Common Hippopotomus

Hippopotamus amphibius

General Description

Scientific Name: Hippopotamus amphibius

Subspecies: 5 subspecies

H. a. amphibius (East African hippo)
H. a. kiboko (Kenyan Hippo)
H. a. capensis (Cape Hippo)
H. a. tschadensis (West African Hippo)
H. a. constrictus (Congo Hippo)

Status: Vulnerable (decreasing)

Population Estimate: 115,000-130,000

Population in Assessed Areas: 5

Diet: Herbivore - grazier

Male Size: 1,400-2,660 Kgs

Female Size: 1,300-1500 Kgs

Trophy Size: N/a

Generation Length: 10 years

Reproductive Season: Year Round

Time of Activity: Diurnal/Semi-nocturnal

Description: The hippopotamus are a megaherbivore exceeded in size among land animals only by elephants and some rhinoceros species. The mean adult weight is around 1,480 kg (3,260 lb) for bulls and 1,365 kg (3,009 lb) for cows. Exceptionally large males have been recorded reaching 2,660 kg (5,860 lb). Male hippos continue growing throughout their lives, while females reach maximum weight at around 25 years old. Hippos measure 2.90-5.05 m (9.5-16.6 ft) long, including a tail of about 35-56 cm (1.15 to 1.84 ft) in length and 1.30 to 1.65 m (4.3 to 5.4 ft) tall at the shoulder, with males and females ranging 1.40 to 1.65 m (4.6 to 5.4 ft) and 1.30 to 1.45 m (4.3 to 4.8 ft) tall at the shoulder respectively. The species has a typical head-body length of 3.3–3.45 m (10.8–11.3 ft) and an average standing height of 1.4 m (4.6 ft) at the shoulder.

Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long snout. Their skeletal structures are graviportal, adapted to carrying their enormous weight, and their dense bones and low center of gravity allows them to sink and move along the bottom of the water. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. The toes are webbed and the pelvis rests at an angle of 45 degrees. Though chubby-looking, hippos have little fat. The eyes, ears, and nostrils of hippos are placed high on the roof of their skulls. This allows these organs to remain above the surface while the rest of the body is submerged. The nostrils and ears can close when underwater while nictitating membranes cover the eyes. The vocal folds of the hippo are more horizontally positioned, much like cetaceans. Underneath are throat tissues, where vibrations are transmitted to produce underwater calls.

The hippo's jaw is powered by huge masseter and digastric muscles which give them large, droopy cheeks. The jaw hinge allows the animal to open its mouth at almost 180°. A folded orbicularis oris muscle allows the hippo to attain an extreme gape without tearing any tissue. On the lower jaw, the incisors and canines grow continuously, the former reaching 40 cm (1 ft 4 in), while the latter can grow to up to 50 cm (1 ft 8 in). The lower canines are sharpened through contact with the smaller upper canines. The canines and incisors are used mainly for combat instead of feeding. Hippos rely on their flattened, horny lips to grasp and pull grasses which are then ground by the molars. The hippo is considered to be a pseudoruminant; it has a complex three-chambered stomach, but does not "chew cud".

Hippo skin is 6 cm (2 in) thick across much of its body with little hair. The animal is mostly purplish-grey or blue-black, but brownish-pink on the underside and around the eyes and ears. Their skin secretes a natural, red-colored sunscreen substance that is sometimes referred to as "blood sweat" but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two highly acidic pigments have been identified in the secretions; one red (hipposudoric acid) and one orange (norhipposudoric acid), which inhibit the growth of disease-causing bacteria and their light-absorption profile peaks in the ultraviolet range, creating a sunscreen effect. Regardless of diet, all hippos secrete these pigments so food does not appear to be their source; rather, they may be synthesized from precursors such as the amino acid tyrosine. This natural sunscreen cannot prevent the animal's skin from cracking if it stays out of water too long.

Hippo-Family-Luangwa-River-South-Luangwa-National-Park-Zambia_203328205-1024x685.jpg

Ecology: Hippos are semiaquatic and require enough water to immerse in, while being close to grass. Like most herbivores, hippos will consume a variety of plants if presented with them in captivity, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants. They prefer relatively still waters with gently sloping shores, though male hippos may also be found in very small numbers in more rapid waters with rocky slopes. Hippos mostly live in freshwater habitat, but can be found in estuaries. Despite being semiaquatic, an adult hippo is not a particularly good swimmer, nor can it float. It rarely enters deep water; when it does, the animal moves by bouncing off the bottom. An adult hippo surfaces every four to six minutes, while young need to breathe every two to three minutes.

Hippos spend most of the day in water to stay cool and hydrated. Just before night begins, they leave the water to forage on land. Hippos usually trot to move quickly on land and can gallop at 30 km/h (19 mph) when needed. They are incapable of jumping but can walk up steep banks. A hippo will travel 3–5 km (1.9–3.1 mi) per night, eating around 40 kg (88 lb) of grass. By dawn, they are back in the water. The hippo sleeps with both hemispheres of the brain resting, as in all land mammals, and usually sleeps on land or in water with the nostrils exposed. Despite this, it may be capable of sleeping while submerged, intermittently surfacing to breathe without waking. They appear to transition between different phases of sleep more quickly than other mammals.

Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land across which they walk, keeping the land clear of vegetation and depressing the ground. Over prolonged periods, hippos can divert the paths of swamps and channels. By defecating in the water, the animals also appear to pass on microbes from their gut, affecting the biogeochemical cycle. On occasion, hippos have been filmed eating carrion, usually near the water. There are other reports of meat-eating and even cannibalism and predation. Hippos' stomach anatomy lacks adaptions to carnivory and meat-eating is likely caused by lack of nutrients or just an abnormal behavior.

Behavior: Hippo pods fluctuate but can contain over 100 hippos. Although they lie close together, adults develop almost no social bonds. Males establish territories in water but not land, and these may range 250–500 m (270–550 yd) in lakes and 50–100 m (55–109 yd) in rivers. Territories are abandoned when the water dries up. The bull has breeding access to all the cows in his territory. Younger bachelors are allowed to stay as long as they defer to him. A younger male may challenge the old bull for control of the territory. Within the pods, the hippos tend to segregate by sex and status. Bachelor males lounge near other bachelors, females with other females, and the territorial male is on his own. When hippos emerge from the water to graze, they do so individually.

Hippos engage in "muck-spreading" which involves defecating while spinning their tails to distribute the faeces over a greater area. Muck-spreading occurs both on land and in water and its function is not well understood. It is unlikely to serve a territorial function, as the animals only establish territories in the water. They may be used as trails between the water and grazing areas. "Yawning" serves as a threat display. When fighting, bulls use their incisors to block each other's attacks and their large canines as offensive weapons. When hippos become over-populated or a habitat shrinks, bulls sometimes attempt infanticide, but this behaviour is not common under normal conditions.

The most common hippo vocalisation is the "wheeze honk", which can travel over long distances in air. This call starts as a high-pitched squeal followed by a deeper, resonant call. The animals can recognise the calls of other individuals. Hippos are more likely to react to the wheeze honks of strangers than to those they are more familiar with. When threatened or alarmed, they produce exhalations, and fighting bulls will bellow loudly. Hippos are recorded to produce clicks underwater which may have echolocative properties. They have the unique ability to hold their heads partially above the water and send out a cry that travels through both water and air; individuals respond both above and below water.

Predation: Hippos share habitat with a variety of large predators in their habitats. Nile crocodiles, lions, and spotted hyenas are known to prey on young hippos. Beyond these, adult hippos are not usually preyed upon by other animals due to their aggression and size. Cases where large lion prides have successfully preyed on adult hippos have been reported, but it is generally rare. Lions occasionally prey on adults at Gorongosa National Park and calves are sometimes taken at Virunga.[85] Crocodiles are frequent targets of hippo aggression, probably because they often inhabit the same riparian habitats; crocodiles may be either aggressively displaced or killed by hippos. In turn, very large Nile crocodiles have been observed preying occasionally on calves, "half-grown" hippos, and possibly also adult female hippos. Groups of crocodiles have also been observed finishing off still-living male hippos that were previously injured in mating battles with other males

Reproduction: Cows reach sexual maturity at five to six years of age and have a gestation period of eight months. A study of endocrine systems revealed cows may begin puberty at as early as three or four years. Males reach maturity at around 7.5 years. Both conceptions and births are highest during the wet season. Male hippos always have mobile spermatozoa and can breed year-round. After becoming pregnant, a female hippo will typically not begin ovulation again for 17 months. Hippos mate in the water, with the cow remaining under the surface, her head emerging periodically to draw breath. Cows give birth in seclusion and return within 10 to 14 days. Calves are born on land or shallow water weighing on average 50 kg (110 lb) and at an average length of around 127 cm (4 ft 2 in). The female lies on her side when nursing, which can occur underwater or on land. The young are carried on their mothers' backs in deep water.

Mother hippos are very protective of their young, not allowing others to get too close. One cow was recorded protecting a calf's carcass after it had died.Calves may be temporarily kept in nurseries, guarded by one or more adults, and will play amongst themselves. Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than many small, poorly developed young several times per year, as is common among small mammals such as rodents). Calves no longer need to suckle when they are a year old.

Conservation Analysis

Current & Historic range: In the late Pleistocene, common hippos once ranged over a huge area of Africa, the levant, and southern Europe, ranging everywhere where water was abundant, and temperatures didn't drop below freezing. They disappeared form their European range around 23,000 years ago, and disappeared from the Levant around 3,000 years ago. The last hippos disappeared from the Nile river in 6th century BCE, after millennia of persecution by North African and Mediterranean empires.

