Body size and activity times mediate mammalian responses to climate change

Abstract

Model predictions of extinction risks from anthropogenic climate change are dire, but still overly simplistic. To reliably predict at-risk species we need to know which species are currently responding, which are not, and what traits are mediating the responses. For mammals, we have yet to identify overarching physiological, behavioral, or biogeographic traits determining species' responses to climate change, but they must exist. To date, 73 mammal species in North America and eight additional species worldwide have been assessed for responses to climate change, including local extirpations, range contractions and shifts, decreased abundance, phenological shifts, morphological or genetic changes. Only 52% of those species have responded as expected, 7% responded opposite to expectations, and the remaining 41% have not responded. Which mammals are and are not responding to climate change is mediated predominantly by body size and activity times (phylogenetic multivariate logistic regressions, P < 0.0001). Large mammals respond more, for example, an elk is 27 times more likely to respond to climate change than a shrew. Obligate diurnal and nocturnal mammals are more than twice as likely to respond as mammals with flexible activity times (P < 0.0001). Among the other traits examined, species with higher latitudinal and elevational ranges were more likely to respond to climate change in some analyses, whereas hibernation, heterothermy, burrowing, nesting, and study location did not influence responses. These results indicate that some mammal species can behaviorally escape climate change whereas others cannot, analogous to paleontology's climate sheltering hypothesis. Including body size and activity flexibility traits into future extinction risk forecasts should substantially improve their predictive utility for conservation and management.

Geographic range did not confer resilience to extinction in terrestrial vertebrates at the end-Triassic crisis

“…Equally, palaeontological data provide a broader perspective on the current biodiversity crisis. Specifically, it enables deep time tests of the purported relationships between present day extinction susceptibility and geographical range size 53,54 , latitudinal distribution 55 , niche breadth 56 and body size 57,58 .…”

Quantification of habitat fragmentation reveals extinction risk in terrestrial mammals

“…S3). We emphasize, however, that arctic and montane species, including high-altitude endemics, are particularly vulnerable to climate change (30,31) and thus still impacted by natural fragmentation that might prevent distributional shifts in response to altered climate regimes.…”

Towards a mechanistic understanding of the responses of large terrestrial mammals to heat and aridity associated with climate change

“…An analysis of mammalian responses to climate change revealed that species that exhibit flexibility in activity times were less likely to respond negatively to climate change [14]. The opportunity for large mammals to shift activity to night, however, may be constrained by factors such as the energetic costs of being active over the cooler night, predation, or night vision ability.…”

“…Through its effects on life history, morphology, physiology and ecology, body size will influence how well mammals are able to buffer the effects of climate change. Although climate change may compromise larger mammals more than smaller mammals, as it has in the Earth's history [13], it will not influence all species of a given body mass to the same extent, and some species actually may benefit from climate change [14]. Understanding how different species will respond to climate change requires an understanding of their exposure and sensitivity to environmental change, as well as the plasticity available to them to buffer such changes.…”