Parasitic presence in animals has been known to effect animal behavior, even when the parasite is passive (living within the animal but not actively controlling the animal’s behavior). Parasite load has been shown to effect species behavior and certain behavioral changes act as indicators to stress. An increase in striking behavior in snakes can be an indicator to the amount of stress the animal is undergoing. On the island of Guam, the Brown Treesnake (Boiga irregularis) is widespread, and there is one local population of snakes infected by a subdermal, parasitic flatworm, Spirometra erinaceieuropaei. Snakes were captured within the infected population and necropsied. We measured parasite presence in each snake, as well as snout vent length (SVL), snake mass (SM), sex, fat mass (FM), and calculated a body condition index (BCI). A strike positive snake struck when being removed from the trap and if a snake did not strike during the removal process than it was considered a strike negative snake. We predicted that infected snakes would strike more often, have a lower BCI, and have lower FM compared to non-infected snakes.
Results/Conclusions
We trapped 101 snakes, of which 69 of them had parasites present (PP) and 32 were absent of parasites (PA). We found that PP snakes struck more often than PA snakes. We also found that SVL, SM, sex, FM, and BCI did not have a significant effect on strike behavior. PP snakes did not have significantly lower BCI’s or FM’s than PA snakes. These results suggest that parasites are causing some form of stress on snakes, causing them to strike more often. Though we did not find a significant effect of the parasites on snakes BCI’s or FM’s, we did see a trend of PP snakes having lower BCI’s and FM’s. In most studies related to parasite induced behavioral change, animals with parasites had lower body conditions and higher risk of being preyed upon. We suspect the reason we are not seeing these results within our study population is because of the abundance of food, absence of predators, and absence of interspecific competition. These results indicate that passive parasitism does effect animal behavior.