Reports of the slaughter of the last hippo in Natal Province were made at the end of the 19th century. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania, and Kenya, north through to Ethiopia, Somalia, and Sudan, west to The Gambia, and south to South Africa. Genetic evidence suggests common hippos in Africa experienced a marked population expansion during or after the Pleistocene, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications, as hippo populations across the continent are currently threatened by loss of access to fresh water

Current & Historic Populations: Though it's unknown exactly how many Southern Giraffe once existed across their historical range, the number likely ranges in the low millions. Current estimates of all of the combined hippo sub-species across their current range between 115,000-130,000, though in reality it could be substantially lower. astern and Southern African countries represent the conservation stronghold for this species and are the regions where the largest numbers of Common Hippos occur. Although Common Hippos are found in many West African nations, overall population sizes tend to be much smaller, either because of less available habitat or the higher density of human population

Map of Common Hippo Distribution

Threats to Species Survival: The primary threats to Common Hippos are habitat loss or degradation and illegal and unregulated hunting for meat and ivory (found in the canine teeth). Habitat loss and conflict with agricultural development and farming are a major problem for hippo conservation in many countries. Common Hippo’s reliance on fresh water habitats appears to put them at odds with human populations and adds to their vulnerability, given the growing pressure on fresh water resources across Africa.

Habitat loss stems from water diversion related to agricultural development as well as larger-scale development in and around wetland areas. In many West and Central African countries, habitat loss has contributed to a growing regional threat of population fragmentation, as isolated and small populations of hippos are confined to protected areas, with poor or even no management and increasing pressure from local communities.

Reports of human mortalities from Common Hippo interactions have also increased in recent years, another indication of habitat loss. In some agricultural areas, hippo population increases in restricted habitat has also fueled conflict (Kanga 2013). Ten countries reported growing numbers of hippo-human conflicts, in several cases exacerbated by drought conditions. Conflicts with fishermen and gold miners have also been reported. In many countries where Common Hippos are found, populations are not confined to protected areas. Although it is likely that the majority of the overall Common Hippo population reside in some form of protected area (national park, biosphere, game or forest reserve, sanctuary, conservation area), the proportion of protected Hippos likely varies among countries. For countries with a high proportion of Hippo populations outside protected areas, the likelihood of persistence is much lower as there is no impediment to hunting or incentive for habitat protection.

Recommended Conservation Actions:

Further resource and manage protected areas where Common Hippo exist.
Encourage the implementation of economic incentives that allow landowners to profit off the presence of healthy Common Hippo populations, whether that be through hunting or ecotourism.
Improve the ability for Hippo populations to move widely across a landscape, allowing for the restorations of historical seasonal migrations between ideal habitats, and access to key water sources.
Improve protections for hippos and the people that live alongside them, to minimize the number of hippo related deaths per year.
Improve survey methods to get accurate population data, such as implementing long-term monitoring programs.

Economic & Cultural Analysis

Ecotourism Value: Extremely High

Hunting Value: Extremely High

Meat Value: High

Average Trophy Value: $4,000 - 15,000 USD

Meat Yield per Animal: 600-1,200 kg

Economic Value/Impacts: Common hippo present considerable value to both the ecotourism and hunting industries across their range, as well as to rural and hunter-gatherer peoples that have hunted this species for thousands of years. Their large body size meant that each animal produces a considerable amount of meat, that can feed and entire village for weeks.

Hippos are one of the most iconic wildlife species on the African continent, only being surpassed by lions, elephants, and possibly rhinos. Because of this, the mere presence of hippos on a property can be a significant drawcard for ecotourism reserves, and are often one of the most sought after species on game drives. They are especially valuable in habitats where they gather in large numbers, such as along the Luangwa river in Zambia, or the Chobe river in Botswana, where hundreds of these animals still exist today. Boat tours guiding tourists up and down the river to view hippos in their natural habitat are common in these places, and a major attraction for visitors.

In the areas of their range where they are still common, especially in African nations like Botswana, south Africa, Zambia and Zimbabwe, hunting is an important conservation revenue source for Hippos. On average, a hunter will pay between $4,000-$15,000 USD for a hunt, usually for a old mature male well past it's prime. As one of the most dangerous members of Africa's big 5, they are a swell sought after quarry for many international hunters.

Cultural Value: The earliest evidence of modern human interaction with hippos comes from butchery cut marks on hippo bones found at the Bouri Formation and dated to around 160,000 years ago. 4,000–5,000 year art showing hippos being hunted have been found in the Tassili n'Ajjer Mountains in the Sahara near Djanet. The ancient Egyptians recognised the hippo as a ferocious denizen of the Nile and representations on the tombs of nobles show the animals were hunted by humans. Hippo hunting also occurred throughout sub-Saharan Africa for thousands of years, though they would have been a difficult quarry, one requiring a large number for hunters to successfully bring down.

The hippo is considered to be extremely aggressive and has frequently been reported charging and attacking boats. Small boats can easily be capsized by hippos and passengers can be injured or killed by the animals, or drown in the water. In one 2014 case in Niger, a boat was capsized by a hippo and 13 people were killed. Hippos will often raid farm crops if the opportunity arises, and humans may come into conflict with them on these occasions. These encounters can be fatal to either humans or hippos.

Back to Ungulates