Anthropogenic noise disrupts response to anti-predator signals in a cooperatively breeding mammal. (#7)
Anthropogenic noise can elevate stress, distract individuals and mask auditory signals, with compelling evidence that it can strongly affect vocal communication. However, most studies have focused on bird song, with little work considering the impact on other vocalisations or whether effects differ depending on caller identity. We conducted a series of playback experiments on the cooperatively breeding dwarf mongoose (Helogale parvula)to investigate: (i) how traffic noise affects receiver responses to two contrasting anti-predator vocalisations (alarm calls and the Watchman’s song); (ii) whether noise-related effects differ depending on caller class (dominant versus subordinate); and (iii) the importance of masking as the underlying mechanism for the demonstrated effects. Traffic noise playback did not affect the immediate response to alarm calls of either dominant or subordinate callers, but receivers were consistently slower to resume foraging. Foragers exposed to playback of the Watchman’s song (low amplitude calls given by sentinels on guard duty) in traffic noise were more vigilant than during ambient noise. However, the pattern of lower vigilance in the presence of a dominant sentinel compared to a subordinate was retained during traffic noise playback, indicating that cues to caller identity were still available. Moreover, an additional experiment found that exposure to playback of traffic noise alone (with no mongoose vocalisations that could be masked) caused foragers to increase vigilance. Our results demonstrate that anthropogenic noise can impact responses to key anti-predator vocalisations and that disruption of vocal communication may not be explained solely by masking. We suggest that future studies explore potential effects on a range of vocalisations and the mechanistic explanations behind behavioural changes associated with anthropogenic noise.