NAIVASHA, KenyaIn May, George Mwaura went fishing with his close friend Babu along the swampy shores of Lake Naivasha, in central Kenya. “Babu was a quiet guy, a nice guy,” Mwaura recalled. “He’s the one who taught me patience. And he was quite good at fishing.”
They couldn’t afford a boat, so they’d wade into the water up to their chests to see what fish—tilapia, carp, catfish—had swum into their nets overnight. “We had a lucky catch that day,” Mwaura said. “But before we got the full catch, the hippo came again.”
They’d seen it that morning, its ears and eyes poking above the surface. “We beat the water with a stick to make noise, so the hippo went away,” he said.
The friends were too focused on their fish to notice when it returned. “Babu always told me hippos are dangerous animals,” Mwaura said. Hippos had attacked Babu four times, but he had always managed to escape. “But the fifth one—he did not make it.”
The hippo lunged first at Mwaura, who was able to dart away because he knew how to swim. Then it lunged for Babu, who couldn’t swim. The hippo’s enormous jaw clamped down on him. Its lower two teeth pierced his back—once, twice, a third time. Dozens of fishermen raced to the water’s edge, but when a hippo takes a human, there’s nothing anyone can do.
When the attack was over, the other fishermen waded in to retrieve Babu, but he was already dead. “It is so sad seeing your best friend’s dying day,” Mwaura said. A few days later, Mwaura returned to the lake to fish.
By some estimates, about 40 people—mostly fishermen—were attacked by hippos on Lake Naivasha in 2020, and as many as 14 of them died. Every year across Africa, hippos kill an estimated 500 people, making them the world’s deadliest mammal, after humans, and nearly twice as deadly as lions. Hippopotamuses are herbivories and rarely bother other animals. But males can become aggressive if they sense danger. Mothers may attack to protect their young. And nearly all hippos become nervous when something—or someone—stands between them and the water where they live.
The second-largest land mammals on Earth, hippos usually appear docile, but they have the ability to become deadly. Although they can weigh up to four tons, they can run up to 20 miles per hour. Their jaws can open to 180 degrees, clamp down with a force 10 times that of human jaws, and their lower canines can grow to more than one and a half feet long. And they can be hard to spot since they can hold their breath under water for up to five minutes.
Despite the dangers posed by hippos, the extent of the tragedy unfolding at Lake Naivasha is unusual, stemming from two extraordinary events that changed how humans and hippos interact.
Heavy rains that began in October 2019 caused Lake Naivasha to swell to its largest size in nearly a century, flooding the land upon which hundreds of hippos had grazed. With the water pushing up against the fences of farms and homes that surround the lake, they’re now forced to mill about at the same shallow edge where fishermen like Mwaura and Babu cast their nets.
And the number of fishermen—once in the dozens, perhaps a few hundred at most—swelled into the thousands after the global economic crisis caused by the COVID-19 pandemic hit the region. Kenya is the fourth-largest flower exporter in the world, but when the pandemic hit, Europeans stopped buying them. Thousands of flower workers around Lake Naivasha were let go. With few other sources of income, many turned to fishing.
Naivasha has long been a place where humans and wildlife converge. On the lake’s eastern edge lies a peninsula whose name, Crescent Island, was a misnomer until the recent flooding submerged the narrow strip of land that connects it to the mainland.
Tourists access the site by boat, then wander on foot to photograph giraffes and buffalo, gazelles and impalas, vervet monkeys and sometimes hyenas—all of which are now stranded because of the lake’s rise. Meanwhile, hundreds, maybe thousands, of hippos bathe near the shore, pressed up against the submerged fences of the now-flooded flower farms, homes, and tourist cabins.
The result is a deadly mix: humans and hippos competing over a thin strip of territory. Nature is reclaiming Naivasha, and the result has led to dangerous melees—ones that humans do not win.
