An Evaluation of Passive Thermal Fumigation for Brown Treesnake Control in Surface Transportation from Guam

The brown treesnake (BTS) has been on Guam for about 50 years and in this period has caused extensive ecological, economic, and social damage. It has also repeatedly dispersed from Guam via the transportation network, arriving at numerous locations. However, the conditions snakes face in surface shipping are unknown, making assessment of the risk of snake survival impossible. To address this, we recorded thermal conditions in surface shipments leaving Guam and identified factors that determine these conditions. We monitored 16 shipments to locations in Micronesia and the United States mainland and conducted a series of intensive studies at the Naval dock facility, using up to 29 containers at a time. Maximum temperatures recorded while containers were in transit were likely too low to consistently kill snakes. Empty exhibited uniformly high temperatures, but filled containers did not heat as much, nor as evenly. Maximum temperatures inside boxes and furniture are even lower, though often still exceed 40 C. Exposed containers reached high temperatures, but shading by other containers greatly decreased the maximum temperature reached inside.