Infectious personalities: Behavioral ecology and risk of parasitism in larval amphibians

Background/Question/Methods

Consistent and predictable correlations among behaviors through time, forming syndromes or personality types, likely have substantial influences on animal life histories and fitness.  However, such behavioral inflexibility can result in maladaptive behaviors when animals cannot optimize their actions in different contexts thus many studies seek to explain why such correlations then exist or how they are maintained.  Understanding the behavioral ecology of host-parasite interactions is becoming increasingly recognized as important for comprehending factors contributing to host susceptibility, yet the role of pre-existing general personality types rather than separate behaviors in acquiring parasitic infections has not been investigated experimentally.  Here we use a model system involving larval amphibians (wood frogs – Lithobates sylvatica) and a trematode parasite (Echinoparyphium sp.) to examine consistency of individual responses in different stressful situations.

Results/Conclusions

We show that individual tadpoles can exhibit behavioral syndromes through similar responses to both novel stimuli and the threat of parasitism and report strong correlations in activity level and refuge use across these different contexts, as well as between these two behaviors.  Additionally, while individual activity level and refuge use under parasite threat were significant predictors of host parasite load, these same behaviors in response to a novel stimulus were also significant, indicating that general personality type is important for disease risk.  We suggest that this system illustrates how multiple benefits could drive selection for behavioral consistency if wood frog larvae reliably exhibit high levels of activity and boldness in different contexts to maximize both their energy acquisition and resistance to trematode parasites due to the particulars of their life histories.  As such, behavioral syndromes need not necessarily be maladaptive since numerous benefits can accrue from a lack of behavioral plasticity under certain ecological conditions.