from http://www.historydetroit.com/ -
In the very early days of Detroit, Belle Isle, then known as Ile Aux Cochons or Hog Island, was used by settlers to house pigs and chickens to protect them from coyotes on the mainland. Ottawas and Ojibwa tribes were the "owners" of the island.
During Pontiac's siege of Detroit in 1763, the houses on Belle Isle were destroyed and the family of resident, James Fisher, was murdered. Jean Myer accused Alexis Cuillerier of drowning one of James Fisher's children. No court existed in Detroit at the time, and Cuillerier had some powerful connections and relationships, thus he was only kicked out of Detroit. After his exile, several witnesses testified in Cuillerier's behalf. Cuillerier was proven innocent and on June 4, 1769, Turnbull called him back to Detroit.
On May 4, 1768, Lieutenant George McDougall, a soldier in the British garrison at Detroit, was given permission by King George III to "occupy" Belle Isle. Despite the fact that the citizens of Detroit would lose their rights to the island and have to find other means of housing cattle and other animals, McDougall purchased the island on June 5, 1769 from the Ojibwa and Ottawa owners for a total of 8 barrels of rum, 3 rolls of tobacco, 6 pounds of vermillion, and a wampum belt.