African bullfrogs are found in desert, savannah, and grasslands of sub-Saharan Africa. They remain underground during the dry season and inhabit seasonal bodies of water during the rainy season.
African bullfrogs are a featured species in The Maryland Zoo’s Animal Embassy collection. Zoo educators introduce African bullfrogs and other Animal Ambassadors to audiences in education programs on and off grounds.
Make no mistake about it, this is one tough, resilient, highly adaptable amphibian. African bullfrogs manage to withstand some of the harshest environmental conditions imaginable, mainly by hunkering down and waiting for conditions to change. During the dry season, which in some parts of the bullfrog’s range could last for more than a year, African bullfrogs stay underground in chambers that they excavate using horny tubercles on their hind feet. While underground, they stay relatively cool and damp but cannot feed. They adapt to this circumstance by entering a dormant state known as estivation that is triggered by excessive heat or drought.
Estivation is functionally similar to hibernation, only it is triggered by excessive heat or drought whereas hibernation is triggered by winter. In either state, the animal becomes physically inactive or dormant, often appearing to be in a deep sleep. The animal’s breathing and metabolism slow and its body temperature drops, allowing it to conserve enough energy to survive for a prolonged period without food.
When the rains begin, African bullfrogs emerge from underground. They gather in and around seasonal pools of water and spend their relatively short active season feeding and mating.
African bullfrogs are ambush predators. They sit partially buried with snouts exposed, waiting for some unsuspecting animal to wander by. African bullfrogs will eat anything that they can fit into their very wide mouths! This includes invertebrates, fish, other amphibians, reptiles, rodents, and small birds. When prey comes within range, an African bullfrog will drop its lower jaw forcefully, unfurl its tongue, and snatch its meal. It makes use of “odontodes” – sharp, tooth-like projections in the lower jaw – to secure struggling prey.
African bullfrogs are very large! Breeding males are easily identified by bright yellow patches under their forelimbs.
African bullfrogs breed during the rainy season. Males and females congregate around temporary puddles and pools created by rainwater. Males gather at the center of a pool in leks, or breeding arenas, and make loud, booming calls to attract females. The larger and more dominant males occupy the center of the lek, and chase away smaller males. They can be very aggressive, often injuring or even killing smaller males that approach.
A female frog will swim along the surface of the pond until she is within a short distance of the males and then dive and resurface at the center of the lek. She thus avoids the smaller, less desirable males and goes directly to the larger ones. One male will successfully jump onto her back and cling to her in the universal frog mating posture known as amplexus.
The breeding couple makes its way to the shallow edge of the pond where the female deposits her eggs. She will lay up to 4,000 eggs per clutch. Her mate – usually the dominant male in the territory – will fertilize the eggs above the waterline. They hatch within two days, and it is the male who exhibits parental care. He guards the eggs and then the tadpoles. If necessary, he will also dig channels to allow the tadpoles to reach deeper water. The tadpoles metamorphose in three weeks.
Turtles and monitor lizards prey on bullfrog tadpoles. Birds are the most likely predators of adult African bullfrogs. People also hunt and eat African bullfrogs.
African bullfrogs are not listed as threatened or endangered, but are possibly stressed by habitat loss, hunting, and over-collection for the pet trade.