BBC WILDLIFE September 2007 - Animal Behaviour
A Conversation with HIPPOS by Karen Paolillo
Volatile and aggressive, hippos are hard to get close to, unless – like KAREN PAOLILLO – you talk to them. Using her voice to pacify these wary animals, she has gained unique access to their intimate society and witnessed behaviour that has never been seen before.
BY THE TURGWE RIVER, on the gentle rise of a sandbank, several Nile crocodile bask in the winter sunlight. As I watch, the six-month-old hippo calf I have named Sabi approaches one of them. I assume that, as usual, her intention is simply to nudge the large, lazing reptile out of her way, so that she can claim its prime sunbathing spot. But this time, she has something else on her mind.
I watch in astonishment as Sabi begins licking the crocodile’s spiky hindquarters and tail, her large tongue lapping lovingly at its back, her drool dribbling down its flanks. I’ve never seen anything like this before – and I’ve lived here for 17 years. But it’s not the first time these Zimbabwean hippos have astonished me with their unusual behaviour.
Home for these hippos is a river of braided channels that flow through a landscape of grasslands and extensive mopane tree forests, interspersed by steep, granite kopjes – isolated stone outcrops rising like mountains from the forest. This land is my home, too. I can recognize all the Turgwe hippos individually, and have known many of them from birth – several even to death. Yet they continue to surprise me with their unusual habits, some of which have never been recorded before.
Hippos have a reputation for being the most dangerous large animals in Africa – and it’s justified, believe me. Though they are herbivorous, they can inflict deadly wounds with their formidable lower canines, which can grow to 30-40 cm long in bulls. In my time at urgwe, two people have been killed by hippos. Both of these incidents occurred during the day. Hippos like to spend the daylight hours in quiet backwaters and the shallows of rivers and lakes. As fresh water is Africa’s most precious resource, hippos come into contact with humans more often than most other African mammals. And they don’t take kindly to people intruding in their waters. It’s all too easy to underestimate the speed at which they can launch an attack – I’ve clocked one hippo running at an incredible 35km per hour.
RIVER HORSE WHISPERER
So, how did I find a way to study these animals without scaring them off or provoking an attack? Well, I became a ‘river horse whisperer. Hippos are social and extremely vocal animals, both above and below the water, and this clearly serves to reassure their social group. I found that talking to them in an endless monologue enabled me to observe them closely without affecting their natural behaviour. I could sit just meters away from a wallowing herd and yet they would ignore me, continuing to roll, play or groom while I talked. If a pair was mating and I spoke to them calmly, they continued with their activity. But the moment I stopped speaking, the hippos became aware of me and abandoned what they were doing.There have been times when I have lost my voice through sheer excitement. The extraordinary interaction between Sabi and the crocodile was one of them. Though I have observed Sabi grooming dung off other juvenile and adult hippos before, this was a first. The crocodile stayed perfectly still as Sabi licked its tail thoroughly. When she finally raised her head, long strings of saliva dripped from her gaping jaws.
While it’s extremely rare to see hippos grooming a predator, they frequently attend to fellow pod members, licking each other’s bodies, particularly around the rear, and often paying special attention to the dominant bull. It’s possible that this is a cleaning response.
Males, in particular, spray their dung sideways, flicking their tails to spread the mess around, so their hindquarters often end up spattered. I believe that the scent of the dung on the animal’s rears stimulates a grooming response in other hippos.If a crocodile happens to get in the way – which is almost unavoidable when living in close quarters – it may be splashed with the dung, which presumably stimulates the surrounding hippos to clean it. I would guess that the crocodile endures this attention as it stands to benefit from the process.
DELICIOUS DUNG
Hippos – particularly calves – also eat their own dung, which probably contains important nutrients. The meal usually begins when a youngster surfaces with a clump of fibrous scat in its mouth. It chews, swallows and submerges, reappearing seconds later with another mouthful. The calf’s behaviour seems to encourage the rest of the family to follow suit, and they will submerge and reappear with mouthfuls of dung for up to 30 minutes. It is quite a comical sight, as the hippos look as if they are chewing gum.As well as being a nutritious treat, dung (and presumably urine) also plays a role in marking territory – a bull hippo may defend an area of up to 28 square km. Male hippos can flick their dung quite far and, over time, deposits accumulate on bankside bushes, tree trunks and boulders. Dominant females also spray dung occasionally. Their pungent deposits act as route markers from their patch of river to their favourite grazing areas, and may also serve to warn neighbouring families not to trespass on their turf. At night, hippos leave their watery havens and wander inland in search of grass, their principal food, following trials for up to 6km. They walk with their noses close to the ground, sniffing out the large piles of dung that will lead them to the most productive grazing.
