Behavioral Reduction of Infection Risk in a Larval Amphibian

Document Type

Article

Journal/Book Title/Conference

Proceedings of the National Academy of Sciences

Volume

16

Issue

96

Publication Date

1999

First Page

9165

Last Page

9168

Abstract

Evolutionary biologists have long postulated that there should be fitness advantages to animals that are able to recognize and avoid conspecifics infected with contacttransmitted disease. This avoidance hypothesis is in direct conflict with much of epidemiological theory, which is founded on the assumptions that the likelihood of infection is equal among members of a population and constant over space. The inconsistency between epidemiological theory and the avoidance hypothesis has received relatively little attention because, to date, there has been no evidence that animals can recognize and reduce infection risk from conspecifics. We investigated the effects of Candida humicola, a pathogen that reduces growth rates and can cause death of tadpoles, on associations between infected and uninfected individuals. Here we demonstrate that bullfrog (Rana catesbeiana) tadpoles avoid infected conspecifics because proximity influences infection. This avoidance behavior is stimulated by chemical cues frominfected individuals and thus does not require direct contact between individuals. Such facultative modulations of disease infection risk may have critical consequences for the population dynamics of disease organisms and their impact on host populations.

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