Effects of habitat disturbance on physiological metrics of deer mice ( Peromyscus sonoriensis )

The effect of anthropogenic disturbance on wildlife physiology has been understudied and has produced inconsistent results. While some species appear unable to tolerate disturbance and disappear from disturbed areas, others seem able to persist, although it may be physiologically costly. One such cost is chronic stress, which likely has a variety of impacts on fitness. We examined the effects of habitat disturbance on Western deer mice ( Peromyscus sonoriensis ) over 4 years on three levels of habitat disturbance. We measured hair corticosterone (hCORT) and white blood cell parameters as metrics of chronic stress and its potential downstream effects on immune function, respectively. Deer mice inhabiting the most disturbed sites exhibited higher levels of hCORT and a lower number of neutrophils compared to those on less disturbed sites. These findings suggest that habitat disturbance acts as a chronic stressor, which in turn suppresses immune function. Because we examined the same species with similar context‐dependent factors, including time of year, sex, age, and reproductive condition, we attribute these differences specifically to how habitat disturbance affected vegetative structure and soil temperature. We suggest some of the inconsistencies in results from previous studies may be due to overlooking important context‐dependent factors and considering all habitat disturbance (e.g., ecotourism, climate change, habitat degradation) the same. Our results suggest that chronic stress and/or white blood cell metrics in deer mice may be useful tools in gauging restoration progress as well as providing a putative link between habitat disturbance and the increased presence of zoonotic pathogens found in several studies.