A failed experiment that resulted in a cross between buffalo and cows has come back to bite Grand Canyon National Park officials.
The hybrid, known as beefalo, are "destroying the Grand Canyon" with their bad-mannered ways. They have trampled on park lands, eaten all the vegetation, knocked over sacred sites and defecated in lakes.
According to a report in the Christian Science Monitor, around 350 beefalo, which are owned by the state of Arizona, have now set up home almost exclusively in the park.
They were introduced to Arizona in the early 1900s in a bid to create hybrid cattle known as beefalo or cattalo. They were supposed to be hardier animals that could cope with the cold weather better.
Federal and state officials are now looking for new ways to manage the unruly creatures to keep them out of the park.
Dave Uberuaga, the superintendent of the Grand Canyon, said: "It's the first step in a long process today. We're just trying to get it out there and get it on everybody's radar screens."
Although the beefalo are legally forbidden from entering the Grand Canyon National Park, the migration actually means fewer are being hunted, as hunting is illegal within the confines of the reservation.
The wild beefalo have about 10% cattle in their genes and no longer resemble cows. Birth control has proved ineffective and as well as their many misdemeanours, they are beginning to infringe on other wildlife in the park.
Uberuaga added: "The massive animals have reduced vegetation in meadows to nubs, travelled into Mexican spotted owl habitat, knocked over walls at American Indian cliff dwellings below the North Rim, defecated in lakes, and left ruts in wetlands."
Public meetings to discuss what to do with the beefalo will be held at the end of April, with more online meetings scheduled.