Despite being gregarious by day, hippos prefer to graze alone and disperse widely at night, though mothers and their offspring stick together.
As dawn breaks, the group reconvenes back in the river, escaping the heat of the day by wallowing in the water and mud. During the hot summer months, they spend more time in the water, only leaving to feed for a few hours at night. In winter, the chilly early mornings see the hippos sunbathing on the banks until the water is warm enough for them.FAMILY LIFE
My study group comprises 25 animals. It is lead by an alpha bull and a dominant female, who takes over leadership duties when the male is away. Family sizes vary from one river system to another, according to habitat, and some of my hippo pods have as many as three generations living together.Unlike other mammals, it’s not just male hippos that disperse from the social group as they grow older, females do, too. On the River Turgwe, this usually occurs at five or six years of age, when the youngsters head off to nearby river systems in search of other colonies. Such dispersal guarantees that there are several unrelated females in each hippo pod, and prevents the dominant bull from mating with his own offspring.
Part of the hippos’ charm is the way they fearlessly defend their families and their territories. But, remarkably, they also intervene on behalf of other animals. One day, I was settled in my normal riverside spot, watching the hippos sleeping in a big heap on the bank, when a flash of movement on the opposite side caught my attention. A dainty bushbuck doe was approaching the water at a hippo exit point, a spot where deep furrows have been worn into the bank by the pod’s constant comings and goings.
As the doe reached the edge and lowered her head to drink, a crocodile exploded from the river, grabbed her and dragged her under. Minutes later, the croc resurfaced with the doe’s lifeless body clamped in its jaws. But before the predator could consume its prize, a sub-adult female hippo named Cheeky reacted in a startling manner.
Extracting herself from her slumbering family, Cheeky raced towards the crocodile. After a brief tussle under water, she somehow managed to steal the bushbuck from its captor, carrying its body close to where I sat, frozen. She began to gently mouth the carcass, but did not draw blood or damage its flesh.
The crocodile had no intention of relinquishing its prize and, taking the hippo by surprise, grabbed hold of the doe. A short tug-of-war ensued before the reptile reclaimed the carcass and quickly swam off upstream, with Cheeky and half of her pod in hot pursuit. The crocodile tucked itself into a rocky backwater, and though the hippos tried to follow, the space was just too narrow for their bulk. Reluctantly, they gave up.
Since then, I have observed several other instances of hippos intervening in crocodile hunts, and their actions often save the lives of the animals under attack. Some of the most spectacular battles have involved vervet monkeys, which have a habit of dangling precariously from overhanging riverbank vegetation to feed. I recently witnessed a croc launch itself from the water at a young monkey, missing it by millimeters. Seconds later, two hippos charged the crocodile, forcing it to beat a hasty retreat.
GUARDIANS OF THE RIVER?
So why do hippos intervene in this way? They appear to know what lives alongside them in the water and anything new pricks their curiosity – they simply have to investigate. I have watched hippos pursue a floating carcass, mouth it, then discard it. Perhaps they consider themselves the guardians of the River Turgwe.I too, am an object of the hippos’ curiosity, and a recent event made me feel that they may have come to accept me as part of their pod. Following unusually heavy rainfall, the Turgwe was dark brown and murky with silt. The family was doing what hippos do best: Sleeping in the shallows. Some were semi-submerged, their heads rising automatically to take a breath of air, then, eyes and nostrils closed, they’d sink below the water again. I couldn’t see the dominant bull and one female calf, so I assumed that they were hidden in the reeds. I stood just a metre from the river, talking to the family in my usual relaxing fashion.
Suddenly, the grass rustled behind me. I turned, expecting to see a bushbuck or something equally harmless, but instead found myself face to face with a two-tonne bull hippo. It was Robin, accompanied by Tsakus, the calf. They were just a couple of metres away, staring at me. This same bull had charged me on numerous occasions in the early years, leaving me stranded up trees.
“I’m dead!” I thought.Instinct took over and I leapt into the river. But submerged rocks snagged me and I floundered, scrambling, going nowhere fast. Glancing up at my pursuers, I saw, to my utter astonishment, that Robin hadn’t moved. He stood, watching me curiously, showing no sign of his usual malice. Then, moving very slowly, he entered the river at the exact spot I had just vacated, with Tsakus following close behind. I was so near Robin I could see each individual hair on his thick, callused hide and his horse-like scent filled my nostrils.
Quietly, he rejoined his family and I realized that my years of talking to these extraordinary hippos had probably just saved my life.
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