Life history and ecological aspects of larval amphibian behavioral consistency

Background/Question/Methods

A tendency for animals to exhibit consistencies in their behavior across time and/or different contexts (i.e. “behavioral syndromes”) may represent selection driven by benefits accrued through consistent behavior.  Many studies have reported the significance of predation and reproductive success in generating and maintaining such syndromes and recent work has highlighted the importance of also considering parasitism.  Our previous research demonstrated that wood frog tadpoles generally showed consistency in their activity level in response to both novel food and trematode parasite (Echinoparyphium sp.) exposure. Not only were individual activity level and exploration in the novel food context correlated with each other and with anti-parasite behavior, all three were significant predictors of host parasite load.  Given that such consistency in activity and exploration is likely to depend on amphibian life history, as well as ecological circumstances influencing threats of trematode parasitism and predation, we hypothesized that differences among amphibian species with respect to these factors could be reflected in the occurrence and strength of behavioral syndromes.  Using a similar methodology, we examined four different amphibian species representing four life history/threat combinations: 1), spring peepers (Pseudacris crucifer: fast development/low threat); 2) wood frogs (Lithobates sylvaticus: medium development/low threat); 2) northern leopard frogs (Lithobates pipiens: medium development/medium threat); and 2) bullfrogs (Rana catesbeiana: long development/high threat). 

 Results/Conclusions

Wood frog tadpoles exhibited a behavioral consistency as described above that was linked to parasite load, with similar results seen for spring peeper larvae.  However, while highly active leopard frog tadpoles were more likely to approach a novel food item, this was not as strongly correlated with anti-parasite behavior or parasite load.  Surprisingly, bullfrog tadpoles exhibited little behavioral consistency and anti-parasite behaviors were not strong predictors of parasite load.  These results demonstrate that host life history and ecological circumstances may influence the evolution of larval amphibian behavioral syndromes involving parasitism but further studies are needed, particularly those including more host species in specific life history/threat combinations.