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Vernacular Name BULLFROG, AFRICAN (aka: pixie frog)

GEOGRAPHIC RANGE Sub-Saharan Africa.

HABITAT Tropical arid and semi-arid habitats: savanna, steppes, brush land, semi-deserts and freshwater lakes.

CONSERVATION STATUS • IUCN: Least Concern (2014). • Population Trend: decreasing.

COOL FACTS • One of the largest frogs of Africa. Males can reach lengths of more than 9” and weigh over 2 lbs. The females are much smaller. This species is unusual in that males are larger than the females. In most frogs, the females are generally larger than the males. • 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, 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 until more suitable conditions occur. When the rainy season begins, they occupy temporary floodplains and rapidly drying puddles scattered around the African countryside. • Frogs, in general, are the most primitive vertebrates to have a middle ear cavity for transferring sound vibrations from the eardrum to the inner ear. • Correlated with this development of the ear in all frogs is the appearance of a true voice box (larynx) and a large expandable vocal sac, making possible a wide variety of vocalizations. Frogs were the first vertebrate to evolve a voice box and vocal cords as adults. Males pump air back and forth over vocal cords into a loose pouch called a vocal sac. Bullfrog, African 2/4

• Metamorphosis, the abrupt transformation from larva to adult, is one of the distinctive characteristics of all amphibians, which are the only 4-limbed animals in which it occurs. • Backbone: short and rigid. The reduced number of vertebrae (9 compared with 25-250 in other amphibians) is essential for the animal to be able to withstand the forces involved in leaping, landing and burrowing in soil.

DIET • In the wild: mice, lizards, other frogs, small mammals and small birds. • In the zoo: mice

MEDIAN LIFE EXPECTANCY • Unknown.

ENEMIES - DEFENSE • Enemies: • Defense: - muddy-looking skin blends into the surroundings (camouflage). - teeth fight off predators. - the skin contains toxic glands.

MATING - CARE OF THE YOUNG • Courtship and Mating Behavior. - These frogs are most conspicuous during the breeding season. Most frog populations are scattered over a wide area when they are feeding and they must migrate to a suitable breeding site when conditions are right. The length of daylight, temperature and rainfall seem to be the 3 main factors that trigger breeding activity. When heavy rains come, they congregate in shallow pools of water to spawn. They can gather together, often in aggregations numbering hundreds or thousands of individuals, and produce an impressive noise that may be heard from a great distance. - Fertilization: external. Eggs are fertilized above the water’s surface. • Gestation: the hundreds of eggs are amniotic: The embryo and yolk are enclosed in a gelatinous envelope with no tough shell so the eggs need to be kept moist. • Litter / Clutch: the female releases hundreds of eggs which the male immediately fertilizes as they swim in an embrace called amplexus. Amplexus occurs in shallow water to allow the pair to stand on the bottom. • Parental Care: the males exhibit parental care. Males will watch over and defend the eggs that hatch in 2 days. The male, however, will often consume many of the tadpoles while he is defending them. Defending males will continue to watch over the tadpoles which will metamorphose in 3 weeks. • Sexual Maturity: 6-8 years.

SOCIAL INTERACTION • Communication, Vocal: loud, like deep bellows. The call is composed of loud, throaty bellows and deep grunts. Mating calls begin only after these frogs have established their territory.

