Ruthven's Frog: Allophrynidae

They are nocturnal (nahk-TER-nuhl), which means that they are active at night. During this time, they move around the forests near rivers and streams. They climb through trees and large bushes and onto the leaves of branches that may be several feet (1 to 3 meters) above the forest floor. Sometimes they sit in bromeliads (BRO-mee-lee-adds), which are plants that grow in warm, usually tropical forests often on other plants. Many bromeliads have leaves that overlap into cup shapes that can hold water and are very attractive spots for frogs and insects.

One of the frog's predators is a snake known by its scientific name of Leimadophis reginae. Scientists learned about the snake's appetite for the frogs when they captured one of the snakes on the edge of a river in Suriname, which is in northern South America. They cut open the snake's stomach and found a pregnant female Ruthven's frog inside.

The rainy season in the part of South America where the Ruthven's frog lives lasts from about January to July, although it is shorter in some places. The rains create small pools of water in dips in the forest floor and also cause rivers and streams to overflow onto banks and into other small pools of water. As long as the rains continue, the pools stay wet, but when the rainy season ends, they start to dry up. Since the pools only remain wet for part of the year, they are called temporary pools. The frogs make use of these temporary pools. The males hop to the edges of the water, or sometimes onto the leaves of low-hanging tree and bush branches, and begin calling. The call is a string of short low notes that together sound like a trill. Researchers studied the call by making a recording as a male trilled. They were able to count eighteen notes per second in its trill. Many males may call from the same place. This kind of group singing is known as a chorus (KOR-us).

Scientists found an especially large chorus in a pond near Pará, which is in northern Brazil. The pond actually formed when rains flooded the Amazon River and its tributaries, which are the smaller rivers and streams that flow into the Amazon. One of the tributaries, the Rio Xingu, overflowed to make the pond. Only a few frogs called from the pond for two months, but on one night in March, several hundred frogs suddenly showed up. Apparently, the frogs waited to mate until the tributary had flooded enough to fill the pond with a great deal of water. This type of mating, which happens during a short period of time and includes a large number of frogs, is called explosive breeding.

To mate, the male grasps the female from behind and near her front legs. While the male is in this piggyback position, called amplexus (am-PLEK-sus), the female lays her eggs, which number in the hundreds, in the water. Scientists learned how many eggs they lay by capturing a pair of mating frogs, dropping them in a plastic bag, and then counting as the female laid three hundred eggs. None of the eggs lived to hatch, however, and scientists still do not know what the Ruthven's frog tadpoles look like.