Parasitized salamanders are inferior competitors for territories and food resources

Parasites have been shown to impair the behaviour of their hosts, compromising the host's ability to exploit and compete for resources. We conducted two experiments to determine whether infestation with an ectoparasitic mite (Hannemania eltoni) was associated with changes in aggressive and foraging behaviour in the Ozark zigzag salamander, Plethodon angusticlavius. In a first experiment, male salamanders with high parasite loads were less aggressive overall than males with low parasite loads during territorial disputes. In addition, males with high parasite loads were more aggressive toward opponents with high parasite loads (symmetric contests) than toward opponents with low parasite loads (asymmetric contests). In contrast, males with low parasite loads did not adjust their level of aggression according to the parasite load of the opponent. In a second experiment, foraging behaviour of females was tested in response to 'familiar' (Drosophila) prey and 'novel' (termite) prey. Latency to first capture was significantly longer for parasitized than non-parasitized females when tested with 'familiar' prey, but not for 'novel' prey. Our results suggest that parasite-mediated effects may have profound influences on individual fitness in nature.