MARAJO ISLAND (Brazil) - Legends flourish about how the first Asian water buffaloes made it to this colossal island in the Amazon river delta.

But however they arrived, the invasive species multiplied in Marajo, and now numbers about 450,000 on an island the size of Switzerland. So much of daily life here revolves around the water buffaloes that islanders haul trash with them, race them during festivals and savour fillets of buffalo steak smothered in cheese made from buffalo milk.

"The importance of the buffalo in Marajo got us thinking," said Major Francisco Nobrega, 41, from the 8th Battalion of the military police of Para, the vast state in Brazil's Amazon that encompasses Marajo. "Why not patrol on buffalo as well?"

Water buffaloes have been domesticated elsewhere for thousands of years and are called "the living tractor of the East" for their role in ploughing fields.

In Marajo, the 8th Battalion police make their rounds on the crescent-horned beasts.

The buffalo unit started in the 1990s, patrolling the sleepy outpost of Soure, which has about 23,000 people, and breaking up the occasional bar fight.

Over the years, the mission has expanded to include pursuing suspects who flee into Marajo's wilds and cracking down on buffalo rustling on the island's far-reaching ranches.

NEW YORK TIMES