Cooperatively breeding Arabian babblers call differently when mobbing in different predator-induced situations

Cooperatively breeding Arabian babblers (Turdoides squamiceps) have a repertoire of different calls that they use in predator-induced contexts. We investigated their vocal mobbing behavior in two different predator-induced situations. We presented territorial groups of babblers a perched, stuffed owl representing an avian predator and a cat representing a ground predator. Babblers approached in both situations and mobbed the predators with the same two call types. In both predator-induced situations their first call was a short, metallic-sounding 'tzwick.' In response to the cat, babblers continued to primarily use tzwicks. However, in continued response to the owl, the babblers primarily used long trills. The experiments indicate that differences in use of two common call types during mobbing provide information on differences in predator-induced situations, although no call type per se identified a specific situation. The experiments suggest that the short tzwicks indicate a higher risk or urgency than trills and that combinations of both call types may provide graded information about differences in predator-induced situations. The relatively stable groups of these cooperative breeders might have favored evolution for using different calls in different mobbing situations.