Body Growth in Sixteen Rodent Species and Subspecies Maintained in Laboratory Colonies

Abstract

Body growth as weight change during the initial year is described for 10 microtines: Microtus pennsylvanicus tananaensis, M. oeconomus macfarlani, M. o. operarius, M. miurus, M. abbreviatus, Lemmus lemmus, L. sibiricus, Dicrostonyx stevensoni and Clethrionomys rutilus; five cricetines: Peromyscus maniculatus borealis, P. m. bairdii, Baiomys taylori, Calomys ducilla, and Calomys callosus; and one murid, Acomys cahirinus. The growth curves constituted sets of linear segments and were characterized by their respective slopes and initiation points. A rapid growth phase was sometimes preceded by a slower initial phase and always succeeded by a slower attenuation phase. A stable adult weight was achieved in some species but not others. Early and later growth were compared using times for 40% and 80% of the weight ( ) at 1 yr ( , ). Early growth as gram per week was relatively stable among subspecies or related species; or between animals of different size when normalized as percent of per week, or by a common weight function. By contrast, later growth ( ) was much more variable and may be viewed as a possible adaptive factor.