Increased risk of predation increases mobbing intensity in tropical birds of French Guiana

Abstract

Abstract:Stressful environments have been suggested to enhance cooperative behaviours in animal communities. Prey animals living in risky environments can also increase long-term benefits by cooperating with neighbours, such as collectively harassing predators. However, empirical studies have rarely tested this prediction in the wild. In this experimental study we explored whether the perceived predation risk influences cooperative mobbing behaviour in tropical forest birds in French Guiana. The predation risk was increased by 5-d-long presentation of visual and acoustic stimuli of pygmy-owls in 24 locations. In order to examine whether mobbing response can vary in relation to the abundance of local predators, we used the Amazonian pygmy-owl (Glaucidium hardyi) as a common predator and the ferruginous pygmy-owl (Glaucidium brasilianum) as a rare predator in the study area. Our results showed that repeated predator-presentations increased mobbing response over time for the rarer owl species, while this effect was not significant for the common owl species. No effect of repeated presentations of either pygmy-owl species was found on the latency of mobbing. Moreover, mobbing latency was shorter and mobbing response was stronger for the common predator species, the Amazonian pygmy-owl. This study provides experimental evidence that birds exhibit stronger mobbing responses when the predator is locally abundant, while repeated encounters can be perceived as more dangerous when the predator is rare.