Hooray for hippos
Like many large mammals in Africa, hippos are in trouble because of loss of habitat, climate change, illegal trade in wildlife body parts and human conflict.
An estimation of hippo populations, according to the IUCN red list, indicates a 7-20% overall decline in the last decade alone. And the most significant population decline has occurred in the Democratic Republic of Congo, which is a country that was once believed to boast some of the largest hippo populations in Africa. At the moment hippos are listed as ‘Vulnerable’, but at this current rate of decline, this could change quite rapidly.
A recent assessment suggests that only between 125,000 and 148,000 common hippos remain in 29 countries across the entire continent, which places the hippo population in Africa at approximately a quarter of the overall elephant population.
And it doesn’t just stop there, as their smaller West African cousin – the pygmy hippo – is also under threat, and has been classified as an endangered species by the Zoological Society of London. Half the height and weighing less than a quarter of an adult hippopotamus, it has been estimated that there are only around 2,000 pygmy hippos left in the wild, with numbers declining as their habitat is destroyed and they are hunted for bushmeat.
Taking these figures into consideration, it is clear that it is time for a greater focus on hippos – a significant player in the African ecosystem.
A BAD REPUTATION
Hippos are often considered to be aggressive and dangerous and have been given the reputation of killing more humans in Africa than any other mammal.
However, they’re not quite the violent creatures that they’re made out to be, and their reputation is not wholly fair.
Where there is water, there are usually people who rely on this critical life source. And as hippos spend at least 14 hours of the day in the water, this means that there is a lot more opportunity for humans to run into hippos compared to other predators.
Hippos typically remain unobtrusive, especially during the day when adults usually sleep and digest the 45 kilogrammes of fodder that they consume during the night. They usually leave the water at dusk to graze and, in times of low rainfall, they move further from their water habitat to feed, before returning to their regular pools approximately an hour before dawn. But it is during these nightly forages that people, such as early-rising fishermen, may bump into hippos – leading to problems.
Hippos have 36 teeth in their cavernous jaws, and the two lower canines in an adult bull can reach up to a metre in length when measured from inside the gum to the tip. If a disturbed hippo attacks a human, it will typically bite twice and then move off. Those bites can prove fatal, even if they are not intended to be so.
Hippos are herbivores, although they have been known to eat meat on occasion. When they kill humans, it is a defensive act and not to eat them. One suggested reason for the hippos reputation for being a leading human-killer is that they leave the dead body behind as evidence, compared to crocodiles which eat what they kill.
RIVER DOCTORS AND ECOSYSTEM ENGINEERS
Hippos play a vital role in our ecosystems, as they benefit the ecology of rivers and dams. They spend long hours in the water digesting their meals and depositing dung that is filled with nutrients that benefit the other inhabitants of the river – namely the fish, insects and terrapins.
Mzima Springs in Kenya is a case in point. These are crystal-clear natural springs, which are naturally lacking any nutrients as the water is filtered through volcanic lava. But luckily, over 60 hippos give life to the springs. They pump hundreds of kilogrammes of dung back into the water every day, which in turn lays the foundation for other lifeforms to thrive. On land, hippos deposit compost heaps of dung, which acts as a natural fertiliser for plants. Snails and insects feed on the dung, then are eaten by birds and smaller mammals, which are in turn eaten by crocodiles and other larger predators. And so the cycles repeat themselves, as nature intended.
Hippos also create regularly used paths that slope into the river. When the rains come, the mud and dirt wash into the catchment, and more nutrients end up in the waters, again benefiting fish and water-based insects.
Furthermore, they help to maintain ecosystems by cropping grass to a very short height when they graze. As a result, they act as nature’s firemen, creating fire breaks in the reed beds and grassy areas – preventing annual fires from obliterating all the vegetation.
The hippo’s large size and continuous movements also help to open up thickly reeded sections in rivers and wetlands, which allows the channels to flow better.
This is best illustrated as you fly over Botswana’s Okavango Delta, where the hippo (and elephant) paths create channels for the annual floodwaters from the Angolan highlands to spread far and wide. If it were not for these two ecosystem engineers, many floodplains would shrink in size as channels silt up and don’t permit water to flow.
So from composting to fire prevention and ecosystem engineering, it is clear that hippos play many essential roles in naturally-functioning ecosystems.
MOTHERS AND BABIES
Most females – no matter what the species – are very protective of their young, but when the female in question weighs about 1,500 kilogrammes and has lower incisors and canines that can bite a crocodile in half, then a predator should be wary of messing with them!
