'When he was shot dead in 1993,, most of the animals were shipped away, but four hippos were left to fend for themselves in a pond.
Although nobody knows exactly how many there are, estimates put the total number between 80 and 100, making them the largest invasive species on the planet. Scientists forecast that the number of hippos will swell to almost 1,500 by 2040. They conclude, that at that point, environmental impacts will be irreversible and numbers impossible to control.
"Nobody likes the idea of shooting a hippo, but we have to accept that no other strategy is going to work," [...]
Environmentalists have been trying to sterilise the hippos for years [...] Male hippos have retractable testes and females' reproductive organs are even harder to find, according to scientists. "We didn't understand the female anatomy," said David Echeverri Lopez, a government environmentalist. "We tried to sterilise females on several occasions and were always unsuccessful."
He is also playing an impossible game of catch-up. Mr Echeverri told The Telegraph that he is able to castrate roughly a hippo per year, whereas scientists estimate that the population grows by 10 percent annually. [...]
"Relocation might have been possible 30 years ago, when there were only four hippos," said Dr Castelblanco-Martínez. "Castration could also have been effective if officials had provided sufficient resources for the programme early on, but a cull is now the only option."