Answer: Hares

While there are a host of changes across the globe brought about by climate change, there is one particularly stark example to be found in the foothills of Montana. There, researchers, led by L. Scott Mills of the University of Montana, have recorded how shifting climates have left the common hare in a tight spot.

The hares shed their dark brown summer coats not in response to the arrival of snow, but in response to the change in the length of the day. Historically, the change in the length of the day also corresponded to the impending snow, so their solar-calendar-guided-molting worked just right: they’d be brown in the summer, a little bit mottled in color when the snow was first arriving, and stark white when the hills were coated in deep powdery snow.

The arrival of the first heavy snowfall has been steadily occurring later, however, and the hares are now shedding their summer coats and adopting the snow-white look without a single snowflake in sight. Further compounding the problem is that the hares still view themselves as being fully camouflaged, despite their brilliant white appearance against the soft brown and green backdrop of the forest.

The researchers are closely monitoring the hares to see if they will eventually reset their internal clocks to match the new reality of later snowfall and earlier spring melts.