Beyond masking: Endangered Stephen’s kangaroo rats respond to traffic noise with footdrumming

On-road vehicles have become a pervasive source of low frequency noise in both urban environments and natural protected areas. Because many species rely on low-frequency signals to communicate with conspecifics, they are likely to be especially vulnerable to signal masking and the concomitant biological effects associated with exposure to traffic noise. Here, we show that the spectral characteristics of traffic noise overlap extensively with footdrumming signals of the endangered Stephens’ kangaroo rat (Dipodomys stephensi; SKR). Playbacks of footdrumming overlaid with experimental and control background noises indicate that traffic noise masks and may mimic footdrumming signals. SKR showed no response to footdrumming playbacks overlaid with traffic noise. Yet, traffic noise itself may mimic footdrumming and prompt a false response in SKR – playbacks of traffic noise alone and footdrumming overlaid with control sounds elicited similar behavioral responses. These results provide the first evidence that anthropogenic noise may function as a deceptive signal to wildlife, causing animals to engage in false responses that may be energetically and biologically costly. More broadly, these results indicate that anthropogenic noise can have multiple, concurrent effects. For SKR, the combined effects of communication disruption and signal deception may further tax already endangered populations. Roads and road margins on and off reserves serve as dispersal corridors and refugia for SKR and other semifossorial taxa; these areas may therefore function as ecological traps if anthropogenic roadway noise negatively affects population persistence.