Frog Voices

Frogs are a favorite nature subject for me (and the reason I have one tatooed onto my hip!). Its the middle of winter here in South Africa and a strange time to be writing about them but perhaps its because I miss the insane caucophony they produce after the rains and throughout a good wet summer. Its one of the charms of wild Africa and as you travel through the bush moving past different habitats the volume and pitch of these small creatures varies from deafening to charming. Its no wonder that a chorus of frogs is known as an antiphony - it certainly is the opposite of a symphony. The reason for this is that there are a number of purposes for which frogs call and a number of different calls that they make:

The most common, incessant calls heard at night are the advertisements of the males singing to attract females. These calls are unique to individual species and attract members of similar species to a particular area and then help the males to space themselves out relative to one another. Although the resultant sound is somewhat frenzied (and confusing to predators wishing to isolate a single frog as a meal), the group chorus does have a degree of order. Two nearby callers will in fact alternate their sounds so that they don’t interfere with one another. This is called timeshare calling and it makes it easier for females to isolate their choice of mate which will depend on his pitch, a deeper tone usually representing a bigger and genetically superior male.

Should one male intrude on another individual’s turf, he may utter aggressive calls to denote his hold over that territory. These are usually heard early on in an evening while the frogs are still establishing their calling sites for the evening. Prime calling sites are in demand since females will select mates based on their calling sites since genetically superior individuals are likely to secure the best sites. To this end, males will even fight, wrestling and kicking to displace one another (as is the case with the painted reed frogs shown in the image and profiled below). Some males maximize on the efforts of the individuals in better calling sites (or with stronger calls) by remaining silent and then intercepting females attracted to these males in prime positions. This is called satellite behaviour.

Females produce a specific call called a release call to indicate to the male that they have completed laying and that he can let go. Sometimes when males are mistakenly grabbed by other males, they too will utter release calls. Distress calls are given by both sexes should they be seized by predators. This is often adequate to startle the predator which then releases the frog.