Hippos live in groups in a territory, a portion of a lake or river, which varies according to the body of water and the season. On a river bank, a smaller space is sufficient for a larger number of animals than on a lake bank. Thus, 33 hippos can share 100 meters of river bank, while only 7 animals coexist in 100 meters of lake.
The dominant male reigns over 50 to 100 meters of river while his territory can reach 500 meters of lake. It is he who is in charge of territorial marking. Positioning himself on the edge, with his back to the shore, he spreads his dung in a radius of 2 meters. This kind of scene seems to fascinate the juveniles, who come to smell the excrement and, sometimes, to consume it.
As long as the juveniles, and especially the almost adult males, adopt a submissive attitude towards the owner, all is well. But, if they keep their heads up, which the chef always considers a challenge, things can get ugly: the large amount of scarring on the body of large males is a reminder to all that arguments can get heated.
Canine teeth play no role in feeding, but can inflict deep wounds (which heal surprisingly quickly). Fights are interspersed with howling, charges into the water and intimidating postures, mouths wide open.
The hippo's jaw, i.e. its lower jaw, can open 150°, which is huge, and as a result is muscular. Hence the famous hippopotamus yawn: far from being just a gesture of tiredness, it can be really threatening, if the male throws his head as far back as possible, exposing his whole throat in a gesture of defiance. This is a way of calming any hint of internal revolution.
RESPECTFUL OF THE HIERARCHY
Fights can be fatal, but these big scenes remain rare, because the hippopotamus is respectful of hierarchy. One of the most characteristic social behaviors of the species could be called "submissive defecation": a dominated animal turns around, pulls its hindquarters out of the water, generously splashes the dominant's snout with its excrement and spills it. by a vigorous lateral flapping of the tail. The hierarchical superior requests this gesture from the young males: he turns them around, pulls their shoulders out of the water, the head for once cocked to one side. Any animal that enters the pond will "greet" the dominant and tell it that it recognizes its status as leader.
The hippos are grouped in 10 to 15 groups under the leadership of one male, who is the leader. The latter is replaced at each change of territory, but, in certain stable sites, such as lakes, the same male can survive for 4 years, even 8 years. During the day, the dominant patrols its territory. Mothers stand to one side and watch their young. The females without young are on the other and the young males are left alone ... waiting to dominate, when the attacks of the dominant do not force them to leave the group.
FULL DAYS IN THE WATER YAWNING OR SLEEPING
Hippos spend their days in the water. As much as they move heavily on land, they show ease in the water but how much does a hippo weigh? (in spanish: ¿Cuánto pesa un hipopótamo?) The male can weigh up to 1800 kg and the female about 1500 kg. When it is deep, they can actually swim. They propel themselves mainly by moving their hind legs, like a frog! When there is less water, they move forward a bit as if they were bouncing, with successive thrusts, resting on the bottom. The water does not reach their eyes or ears. Hippos do everything in the water, including sleeping, during naps.
It is also in the water that mating takes place. The only male is then visible, the female is completely underwater. Only her nostrils come to the surface from time to time. The courtship of the male, before and during mating, is relatively aggressive, and the female seems to hold on with some force underwater.
In the past, hippopotamuses were classified in the order of pachyderms, a word meaning "having thick skin" in Greek. However, the opposite is true: the horny layer of its skin is so thin that the hippopotamus is very sensitive to water loss through evaporation ... It could be that this species spends its days in the water simply because it could not overcome the rate of water loss imposed on it by a day in the tropical African sun.
The other reason they live in the water is to save energy because they eat little. Since the water temperature is almost the same as their body temperature, hippos do not have to burn calories to remain homeothermic (i.e., to maintain a constant internal temperature).
THE HIPPOPOTAMUS EATS ONLY AT NIGHT
The hippopotamus eats very little, in proportion to its weight. Its daily ration, 40 kg of fresh grass, represents only 1 to 1.5% of its weight in dry matter, while all other ungulates - hoofed animals - need to eat 2.5% of their weight to live. When all goes well, its pastures are, on average, located between 2.8 and 3.2 km from a water point, but, in case of food shortage, it can walk up to 10 km, alone or in small groups. During the dry season, it can even fast for a long time...
Another characteristic, mentioned on animal websites (web de animales), is that the hippopotamus only feeds after sunset. In the late afternoon, the acoustic signals become more numerous, the frequency of yawning increases, announcing the approach of food movements. Thus, groups of hippos continue to communicate at night while foraging for food. The animals respond to each other. The sound traveling up to 1 km along the river, a chain of echoes gradually resonates, and from group to group, echoes throughout the river.
Hippos may begin foraging for several kilometers in the stream itself. To get out of the water, they regularly take the same passages, digging hard, to the point of breaking the banks when many of them use the same pathways, night after night ...
The food of the hippopotamus is composed of various species of grasses, of the genera Panicum , Urocholora or Cynodon . Depending on the location, its diet can include a dozen different grasses. It is quite selective, choosing the most palatable species and neglecting the others. For example, it still disdains species of the genus Spirobolus . In fact, its tastes may vary according to the region. The hippopotamus has its local habits: in a reserve in Kwazulu-Natal, South Africa, it feeds on buffalo grass ( Panicum maximum ) and quackgrass ( Cynodon dactylon ).