With most work in the area tied to the lake, there’s no clear solution in sight. Ruth Mumbi lost her husband when a hippo overturned his fishing boat four years ago. The family’s sole income earner, he left behind four children, one of whom now spends his days mending fishing nets. “If it was up to me, I wouldn’t allow my children to work on the lake,” Mumbi said. “But because I don’t have much money and there’s nothing else to do, if that’s what they want to do, then I’ll just have to accept it.”
A rift in the valley
Lake Naivasha is what scientists call an “amplifier lake” because it shrinks and swells quickly, along with the rains. “When there’s a change in the climate, they will show that—changes in lake level, salinity,” said Lydia Olaka, a professor of environmental geology and climate science at the University of Nairobi.
Covering some 70 square miles during normal times, Lake Naivasha’s surface is more than three times the size of Manhattan, but a mere 60 feet deep at most. It’s fed by three rivers as well as runoff from the surrounding land. The lake has no outlet. Each year, about six feet of water evaporates from its surface into the sunny sky. A decade ago, after a series of droughts, residents feared the lake might disappear, taking an entire ecosystem and the tourism industry down with it.
But in late 2019, Lake Naivasha’s basin received three times its usual rainfall—the result of a phenomenon thousands of miles east, called the Indian Ocean Dipole. It occurs when the surface waters of the ocean beyond Africa’s east coast turn unusually warm, as waters near Asia turn cool. (Read more: The Indian Ocean Dipole also contributed to the plague of locusts in East Africa in 2020.)
The 2020 rainy seasons were also wetter than usual. More rainfall brought increased cloud cover, reducing evaporation from the lake. Part of the lake’s rise also is manmade—the result of decades of deforestation in the lake’s basin, which has increased the amount of runoff that reaches the lake. Naivasha is not alone. A four-hour drive north of Naivasha in Kenya’s Great Rift Valley, Lake Bogoria and Lake Baringo have flooded, displacing thousands of people and countless wildlife.
The disappearance of dry land for the hippos to graze upon is due not only to Lake Naivasha’s rising waters, which have climbed 12 vertical feet, but also to illegal human encroachment on the protected riparian boundary. People built houses, tourist cabins, and even greenhouses on this land, but now many of these structures are underwater. The lakeside town of Kihoto, for example, drowned last year. Today, walls of concrete blocks jut up above the dark waters. Several miles west, the curved tops of flooded greenhouses mark where flower farms have been swallowed.
If the lake keeps growing, more buildings will submerge. Yet recently, Kenya’s Water Resources Authority considered allowing people to settle even closer.
“We are living through very unprecedented times,” Olaka said, noting that climate models project more rain to come and that Lake Naivasha’s larger size “could be a new normal.”
Naivasha’s commercial fishing industry began by accident, decades ago, when a torrent of rain flooded a fish farm upstream on the Malewa River. A trove of common carp escaped into the lake, where they ate up most the crayfish and ravished the eggs of the tilapia, black bass, and other species prized by sport fishers.
The carp multiplied, and fishing became a livelihood. When Lake Naivasha suddenly expanded in 2019, it seemed at first like a boon to the fishing industry. Fish bred in the rich, untouched soil of newly inundated riparian land. They grew into thousands of pounds of fresh food—more fish than anyone can remember.
“All of the activities—tourism, pastoralists, floriculture—they all depend on Lake Naivasha,” said David Kilo, chairman of the Naivasha Boat Owners Association. Before COVID-19 arrived, there were 180 licensed fishing boats on the lake—already as many as the lake’s ecosystem could sustainably handle. Now, on the southwestern shore, Karagita boat landing is overrun each morning with fishermen unloading their catches.
In town, women weave long strands of string into fishing nets, which they sell for 1,000 shillings ($9). Teenage boys are paid pennies to repair old nets that have been tangled or cut by a propeller. And each day, tourists arrive at the landing and hire boat captains to take them on hippo tours.
