Northern pikas experience reduced occupancy due to surrounding human land use despite the occurrence of suitable microclimates

AimDespite warming temperatures, some species are found persisting at the trailing edge of their distribution. Microclimates provided by complex topography are considered a key factor in these cases of range stationarity, buffering stress from exposure to warming and enabling persistence. However, for species with trailing-edges located in human-modified landscapes, refugial conditions provided by microclimates could be disrupted by human activities. Here, we aimed to understand the determinants of trailing-edge occupancy for a small lagomorph found in rocky patches harbouring cool microclimates.LocationHokkaido Island, Japan.TaxonNorthern pika (Ochotona hyperborea).MethodsWe surveyed the occupancy of northern pikas across a wide elevational gradient (350-2200 m) for two consecutive summers. Ambient air and microhabitat (i.e. rock interstices) thermal conditions were measured to assess their relationship. We then analysed their effects on occupancy at two nested spatial scales: (1) whole-distribution, and (2) at identified trailing-edge sites where we explored the effects of microclimates and surrounding human activities (i.e. distance to nearest road and area of human land use such as plantation forests or agricultural fields).ResultsOverall, rock interstices exhibited cooler conditions than ambient air with temperature differences of 1-2 degrees C. The overall distribution of northern pikas was affected by both mean ambient temperature and microhabitat availability, with warmer (lower elevation) sites with less microhabitats corresponding to the trailing edge of its distribution. Interestingly, trailing edge occupancy patterns were best explained by the negative effect of surrounding human land despite the existence of suitable microclimates in the rocky patches.Main ConclusionsOur findings suggest that the local refugial conditions supported by cool microclimates are likely to be disrupted by the effects of human land alterations at the larger landscape scale. This result highlights the importance of considering the effects of human activities and landscape alteration for effective microrefugia conservation.