Ground Squirrel Information

RICHARDSON'S GROUND SQUIRRELS / Original source of information - http://research.uleth.ca/rgs

Richardson's ground squirrels are known by a variety of names, including gophers, prairie gophers, yellow gophers, picket pins, flickertails, and tawny American marmots. They are sometimes confused with their relatives the prairie dogs. But whatever they may be called, Richardson's ground squirrels are still the same, delightful animals they have always been.

A member of the squirrel family in the order Rodentia, Richardson's ground squirrels make their home in the northern plains of North America. They are diurnal, obligate hibernators that live out most of their lives in underground burrows.

Some people seek to exterminate Richardson's ground Squirrels as agricultural pests, where as others seek them out as pets. Because Richardson's Ground squirrels play an important role as a prey item for many carnivores and raptors and in creating microhabitats for other organisms such as burrowing owls, many people are interested in maintaining their status as a key element of the prairie ecosystem. They are also used for scientific and medical research.

GROUND SQUIRRELS AS PETS

People who do acquire a Richardson’s ground squirrel must assume full responsibility for the care of that animal throughout its lifetime. These animals CANNOT be released back into the wild successfully because they can only survive as part of the family unit from which they came. They will certainly die an unpleasant death after release, either from harassment from ground squirrels who are not their kin, from predators, or from exposure through not having a burrow system.

When caring for a ground squirrel, most of the supplies needed can be found on this web site. Cages designed for medium-sized animals such as Prairie dogs or Chinchillas are ideal. Other necessities include a food dish, water bottle, CareFresh bedding, and a wooden hide away for nesting.

Cages and food bowls must be cleaned regularly, and uneaten produce removed daily before it spoils. Veterinary care is also recommended.

DIET

Richardson's ground squirrels are predominantly herbivores, with vegetation composing 80-100% of their total diet. The remainder is comprised mostly of insects. Richardson’s ground squirrels do not kill for food, but they sometimes nibble on easy-to-obtain meat such as road kills.

Richardson's ground squirrels primarily eat leaves, flowers and seeds, though the precise type of vegetation eaten depends on where they live. Because so much of the native prairie has been destroyed by human agricultural practices, it is now difficult to assess the natural and preferred diet. Forage grasses and legumes are major food items on overgrazed pastures in eastern North Dakota. In cultivated areas, where little native vegetation remains, Richardson’s ground squirrels have no choice other than to eat the seeds and seedlings of domesticated cereals such as wheat, barley and oats.

Captive ground squirrels can be fed a staple diet of commercial food with a protein content of 18%-20% such as Exotic Nutrition's Squirrel Diet supplemented daily by raw whole oats and fresh vegetables. Chew toys should be made available for gnawing.

Ground squirrels feeding in cultivated areas tend to be larger and bear more live young than those feeding in native grasslands, presumably because more high quality food is available in crop fields than on native grassland.

HIBERNATION

Richardson's ground squirrels hibernate alone in a special chamber called a hibernaculum. The hibernaculum chamber is initially constructed as an excavation off the main burrow system, but that connection is plugged off with soil when the animal enters hibernation. The hibernaculum system is a closed system consisting of a hibernaculum chamber, a drain tunnel to carry away moisture, and an exit tunnel that reaches almost to the surface. In spring, the animal emerges above ground by connecting the exit tunnel to the surface.

The hibernaculum is a grass-filled chamber in which the ground squirrel curls into a ball with its nose tucked between the hind legs and enters a state of torpor. Adults hibernate for 7-9 months, juvenile females for 6-7 months, and juvenile males for 4-5 months.

During torpor, a ground squirrel's body temperature drops to that of the surrounding soil. By late winter, body temperature may fall as low at 0°C during torpor bouts. Respiration slows, as does the heartbeat. Torpor is not continuous, as ground squirrels arouse periodically throughout hibernation.

