Reproductive biology

Hibernation imposes a constraint on reproduction. The preparation and duration of hibernation allow for only a single litter per year. For some species of marmots, many females will skip a year in order to build the necessary energy reserves for reproduction. Remaining spring seed caches allow chipmunks to initiate mating early in the season relative to non-caching hibernating ground squirrels. This early start ensures chipmunks have the opportunity to reproduce again if the first litter fails, or they may successfully raise more than one litter in a good year. Non-hibernating ground squirrels can reproduce more than once per year in good years as they are not constrained by hibernation.

A Belding's ground squirrel (Spermophilus beldingi) family emerging from burrow. (Photo by J. VanWormer. Bruce Coleman, Inc. Reproduced by permission.)

Litters tend to be born in underground chambers. The pups are born naked and helpless and remain in the natal nest for 3-5 weeks depending on the species. Weaning usually occurs shortly after pups emerge from the natal chamber and begin foraging for themselves. Mating systems are not well-known.

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