females prefer the mating call of frogs who produce chucks with lower frequencies.The chuck portion of the call is produced by vibrations of a fibrous mass suspended near the frog's larynx. Larger fibrous masses allow a frog to produce more chucks for each whine.One explanation for this preference is that lower frequency calls are found in males of larger size. A larger body size usually correlates with a higher rate of fertilization.

So to sum it up, females interested in larger sized males with good genes for the local environment, usually find the partner by the complexity of their mating calls and they prefer males with a lower frequency chuck.