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The guttural honking of hippos is as much part of the safari soundtrack as the cry of a fish eagle or the roar of a lion. The characteristic bursts of mist ejected from nostrils breaking the surface of the water bely the sheer mass of the creature suspended below it. Surprisingly graceful and manoeuvrable below the water, a hippo is an ungainly sight when on land – a barrel-shaped body propped upon four short, stubby legs, completed by a somewhat ridiculous flap of a tail relative to the size of the animal. This feature made more ridiculous when spinning like a miniature propeller to spread its dung in display. They may not be able to clear any terrestrial obstacle with any elegance, but a hippo hot-footing it along a game path, back to the safety of the water from its night time foraging, is a formidable force indeed. Beware the man or beast in its way. Yet, most of the time, a raft of these floating, honking, phff-ing behemoths is a very pleasant scene to behold.
A bloat of hippopotamuses
Adapted from Game Ranger in your Backpack © Megan Emmett
Hippos are well adapted for life in the water, with all their vital senses well-developed and perched high on the top of the head, including the eyes, nostrils and ears.
When hippos submerge, they can stay underwater for five or six minutes. The nostrils and ears close off to stop any water from getting inside them.
Unmistakable with their huge, grey, barrel-shaped bodies, enormous heads and large, four-toed feet, hippos are the largest terrestrial animals after elephants and rhinos.
While a hippo’s skin is generally thick, the epidermis is thin and dries out easily, so hippos generally spend daytime hours submerged in water.
Hippos have incredible muzzles that can stretch very wide open. This puts their lower canines, which are modified into huge tusks on display for all the world to see.
These grow continuously, may reach 30-50 cm (12-20 in) long and are continually sharpened through articulation against the pair on the upper jaw. A hippo uses its tusks to defend itself and it’s young, or to fight. Territorial bulls show off their dominance by yawning, thereby displaying their weapons to any would-be contenders.
Males and females are difficult to tell apart since the bulls’ testicles are internal, but bulls are generally larger, more active and scarred.
Hippos come out of the water to bask in the sun to warm up. Often an entire pod will haul onto a sand bank at once to bask. They tend to do this at cooler times of the day.
A thick layer of fat insulates them against the cold.
Hippos spend the daytime submerged in water, saving on the amount of food they need because they reserve much energy by being buoyed-up by the water.
To protect themselves from desiccation, hippos have a natural sunscreen, which they can secrete from their mucous glands if their bodies are exposed for long periods. This blood-red fluid helps for a while but, after an extended time, the skin dehydrates and cracks. When water is scarce, hippo pods pack together in muddy pools to keep moist and move long distances at night to find deeper water. Cows will attempt to hydrate calves with dribbled saliva.
Hippos feed on grass at night when it’s cool enough to leave the water. An adult hippo usually eats 15-40 kg (30-90 lb) of grass in a night, about 1.5% of its body weight.
Leaving the water at dusk, they head to favoured short-grass feeding grounds within 1-2 km (half a mile to a mile) along well-used pathways. They feed alone except for cows and calves and they feed noisily, plucking grass unselectively with their wide lips. They return to the water before the sun gets hot. During times of drought, hippos may walk 15 km (9 miles) in a night. Hippos mostly graze grass and only occasionally eat the water plants growing in the rivers where they live
To stay under water, hippos breathe out before submerging and create negative buoyancy. They are not well adapted to swimming, lacking webbed limbs or flippers.
To move in the water, they simply walk along the bottom, pushing off with their feet. This action dredges water channels, keeping them open and flowing. They need to resurface to breath, which they do with a puff of air and water spray from their nostrils. Hippos can even sleep underwater but surface involuntarily every few minutes to breathe. Baby hippos only submerge for short periods. Hippos do porpoise with some success.
When threatened, hippos head straight back to the of water along the well-used pathways by which they left it. At full charge a hippo may reach 40 kmph (25 mph).
Hippos are fairly immune to predation but lions, hyenas and humans do kill the adults. Calves are more susceptible to predation especially by crocodiles. Hippos don’t navigate obstacles well and they can’t jump. Because hippo paths are convenient footpaths for human use, many humans have come face to face with hippos in this way, to their detriment.
Hippos live in pods. An average group of hippos is about 10-15 animals strong but anything from two to 2000 can be found. Each pod is presided over by a territorial bull.
Bull hippos defend territories, which may contain more than one nursery herd of females and their young. Hippos growl, grunt, honk or squeals to communicate social innuendos.
Territorial displays of charging or porpoising ensure only the most serious challengers fight. Ritualised tail-paddling that showers dung widely is also used.
At the other end, the mouth opens to show off the sharp canines. Much roaring accompanies this. Territories are marked on land with tail paddling of dung against trees and the iconic hippo-honk advertises territory vocally. Dung deposited in and near the water bodies where hippos live contributes to the ecology of these systems by adding nutrients for fish and invertebrates.
Bulls are very aggressive and much conflict occurs. When fighting, they attempt to wound the upper body of their opponent with their sharp canine teeth.
This may result in deep gashes that bleed profusely and leave scars, the tell-tale of an experienced territorial contender. In full-blown combat, opponents may collide so aggressively that they lift one another off the ground with their forequarters. Like the displays, much roaring may accompany fighting.
When it comes to mating, bulls are not very tactful and a female in heat is simply accessed by the dominant bull pushing through the pod while smelling rumps.
An oestrus female is chased into the water and forced into position even if this means she has to dodge grumpy snaps from the bull in order to steal breaths. The water buoys up their massive bodies during mating alleviating the cow’s discomfort from having a bull twice her weight upon her.
Born in shallow water, calves can swim and walk within minutes. They lose heat rapidly and so they often pull themselves onto their mothers’ backs to warm up.
Calves suckle underwater by pinching the cow’s teat between the tongue and palate. While they drink, their ears and nostrils are folded closed to avoid drowning. Cows protect their calves fiercely, not even tolerating attention from a bull hippo.
There is an eagle in me that wants to soar, and a hippo in me that wants to wallow in mud Carl Sandburg