An experimental translocation identifies habitat features that buffer camouflage mismatch in snowshoe hares

Abstract

Conservation for species impacted by climate change often occurs at scales impractical for local land managers. Snowshoe hares (Lepus americanus) are one of the most well‐documented species declining from climate change–specifically a reduction in snowcover–yet clear management strategies have yet to emerge. To test whether camouflage mismatch is reducing hare survival we translocated 96 hares to a site recently extirpated of snowshoe hares, and monitored coat color change, mismatch with snow, habitat use, and weekly survival in winter‐spring of 2017. Hare survival was low during periods of camouflage mismatch, and mismatched hares were 3.2 × less likely to survive, but this pattern varied by habitat. We found that aspen‐alder stands >5 hectares negated the mortality costs of mismatch. We provide experimental evidence that mismatch is driving the range contraction of snowshoe hares, and identify specific habitats to buffer the consequences of climate change on this declining winter specialist.

Local climate determines vulnerability to camouflage mismatch in snowshoe hares

“…Previous quantifications of survival costs were carried out for 'absolute mismatch', that is both white and brown mismatch combined (Wilson et al, 2018;Zimova et al, 2016). Perhaps due in part to this frequency difference in the two mismatch types, a white hare against a snowless background appears far more conspicuous than a brown hare resting on snow.…”

“…Because of their broad distribution (Figure 1a), hares inhabit a large range of environmental conditions, making them an ideal species for investigating variation in moult phenology and camouflage mismatch. In the only two areas where moults have been recently investigated in relation to climate change (i.e., Montana and Wisconsin, USA), phenotypic plasticity is not sufficient to prevent camouflage mismatch (e.g., Mills et al, 2013;Wilson, Shipley, Zuckerberg, Peery, & Pauli, 2018). For example, hares in Montana experience about a week of mismatch annually whereby hares are in the wrong coat colour in relation to their background (i.e., white hares on snowless background or brown hares on snow; Mills et al, 2013;Zimova, Mills, Lukacs, & Mitchell, 2014;Zimova et al, 2016).…”

“…For example, hares in Montana experience about a week of mismatch annually whereby hares are in the wrong coat colour in relation to their background (i.e., white hares on snowless background or brown hares on snow; Mills et al, 2013;Zimova, Mills, Lukacs, & Mitchell, 2014;Zimova et al, 2016). Because hares rely heavily on their camouflage for survival, mismatch has strong negative fitness costs (i.e., 7-12% reduced weekly survival) that in the absence of evolutionary shifts and under projected snow declines would be sufficient to cause steep population declines and local extinction (Wilson et al, 2018;Zimova et al, 2016). To date, no study has evaluated the phenological drivers and camouflage To understand snowshoe hare vulnerability to camouflage mismatch, we quantified the spatial and temporal variation in colour moult phenology, phenotypic plasticity, and the occurrence of camouflage mismatch across three disjunct, climatically and geographically distinct populations.…”

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

“…Range contraction was also observed for herbivores when the strength of an abiotic factor reduced, exposing populations to predation, disease or parasitism. For example, recent studies indicate snowshoe hares experience higher predation rates and population declines when their white winter coats contrast with snowless environments (Wilson, Shipley, Zuckerberg, Peery, & Pauli, 2018;Zimova, Mills, & Nowak, 2016). Consequently, reduced snow duration over the past several decades is associated with range contraction along the snowshoe hare's southern limit (Burt, Roloff, & Etter, 2017;Sultaire et al, 2016) with future declines expected due to climate change (Zimova et al, 2016).…”

A camouflage conundrum: unexpected differences in winter coat color between sympatric species

“…One of the most persistent and widespread signals of climate change in the northern hemisphere, however, is a reduction in the number of days with snow on the ground. As snow duration decreases, animals in white winter coats become more conspicuous against snowless ground, suffering increased mortality (Mills et al 2013, Zimova et al 2016, Wilson et al 2018.…”