| seasonal glucocorticoid responses to capture in wild free-living mammals. | we determined baseline and capture-induced glucocorticoid concentrations during two different seasons in three species of wild free-living rodents: brown lemmings (lemmus trimucronatus), golden-mantled ground squirrels (spermophilus saturatus), and yellow-pine chipmunks (tamias amoenus). initial blood samples were obtained within 3 min of capture, so that initial glucocorticoid levels reflect baseline titers of undisturbed animals. animals were held for an additional 30 min, when a second blood ... | 2008 | 18094060 |
| annual cycle of energy and time expenditure in a golden-mantled ground squirrel population. | we have analyzed seasonal shifts of energy and time allocation in a population of golden-mantled ground squirrels (spermophilus saturatus) by directly measuring total daily energy expenditure (dee) with an isotopic technique ("doubly labeled water"=dlw), and by estimating components of total dee through an integration of field behavioral observations with laboratory-measured rates of energy expenditure (oxygen consumption) associated with major behavioral and physiological states. hibernation la ... | 1989 | 28312369 |
| effects of solar radiation and wind speed on metabolic heat production by two mammals with contrasting coat colours. | we report the first empirical data describing the interactive effects of simultaneous changes in irradiance and convection on energy expenditure by live mammals. whole-animal rates of solar heat gain and convective heat loss were measured for representatives of two ground squirrel species, spermophilus lateralis and spermophilus saturatus, that contrast in coloration. radiative heat gain was quantified as the decrease in metabolic heat production caused by the animal's exposure to simulated sola ... | 1995 | 7658187 |
| seasonal changes in body mass, insulin, and glucocorticoids of free-living golden-mantled ground squirrels. | the aim of the present study was to determine the relationship between seasonal variation in levels of insulin, cortisol, and corticosterone and body mass in a natural population of golden-mantled ground squirrels (spermophilus saturatus) over the active season, from april to august. the body mass of females is at an active season minimum on emergence from hibernation, increases during pregnancy and lactation, and shows a further rise during fattening, reaching a peak in august. males are heavie ... | 1994 | 7883140 |
| npy and galanin in a hibernator: hypothalamic gene expression and effects on feeding. | neuropeptides such as neuropeptide y (npy) and galanin may play a role in regulating the pronounced seasonal changes in food intake shown by golden-mantled ground squirrels (spermophilus saturatus). we used in situ hybridization histochemistry to localize the expression of npy and galanin mrna in the hypothalamus of normally feeding animals. npy mrna was abundantly expressed in the arcuate nucleus, while galanin mrna was concentrated in both the arcuate nucleus and the dorsomedial nuclei. when n ... | 1993 | 7693306 |