Mother hippos leave their pod about a week before giving birth, finding a quiet, shallow river channel in which to bring their offspring into the world. For the first 10 to 14 days of their calf’s life, they remain alone together – ensuring valuable imprinting.
Once the pair return to their pod, no other hippo makes contact with the calf until it is around three and a half weeks old. Then the mother will introduce it to the dominant bull. Once the bull has sniffed and recognised the calf, younger members of the family are then allowed physical contact – sniffing and moving closer to the baby. But they are only permitted interaction with the calf once it reaches around five weeks of age. This is the time when playing and touching starts to become important, and older calves will play open-mouthed, gaping games with the youngster. But if the play becomes too boisterous, the mother will move the older calves away, keeping her new baby close to her side.
Usually, a young hippo is so well protected that nothing will attempt to attack it, but one fact that many people do not know is that when the calf is around five to six weeks of age, it is very typical for the mother to leave the calf tucked under reeds in a river channel or alone on a sandbank for many hours. This is because she may be back on heat and does not want her newborn to get in the way of mating opportunities. The hippo calf is sometimes mistakenly seen as an orphan, but its mother has deliberately left it out of harm’s way.
Due to its size, a hippo doesn’t have many enemies, but once a hippo calf has been fully weaned and is on its own, it may come up against its main predator – the lion. And if a hippo does meet an untimely end, it has recently been discovered that other hippos will mourn its death. A dead hippo will be visited by a relative who will proceed to mouth the dead animal and, if the body is found on land, this can continue for some days. If a calf dies in the water, then often the mother will carry it in her mouth or try to drag it along with her for some time. I have also watched footage from trail cameras of hippos doing this with other dead mammals too; licking or nuzzling the body for some time before moving away.
Hippos have even been known to ‘rescue’ other animals that have been hunted and ended up in their water home. They have been filmed helping wildebeest calves or weakened animals during the time of the Great Migration in East Africa when numbers of wildebeest and zebra cross the main rivers. And they have been seen to push or even carry animals to shore in their mouths.
Having studied individual hippos from birth for the last two decades, I believe they should be renamed the ‘Guardians of the River’. This is because I have watched hippos intervene and often help other animals. I have watched them chase away crocodiles that have caught an antelope or even chase crocodiles that were stalking and feeding on thousands of quelea drinking at the river’s edge.
I have witnessed hippos moving in quickly to save the day, removing prey from a crocodile’s jaws, then carrying the targeted creature in their mouth to safety on the riverbank. I have even seen a hippo wait to see if the animal is dead or alive, and I have watched a hippo remain with a dead body for up to 15 minutes.
HIPPOS AND CROCODILES
Hippos groom each other. One hippo will lick another on their hindquarter for up to 15 minutes, and at the end, they always gape, with saliva dripping from their mouths. But what you may not know is that hippos also groom crocodiles in the same way.
They start by approaching a sleeping croc on a sandbank, then they proceed to lick at its tail area, often actually chewing the tail. The crocodile tends to lay still for up to 15 minutes and then the hippo gapes and moves off.
Hippo calves also have been known to play with crocodiles, often chewing at their tails or sometimes even putting the whole side of a tail into their mouth. When the crocodile starts to move away, the hippo will often follow; nudging and mouthing the tail. But the crocodile will tend not to react aggressively – it will either cooperate or slowly move its tail and vacate the area.
Hippos ideally live in family groups of up to 15 individuals. Higher group numbers occur because of pressure on resources – such as during the dry season and droughts – when family groups have to share shrinking habitat with more with their own kind.
A family will typically have a stake along the river channel during the rains. A pod usually consists of a mature bull, related females and their offspring. Young males, when not in an overcrowded area, will have to leave the family when about two-and-a-half years old, after being chased out by their mothers.
Female juveniles, on the other hand, generally remain with the pod for life or until they need to mate with an unrelated male. After conceiving, they then often return to their own family.
As it is unusual for there to be more than one male over the age of three in a family, there is a lead cow who plays a dominant role, especially if the bull moves away for a day or so. The lead female is not always the oldest but is often the most assertive of the females.
A young female will give birth roughly every two to three years, whereas an older cow produces a calf every five to six years. This means that the average female hippo can have approximately ten calves in her lifetime – the firstborn when she is around five years old, and the last born when she is in her forties.
On average, a hippo in the wild can live up to 45 years under favourable conditions. Although hippos pull up the grass that they feed on with their lips, they require their back molars to crush the grass before swallowing. Once these molars have worn down, they will starve to death.
