Drug lord Pablo Escobar's hippos have become the first animals to be legally recognised as "people" by a US court.
In a legal case brought by the "community of hippopotamuses living in the Magdalena River", the plaintiffs were accepted as "persons of interest".
Escobar became one of the richest men in the world during the Eighties due to his drug trafficking empire, and purchased a variety of exotic animals for his Hacienda Napoles ranch in Colombia.
After he was shot dead by police in 1993, giraffes, zebras and flamingos were sent off to zoos but four giant hippos - one male and three female - were allowed to remain in a pond.
The so-called "cocaine hippos" have since multiplied to up to 100, the largest herd outside Africa, and could reach 1,500 by 2040.
They are destroying the local ecosystem, have become an increasing menace, and are responsible for attacks on local fishermen.
Last week, the Colombian government announced it had sterilised 24 of them. Wildlife officials used darts containing a contraceptive medicine called GonaCon, which reportedly requires three doses.
The Animal Legal Defense Fund [ALDF], a US charity, has argued for the use instead of another contraceptive called PZP, which it says has "historical success" with hippos in captivity.
There is an ongoing court case in Colombia, in which the hippos are the plaintiffs.
Colombia accepts that animals have the right to bring cases to protect their interests.
The ALDF wants to bring evidence on the hippos' behalf from two experts in nonsurgical animal sterilisation, but the experts are based in Ohio in the US.
Under US law an “interested person” in a foreign legal case can apply to an American court to take depositions from experts. The ALDF applied to the US District Court for the Southern District of Ohio, which accepted the request.
A spokesman for the animal charity said: "In granting the application the court recognised the hippos as legal persons."
Stephen Wells, ALDF executive director, said: "The court’s order authorising the hippos to exercise their legal right to obtain information in the United States is a critical milestone in the broader animal status fight to recognise that animals have enforceable rights."
He added: "Animals have the right to be free from cruelty and exploitation, and the failure of US courts to recognise their rights [in other cases] impedes the ability to enforce existing legislative protections."
In the US animals are legally regarded as property.
Next year the New New York Court of Appeals is expected to hear a potentially landmark case brought by animal rights activists over Happy, an elephant that lives at the Bronx Zoo.
The activists are attempting to use a writ of habeas corpus, usually used in relation to human prisoners, to have Happy moved from the zoo.