らい菌
The island is one of the few places in southern England where indigenous red squirrels survive, largely because non-native grey squirrels have never been introduced to the island. The Brownsea red squirrel population is the only population known in the UK to carry the human form of the bacteria stem "Mycobacterium leprae" that causes leprosy in humans. Brownsea also has a small ornamental population of peacocks. The island has a heronry, in which both grey heron and little egret nest.