Body Composition, Energy Content, and Lipid Cycles of Four Species of Rodents

Abstract

GroSS body composition, energy content, and lipid cycles of Peromyscus maniculatus, Reithrodontomys megalotis, Sigmodon hispidus, and Microtus ochrogaster were studied. Ash values for adults ranged from 14.2 to 16.1 per cent of dry body weight, and water content varied from 61.5 to 74.2 per cent. Lipid content ranged from a low of 14.6 per cent dry body weight in M. ochrogaster to a high of 25.6 per cent in S. hispidus. Annually, kilocalories per gram live weight averaged 1.61 in P. maniculatus, 1.65 in R. megalotis, 1.74 in S. hispidus, and 1.42 in M. ochrogaster. Energy content of subadults and adults of S. hispidus differed significantly during summer, autumn, and winter; no such differences were noted for age categories of the other species. The four species exhibited three different types of lipid cycles: in both P. maniculatus and R. megalotis, lipid content was lowest in summer and highest in winter; in S. hispidus, the lowest readings were in spring and the highest in winter; in M. ochrogaster, lipid content fluctuated on a monthly basis but exhibited no annual cycle. We postulate that annual lipid cycles reflect the zoogeographic history of the species, and might thus serve as a measure of physiological adaptation to climatic conditions unlike those that existed at the respective times and places of evolution of the four species.The current interest in energy flow through ecosystems has brought about a need for comprehensive data on body composition and lipid cycles in animals. Body composition of certain small mammals has been studied by Pitts ( 1960), Hayward (1965), and Gorecki (1965. Lipid cycles of certain rodents have been described by Connell (1959), Jameson andMead (1964), andSawicka-Kapusta (1968). A few other studies have dealt with various aspects of lipid deposition in rodents (for example, Hsia-Wu-ping and Sun-Chung-lu, 1963;Gaertner, 1968; and Golley, 1969), but few data are available as yet for even the commonest species of small native mammals.Our purposes in this study were: 1) to determine gross body composition in four species of rodents with overlapping geographic ranges on the Great Plains-namely, the deer mouse (Peromyscus maniculatus), the western harvest mouse (Reithrodontomys megalotis) , the hispid cotton rat (Sigmodon hispidus), and the prairie vole (Microtus ochrogaster); 2) to elucidate their intraspecific and interspecific variation in body composition; and 3) to delineate their lipid cycles. MATERIALS AND METHODSSamples studied included 122 specimens of P. maniculatus, 124 of R. megalotis, 132 of S. hispidus, and 109 of M. ochrogaster. Individuals of the four species were collected in Ellis County, Kansas, in each month during the period October 1969 to September 1970. As soon as possible after they were trapped, rodents were sexed, weighed, and frozen. Just prior to study, each specimen was reweighed; any decrease in weight while frozen was 426

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

“…Values were similar to those reported for other species {e.g., Bailey et al 1960;Górecki, 1965;Fleharty et al 1973) and support the suggestion that this component varies within narrow limits in small mammals. It is reasonable, therefore, to assume ash content has no appreciable effect on seasonal variation in live weight caloric content.…”

Caloric values of small mammals of southeastern Quebec

“…The interspecific comparison of the means shows that S. cinereus is 4% lower than the other species, which is about twice the value found by Górecki (1965). Fleharty et al (1973) found high values of ash contents (14.2-16.2%) and suggested that this might have been due to the age structure of the population. I mentioned in an earlier section that my smalLmammal sample was not at an uniform adult stage, and contained thus several juvenile and subadult animals.…”

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.…”