Variation in head and pinna morphology of preserved Peromyscus spp. specimens and implications for auditory function

The physical characteristics of an animal's head and pinna mark the beginning of auditory communication. Auditory communication is broadly achieved by receiving sounds from the environment and plays a vital role in an animal's ability to perceive and localize sounds. Natural history museums and collections, along with their vast repositories of specimens, provide a unique resource for examining how the variability in both the size and shape of the head and pinna causes variability in the detection of acoustic signals across species. Using this approach, we measured morphological features of the head and pinna on over 1200 preserved specimens of Peromyscus boylii, P. californicus, P. gossypinus, P. leucopus, P. maniculatus, and P. truei, followed by a series of head-related transfer functions (HRTFs) on several individuals to study the relationship between morphology and available auditory information. Our morphological results show significant variation in pinna length and width, as well as in the distance between the two ears across the six species. Interaural time differences and interaural level differences were calculated and demonstrated consistent results across species, suggesting the differences in head and pinna size do not significantly modify these cues. Not only does this study contribute to existing research on external morphology and auditory function, but it also provides valuable insight into the use of preserved zoological specimens in auditory research, an area that is currently understudied.