Evidence For Selective Avoidance Of Traffic Noise By Anuran Amphibians

Roads create many challenges for conservation, and amphibians are particularly vulnerable to their negative effects. This experiment evaluates the impact that traffic noise has on amphibian populations, specifically anurans (frogs and toads). It is thought that traffic noise may act to reduce population abundances; however, it is difficult to disentangle the impact of noise from other road effects, such as roadkill and chemical pollution. To test this, we created a ‘phantom road’ by playing different traffic noise treatments in three roadless areas and measured resulting anuran abundance using vocalizations as a proxy. We also tested the vocalizations of one species, the Oak Toad Anaxyrus quercicus for changes in response to noise. We found that broadcasting traffic noise caused a significant reduction in vocalizations heard, but, intriguingly, we did not observe this effect when the traffic noise was digitally altered to remove frequencies that overlap with anuran vocalizations. This suggests that avoidance of traffic noise could be a tactic that increases the success of communication with conspecifics. We also found that Oak Toads increase the redundancy of their calls in response to traffic noise, but not in response to the altered noise