An incongruous sight meets visitors of the northern Brazilian island of Marajo: thousands and thousands of water buffalo, animals endemic to India and Southeast Asia that have found a new home in South America. The buffalo are employed as patrol animals by the military police in Soure, where heavily-armed officers ride on their backs in specially-adapted seats. There are currently around half-a-million water buffalos on Marajo today, more than then island’s human population of 440,000.