scholarly journals Repeatability of Maximal Aerobic Performance in Belding's Ground Squirrels, Spermophilus beldingi

1995 ◽  
Vol 9 (3) ◽  
pp. 498 ◽  
Author(s):  
M. A. Chappell ◽  
G. C. Bachman ◽  
J. P. Odell
Keyword(s):  
Ground Squirrels ◽  
Aerobic Performance ◽  
Spermophilus 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.

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.

Ketone body metabolism in a ground squirrel during hibernation and fasting

1985 ◽  
Vol 249 (4) ◽  
pp. R462-R470 ◽  
Author(s):  
B. L. Krilowicz
Keyword(s):  
Energy Source ◽  
Glucose Uptake ◽  
Ground Squirrel ◽  
Ketone Body ◽  
Glucose Utilization ◽  
Ground Squirrels ◽  
Body Protein ◽  
Muscle Tissues ◽  
Spermophilus Beldingi

Hibernating Belding's ground squirrels (Spermophilus beldingi) are ketotic relative to fed nonhibernators. Muscles from torpid individuals, when incubated in media containing physiological concentrations of glucose and ketone, show reduced uptake of glucose in the presence of ketone. The magnitude of the reduction is dependent on ketone concentration and reaches 60% in heart and 100% in pectoralis at 1.4 mM ketone. Fasted squirrels are also ketotic. However, ketone does not reduce glucose uptake in muscles from fed or fasted animals. Glucose utilization by muscles decreases during a long-term fast, but the reduction is independent of ketone. Thus both a long-term fast and hibernation lead to changes in muscle tissues that decrease their reliance on glucose as an energy source. Ketosis leads to glucose sparing during hibernation, whereas muscle glucose utilization is decreased independently of ketone during a fast. The glucose sparing achieved in both hibernation and fasting leads to conservation of body protein, the major source of gluconeogenic precursors in fasting mammals.

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.

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