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LIFE STYLE • Activity Period: some frogs increase their body temperature during the day by basking in the sun with their bodies and legs outstretched, but, as this involves water loss, basking is restricted to species that live close to permanent water. Frogs living in very hot climates avoid heat by burrowing during the day and only come to the surface at night. • Feeding: - cannibalism is a common occurrence beginning the moment they metamorphose; many of their first meals will be a member of the same egg mass. - after hatching, the tadpoles will feed on each other, as well as on small fish and invertebrates. - carnivorous as adults; herbivorous when young. - the tongue is folded over inside the mouth. To capture a meal, the lower jaw is drooped with considerable force, causing the tongue to flip over and out of the mouth, seizing the prey. - during the rainy season frogs will sit partially buried with the nose exposed, taking advantage of any smaller animal unfortunate enough to pass by. • Locomotion: they live a jumping life style • They spend at least some stage of their life cycle in water and must return to the water to breed, but they spend as much time out of the water as in it. • They spend much of their life underground during the dry season. Using the metatarsal tubercles on the feet of their powerful hind legs, they burrow into the drying mud at the start of the long dry season and go into a dormant state, a “long sleep”, to avoid the harsh summer conditions in sub-Saharan Africa. To prevent body fluids from evaporating, they cloak themselves in a watertight skin cocoon made up of dead skin layers from the epidermal cells. This period of dormancy may last a year or more. • Frogs are primarily dependent on environmental sources of heat to regulate body temperature. • Their body temperature is usually very close to that of their surroundings.

PHYSICAL • General Description: stout. • Sexual Dimorphism (color and size). - Color: males are olive in color, with bright yellow to orange on the throat region; females are olive to light brown with cream to white throat areas. - Size: females are much smaller than males. • Both sexes have ridges running laterally on the dorsal surface. • Body Covering: soft, moist, smooth and glandular skin is used as an organ of respiration (“cutaneous respiration”). Applicable to frogs in general. • Head: large and flush with body and no constricted neck. • Mouth: large. • Teeth: sharp. Used to fight off predators and also to hold fast, and chew, big prey. 3 canine- like teeth (odontodes) protrude from the lower jaw. All are the same. Replaced continually throughout life.

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• Sensory Organs. - Nostrils and Eyes: usually on top of the skull so that, when sitting in water, the animal can breathe and watch, with the rest of the body hidden from view. - Eyes: large with special glands to keep them moist. They are protected from dust and soil by movable eyelids. Color: bronze. Vision: excellent. - Eardrum: large. Hearing: excellent. • Arms, Legs, Feet. - Legs: present in adults; absent in the young. Adults have a spade-like, sharp, tough metatarsal tubercle on the inner toes of each hind foot to aid in digging. The hind legs are very strong and the feet are powerful to dig holes for keeping cool and for shelter. - Toes: the front toes are thick and blunt with no webbing; the rear toes are slightly webbed. • Tail: absent in the adults, present in the young. • Lungs: present in adults for breathing on land. The young breathe through gills. Also obtain oxygen directly through the skin. Applicable to frogs in general.

TAXONOMY Phylum Chordata Class Amphibia Order / Suborder Anura / Neobatrachia Family Ranidae Genus / species Pyxicephalus adspersus

• Pyxicephalus (Pyxis = "(round) box," cephalus = "head")

REFERENCES - Halliday, Dr. Tim and Dr. Kraig Adler, Editors. 1986. Encyclopedia of Reptiles and Amphibians. Facts on File, Inc. New York, NY. - Channing, Alan, John Poynton, Leslie Minter, Kim Howell, James Harrison 2004. Pyxicephalus adspersus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. www.iucnredlist.org. - African Bullfrogs at Etosha; www.pbs.org - Fort Worth Zoo: www.whozoo.org - Herpetological Care Collection: www.anapsid.org - University of Michigan, Museum of Zoology, Animal Diversity Web. www.animaldiversity.ummz.umich.edu - African Bullfrogs at Etosha; www.pbs.org - IUCN 2014. IUCN Red List of Threatened Species. Version 2014.1. www.iucnredlist.org. Downloaded on 13 June 2014.

Prepared by: Judith Ehrman, docent Date: 01-15-03 Photo: Bob Sloane, docent Map: Dave Schaffer - Bob Sloane, docents Approved by PZ: Date: 12-15-06 Tanya Minott/Greg O’Neill, Keepers, Reptile House Reformatted by: Judy Ehrman and Bob Sloane, docents Date: 06-24-12