REDUCED AGGRESSION TOWARD SIBLINGS AS EVIDENCE OF KIN RECOGNITION IN CANNIBALISTIC SALAMANDERS

In amphibians, evidence of kin recognition is limited to anurans, and neighbor recognition has only been documented in the territorial adults of a frog and a terrestrial salamander. We examined whether kin and neighbor recognition occur among larval salamanders (Ambystoma opacum: Ambystomatidae) that are known to be aggressive and cannibalistic. Our results indicate that larval A. opacum discriminate siblings from nonsiblings on the basis of four types of agonistic behavior. Larvae were significantly less aggressive and more submissive to siblings than to nonsiblings, regardless of whether larvae were presented with familiar or unfamiliar opponents. However, larvae made no distinction between familiar and unfamiliar individuals, which suggests that neighbor recognition does not occur in this species. Suppressed aggression and increased submission toward siblings in larval A. opacum may function to minimize harmful acts of aggression (biting and, ultimately, cannibalism) among siblings, thus enhancing the inclusive fitness of related individuals. This avoidance of siblings in larval salamanders, in contrast to the preferential aggregation of siblings in larval anurans, suggests a divergence in the possible function of kin recognition among amphibians.