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.

Body fat influences sexual maturation in captive male Belding's ground squirrels

1988 ◽  
Vol 66 (7) ◽  
pp. 1620-1625 ◽  
Author(s):  
Warren G. Holmes
Keyword(s):  
Body Fat ◽  
Sexual Maturation ◽  
Serum Testosterone ◽  
Ground Squirrels ◽  
Constant Darkness ◽  
Physiological Indicators ◽  
Abundant Food ◽  
Cold Room ◽  
Fat Stores ◽  
Spermophilus Beldingi

The influence of white adipose tissue on sexual maturation was investigated in captive-born male Belding's ground squirrels (Spermophilus beldingi). Juveniles were given abundant food during the summer and by fall achieved prehibernation body masses approximating those of sexually mature males. Immediately before being placed in a cold room (5–8 °C, constant darkness) for a 7-month hibernation period, fat was surgically removed (lipectomy) or left intact (sham lipectomy). The following spring, paired testes mass, serum testosterone, and spermatogenesis were monitored, mating tests were conducted, and body fat levels were determined. All three physiological indicators of reproductive status were significantly higher in sham-lipectomized than in lipectomized males, only sham-lipectomized males inseminated females, and body fat levels were significantly higher in sham-lipectomized than in lipectomized males. Thus, sexual maturation was accelerated in male Belding's ground squirrels by providing juveniles abundant food so they achieved body masses typical of adults; body fat was essential for accelerated development. In nature, males may forego reproductive development until they can acquire adequate fat stores to survive hibernation and activate their reproductive system and until they gain social experience important in male–male competition for mates.

Maternal influence on juvenile growth rates in Belding's ground squirrel (Spermophilus beldingi)

1991 ◽  
Vol 69 (8) ◽  
pp. 2140-2145 ◽  
Author(s):  
Stephen C. Trombulak
Keyword(s):  
Body Mass ◽  
Sierra Nevada ◽  
Early Summer ◽  
Ground Squirrels ◽  
The Body ◽  
Supplemental Food ◽  
Sierra Nevada Mountains ◽  
Extra Food ◽  
Spermophilus Beldingi ◽  
Reproductive Females

The influence of food acquisition by pregnant and lactating Belding's ground squirrels (Spermophilus beldingi) on the body mass and growth rate of their offspring was assessed in a free-ranging population. In late spring and early summer of 1985 and 1986, individual females in a population of Belding's ground squirrels in the Sierra Nevada Mountains of California were given 300–500 g of sunflower seeds daily at the entrances to their burrows. Juveniles born to mothers who received supplemental food emerged from natal burrows on average 28% heavier than did controls (73.0 vs. 57.1 g, P < 0.001) and maintained a greater body mass throughout the remainder of the summer (P < 0.01). Also, females had a nonsignificant tendency towards greater survivorship during their first winter (P = 0.09). Supplemental feeding had no effect on litter size or sex ratio of offspring, or on the mass of the mothers up to the time of weaning, indicating that extra food available in the spring to reproductive females is converted primarily, if not exclusively, into larger offspring. Because the lengths of gestation and lactation are relatively invariable, the greater body mass of emerging juveniles must result from faster growth prior to weaning.

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.

A comparison of time-specific and cohort-specific life tables for Belding's ground squirrels, Spermophilus beldingi

1986 ◽  
Vol 64 (3) ◽  
pp. 602-605 ◽  
Author(s):  
Richard M. Zammuto ◽  
Paul W. Sherman
Keyword(s):  
Life Table ◽  
Survival Data ◽  
Life Tables ◽  
Ground Squirrels ◽  
Age Classes ◽  
Free Living ◽  
Female Population ◽  
Spermophilus Beldingi ◽  
Time Specific ◽  
Combined Data

Eight years of age-specific survival data and 6 years of fecundity data from a free-living population of Belding's ground squirrels (Spermophilus beldingi) at Tioga Pass, California, were used to test the hypothesis that time-specific life tables, based on data from individual years, were different from the cohort-specific life table, based on the combined data from all years. The results indicated that neither the age structure of the male nor the female population significantly differed among years (all P > 0.05). Furthermore, the means and the variances in the sizes of weaned litters did not differ among years either in the population at large or within individual age-classes (all P > 0.05). A 27-day snowstorm that occurred in the spring of 1977 increased mortality and reduced reproduction, but it did not change the ground squirrels' age-specific survival or fecundity patterns. Taken together, our analyses revealed that each time-specific life table provided age-specific survival and fecundity estimates that were statistically indistinguishable (P > 0.05) from the composite, cohort-specific life table for each sex, regardless of severe environmental conditions. This is the first demonstration of the equivalence of time- and cohort-specific life tables for a free-living population of mammals.

