Hippopotamus amphibius, Linnaeus, 1758

Don E. Wilson & Russell A. Mittermeier, 2011, Hippopotamidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 308-319 : 318

1.

Common Hippopotamus

Hippopotamus amphibius

French: Grand Hippopotame / German: Flusspferd / Spanish: Hipop 6 tamo

Taxonomy. Hippopotamus amphibius Linnaeus, 1758 ,

type locality restricted to River Nile in Africa.

Three subspecies recognized.

Subspecies and Distribution.

H.a.amphibiusLinnaeus,1758—sub-SaharanAfrica,exceptasbelow.

H.a.capensisDesmoulins,1825—ZambiaStoSouthAfrica.

H. a. kiboko Heller, 1914 — Kenya and Somalia.

Descriptive notes. Head-body 290-505 cm, tail 40-56 cm, shoulder height 150-165 cm; weight 1000-4500 kg. Massive animal with distinctly barrel shaped-body, short limbs, and large head. Adult males may be slightly larger than females, although no obvious sexual dimorphism. Numerous morphological adaptations for the aquatic environment in which it spends most daylight hours, including muscular valves in nose that close in response to contact with water, and webbed feet. Skin is gray and appears greasy, and is known for its remarkable strength. Body virtually hairless except on snout and tail. Graviportal skeleton. Feet have four toes. Canines and incisors are quite large, primarily used in aggressive interactions. Incisors may also be used for digging. There are marked sex differences in canine and incisor growth and size. Dental formula: 12/2, C1/1,P 4/4, M 3/3; P also found as 3/3. Long-lived animals, c.35 years.

Habitat. Found in sub-Saharan African countries in grassland and miombo woodlands, always associated with water sources, e.g. rivers, lakes, streams. They are absent from rain forest habitats, except for large rivers. They are restricted to the lower reaches of rivers and estuaries in West Africa and occasionally even extend into the sea. Elevations range from sea level to 2000 m. Bouyant but does not swim, rather walks or runs along bottom. At high population densities, hippos have been linked to widespread loss of vegetation in certain areas, which then leads to erosion. Culling occurred in the 1950s-1960s in some protected areas where hippo populations were deemed to exceed capacity. In lakes and rivers where they reside, hippo dung has been shown to alter the chemical composition of the water. Nutrients from hippo dung have been linked to productive fisheries and there are anectodal accounts of loss of fisheries when hippo populations are extirpated.

Food and Feeding. Although predominantly grazers, Common Hippos have been observed to consume aquatic vegetation and carcass remains, likely in response to nutritional constraints. Frequently reported to raid crops, particularly rice. Uses thick lips to tear and remove forage. Nightly feeding amounts may range from 20-45 kg, although in times of poor forage quality, individuals may not forage nightly. Gut rentention times have been estimated to be far higher than most large herbivores to maximize digestive efficiency. Because of their ability to remove wide swaths of grass, they have been linked to loss of vegetative and soil cover in areas of high densities.

Breeding. Conception and birth peaks have been found to correspond to peak rainfall months in several study sites. Common Hippos are believed to have a two-year cycle, with gestation lasting for eight months and lactation lasting for 10-12 months, although it can extend to 18 months. Low proportions of simultaneously pregnant and lactating females suggest that the likelihood of successful conception or pregnancy during lactation is low. Mating and birth occur in water.

Activity patterns. Daytime hours spent primarily submerged in water, although in cool ambient temperatures hippos can be observed foraging during the day or basking on river banks. During daylight hours, social behavioris believed to occur within the herd, although underwater activity is impossible to observe in most water sources. At night, hippos typically leave the water to find forage.

Movements, Home range and Social organization. Only indirect measurements have been made of the distance hippos travel from a water source. On average, they move 1-3 km, although larger distances have been suggested from some study sites. This may reflect seasonal and regional differences in movement. Animals occur in herds of various sizes, with herd size reflecting water availability. Herds are polygynous, with a dominant male, adult females, and juveniles, although relatedness within a herd has not been studied. All other males are found in separate bachelor herds. More detailed movement studies will require telemetry which has been impeded because of hippo’s sensitivity to chemical restraint and immobilization as well as lack of telemetry designs that accomodate their neck morphology.

Status and Conservation. CITES Appendix II. Classified as Vulnerable on The IUCN Red List. Primary threats include wetland habitat loss, water diversion, and direct harvest for meat and ivory. West African populations, far smaller than those found in East Africa, have the poorest conservation outlook. The Common Hippo was rare in North Africa by 1600, although it persisted along the Nile until around 1700. The last definite records from this area are from the early 19" century. Today, the largest populations are in East Africa with between 125,000 and 148,000 Common Hippos remaining. Common Hippos are found in 29 countries and confirmed population declines have been reported in half of those. The largest declines are in the DR Congo, a country once thought to have the largest populations.

Bibliography. Arman & Field (1973), Barklow (1997, 2004), Bere (1959), Boisserie (2005), Boisserie & Lihoreau (2006), Boisserie, Lihoreau & Brunet (2005), Boisserie, Zazzo et al. (2005), Dudley (1996), Eltringham (1974, 1993, 1999), Karstad & Hudson (1984), Laws (1968), Laws & Clough (1965), Lewison (2007), Lewison & Carter (2004), Lewison & Oliver (2008b), Luck & Wright (1959), McCarthy et al. (1998), Nomura & Yasue (1999), Okello et al. (2005), Olivier & Laurie (1974), Owen-Smith (1989), Sayer & Rakha (1974), Smuts & Whyte (1981), Wright (1987).

Figures

Plato 12 Specıes Acoounts

Subspecies and Distribution. H.a.amphibiusLinnaeus,1758—sub-SaharanAfrica,exceptasbelow. H.a.capensisDesmoulins,1825—ZambiaStoSouthAfrica. H. a. kiboko Heller, 1914 — Kenya and Somalia .