A direct comparison of trapping and spotlight searches for capturing Brown Tree Snakes on Guam

Abstract

Brown Tree Snake populations on Guam are controlled in the vicinities of cargo staging and transport areas to prevent their dispersal from Guam, and their populations are controlled in areas where endangered species are to be reintroduced. Trapping and night-time spotlight searches of fences are the two primary Brown Tree Snake population reduction methods used on Guam. We conducted a three month study comparing Brown Tree Snake captures by spotlighting fences to captures by trapping. Traps were placed either on the edge of the forest paralleling the fences, or they were hung on the fences. Applications of each capture method followed the standard practices used within the operational programme charged with deterring the spread of Brown Tree Snakes from Guam. We found captures by trapping to exceed those by spotlighting each month, but the captures by trapping decreased substantially over time, while those by spotlighting did not. We detected no differences statistically between numbers of captures taken by traps hung on the forest edge versus those hung on the fences. We found no differences in sizes of Brown Tree Snakes captured by spotlighting and trapping, based on average snout-vent length (SVL) or the distribution of SVLs. We feel that the two capture methods complement each other in an integrated pest management programme.