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.

Behavioural and physiological responses to simulated predator-induced stress in the eastern box turtle, Terrapene carolina carolina

2020 ◽  
Vol 41 (3) ◽  
pp. 387-398
Author(s):  
Victoria L. Preston ◽  
Jessica M. Vannatta ◽  
Matthew Klukowski
Keyword(s):  
Physiological Responses ◽  
Plasma Corticosterone ◽  
Seasonal Effects ◽  
Graded Response ◽  
Box Turtles ◽  
Eastern Box Turtles ◽  
Lactate Levels ◽  
Terrapene Carolina Carolina ◽  
Almost All ◽  
Free Ranging

Abstract In spite of the fully-hinged shell being the defining characteristic of box turtles, few studies have quantified the behavioural use of the shell in response to predator encounters. While it is often assumed that box turtles simply withdraw into their shell in response to threats, we expected variability among individuals in shell usage and in the degree of head and limb retraction because withdrawal is likely to be costly. We tested the behavioural and physiological responses of free-ranging eastern box turtles to stimuli of varying intensity: observation only, a visual stimulus, a poke on the leg, or a pinch on the leg before being flipped. The more intense the simulated predatory stimulus, the more likely turtles were to fully close their shell. However, stimulus intensity did not affect plasma corticosterone or lactate levels. This may be due to too brief or weak of a stimulus, increased parasympathetic activity, or seasonal effects. Upon capture and during handling, almost all turtles withdrew into their shells and closed their anterior plastron, although fewer closed their posterior plastron, and a few engaged in other behaviours such as biting and urinating. Older, larger turtles were able to close their shells with greater strength than younger and smaller turtles. Our results indicate that in spite of their fully closable shell, box turtles exhibit a graded response to perceived threats. This suggests that full closure of the shell is likely to be costly and occurs only in response to the most intense stimuli.

scholarly journals A Five-Ingredient Nutritional Supplement and Home-Based Resistance Exercise Improve Lean Mass and Strength in Free-Living Elderly

Nutrients ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2391 ◽  
Author(s):  
Mats I. Nilsson ◽  
Andrew Mikhail ◽  
Lucy Lan ◽  
Alessia Di Carlo ◽  
Bethanie Hamilton ◽  
...  
Keyword(s):  
Resistance Exercise ◽  
Old Age ◽  
Body Fat ◽  
Lean Mass ◽  
Daily Intake ◽  
Protein Supplementation ◽  
Muscle Quality ◽  
Free Living ◽  
Home Based ◽  
And Function

Old age is associated with lower physical activity levels, suboptimal protein intake, and desensitization to anabolic stimuli, predisposing for age-related muscle loss (sarcopenia). Although resistance exercise (RE) and protein supplementation partially protect against sarcopenia under controlled conditions, the efficacy of home-based, unsupervised RE (HBRE) and multi-ingredient supplementation (MIS) is largely unknown. In this randomized, placebo-controlled and double-blind trial, we examined the effects of HBRE/MIS on muscle mass, strength, and function in free-living, older men. Thirty-two sedentary men underwent twelve weeks of home-based resistance band training (3 d/week), in combination with daily intake of a novel five-nutrient supplement (‘Muscle5’; M5, n = 16, 77.4 ± 2.8 y) containing whey, micellar casein, creatine, vitamin D, and omega-3 fatty acids, or an isocaloric/isonitrogenous placebo (PLA; n = 16, 74.4 ± 1.3 y), containing collagen and sunflower oil. Appendicular and total lean mass (ASM; +3%, TLM; +2%), lean mass to fat ratios (ASM/% body fat; +6%, TLM/% body fat; +5%), maximal strength (grip; +8%, leg press; +17%), and function (5-Times Sit-to-Stand time; −9%) were significantly improved in the M5 group following HBRE/MIS therapy (pre vs. post tests; p < 0.05). Fast-twitch muscle fiber cross-sectional areas of the quadriceps muscle were also significantly increased in the M5 group post intervention (Type IIa; +30.9%, Type IIx, +28.5%, p < 0.05). Sub-group analysis indicated even greater gains in total lean mass in sarcopenic individuals following HBRE/MIS therapy (TLM; +1.65 kg/+3.4%, p < 0.05). We conclude that the Muscle5 supplement is a safe, well-tolerated, and effective complement to low-intensity, home-based resistance exercise and improves lean mass, strength, and overall muscle quality in old age.

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