Seasonal body mass change in rodents could be due to: (1) an adaptive strat
egy that reduces energy requirements during unfavorable seasons and (2) a r
esponse to fluctuations in food resources. We measured seasonal body mass c
hanges and habitat distribution in four Negev highland rodent species, Meri
ones crassus, Gerbillus dasyurus, G. henleyi, and Acomys cahirinus. Analyse
s were done to determine the effect of habitat, season, sex, and residence
on body mass. The species exhibited differences in body mass (a) among seas
ons, except for A. cahirinus, and (b) between sexes, except for G. henleyi.
G. dasyurus was the only species in which body mass was influenced by habi
tat. During summer and winter, M. crassus and G. henleyi made widespread mo
vements whereas G. dasyurus and A. cahirinus did not. Meriones crassus exhi
bited regular dispersal when most individuals moved to the same area and ch
anged habitats seasonally, while movements of G. henleyi occurred non-direc
tionally within the same habitat. In the three gerbil species, M. crassus.
G. dasyurus, and G. henleyi, there was a significant reduction in body mass
in winter, ranging from 8.9% to 20.2%; but no change was found in the spin
y mouse, A. cahirinus. Thus the pattern of reduced body mass during the har
sh, non-breeding season is applicable to some desert rodents. However, more
studies are required to examine whether these changes are an adaptational
strategy to reduce energy requirements or simply a result of reduced food a
vailability.