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
To avoid unnecessary energy expenditures in territorial defense,many species(e.g.,insects,amphibians,birds,and mammals)have developed the capability to distinguish between different intruder types using visual,acousti...To avoid unnecessary energy expenditures in territorial defense,many species(e.g.,insects,amphibians,birds,and mammals)have developed the capability to distinguish between different intruder types using visual,acoustic,and/or chemical signals.Determining the mechanism used for intruder recognition is key to understanding the dynamics of territorial behaviors.In birds that use vocalizations for territorial defense,the frequency and duration of vocalizations or the familiarity with the intruder may be the main mechanism used for intruder recognition.Here,we conducted a playback experiment with territorial White-eared Ground-sparrows(Melozone leucotis),to analyze if territorial pairs recognize intruders using frequency and duration characteristics(a bird’s response is based on how structurally similar the intruders’duets are to their own)or by familiarity with the intruders(neighbors vs.non-neighbors).We focused on duets because this species uses duets exclusively for territorial defense.We broadcasted a duet from a territorial neighbor,two duets from non-neighbors(with different frequency and duration characteristics),and a duet from a control species in 39 territorial pair from three populations.During playback we measured five behavioral responses:latency of the first vocalization,latency of the approach to the speaker,time spent close the speaker(within 5 m),number of individuals that approached the speaker,and the number of vocalizations.We found that territorial White-eared Ground-sparrow pairs responded stronger to neighbors than non-neighbors,and this response is not influenced by duet duration or frequency characteristics.This result suggests that neighbors represent a greater territorial threat for White-eared Ground-sparrows than non-neighbors.Further work is necessary to understand how common this observation is for tropical species that defend small territories year-round.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.
基金provided by the Vicerrectoria de Investigacion Universidad de Costa Rica through the project numbers B9123,B9469,and C1085。
文摘To avoid unnecessary energy expenditures in territorial defense,many species(e.g.,insects,amphibians,birds,and mammals)have developed the capability to distinguish between different intruder types using visual,acoustic,and/or chemical signals.Determining the mechanism used for intruder recognition is key to understanding the dynamics of territorial behaviors.In birds that use vocalizations for territorial defense,the frequency and duration of vocalizations or the familiarity with the intruder may be the main mechanism used for intruder recognition.Here,we conducted a playback experiment with territorial White-eared Ground-sparrows(Melozone leucotis),to analyze if territorial pairs recognize intruders using frequency and duration characteristics(a bird’s response is based on how structurally similar the intruders’duets are to their own)or by familiarity with the intruders(neighbors vs.non-neighbors).We focused on duets because this species uses duets exclusively for territorial defense.We broadcasted a duet from a territorial neighbor,two duets from non-neighbors(with different frequency and duration characteristics),and a duet from a control species in 39 territorial pair from three populations.During playback we measured five behavioral responses:latency of the first vocalization,latency of the approach to the speaker,time spent close the speaker(within 5 m),number of individuals that approached the speaker,and the number of vocalizations.We found that territorial White-eared Ground-sparrow pairs responded stronger to neighbors than non-neighbors,and this response is not influenced by duet duration or frequency characteristics.This result suggests that neighbors represent a greater territorial threat for White-eared Ground-sparrows than non-neighbors.Further work is necessary to understand how common this observation is for tropical species that defend small territories year-round.
