Common Hippopotamus (Hippopotamus amphibius)
Size:
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
Description:
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 Status:
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)
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