Multi-species community response to extirpation of a top carnivore on San Miguel Island, Channel Islands, California

The island fox (Urocyon littoralis) was the sole terrestrial carnivore in the simplified ecosystem on San Miguel Island, part of the southern California Channel Islands.  The loss of the fox from the system in the last 10 years has been followed by a wide range of dramatic community changes.  The population of deer mice (Peromyscus maniculatus; the only native small mammal on the island) now exhibits cyclic multi-year fluctuations, and changes in deer mouse population dynamics may have in turn affected aspects of vegetation and plant species ecology.  There have been increases in avian predators on the island as well, particularly the northern harrier (Circus cyaneus).  Previously, harriers were uncommon winter visitors to San Miguel; numbers of these ground-nesting raptors now breed on the island every year.  Non-native black rats (Rattus rattus) were formerly restricted to a few isolated areas around the periphery of the island, and have now spread more widely.  Likewise, western gulls (Larus occidentalis) were formerly restricted to offshore rocks, and now nest on the main island of San Miguel.  I will discuss these myriad changes in relation to management of San Miguel Island, with a specific focus on the rats and gulls.  The changes on San Miguel have direct implications for other islands in the Channel Islands group, and probably for other island systems as well.