The pika is one of my all time favorite species of animal. Pika are small and round. About the same size as a tennis ball. While they resemble ground squirrels, they are actually members of the rabbit family. In Colorado, pika live exclusively in the high mountains above timberline, and make their dens in talus fields that have access to vegetation.
Perhaps what makes pika most impressive to me is the fact that unlike nearly all other high elevation animals, in the winter they do not migrate or hibernate. Rather pika spend the entire winter (which in some instances lasts for 8 or 9 months) active in their dens under the snow! What's even more fascinating is that as I understand it, scientists don't really know what they do that whole time.
In order to prepare for the winter, pika must spend nearly all of their time in the summer gathering food in the form of vegetation into what are known as "hay stacks". Often they will place cut bits of plants in the sun to dry before carrying them down under the rocks to their dens. Because of this, you will often see pika frantically running around with big mouthfuls of vegetation.
Pika are very intolerant of heat. In fact, they will die of heat exhaustion after six hours at 77 degrees F. Because of this, and their isolated "sky island" habitat, they cannot easily migrate as the climate warms. Their only direction to migrate is up, and in many areas they are already running out of vertical real estate. While Congress declined to list them as a threatened or endangered species in 2010, their habitat is shrinking with no way for them to escape.