Moisture and development
In arid habitats, development is limited not by temperature but by moisture. One example are the rainfrogs Breviceps (Family Microhylidae) which lives in arid regions of Africa. These animals only emerge above ground during heavy downpours. Although much of the biology of this elusive group of frogs is unknown, it appears that they form pairs during the breeding season. Adults emerge from their underground burrows and absorb rainwater through their skins, thus replenishing their body fluids. In particular the bladder is filled with water. The male is far smaller than the female and is unable to clasp the female in order to copulate with her. Instead the male glues himself to the female's back. With the male riding on her back, the female burrows into the ground and proceeds to lay eggs that are then fertilized by the attached male partner. Periodically the female wets the eggs from her extended bladder, keeping them moist until the froglets hatch. This breeding process takes place on only one or two nights per year, when there is a sufficiently heavy downpour. Once fertilization occurs, growth proceeds rapidly. The Spadefoot toads (Scaphiopus) in southwestern deserts of the USA, have tadpoles that develop into frogs in less than two weeks. Such rapid development is necessary in a habitat where the water will only last for a few weeks.