Ridley Amanda R, Child Matthew F, Bell Matthew B V
Percy Fitzpatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch, Cape Town 7701, Republic of South Africa.
Biol Lett. 2007 Dec 22;3(6):589-91. doi: 10.1098/rsbl.2007.0325.
Audience effects are increasingly recognized as an important aspect of intraspecific communication. Yet despite the common occurrence of interspecific interactions and considerable evidence that individuals respond to the calls of heterospecifics, empirical evidence for interspecific audience effects on signalling behaviour is lacking. Here we present evidence of an interspecific audience effect on the alarm-calling behaviour of the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis). When foraging solitarily, drongos regularly alarm at aerial predators, but rarely alarm at terrestrial predators. In contrast, when drongos are following terrestrially foraging pied babblers (Turdoides bicolor) for kleptoparasitic opportunities, they consistently give alarm calls to both aerial and terrestrial predators. This change occurs despite no difference in the amount of time that drongos spend foraging terrestrially. Babblers respond to drongo alarm calls by fleeing to cover, providing drongos with opportunities to steal babbler food items by occasionally giving false alarm calls. This provides an example of an interspecific audience effect on alarm-calling behaviour that may be explained by the benefits received from audience response.
听众效应日益被视为种内交流的一个重要方面。然而，尽管种间互动普遍存在，且有大量证据表明个体对异种个体的叫声会做出反应，但种间听众效应影响信号行为的实证证据却很缺乏。在此，我们展示了种间听众效应影响偷窃寄生性叉尾卷尾（Dicrurus adsimilis）警报行为的证据。单独觅食时，卷尾经常会对空中捕食者发出警报，但很少对地面捕食者发出警报。相比之下，当卷尾跟随在地面觅食的双色蚁鵙（Turdoides bicolor）以寻找偷窃寄生机会时，它们会持续对空中和地面捕食者都发出警报。尽管卷尾在地面觅食的时间量没有差异，但这种变化依然发生。蚁鵙会通过逃到掩体中来回应卷尾的警报叫声，这为卷尾偶尔发出假警报来偷取蚁鵙食物提供了机会。这提供了一个种间听众效应影响警报行为的例子，这种效应可能由听众反应带来的益处来解释。
