THE ECOLOGICAL SIGNIFICANCE OF RESTING METABOLIC-RATE AND NONSHIVERING THERMOGENESIS FOR RODENTS

1. Resting metabolic rates (RMR) lower than those expected for body mass according to allometric equations have been recorded for species of rodents inhabiting arid and semi-arid environments. Such a phenomenon was also noted in non-arid rodent species which are adapted to various modes of life. Non-shivering thermogenesis (NST) is an important mechanism for heat production in small cold-acclimated mammals. 2. The aim of this study was to try to assess the ecological significance of NST by comparing various parameters concerning NST, RMR and overall minimal thermal conductance. The analysis was carried out on data obtained from 21 species, 4 chromosomal types of Spalax ehrenbergi and 2 different populations of Acomys russatus. The studied species were from Israel and South Africa. 3. The analysis revealed that RMR is an adaptive parameter and has an allometric relation with body mass. It depends on habitat and time of activity. Species which have low RMR values show high values of NST.