Common Hippopotamus

Hippopotamus amphibius

Head and body length:  2.8 – 3.5 meters

Shoulder height:  130 – 165 cm

Weight:  Female 510 – 2,500 kg; Male 650 – 3,200 kg

DescriptionHippos 300x228 Common Hippopotamus

Although “hippopotamus” is Greek for “river horse,” they look much more like a giant pig that lives in the water.  It is estimated that their evolutionary line branched from the pigs about 40 million years ago.  Their eyes and nostrils are perched on top of their heads, allowing them to stay almost entirely submerged for much of the day.  They are almost completely vegetarian, so the four large tusks are used exclusively for fighting.  Fights between hippos are frequent, vicious, and sometimes deadly.

Breeding

In general, most mating happens during the dry season and most births during the wet season.  Gestation lasts for 6 – 8 months.  Young are sometimes delivered under water, and have adapted the ability to suckle under water by wrapping their tongues around the nipple.  They begin grazing a little by 1 month, a lot by 5 months, and are weaned around 8 months.

Where to look for them

You can expect to see several hundred hippos on the boat launch to the base of Murchison Falls.  While on game drives you will likely see them along the delta, in wallows in the savanna areas and, at night, look right outside your tent.  While hippos are entirely dependent on water during the day, at night they may travel as far as 15 or 20 kilometers away from water to find good grasses to graze.

Interesting Facts:

  • Hippos invented sunscreen!  Their naked, porous skin is very vulnerable to both sunburn and dehydration.  As a defense, they secrete a red fluid that acts as sunscreen, antiseptic, and water-loss sealant.  Because of this secretion, the ancient Greeks claimed the hippo “sweats blood.”
  • Hippos can be up to half the weight of an elephant, but only eat about one fourth the amount of food.  Spending their days in the buoyancy of water reduces their energy expenditure significantly.
  • When it hits the fan… Never stand too close to a defecating hippo.  They spin their tails like a propeller to spray the feces on the shore to advertise their presence or during conflicts with rivals.

Conservation

Their range in Africa has been severely restricted.  Their population within national parks is stable, although they are a desirable target for poachers due to their reportedly delicious meat.

Lifespan:

35 to 50 years

Detailed Information:

Order:  Artiodactyla

Family:  Hippopotamidae

Genus:  Hippopotamus

Species:  amphibius

Habitat:

They spend days in water and nights grazing on land.  Spending days in water has many benefits – protection, buoyancy for reduced energy expenditure, and protection from the sun. (Kingdon, p. 324)

Upper altitude limit is about 2,000 meters. (Kingdon, p. 325)

Large groups favor slow-moving water or lakes with shallow, sloping shorelines.  Individuals or small groups may spend days in small wallows or quick-moving rivers (Kingdon, p. 325 and personal observation)

Range/Parks:

Originally, hippos were found throughout Africa and much of Asia (esp. India), with up to 8 species living in Africa alone.  At least three species have been eliminated during historical times from Madagascar.  Now restricted to waterways in southern Africa. (Kingdon, p. 324)

Murchison Falls National Park has one of the highest concentrations of hippos on earth, along the stretch of the River Nile below the falls.

Food/Water:

Creeping and tussock grasses, especially Cynodon and Panicum species.  Also favor Brachiara, Themeda, Chloris and Setaria.  Can ingest up to 60kg per night by grabbing clumps of grass and tearing it out by swinging its head.  Seldom spends more than 5 hours out of the water feeding each night. (Kingdon, p. 325)

Grassy lawns that have been kept short through continual grazing are preferred to longer, coarser grasses. (Estes, p. 223)

Breeding:

Gestation period of 6 – 8 months, after which usually only one young is born. (Estes, p. 222)

Young have adapted the ability to suckle under water by wrapping their tongues around the nipple. (Kingdon, p. 324)

Breeding is not strictly seasonal, but most mating happens during the dry season and most births during the wet season.  Females conceive the first time around 9 years of age and calve at 2-year intervals.  Pregnant mothers isolate themselves prior to calving and will avoid the herd for up to 2 weeks.  Young are born underwater.  They begin grazing a little by 1 month, a lot by 5 months, and are weaned around 8 months.  (Estes, p. 225)

