Abundance and management of Mariana Fruit Bats and feral ungulates on Anatahan, Mariana Islands

Abstract

A survey of Mariana Fruit Bats Pteropus mariannus and feral ungulates was conducted on Anatahan, Mariana Islands, in July 1995. We estimated that a population of 1 902-2 136 bats persists on the island, based on a combination of direct colony counts, departure counts, and station counts of non-colonial animals. Our data suggest that bat numbers have declined since the last surveys were made in 1983 and 1984. We located seven colonies, which held approximately 85-92% of the total population. Most colonies and foraging animals were associated with native forest or isolated native trees in other habitats. Bats fed on five species of plants, with the fruit of Pandanus tectorius eaten most frequently. Anatahan supports a very large Feral Goat Capra hircus population estimated at roughly 5 000-6 000 animals. Feral Pigs Sus scrofa are less common. Both species cause severe damage to plant communities of the island. We recommend that a legal hunting programme for fruit bats be deferred until 1) population censuses on neighbouring islands are completed and it is determined that bat populations can sustain harvesting, 2) habitat degradation is reversed through the control of feral animals, and 3) illegal hunting is curtailed.