Winter preparation

It’s too early for us (humans) to start thinking about winter with its short days, cold temperatures, and blah landscapes. But not too early for the 13-lined ground squirrels that live out on the short grass meadows and prairies near Fort Ridgley state park. For them, it’s a race to eat enough to fatten up so they can hibernate in their deep burrows before cold weather arrives and the grasses dry up and their seeds disperse.

These small seed-eating rodents scurry around the meadows in late summer, scarfing up as much seed as they can find. Most will be consumed and turned into body fat, and some may be stored in their burrows for an early spring snack.

These ground squirrels are aptly named for the 13 dark brown and white stripes that line their backs. They can be found anywhere there are grassy meadows in the central part of the North America from Texas to southern Canada. But you’ll only find them above ground for about six months of the year. The rest of the time they are hibernating (deep sleep) in a deep burrow beneath the prairie plants.

I think these might have been young of the year — they were quite slim and small. Adults typically fatten up and go into hibernation long before their offspring do.

The coloration is apparently good camouflage for them as they run through blotchy patterns of grasses heavy with dark stripes of seed heads, and the striped pattern may help reduce their visibility to their number one predator – the Northern Harrier.

Rodents, like the ground squirrels, are one of the favorite prey in the diet of Northern Harriers. These long-winged raptors fly back and forth across grassy fields listening (not necessarily looking) for movements of small mammals as they fly. They are easily identified by the white rump patch in both the brown plumaged females and the grey plumaged males.

Northern Harriers have a round facial disk, similar to owls, that helps collect sound and transmit it to their asymmetrically placed ears so they can localize exactly where the sounds are coming from. (Photo by the Missouri Department of Conservation)

13-lined Ground Squirrels don’t seem particularly social; their burrows are not placed near each other, and they live and forage individually, unlike prairie dogs. These little squirrels seemed particularly naive and tolerated me approaching on foot, so they might well wind up in a Harrier’s gut sometime if they aren’t cautious.

It was interesting to watch how they handled the grass stems with their forepaws to harvest the seed.

Sometime in October all the ground squirrels will disappear underground to sleep away the winter cold in a state of torpor in which respiration is profoundly depressed from 100-200 breaths per minute during activity to one breath every 5 minutes in deep torpor. In addition, they usually do not eat or drink for almost all of the hibernation period, but survive in a very low metabolic state by oxidizing their fat stores.