PRETTY IN PINK
In the past, it was widely thought that hippos sweated blood and that this was responsible for their pink tinge. However, scientists have realised that what hippos secrete is a red gel, and this is particularly the case in times of stress.
I have seen it happen every year when the river is flooded and the hippos are subjected to deep and rough water. Often I find them out of the torrent in smaller streams adjacent to their usual areas, and their heads tend to have a reddish hue.
Others have witnessed hippos secreting this pink liquid in times of intense heat when they are on land, as it is said to act as a sunscreen. Their hides are not very thick, which means that they can quickly burn if the heat is excessive and when water levels are low, and they cannot fully submerge. But thanks to this layer of sweat, there is a degree of inbuilt protection from the sun’s harsh rays.
However, this secretion is not the reason for the rare pink hippo seen above. Instead, these hippos are believed to have a form of leucism – a condition characterised by reduced skin pigmentation, which differs from albinism as pigment remains in the eyes. Pink hippos with this condition have been sighted in Uganda, the Maasai Mara in Kenya and South Luangwa in Zambia. Usually, leucistic animals do not survive long in the wild as they are more visible to predators and can suffer from severe sunburn. But thanks to the hippo’s size, even the leucistic among them are rarely attacked by predators, and luckily their pink sweat still acts as a sunscreen for their pink bodies.
Various suppositions surround whether the hippo swims or instead floats on the water. But after 25 years of studying hippos, I believe the answer is that they do neither.
Adult hippos can hold their breath underwater for up to five minutes. In that time the animal sinks to the bottom of a river or dam, as long as it is not too deep, and walk or even race along the bottom. We have clocked hippos running on land alongside our vehicle at a speed of 35km/hour, so I am sure that they can run underwater at the speed of at least 8km/hour.
Often the hippo will push itself up from its position at the bottom, resurface to breathe and then go down again. So from above the water, it may appear that the hippo is swimming when it is propelling itself, sometimes at speed, along the river floor.
In my opinion, they do not float either unless they are dead, and even then they will eventually sink. Hippos may sit quietly on the river bottom, then pushes itself back up to the surface with some part of its body supporting it at an angle, which makes it appear as if it is floating.
HOW TO HELP HIPPOS
One of the main things that will help to save this species is to reduce human-hippo conflict. No form of antagonism or aggression should ever be employed when facing a hippo, and they should be given a reasonable berth by all boats. So long as their space is respected, hippos can be as calm as a domestic cow, and everyone can live in harmony.
However, not many people in Africa have the good fortune of going on a safari, so they do not always understand how animals can benefit them and future generations. It is crucial, therefore, that education starts at a grass-roots level in local communities. If villagers realise, for example, how hippos can help to create an abundance of fish in areas where they are left alone, perhaps this will change some of their feelings towards them. It is also essential that farmers understand that hippos are selective grazers, which means that they do not necessarily compete with cattle, as cattle eat types of grass that a hippo will not eat.
If hippos are causing problems concerning crops or homesteads, people should be educated to understand that there are ways of preventing this. For example, constructing narrow ditches around crops, so that a hippo cannot reach them, is a way to protect harvests and avoid problems.
ABOUT THE AUTHOR
Karen Paolillo was born in England and was genetically dispositioned to love animals – her father was a vet, and her mother was the manager of a small zoo in Bedfordshire.
As an adult, Karen’s dream to move to Africa to live and work with wild animals became a reality, and she ended up in Zimbabwe. She was the first woman to obtain the National Parks Professional Guide’s licence, which gave her the chance to lead tourists around the Gonarezhou National Park and the south-east Lowveld of Zimbabwe.
Once married, she moved to Holland with her French geologist husband, before moving to Gabon in West Africa, then eventually returning to Zimbabwe in 1990. Interestingly, she ended up back exactly where she started – the south-east Lowveld.
Then, one day, they were camping above the Turgwe River during the worst drought in the history of the area. It was then a cattle ranching and game area, and Karen asked the landowners if she could somehow help the Turgwe hippos. The owner was feeding his rhinos, but could not also afford to help the other wildlife, and so Karen took it upon herself to raise enough funds, with the help of the British animal charity, Care for the Wild, to feed the last Turgwe hippos in their natural habitat. This was something that had never been done on a long-term basis before.
The couple also designed and built a cemented pan that was large enough to sustain those hippos when the entire Turgwe River system dried up. They installed a 19-kilometre pipeline to their neighbours’ boreholes to pump water into this cemented pan. As a result, every hippo that she fed survived, and two even managed to conceive. And so began the Turgwe Hippo Trust, which has continued since that time to take care of the hippos in the region.
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