On a summer day a bird-like chirp travels on the breeze across a sandy river bank. It's not a bird, it's an arctic ground squirrel. Arctic ground squirrels spend most of their lives hibernating. In summer, they have just about 100 days to mate, raise a litter of pups, and fatten up for another 270 days of sub-zero hibernation.
Males come out in the first and go back last. They rouse from hibernation in March, but they stay underground for about three weeks, eating from a food cache they stored the fall. In April, they emerge from the den in the spring daylight in search of a mate.
The females are out around the second week in April and within a day or two, they're pregnant. They gestate five to seven pups for about three weeks, they're born tiny and hairless and nurse for about six weeks. Then they fatten up quickly on the vegetation at the summer's peak.. By the end of July, the females and young head back to the burrow. The males follow in mid to late September.
Arctic ground squirrels are extreme hibernators. Their body temperature drops to minus 3 degrees Celsius, below the freezing point of water. They are super cooled, but they don't freeze. Their heart rate slows to a few beats per minute and they breathe once every few minutes. Come spring, with no external cues like light or warming soils, they begin the whole cycle again.