scholarly journals Seasonal changes in glucocorticoid and testosterone concentrations in free-living arctic ground squirrels from the boreal forest of the Yukon

2001 ◽  
Vol 79 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Rudy Boonstra ◽  
Anne H Hubbs ◽  
Eileen A Lacey ◽  
Carolyn J McColl
Keyword(s):  
Binding Capacity ◽  
Ground Squirrels ◽  
Base Line ◽  
Adult Males ◽  
Free Living ◽  
Active Season ◽  
Spermophilus Parryii ◽  
Free Cortisol ◽  
Arctic Ground Squirrels ◽  
Juvenile Males

We examined how glucocorticoid and testosterone concentrations changed from spring to summer by livetrapping free-living populations of arctic ground squirrels (Spermophilus parryii). The primary glucocorticoid was found to be cortisol, with corticosterone below measurable concentrations in most individuals. Livetrapping elicited a strong stress response in both sexes: breeding males and females trapped in spring had free cortisol concentrations 4 and 34 times, respectively, those of base-line animals. The maximum corticosteroid-binding capacity (MCBC) was unaffected by trapping and was about 3 times higher in breeding females than in breeding males. Over the active season, MCBC values were lowest in all male classes (juveniles, nonreproductive adults, and reproductive adults), being less than half those in all female classes; pregnant females had values approximately twice those of juvenile females. However, free cortisol concentrations were similar in all female classes and in juvenile males and about half those in adult males. Livetrapping increased testosterone concentrations in males over those found in samples from base-line males, and testosterone concentrations did not affect MCBC values. Testosterone concentrations in livetrapped animals differed significantly among male classes, with nonreproductive males maintaining concentrations 64% of those in breeding males and 10 times those in juveniles.

scholarly journals Daily body temperature rhythms persist under the midnight sun but are absent during hibernation in free-living arctic ground squirrels

2011 ◽  
Vol 8 (1) ◽  
pp. 31-34 ◽  
Author(s):  
Cory T. Williams ◽  
Brian M. Barnes ◽  
C. Loren Buck
Keyword(s):  
Body Temperature ◽  
Circadian Rhythms ◽  
Ground Squirrels ◽  
The Arctic ◽  
Constant Light ◽  
Polar Regions ◽  
Free Living ◽  
Active Season ◽  
Temperature Rhythms ◽  
Arctic Ground Squirrels

In indigenous arctic reindeer and ptarmigan, circadian rhythms are not expressed during the constant light of summer or constant dark of winter, and it has been hypothesized that a seasonal absence of circadian rhythms is common to all vertebrate residents of polar regions. Here, we show that, while free-living arctic ground squirrels do not express circadian rhythms during the heterothermic and pre-emergent euthermic intervals of hibernation, they display entrained daily rhythms of body temperature ( T b ) throughout their active season, which includes six weeks of constant sun. In winter, ground squirrels are arrhythmic and regulate core body temperatures to within ±0.2°C for up to 18 days during steady-state torpor. In spring, after the use of torpor ends, male but not female ground squirrels, resume euthermic levels of T b in their dark burrows but remain arrhythmic for up to 27 days. However, once activity on the surface begins, both sexes exhibit robust 24 h cycles of body temperature. We suggest that persistence of nycthemeral rhythms through the polar summer enables ground squirrels to minimize thermoregulatory costs. However, the environmental cues (zeitgebers) used to entrain rhythms during the constant light of the arctic summer in these semi-fossorial rodents are unknown.

scholarly journals Habitat selection by arctic ground squirrels (Spermophilus parryii)

2010 ◽  
Vol 91 (5) ◽  
pp. 1251-1260 ◽  
Author(s):  
Oliver E. Barker ◽  
Andrew E. Derocher
Keyword(s):  
Habitat Selection ◽  
Ground Squirrels ◽  
Spermophilus Parryii ◽  
Arctic Ground Squirrels

Seasonal effects of food provisioning on body fat, insulin, and corticosterone in free-living juvenile Belding's ground squirrels (Spermophilus beldingi)

2002 ◽  
Vol 80 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Scott Nunes ◽  
Eva-Maria Muecke ◽  
Kay E Holekamp
Keyword(s):  
Body Fat ◽  
Plasma Insulin ◽  
Plasma Concentrations ◽  
Plasma Corticosterone ◽  
Ground Squirrels ◽  
Seasonal Effects ◽  
Free Living ◽  
Active Season ◽  
Extra Food ◽  
Spermophilus Beldingi

We evaluated the relationship between body fat and the metabolic hormones insulin and corticosterone in free-living juvenile Belding's ground squirrels (Spermophilus beldingi). Some free-living juveniles were provisioned with extra food high in fat and calories, and unprovisioned juveniles were used as controls. Body fat (as a percentage of body mass) of squirrels was regularly evaluated using non-invasive methods. Blood samples were also regularly collected from juveniles and assayed for plasma concentrations of insulin and corticosterone. Provisioned juveniles were fatter than unprovisioned juveniles during most of the active season, but differences in body fat disappeared near the end of summer as juveniles began fattening for hibernation. Thus, our data indicate that although body fat may fluctuate with energy availability early in the active season, it is regulated at precise levels as squirrels prepare for winter. Plasma corticosterone concentrations did not differ between provisioned and unprovisioned juveniles. However, plasma insulin concentrations were greater in provisioned than in unprovisioned juveniles early in the summer. Differences in insulin concentrations disappeared later in the active season, just prior to the disappearance of differences in body fat. Moreover, plasma insulin concentrations were significantly correlated with subsequent changes in body fat. Thus, our data suggest a link between insulin and seasonal regulation of body fat in juvenile S. beldingi.