Early one morning, a captain named Douglas Mokano puttered toward a pod of hippos. “They’re sleeping now,” he said. Pointing to a hippo whose head and back broke the water’s surface, he said, “This one’s the baby.” It was the size of a full-grown cow. (Watch: Is this hippo in Botswana grieving the loss of her baby?)
The hippos nestle their giant heads against each other’s backs. Despite their girth, they manage to squeeze together so tightly that a pod of five hippos looks like a single blob of grey and pink flesh. It’s impossible to tell where one hippo ends and the next begins. Mokano revs the motor, trying to agitate them so they’ll lift their magnificent heads above the surface. The hippos can’t be bothered.
“You can’t allow everybody to fish. It will affect the ecosystem of the lake,” Kilo said. And yet, that’s what has happened since COVID-19 arrived.
Kenya Wildlife Service has been unable or unwilling to put a stop to the illegal fishing. The agency did not respond to repeated requests for comment.
Volunteers from the Naivasha Fishermen’s Association have helped the rangers conduct night patrols, with spotlights scanning for illegal fishers. One night when they tried to arrest a group of fishermen, the fishermen fought back. They tied up the rangers, overturned their boat, and set it on fire, stranding the rangers until they could be rescued.
These days, “they rarely patrol,” Kilo said.
Scientists estimate that between 29 and 87 percent of hippo attacks are fatal. You’d have a better chance of surviving a shark attack, a crocodile encounter—and magnitudes better odds at surviving a grizzly bear attack. Though hippos are herbivores, when grass is hard to come by, on rare occasions they have been known to eat other animals—even deceased hippos.
Kilo has witnessed or investigated eight attacks in which fishermen died. Attacks have become so common that he has transformed his car into a makeshift rescue vehicle, removing the back seats so victims can be loaded easily and laying down plastic to catch the blood. “My vehicle, it looks like an ambulance,” Kilo said. “If people see my vehicle reversing, they say—there’s a hippo attack!”
But Kilo is no EMT. He doesn’t know how to apply tourniquets or pack wounds, interventions that are crucial for saving a victim’s life, according to George Wabomba, a doctor at Naivasha County Referral Hospital. Wabomba treats an average of one or two hippo victims each week. “When you mention there’s a hippo victim, everyone is anxious in the hospital,” he said. “You never know what you’re going to get.”
Hippos can trample victims or drag them. “Sometimes it’s just a bite, and the hippo lets go. But you also get lots of abdominal injuries,” Wabomba said, adding that lacerations may be filled with soil and grass. “We don’t know what’s in a hippo’s mouth, what’s in the water.”
Such injuries require immediate attention, Wabomba said, but often victims don’t arrive for hours. Fishermen have to wait until it’s safe to retrieve the victim—when the hippo moves away—then transport the injured man to the hospital. The closest hospital is only five miles from Karagita, but it’s 24 miles along rough roads from the far side of the lake. (Related: Delayed treatment and antivenom shortages put tens of thousands in Africa at risk of dying from snakebites.)
Wabomba estimates that 40 percent of the hippo victims he sees ultimately die. He recalled a 35-year-old fisherman he treated last year who was attacked before sunrise as he was placing his nets but didn’t get to the hospital until noon. “Some of his bowels were sticking out,” Wabomba said. “We repaired what could be repaired. This is what we call damage-control surgery.”
“We couldn’t save him,” he said. Less than a half-hour after the surgery, he died.
Cull the hippos?
The only solution to Naivasha’s standoff is “to work things around hippo behavior,” said Richard Hartley, who manages two conservation areas around the lake. Driving his Land Cruiser across one of them on a recent afternoon, he stopped to watch a lone hippo resting in a shallow pool of mud. “He’s a maturing male who’s looking for females, and the old bulls don’t want him around,” Hartley said.
Signs reading “Danger” warn tourists not to go out walking at night. But jump in a Land Cruiser, turn on your brights, and you’re sure to spot the silhouettes of hippos grazing in the grasslands. Sometimes they stare at you, caught in the headlights. But usually they trot away, showing you only their pink behinds as their tiny tails wag frantically.
