Seasonal changes in body composition and caloric content of Great Basin rodents

Seasonal changes in the water content and level in the bank vole against the background of other gross body components

“…Seasonal differences in water content have been demonstrated in ten species inhabiting different geographical regions and differentiated in respect of their ways of living (Górecki, 1965;Fleharty, et al, 1973; Sa wicka-Kapusta, 1974; Schreiber & Johnson, 1975). In these rodents the water content was compared with the body weight and sometimes with the contents removed from the stomachs.…”

“…Seasonal fluctuations in the basic body components of these animals have also been recorded, especially changes in fatness (for extensive references see Schreiber & Johnson, 1975). As regards other body components, only the regularities and succesion of changes in the amounts and proportions of water, protein and mineral substances in the postnatal development of several rodent species have been studied more extensivelly (see Fedyk, 1974aFedyk, , 1974b for a review of literature).…”

“…The data on seasonal changes in water content and level in an organism are controversial. There is evidence that the amount and proportion of water in the organism of rodents and insectivores are lower in winter than in summer (Jameson & Mead, 1964;Górecki, 1965; M y r c h a, 1969; Fleharty, Krause & Stinnet, 1973; Sa wick a-K a pusta, 1974; Schreiber & Johnson, 1975). There are also data which indicate that the changes in the hydration of animals are associated with their age and physiological conditions (e.g.…”

Bioenergetics of the Great Basin pocket mouse, Perognathus parvus

“…1). Since this species accumulates no appreciable body fat, their overwinter survival depends on food caches and periodic torpor (Schreiber & Johnson, 1975). Although heteromyids are highly individualistic in their proclivity for torpor, the pattern and periodicity is apparently a function of the amount of food stored and environmental conditions of the.…”

“…Subadult weights for males and non-gravid females were 13.0 and 11.5 g, respectively. I used the following caloric values for the tissues (K): for the embryo, 0.98 kcal/g fresh weight, based on the average caloric values of five species of newborn rodents (G o r e c k i, 1965; Myrcha & Walkowa, 1968; S o h o 11, 1973); for the unweaned young, 1.39 kcal/g, assuming an average weaning age of 25 days and the mean caloric value of two species of rodents (Myrcha & Walkowa, 1968; So ho It, 1973), and for weaned young, 1.55 kcal/g (Schreiber & Johnson, 1975). Lacking specific data for growth efficiency (G) during gestation and lactation, I used that calculated by Kaczmarski (1966) for the bank vole (Clethrionomys glareolus) and by Mig ula (1969) for the common vole (Microtus arvalis).…”