Captive Ground Squirrels Research Articles

Energetics of arousal episodes in hibernating arctic ground squirrels

Arctic ground squirrels overwintering in northern Alaska experience average soil temperature of -10 degrees C. To examine energetic costs of arousing from hibernation under arctic compared to temperate conditions, captive ground squirrels were maintained in ambient temperatures (T(a)) of 2, -5 and -12 degrees C. Rates of oxygen consumption and carbon dioxide production were used to estimate metabolic rate and fuel use during the three phases of arousal episodes: rewarming, euthermia, and recooling. Respiratory quotient comparisons suggest exclusive use of lipid during rewarming and mixed fuel use during euthermia. Animals rewarming from torpor at T(a) -12 degrees C took longer, consumed more oxygen, and attained higher peak rates of oxygen consumption when compared to 2 degrees C. T(a) had no significant effect on cost or duration of the euthermic phase. Animals recooled faster at -12 degrees C than at 2 degrees C, but total oxygen consumption was not different. T(a) had no significant effect on the total cost of arousal episodes when all three phases are included. Arousal episodes account for 86% of estimated costs of a complete hibernation cycle including torpor when at 2 degrees C and only 23% at -12 degrees C. Thus, due to the higher costs of steady-state metabolism during torpor, proportional metabolic costs of arousal episodes at T(a) characteristic of the Arctic are diminished compared to relative costs of arousals in more temperate conditions.

Development of alarm-call responses in Belding's ground squirrels: the role of dams

Experiences with adult conspecifics can influence the ontogeny of species-typical behaviours in naive young of many species. Two processes of influence, direct and indirect, are proposed to describe the effect of adult behaviours on juvenile development. In Belding’s ground squirrels,Spermophilus beldingiexposure to adults experienced with responding to alarm calls may affect how juveniles respond to calls and/or the rate at which juveniles acquire adult-like responses to calls. Because dams and their juvenile offspring interact extensively during early development, the influence of dams on the ontogeny of juvenile alarm-call responses was investigated by conducting playbacks of alarm calls and non-alarm calls to captive ground squirrels. Juveniles were more likely to respond to auditory stimuli if their dam responded, but the responses of unrelated adult females did not influence juveniles. A dam's presence at the time of a playback had no consistent effect, however, on the type of initial response made by her juvenile, its response duration or the vigilance of its postures. The permanent absence of adult models (dams) after weaning appeared to delay the rate at which juveniles developed a discrimination between alarm calls and non-alarm calls, but had no long-term influence on juveniles' expression of responses. Thus, dams indirectly influenced juvenile response development by acting as models of species-typical responses. The outcome of dams' influence was facilitative rather than inductive, because exposure to dams affected the rate of response development but was not necessary for juveniles to acquire alarm-call responses.

Seasonal changes in mucosal structure and function in ground squirrel intestine

Seasonal variations in mucosal structure and transport function were examined in active and hibernating ground squirrel jejunum. Mucosal wet weight and protein content, villus height, and mucosal surface area were lowest in hibernators, increased in spring, peaked in summer, and declined in fall. Transepithelial electrical parameters and net Na+ and 3-O-methylglucose (3-OMG) absorption measured in flux chambers were greatly reduced in hibernator tissues tested at 7 degrees C compared with tissues from hibernators or active squirrels studied at 37 degrees C. At 37 degrees C, net Na+ and 3-OMG absorption normalized to serosal surface area was similar in tissues from all squirrels. When normalized to mucosal surface area, absorption in hibernators was greater than in spring or summer squirrels but was not significantly different from fall values. Absorption normalized to mucosal area was similar among spring, summer, and fall squirrels. Increases in short-circuit current evoked by mucosal addition of D-glucose or L-alanine were significantly greater in hibernators than in fall squirrels. These results demonstrate seasonal variations in mucosal structure and transport function in captive ground squirrels. Enhanced area-specific absorption in hibernator tissues at 37 degrees C may represent a compensatory response to pronounced mucosal atrophy that occurs during hibernation.

Circannual changes in nesting behavior of captive ground squirrels(Spermophilus beecheyi)

Abstract California ground squirrels (Spermophilus beecheyi) were kept for 5–7 years at 20°C with excess food. Presence or absence of nests, built from newspapers, was noted semiweekly, The squirrels were weighed semimonthly. Squirrels were kept in small rooms at natural (SB) length of day and at LD 12:12. Nests were built by squirrels in SB from May to January with a minimum in February to April. Squirrels in LD 12:12 ran freely. The date of the minimum building advanced steadily about a month a year. The persistence of rhythms in LD 12:12 conditions shows that building of nests is an endogenous rhythm and properly called circannual.

Comparison of body weights between captive and free-ranging juvenile Richardson's ground squirrels (Spermophilus richardsoni)

Body weights of free-ranging and captive juvenile Richardson's ground squirrels (Spermophilus richardsoni) were determined at regular intervals during the nonhibernating season. Animals in captivity gained weight at a faster rate and to a greater extent than those in their natural habitat. Attainment of maximum weights in captive ground squirrels was associated with a reduction in food intake and could not be related to food availability, a change in temperature, or in photoperiod.

Myocardial lesions: spontaneous development in captive ground squirrels.

Myocardial lesions: spontaneous development in captive ground squirrels.

Cannibalism and Other Observations of Captive Ground Squirrels

Cannibalism and Other Observations of Captive Ground Squirrels