Non-specific alarm calls trigger mobbing behavior in Hainan gibbons (Nomascus hainanus)

Huaiqing Deng,Kai Gao,Jiang Zhou

doi:10.1038/srep34471

Abstract

Alarm calls are important defensive behaviors. Here, we report the acoustic spectrum characteristics of alarm calls produced by Hainan gibbons (Nomascus hainanus) inhabiting Bawangling National Nature Reserve in Hainan, China. Analysis of call data collected from 2002–2014 shows that alarm calls are emitted by all family group members, except infants. Alarm behavior included simple short alarming calls (7–10 min) followed by longer variable-frequency mobbing calls lasting 5–12 min. The duration of individual alarming and mobbing calls was 0.078 ± 0.014 s and 0.154 ± 0.041 s at frequency ranges of 520–1000 Hz and 690–3920 Hz, respectively. Alarming call duration was positively associated with group size. The alarm calls can trigger mobbing behavior in Hainan gibbons; this is a defense way of social animals, and first report among the primates’ species. The system of vocal alarm behavior described in this critically endangered species is simple and effective.

Highlights

Upon detecting a potential predator, many primates emit acoustic signals that influence the predator and cause group members to behave in a way that benefits the caller, regardless of relatedness or group association[1]
We report alarm call behavior and acoustic spectrum characteristics and attempt to answer the following questions: Does the Hainan gibbon use different alarm calls for different predators? What is the composition and highest and lowest frequency of the alarm call? Is alarm call duration associated with group size? And what is the response time of individuals to alarm calls?
The alarm calls of most animals are divided into functional and urgency reference systems according to the alarm functions of calls[16,17]

Summary

Introduction

Upon detecting a potential predator, many primates emit acoustic signals that influence the predator and cause group members to behave in a way that benefits the caller, regardless of relatedness or group association[1]. If the alarm call is emitted in a timely and reliable manner after predator detection, individuals in the group can respond and reduce their risk of being preyed upon[2]. Predator-induced songs were identical to normal songs in the call note repertoire, for example, Lar gibbons (Hylobates lar) generate significant, context-dependent acoustic variations of their main social call, which potentially allows recipients to make inferences about events experienced by the caller[8,9,10,11]. We report alarm call behavior and acoustic spectrum characteristics and attempt to answer the following questions: Does the Hainan gibbon use different alarm calls for different predators? What is the response time of individuals to alarm calls? We report alarm call behavior and acoustic spectrum characteristics and attempt to answer the following questions: Does the Hainan gibbon use different alarm calls for different predators? What is the composition and highest and lowest frequency of the alarm call? Is alarm call duration associated with group size? And what is the response time of individuals to alarm calls?

Methods

Results

Conclusion