Abstract
Many species produce alarm calls in response to predator threats. Whilst these can be general alert calls, some are urgency-based, indicating perceived threat level, some are predator-specific, indicating the predator type present, and some encode information about both urgency level and predator type. Predator-specific calls given to a narrow range of stimuli and which elicit a specific, adaptive, response from the receiver are termed functionally referential. Differing escape strategies, habitat structural complexity and sociality may favor the evolution of functionally referential calls. A study of one captive group of dwarf mongooses (Helogale parvula) suggested their alarm calls could transmit information about species, distance, and elevation of predators. Using recordings of natural predator encounters, predator presentations and audio playbacks, we investigated the alarm-call system in 7 wild dwarf mongoose groups.
We recorded 11 different alarm-call types given to 9 stimulus categories. Of the 5 commonly emitted alarm-call types, 3 appeared to be non-specific and 2 predator-specific, given to aerial and terrestrial predators respectively. The remaining 6 call types were rarely produced. Furthermore, aerial alarms were given to a narrower range of stimuli than their terrestrial alarm calls, which were given to both visible terrestrial predators and secondary cues of predators. Unlike other mongoose species, dwarf mongoose seem to use the same alarm-call type for both physically present terrestrial predators and secondary cues of their presence. We argue that detailed knowledge of species’ alarm-call systems under natural conditions can shed light on the evolutionary emergence of different types of alarm calls.
Collier, Katie