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GEOGRAPHIC RANGE AND HABITAT
The range of the African Bullfrog, Pyxicephalus
adspersus, is Central, East and Southern Africa. This type of
frog is found mostly in open grasslands near ponds, lakes and rivers
at low elevations in the sub-Saharan African countries of Malawi,
Zambia, Nigeria, Somalia, Mozambique, Angola, South Africa (except
for the southwestern Cape Province), Kenya, Rhodesia, Tanzania and
the Sudan.
One of the most adaptable amphibians on earth,
the African Bullfrog can tolerate some of the harshest environments
in Africa. Certain areas of their range can be completely dry for
years at a time, and can reach surface temperatures over 100 degrees
F, and drop to below freezing during the winter. Protected in an
underground estivation chamber, the frogs wait it out, sometimes
for up to 2 years, until more suitable conditions occur. When the
rainy season begins, they occupy temporary floodplains and rapidly
drying puddles scattered around the African countryside. They have
been known to inhabit extremely hostile regions from the Kalihari
desert, to the high veld domains between 4000 and 5000 feet above
sea level (Switak 1997). |
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DESCRIPTION
Male Pyxicephalus adspersus can reach lengths
of more than 9 inches and weigh over 2 pounds. Females are
much smaller. Males are olive in color, with yellow to orange
on the throat region. Females are olive to light brown with
cream to white throat areas. Both sexes have ridges running
laterally on the dorsal surface. Juveniles are much more colorful
than adults. Several white to yellow lines run down the animal's
dorsal area on an overall mottled background. Both these dorsal
lines, and mottling disappear with age. Adults have a spade
like metatarsal tubercle on each hind foot to aid in digging.
The front toes are thick and blunt with no webbing, the rear
toes are slightly webbed. These frogs have massive skeletons
with extremely |
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has tooth-like projections used in restraining struggling
prey (Moore 1997, Switak 1997). |
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DIET
The African Bullfrog is carnivorous and will
consume nearly any animal that can be overpowered and can fit in
their huge mouths. Cannibalism is a common occurrence. Many of their
first meals will be a member of the same egg mass. Other prey items
may include invertebrates, other species of frogs, reptiles, small
mammals, and even small birds. The tongue is folded over inside
the mouth. To capture a potential meal, it will drop its lower jaw
with considerable force, causing the tongue to flip over and out
of the animal's mouth, siezing the prey (Moore 1997, Switak 1997).! |
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LIFE CYCLE/SOCIAL BEHAVIOR
These frogs have a short active period depending
on the rainy season. The majority of their lives are spent estivating
underground. While underground, they slough off several layers of
their skin's epidermal cells which form a tough cocoon. Most of
their bodily functions slow or shut down all together. This period
of dormancy may last a year or more. During the rainy season frogs
will sit partially buried with the nose exposed, taking advantage
of any smaller animal unfortunate enough to pass by (Switak 1997,
Moore 1997).
It is quite aggressive, and has been known
to jump at things that it views to be a threat. Because of its sharp
teeth, its bite can be quite serious. The male bullfrog will also
aggressively defend his eggs if an animal or a human should approach.
The males make calls only during the rainy season, which is when
they come out of estivation to breed in pools of water. They tend
to congregate around watering holes, including ones occupied by
large animals like elephants. The call of thne African Bullfrog
is composed of loud, throaty bellows and deep grunts. These frogs
can get rather territorial during mating and begin their mating
calls only when they have established their territory. |
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REPRODUCTION
The African bullfrog lays about three thousand
to four thousand eggs in shallow water. The tiny eggs are
only about 2 mm, are black and white and are encased in a
4 mm jelly capsule. These eggs hatch about 2 days after being
laid. The tadpoles are fat, heart-shaped, grey to black in
color and their eyes are very close together, situated on
the top of their heads. About 18 days after hatching, the
small frogs are 20 mm long and are able to leave the water
to live on dry land. After this happens, these frogs have
occasionally been known to eat each other. Unfortunately,
there is not a very good survival rate for these frogs; only
about 20% of young adult females survive. |
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INTERESTING FACTS
1. The African Bullfrog’s biggest advantage
against its predators is its size. It also uses its teeth to fight
off would-be enemies, and will swell its body up to make itself
look even bigger and more intimidating. Its aggressive behavior
and a tendency to defend itself by attacking intruders with mouth
agape can often protect it from predators such as larger wading
birds, pelicans, Nile monitor lizards, driver ants, mammals, and
even humans (who consider this bullfrog a delicacy to eat).
2. The African Bullfrog has a good sense of smell
and sight. However its hearing is one of its most important senses,
for bullfrogs use their calls (voices) to locate one another, especially
during mating season. The loud, roar-like bellowing call of the
African bullfrog is especially notable, and seems to suit its large
size. |
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