Indris Indri indri are group-living lemurs that occupy stable territories over several years and perform remarkable long-distance vocal displays.Vocal exchanges between long-term territory neighbors may contribute to ...Indris Indri indri are group-living lemurs that occupy stable territories over several years and perform remarkable long-distance vocal displays.Vocal exchanges between long-term territory neighbors may contribute to assessing reciprocal resource-holding potentials, thus adaptivelyreducing the costs of territorial defense by limiting aggressive escalation. Previous work showed that indris’ songs show distinctive acousticfeatures at individual and group level. However, the possibility that indris use such cues for individual or group-level recognition has never beeninvestigated experimentally. We conducted a playback experiment to test whether indris discriminate between familiar and nonfamiliar songs.Our rationale lies in the hypothesis of the dear enemy phenomenon, which predicts that territorial animals will show reduced aggression levelstoward familiar neighbors compared with novel rivals. We played back stimulus recordings to wild indris from their territory boundaries andexamined their responses in terms of vocal and behavioral indicators of willingness to engage in a fight. In line with our predictions, focal animals responded more rapidly and approached more often the speaker in response to playback stimuli of nonfamiliar individuals than to stimuliof neighboring groups. These results indicate that indris can discriminate between different classes of intruders based on distinctive acousticfeatures of their song choruses. We suggest that increased aggression directed toward unfamiliar intruders may be explained by higher threatlevels associated with dispersal and group formation dynamics. We further discuss the relevance of these findings in a strepsirrhine primatemodel for comparative studies of vocal communication and sociality.展开更多
文摘Indris Indri indri are group-living lemurs that occupy stable territories over several years and perform remarkable long-distance vocal displays.Vocal exchanges between long-term territory neighbors may contribute to assessing reciprocal resource-holding potentials, thus adaptivelyreducing the costs of territorial defense by limiting aggressive escalation. Previous work showed that indris’ songs show distinctive acousticfeatures at individual and group level. However, the possibility that indris use such cues for individual or group-level recognition has never beeninvestigated experimentally. We conducted a playback experiment to test whether indris discriminate between familiar and nonfamiliar songs.Our rationale lies in the hypothesis of the dear enemy phenomenon, which predicts that territorial animals will show reduced aggression levelstoward familiar neighbors compared with novel rivals. We played back stimulus recordings to wild indris from their territory boundaries andexamined their responses in terms of vocal and behavioral indicators of willingness to engage in a fight. In line with our predictions, focal animals responded more rapidly and approached more often the speaker in response to playback stimuli of nonfamiliar individuals than to stimuliof neighboring groups. These results indicate that indris can discriminate between different classes of intruders based on distinctive acousticfeatures of their song choruses. We suggest that increased aggression directed toward unfamiliar intruders may be explained by higher threatlevels associated with dispersal and group formation dynamics. We further discuss the relevance of these findings in a strepsirrhine primatemodel for comparative studies of vocal communication and sociality.
