The mildly venemous brown tree snake (Boiga irregularis) is an introduced species on some Pacific islands that has become a serious pest, especially on Guam. In the absence of natural population controls and with vulnerable prey on Guam, the snakes have become an exceptionally common pest causing major ecological and economic problems. The snakes probably arrived on Guam hidden in ship cargo from the New Guinea area. By 1968, they had dispersed throughout the island and caused havoc by virtually wiping out Guam's native bird species and helped decimate their fruit bat populations. In addition to Guam, brown tree snakes have been sighted on Saipan, Tinian, Rota, Kwajalein, Wake, Oahu, Pohnpei, Okinawa, and Diego Garcia. To date, this snake is not known to be established on any of these islands except Guam.