Male ground squirrels tend to cache food, such as grass seeds, which they carry to the hibernaculum in cheek pouches. Seeds are cached under the grass bedding in the hibernaculum chamber. This food store is used at the end of the hibernation season when male ground squirrels remain in their burrows at normal body temperature for several days to permit testicular recrudescence. Males rarely exhaust food caches before emergence, but they do not return to the hibernaculum to eat remaining seeds after they have emerged.

SEX DIFFERENCES

As would be expected, the majority of differences between male and female Richardson's ground squirrel behavior relate to reproduction. Sexes differ in behaviors related to male's intrasexual competition for mates, the male-biased operational sex ratio, and the sexual difference between the effective length of the mating season.

During the mating season, male ground squirrels move longer distances, occupy larger ranges, engaged in more injury-producing fights, feed less, lose more body weight, and spend less time on burrow maintenance than females. Males are less sedentary than females and shift their home ranges on a daily basis during the mating season in relation to daily changes in the availability of estrous females.

Adult male ground squirrels immerge into hibernation earlier than adult females, whereas juvenile males immerge later than juvenile females. All male ground squirrels emerge from hibernation earlier than females, regardless of age. The timing of hibernation is based on different criteria, with females timing their emergence in spring to coincide with vegetative growth during lactation and males timing their emergence to coincide with what the females are doing.

Male Richardson's ground squirrels disperse more often and further than females, form no lasting social bonds, and take no part in offspring care. Also, males show little fidelity to burrows during the mating season. In contrast, females usually settle near their female kin and form life-long social bonds with their closest relatives such as mother, sisters, aunts, and nieces.

Male ground squirrels show a tendency to cache large amounts of food in the hibernaculum, whereas females do not. Males spend less time in the physiological state of torpor during hibernation than females.

COMMUNICATION

The basic 'vocabulary' of Richardson's ground squirrels consists of a variety of squeals, chirps, chirrs, whistles, and teeth clatters. They also give two distinct alarm calls, which humans can easily learn to recognize.

The first alarm call is for aerial predators, which tend to approach rapidly in a straight line. It consists of a short, low-pitched chirp that changes frequency. Upon hearing this call, ground squirrels run for cover.

The other alarm call is for terrestrial predators, which tend to approach relatively slowly. This one consists of a long, high-pitched whistle with a constant frequency. When this call is heard, ground squirrels stand up and scan the area.

LITTER SIZE

Female Richardson's ground squirrels produce a single litter each year, and if they lose their litter, they are incapable of breeding again until the following year. They give birth underground after a 23-day gestation period. The litter is born overnight in the chamber which the female uses for sleeping during late pregnancy. Litters remain permanently underground for 29-30 days, and the mother is the only ground squirrel who has contact with the infants. Mothers sleep with their infants at night and visit them several times during the day to suckle them. Mothers raise the young on their own, with no assistance from the father or any of her female kin.

Litter size at birth is usually 6 to 8 young, but extremes of 4 to 14 have been noted. Unless the litter is killed by predators such as long-tailed weasels or badgers, most mothers are able to rear all offspring to weaning age. Consequently litter size at first emergence above ground is also usually 6 to 8 young.

At birth, infants weigh an average of 6.5 grams. They are hairless with ears and eyes closed, digits fused, and teeth unerupted. Helpless, they are totally dependent on their mother.

The first hints of fur begin to appear after four days, and fore digits separate at 13 days. By 15 days of age, the infants begin to look like miniature ground squirrels but they are still incapable of locomotion, and the eyes are still closed. By 22-24 days, ears and eyes are open, teeth are present, and the fur coat is well developed.

At the age of 29-30 days and weighing between 65 and 85 grams, the young first emerge from their natal burrow. They immediately begin eating solid food, soon becoming nutritionally independent of their mother. At 50 days of age, juveniles molt the baby fur and grow in their adult fur coat.

Young from large litters are relatively small, yet they emerge above ground at the same age as do larger juveniles from small litters, and make the transition from milk to solid food at the same age. This indicates that age is a more important factor than size in making the transition to solid food and above ground activity.