Social Organization/Behaviors:

Hippos can remain under water for up to six minutes. In a bluff charge, they will lunge above the water line.  In a real attack, they remain below the surface.  (Walker, p. 140)

Very gregarious when in the water – will spend time in groups of over 100.  Solitary while foraging at night unless female with dependent offspring.  (Estes, p. 223)

Will be far more condensed during the dry season around sources of permanent water.  During rainy season will be much more dispersed in temporary wallows and smaller water sources. (Estes, p. 223)

Mature bulls (20 years and older) will control sections of a river or lakeshore as exclusive mating territory.  They have been known to hold territories for up to 8 years, but in areas with high competition, turnover may happen every few months.  Dominant bulls will tolerate other males as long as they show submission and do not try to mate.  They deal with rivals fiercely.  Lone hippos may be either outcasts or territorial bulls without herds. (Estes, p. 223)

Bonds between mothers and daughters are persistent and may last until the subadult stage, meaning that a mother may have up to 4 daughters with her at any given time. (Estes, p. 223)

Hippos in water surface generally every minute and a half, although they can stay submerged much longer.  They will even sleep under water and emerge involuntarily to breath.  They can walk easily underwater, and even on land, where they are much clumsier, they can reach speeds of 30 kph. (Estes, p. 224)

Bulls will sometimes kill calves, and mothers may attack bulls who threaten a nursery herd. (Estes, p. 225)

Young males begin practice-sparring by the time they are 7 years old.  Actual fights often result in deep gashes to the loser, but skin 6 cm thick keeps real damage to a minimum.  Crushing bites to head, neck and legs are the most serious, and not uncommonly result in death. (Estes, p. 225)

Communication:

Scent-marking is very important.  When they defecate, they wag their tails like a propeller to spread the feces. (Kingdon, p. 324)

There is little sexual dimorphism, inconspicuous coloration and appendages, and no facial expressions.  This limits communication to auditory, olfactory and possibly tactile.  They are extremely vocal in the water [personal observation], but mostly silent on land (Kingdon, p. 224)

Territorial bulls, when they encounter each other, will turn around and dung-shower each other with their tails.  I have found no indication of how they determine the winner of the encounter.  Perhaps it is simply to give an intruder the chance to compare the odor to that found in dung piles placed around the territory.  (Estes, p. 224)

Threat displays:  yawning, with or without water scooping, head shaking, rearing, lunging, roaring, grunting, chasing, explosive exhalation, dung-showering.

Submissive displays:  face aggressor with mouth open or turning around, lying prone or fleeing. (Estes, p. 225)

Activity Patterns:

Daytime is spent in water resting and digesting.  Late evening into night time is spent foraging, with a maximum distance traveled of 10 km (usually more like 5 km). (Estes, p. 224)

Sign:

Look for huge tracks, pathways leading from water, closely cropped lawns and accumulation of dung. (Kingdon, p. 325)

Dung looks much like the dung of an elephant that has been feeding on grass.  When defecation happens in the water, it is eaten by fish. (Walker, p. 141)

Trails are surprisingly narrow for such a wide animal – about 20 cm wide. (Walker, p. 141 and personal observation)

Predators:

Humans are the primary predators.  No other natural predators except occasional crocodile taking young.  Calves may be trampled by adults hippos, especially bulls.  (Estes, p. 223)

Conservation/Commercial value:

Over 200 hippos recently died from Anthrax in Queen Elizabeth National Park.  Although the death-rate has slowed in hippos, it has spread to the buffalo population.

Huge potential for domestication due to their efficiency in turning vegetation into protein. (Kingdon, p. 324)  Unfortunately, they are extremely ornery.

References:

Estes, R. (1991). The Behavior Guide to African Mammals. Berkeley, CA:  The University of California Press.

Kingdon, J. (1997). The Kingdon Field Guide to African Mammals. Princeton, NJ:  Princeton University Press.

Walker, C. (1996). Signs of the Wild: A Field Guide to the Spoor & Signs of the Mammals of Southern Africa. (5th Edition). Cape Town, South Africa:  Struik Publishers Ltd.

Photo by Charles Steinberg

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