scholarly journals Interrelationships Among Timing of Hibernation, Reproduction, and Warming Soil in Free-Living Female Arctic Ground Squirrels

2012 ◽  
pp. 63-72 ◽  
Author(s):  
Cory T. Williams ◽  
Michael J. Sheriff ◽  
Franziska Kohl ◽  
Brian M. Barnes ◽  
C. Loren Buck
Keyword(s):  
Ground Squirrels ◽  
Free Living ◽  
Arctic Ground Squirrels

Hematological and serum chemical characteristics of the Iberian lynx (Lynx pardina) in southwestern Spain

1991 ◽  
Vol 69 (4) ◽  
pp. 840-846 ◽  
Author(s):  
J. F. Beltrán ◽  
M. Delibes ◽  
F. Recio ◽  
C. Aza
Keyword(s):  
Blood Cell ◽  
Serum Levels ◽  
Mean Corpuscular Hemoglobin ◽  
Base Line ◽  
Lynx Lynx ◽  
Adult Males ◽  
Corpuscular Hemoglobin ◽  
Cell Counts ◽  
Capture Method ◽  
Juvenile Males

Hematological and serum chemical values were determined for 16 wild Iberian lynxes, Lynx pardina (5 adult males, 4 adult females, 4 juvenile males, and 3 juvenile females) captured with box traps and coil-spring traps. The results include reference values, analysis of sex and age differences, and data on the influence of capture method on blood values. Males had higher red blood cell counts (p = 0.03) and packed cell volumes (p = 0.06) than females, which presented higher mean corpuscular hemoglobin levels (p = 0.08) and mean corpuscular hemoglobin concentrations (p = 0.07) than males. Juveniles had higher serum levels of alkaline phosphatase (p = 0.01), urea (p = 0.02), and cholesterol (p = 0.02) and lower levels of creatinine (p = 0.07) than adults. Four hematological variables (mean platelet volume, platelet size distribution, white blood cell count, and mean corpuscular volume) and two serum variables (concentrations of amylase and calcium) were influenced by capture method. The use of standard procedures to assess base-line blood values in wild carnivores is encouraged.

scholarly journals Ascorbate dynamics and oxygen consumption during arousal from hibernation in Arctic ground squirrels

2001 ◽  
Vol 281 (2) ◽  
pp. R572-R583 ◽  
Author(s):  
Ø. Tøien ◽  
K. L. Drew ◽  
M. L. Chao ◽  
M. E. Rice
Keyword(s):  
Peak Plasma ◽  
Plasma Concentrations ◽  
Metabolic Stress ◽  
Ground Squirrels ◽  
Electromyographic Activity ◽  
Spermophilus Parryii ◽  
Plasma Ascorbate ◽  
Leukocyte Counts ◽  
Plasma Urate ◽  
Arctic Ground Squirrels

During hibernation in Arctic ground squirrels ( Spermophilus parryii), O2 consumption and plasma leukocyte counts decrease by >90%, whereas plasma concentrations of the antioxidant ascorbate increase fourfold. During rewarming, O2 consumption increases profoundly and plasma ascorbate and leukocyte counts return to normal. Here we investigated the dynamic interrelationships among these changes. Plasma ascorbate and uric acid (urate) concentrations were determined by HPLC from blood samples collected at ∼15-min intervals via arterial catheter; leukocyte count and hematocrit were also determined. Body temperature, O2 consumption, and electromyographic activity were recorded continuously. Ascorbate, urate, and glutathione contents in body and brain samples were determined during hibernation and after arousal. During rewarming, the maximum rate of plasma ascorbate decrease occurred at the time of peak O2 consumption and peak plasma urate production. The ascorbate decrease did not correlate with mouth or abdominal temperature; uptake into leukocytes could account for only a small percentage. By contrast, liver and spleen ascorbate levels increased significantly after arousal, which could more than account for ascorbate clearance from plasma. Brain ascorbate levels remained constant. These data suggest that elevated concentrations of ascorbate {[Asc]} in plasma {[Asc]p} provide an antioxidant source that is redistributed to tissues during the metabolic stress that accompanies arousal.

Effects of food and predators on the home-range sizes of Arctic ground squirrel (Spermophilus parryii)

1998 ◽  
Vol 76 (3) ◽  
pp. 592-596 ◽  
Author(s):  
Anne H Hubbs ◽  
Rudy Boonstra
Keyword(s):  
Home Range ◽  
Ground Squirrel ◽  
Large Scale ◽  
Yukon Territory ◽  
Ground Squirrels ◽  
Home Ranges ◽  
Spermophilus Parryii ◽  
Mammalian Predators ◽  
Core Areas ◽  
Arctic Ground Squirrels

We used radiotelemetry to study the effects of food addition and predator reduction on the home-range sizes of adult Arctic ground squirrels (Spermophilus parryii) on large-scale experimental grids in the boreal forest of the southwestern Yukon Territory. Home ranges were 2-7 times smaller on food-supplemented grids than on nonsupplemented grids, regardless of whether large mammalian predators were present. Similarly, core areas (where 50% of activities occur) were 8-11 times smaller on food-supplemented grids. Food availability rather than predator presence primarily determined the sizes of home ranges and core areas of Arctic ground squirrels.

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