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Snow­shoe hares that cam­ou­flage them­selves by chang­ing their coats from brown in sum­mer to white in win­ter face seri­ous threats from cli­mate change, and it’s uncer­tain whether hare pop­u­la­tions will be able to adapt in time, accord­ing to a North Car­olina (NC) State Uni­ver­sity study.

Based on field research with radio-​collared snow­shoe hares in Mon­tana, mis­matched snow­shoe hares suf­fer a 7 per­cent drop in their weekly sur­vival rate when snow comes late or leaves early and white hares stand out to preda­tors like “light bulbs” against their snow­less backgrounds.

“In pre­vi­ous research we showed that cli­mate change is caus­ing snow dura­tion to decrease, and that hares have lit­tle abil­ity to adjust their molt tim­ing or behav­iours to com­pen­sate for the mis­match. Here we take the next step of show­ing that mis­match does indeed kill.”

“This paper shows that the mis­match costs are severe enough to cause hare pop­u­la­tions to steeply decline in the future unless they can adapt to the change,” says Mar­keta Zimova, doc­toral stu­dent with Mills at NC State and lead author of the arti­cle pub­lished on 21 Jan­u­ary in the jour­nal Ecol­ogy Let­ters.

Effect of indi­vid­ual colour con­trast on weekly snow­shoe hare sur­vival. Dashed lines indi­cate 95% cred­i­ble inter­vals, while the solid line depicts mean sur­vival at a given level of colour con­trast between an indi­vid­ual hare and its back­ground. Pho­tographs depict radio­col­lared hares from our study show­ing (a) 0% and (b) 100% con­trast. (Ecol­ogy Let­ters 21 JAN 2016 DOI: 10.1111/ele.12568)

The good news for snow­shoe hares is the find­ing that dif­fer­ent indi­vid­u­als molt at dif­fer­ent times, enabling nat­ural selec­tion to favour those bet­ter suited for the chang­ing snow con­di­tions. How­ever, whether evo­lu­tion through nat­ural selec­tion can save hares quickly enough is uncer­tain, espe­cially given the rapid rate of change.

“Ulti­mately, to pro­mote species per­sis­tence in the face of cli­mate change induced mis­match, the reduc­tion of its cause is essen­tial and must be done via cli­mate change mit­i­ga­tion,” Zimova says. “But in the mean­time, we should main­tain large and con­nected pop­u­la­tions to fos­ter evo­lu­tion­ary res­cue and its abil­ity to allow wild ani­mals to adapt to the chang­ing conditions.”

Cam­ou­flage mis­match has the poten­tial to impact at least 14 species world­wide that change coat colours sea­son­ally, Mills says. His team of researchers is expand­ing the coat colour research to other species glob­ally, includ­ing moun­tain hares, white-​tailed jackrab­bits, weasels and Arc­tic foxes.

(Source: NC State Uni­ver­sity news release, 21.01.2016)