Colombia’s invasive hippo population is even higher than researchers thought, according to the most thorough hippo census ever conducted. Scientists are already concerned that hippos, thought to be the world’s largest invasive species, are threatening native plants and animals, and are calling for drastic measures to reduce their numbers. rice field. The census results only heightened that fear.
A few years ago, researchers estimated the breeding rate of the animals and predicted that by 2020 there would be about 98 hippos along the country’s Magdalena River and its tributaries. However, in the current study, in which the researchers directly counted the animals, using drones and other tracking methods, it is estimated that between 181 and 215 of them live in Colombia.
Rafael Moreno, an ecologist who participated in the study while at the Alexander von Humboldt Institute of Biological Resources in Bogotá, said: and our arguments were theoretical,” he said. “But we have shelved that debate. This study shows that this is a real problem and that states must act urgently.”
by drone and on foot
All of Colombia’s “cocaine hippos” are descended from three females and one male illegally imported by drug cartel leader Pablo Escobar. After he died in 1993, Hippo (hippopotamus amphibius) fled from their territory and settled on the Magdalena River. Unable to defend against natural enemies and drought in their African homeland, giant herbivores multiplied rapidly to form the largest animal population outside the African continent.
Colombian authorities are struggling to control hippos. After ordering the killing of an aggressive man in 2009, a photo of a soldier posing with his corpse sparked outrage, and the crackdown effort was called off. Some communities now rely on the tourism that hippos provide, while others, especially fishing communities, survive. Fear of territorial animals that can weigh up to 3 tons and can rip off or trample on people’s limbs.
Colombia’s Ministry of Environment commissioned a census to better understand the problem and how to address it. Despite their large size, hippos were difficult to locate and count accurately. They are nocturnal, staying in water for 16 hours a day and roaming long distances.
A team of researchers from the National University of Colombia in Bogota, the Humboldt Institute and the environmental group Cornare, which manages the hippo habitat, is aiming to count hippos by car, boat and on foot in 2021 and 2022. I have made various trips. Drones were used to count animals in places where animals couldn’t be safely approached, and footprints were used to estimate population numbers.
Researchers found 37% to be juveniles, indicating that the animals are breeding rapidly. One hypothesis is that Columbia’s lush environment allows hippos to reach sexual maturity earlier than in Africa. Another is that the animals are breeding better because they fight less over territory and resources, Moreno said. But we need evidence to confirm the actual cause.
While counting hippos, the research team documented the myriad ways hippos are harming Colombia’s ecosystems. Hippos waddle up and down the river, carving out the muddy trails that erode the riverbanks and divide the forest. In addition, it competes with other animals for habitat and resources, and the West Indian manatee (Trikex manatee), neotropical otters (long-tailed otter) and capybara (Hydrocoelus hydrocaeris) are the most threatened.
Seeking a solution
With serious attacks on humans in 2020 and 2021 and a car crash that killed a hippopotamus on a highway in April, scientists say a solution is needed.
One strategy currently being tried is to administer contraceptives to animals via darts. While this might stop the hippos from breeding and eventually kill them, it would be time-consuming, costly, and no experiments on such large-scale hippos have been done before. A modeling study published in April estimated that the method would cost at least $850,000 and could eradicate the hippopotamus within 45 years.
An alternative strategy — capturing hippos, anesthetizing them, and transporting them by helicopter to a neutering facility — would cost at least $530,000 and take up to 52 years to eradicate, the study found. Both calculations are underestimated given that the model was given a lower estimate of the hippopotamus population before the census results were published.
Meanwhile, regional agencies tasked with responding to hippos are cash-strapped and rely on donations of contraceptives from the United States. Agency officials are negotiating with countries such as India and Mexico to export some of the animals to overseas sanctuaries. But it will cost $3.5 million, according to people working on the strategy.
Olga Montenegro, a national university biologist who worked on the census, says there is no single best solution. Hippos live in different groups, some easily migrating, others firmly established and breeding rapidly.
Many researchers advocate culling animals. They argue that it would be the quickest and most humane action and would solve the problem before it became impossible to fix. The cost of killing hippos must be weighed against the loss of native flora and fauna in Colombia, the second most biodiverse country in the world, they added.
Nature The environment ministry declined to comment when asked how it would manage the growing hippopotamus population in light of the new findings.
“The decision to kill the hippos carries moral weight, but the other decision, which is to do nothing, carries much more weight,” says Moreno. “I hope politicians understand this.”
This article is reprinted with permission and was first published on June 2, 2023.