Hoplobatrachus occipitalis (Günther, 1858)
Original Published Description:
African Tigrine Frog (English), Crowned Bullfrog (English), Eastern Groove-crowned Bullfrog (English), Ethiopia Peters Frog (English), Giant Swamp Frog (English), Groove-crowned Bullfrog (English)
This large frog is found over a relatively broad, but disjunctive, range of North Africa as well as sub-Saharan Africa. The sexually dimorphic anuran prefers savanna habitat, but is also found in grasslands and certain forests. Eggs are laid in slow moving heavily vegetated streams. As an important predator of mosquitos, Hoplobatrachus occipitalis may play a significant role in preventing spread of certain diseases such as malaria.
The distribution of H. occipitalis is fundamentally disjunctive, including a swath in North Africa and a much larger range in sub-Saharan Africa. The North African range includes portions of Morocco, Algeria and Libya in the subcoastal areas of the Mediterranean Basin; these North African populations can be further regarded as isolated with sub-populations in southwestern Libyan Arab Jamahiriya, southeastern Western Sahara and nearby Mauritania, the Air mountains of Niger, and northern Mali. The sub-Saharan range extends from the Atlantic coast of West Africa, ranging eastward to Ethiopia, Chad, Eritrea, Sudan and south to Angola and Mozambique. Other specific sub-Saharan countries of occurrence include northern Zambia, western Congo, Senegal, Gambia, Guinea Bissau, Liberia, Sierra Leone, Guinea, Mali, Burkina Faso, Ivory Coast, Ghana, Togo, Benin, Niger, Nigeria, Cameroon, Equatorial Guinea (including the island of Fernando Pó), Congo, R.D. Congo, Central African Republic, Uganda, Kenya, Tanzania, Rwanda and Burundi. (Rödel.2000)
Perret suggests sexual dimorphism, with females being larger. The Perret data (Perret. 1966) illustrate a male snout to vent length range of 68 to 110 millimetres and a female length range of 110 to 135 millimetres. One outlier female specimen at a separate location measured 160 millimetres.
H. occipitalis is a sizable flat ranid manifesting protruding eyes, numerous dorsal warts, and a minute inner metatarsal tubercle. This anuran exhibits complete webbing between all the toes and fingers. This large dorso-ventrally flattened ranid frog features warty skin, with eye and nostril dorsal placement. Viewed from above, the eyes are completely contained within the outline of the frog's head. Owing to the presence of numerous glands, the exterior skin is extremely slippery. (Rodel. 2000)
The colour of the body and limbs is a yellow-green, olive or drab brown. Large dark green to blackish spots occasionally form rows, are exhibited on the dorsum. Spots of this same dark green to black present on the upper lip and on the extremities. A light green to yellow transverse line behind the eyes is exhibited in juvenile frogs,and often in adults as well. The outer elements of the thighs are marbled. The venter is white, occasionally punctuated with black spots.
Habitat and Ecology
H. occipitalis is found along river banks, rock-pools and savanna ponds, with a preference being observed for savanna environments. (Poynton & Broadley. 1985) At Comoé National Park, this species avoids forests, but in other locales this anuran has been found in wooded areas. (Gruschwitz et al. 1991) An example ecoregion where H. occipitalis can be found that features both savanna and woodland is the Central Zambezian miombo woodlands. (World Wildlife Fund & Hogan. 2007) As an example of forest habitat H. occipitalis is found in Tai National Park, (Rödel. 2000) where it can be observed in rocky pools along the Hana River, which riparian zone is surrounded by primary forest. Breeding water temperatures have sometimes been recorded at elevated temperatures at up to 40 degrees Celsius.
Hoplobatrachus occipitalis larvae prey on small aquatic animals like tadpoles and mosquitos, making them an important part of the food chain within temporary savanna ponds. As adults, they consume various other organisms. The loss of H. occipitalis as a predator, due to overexploitation of the species, could lead to increases in prey populations (Mohneke, 2010).
The African Tiger Frog is the species most commonly caught, for both consumption and trade, in Burkino Faso, Benin, and especially in Nigeria, where it was mentioned by every trader interviewed by Mohneke (2010). Villagers interviewed in Burkino Faso observed that Hoplobatrachus occipitalis had the second highest decline rate. This increased rate of overexploitation could affect the entire frog population and even potentially lead to local extinction of the species. In Nigeria, however, most collectors did not percieve a decline in H. occipitalis (Mohneke, 2010).
Though the preferred species varied across the regions studied, the majority of customers and collectors favoured larger specie. Hoplobatrachus occipitalis is a large frog and therefore is often a main species used for food (Mohneke, 2010).
- Rana occipitalis Günther, 1858 (synonym)
- Rana bragantina Bocage, 1864 (synonym)
- Rana (Fejervarya) occipitalis — Bolkay, 1915 (synonym)
- Rana tigrina var. occipitalis — Boulenger, 1918 (synonym)
- Rana (Rana) tigrina occipitalis — Chabanaud, 1921 (synonym)
- Ranosoma schereri Ahl, 1924 (synonym)
- Rana occipitalis — Noble, 1924 (synonym)
- Rana mwanzae Loveridge, 1925 (synonym)
- Rana (Rana) occipitalis — De Witte, 1930 (synonym)
- Rana esculenta bilmaensis Angel, 1936 (synonym)
- Limnonectes (Hoplobatrachus) occipitalis — Dubois, 1987 "1986" (synonym)
- Rana (Dicroglossus) occipitalis — De Witte, 1952 (synonym)
- Rana (Euphlyctis) occipitalis — Dubois, 1981 (synonym)
- Euphlyctis occipitalis — Poynton and Broadley, 1985 (synonym)
- Hoplobatrachus occipitalis — Dubois, 1992 (synonym)