Since the lake’s rise, partially submerged trees topple daily with a splash as their roots are dislodged. Fishermen have taken to casting lines from these trunks, their legs dangling just feet above the heads of hippos. Periodically the hippos grunt, reminding the fishermen that danger is only a slip away.
“You have fishermen who quite honestly don’t seem to feel any fear whatsoever. They will park themselves literally feet away—and they get it wrong,” Hartley said. “There’s a mama with a calf, or there is an aggressive male hippo that’s going to go for you or your boat. And you don’t see them coming because they’re submerged—and they come fast.”
When a particular hippo is believed to have attacked multiple times, fishermen sometimes ask rangers to kill it. “There’s so much community pressure for that animal to be destroyed. And yet it’s almost never the hippo’s fault,” Hartley said. He said one ranger tasked with the job sometimes shoots to miss on purpose, saving the hippo’s life. As more and more fishermen take to the lake, some have called for the hippos to be culled, to decrease their numbers.
Naivasha’s last thorough hippo census was conducted in the 1990s. It estimated that there were 1,250 hippos. Last year, according to Kilo, the Kenya Wildlife Service estimated the number was closer to 700. Hippos are notoriously difficult to count, spending their days underwater in pods, often with only their eyes and ears above the water. Kilo and Hartley say that, while there is some poaching, there’s no reason to believe the hippo population has decreased that drastically. (Learn more: Poaching for hippo teeth has led to declines in Uganda and Tanzania.)
Culling is sometimes considered when a habitat can no longer support the number of animals living on it—when the population exceeds the supply of grass needed to feed them, said Hartley. If the lake continues to swallow more grassland, he says wildlife rangers might consider culling the hippos rather than let dozens starve to death. That would be an international embarrassment for Kenya, a nation known for its wildlife, Hartley says. “Culling would be admitting defeat. Culling would be saying we no longer care about the wildlife.”
“At times I don’t feel like myself”
Standing by the lake, Meshack Ogjah limped toward the swampy shore. He pointed to a small area of open water, surrounded by water hyacinth and fallen trees. He said that one evening at dusk he was working in the dark water when a hippo brushed his left side.
He knew the dangers of fishing in a hippo-infested lake. “There was a friend of ours who was attacked—and he didn’t know how to swim,” Ogjah said. The hippo bit him at least twice. He did not survive. Still, Ogjah kept fishing. “It’s only when you feel it yourself that you understand,” he said.
Ogjah was diving into murky water to place a fish trap made of plastic netting when the hippo grazed him. “It started touching me, its belly to my thigh,” he recalled. “I moved to the surface so I could see its movement. Then I started to swim—but it chased me.”
He screamed for help, but there was nothing other fishermen could do. He dived down, hoping the hippo wouldn’t see him. When he reached the shallows, “it saw me well,” said Ogjah—and took a bite.
The hippo’s teeth were “six inches long—and thick,” he said. They pierced his right thigh, and his blood colored the water. “I was feeling like my heart wasn’t there.”
Ogjah managed to escape. Another fisherman hoisted him onto a motorcycle and drove him to the hospital. Doctors cleaned the wound and sewed it shut. Ogjah was lucky to survive. Even so, he says a part of him is missing. “At times I don’t feel like myself. It’s torture,” said Ogjah, who now struggles to walk. “I still have a long way to go.”
Asked whether he blames the hippo—whether he thinks the government should cull the hippos—Ogjah’s friend Wycliffe Injindi, who saw the attack from shore, interjects. Could you burn all the vehicles just because one had an accident?” Injindi said. “Hippos in Kenya, we are very lucky—other countries have no hippos.”
The solution, he says, is for humans to learn to live with them—to fish more safely from a boat, rather than wading into a murky lake. “Killing the hippos—no, that is not fair.”
Ogjah and Injindi both shake their heads no when asked if they will return to fishing. “I cannot go back into the water,” Injindi said. “That was a terrible day.”