From Joel Sartore’s fantastic Biodiversity Project:
Hibernating Arctic ground squirrels (Spermopilus parryii) at the University of Alaska at Fairbanks. This animal is the grand champion of all hibernators. It’s the only mammal that can drop its body temperature to below freezing. They hibernate for seven months. Females go in first, in August. Males follow a month later. They come out again to feed on tundra plants in May. Biologists at UAF have been studying the animal for 20 years, but still can’t figure out how this animal maintains a flat body temperature for all those months just above freezing. “You could put people into hibernation for space trips if you could understand it better,” said Franziska ‘Fran’ Kohl, one of the biologists here. “They also show symptoms of Alzheimers during hibernation.” She added that traumatic head injuries heal when in hibernation, another thing scientists are trying to figure out.