The accidental introduction of the Brown Treesnake Boiga irregularis to Guam led to catastrophic ecological and economic consequences, including the extirpation of most native forest birds and millions of dollars in damages to the island's power distribution system. Since colonizing the island in the late 1940s, Brown Treesnakes associated with cargo from Guam have arrived at numerous locations throughout the world. Concerns for the potential establishment of other populations have led to intensive control efforts, aimed at the prevention of snake dispersal from the island. Information regarding snakes entering the outbound cargo flow is critical in the development and implementation of both operational control strategies and research necessary to improve available control technologies. Data collected from 31 snakes removed from the outbound cargo network on Guam reveal the typical snake in cargo is smaller in snout-vent length than the average snake captured using traps or hand capture in support of operational control. Potential reasons for small snakes in cargo include the presence of a snake cohort refractory to capture methods, and/or the nomadic behaviour of sub-adults. Additionally, snakes have been found in nearly every location that handles or processes cargo, indicating the need for containment efforts throughout the outbound shipping process. Intensive containment, coupled with the continued development of techniques that effectively capture small snakes, is necessary for successful interdiction efforts.
