Acoustic niche hypothesis and the role of the social environment in red squirrel (Tamiasciurus hudsonicus) territorial vocalizations
The Acoustic Niche Hypothesis proposes that during communication it is beneficial to occupy an ‘acoustic niche’ different from other organisms in the environment by producing calls that are acoustically distinct from those around them. I hypothesized that red squirrels (Tamiasciurus hudsonicus) have territorial vocalizations ('rattles') that occupy different acoustic niches from their conspecific neighbours, providing benefits in resource acquisition and overwinter survival. I recorded rattles from 129 adult red squirrels to compare acoustic dissimilarity between individuals. Acoustic properties were repeatable within individuals, meaning red squirrels have uniquely identifiable acoustic signatures during territory defense. Contrary to predictions of the ANH, individual rattles were no more distinct from neighbours than other squirrels in the population, and dissimilarity did not provide detectable survival benefits. I found evidence that squirrels with higher pulse rate dissimilarity between individuals tended to have larger hoards, but due to marginal significance level, it should be interpreted with caution.