REPRODUCTION AND NUTRIENT RESERVES OF BUSHY-TAILED WOOD RATS (NEOTOMA-CINEREA)

Body composition and energy content of female bushy-tailed wood rats ( Neotoma cinerea) were examined in relation to reproductive status. We assessed the extent to which nutrients for offspring were obtained fro m endogenous reserves, and whether use of these reserves might influen ce the timing of spring breeding. Among breeding females, fat levels w ere highest during pregnancy, and were depleted during lactation. The mean reduction in energy content from pregnancy through lactation (266 kJ) accounted for 21% of the estimated 1260 kJ contributed by a femal e to her offspring in this period. Females potentially gained 3.0 days of nutritional support from their endogenous reserves during winter, but this fell to 2.0 days during summer and was only 0.8 days during l actation. Thus, females support the nutritional demands of lactation p rimarily by increasing their ingestion of food. Nevertheless, large en dogenous reserves may enable some females to begin breeding early in t he spring, when the abundance of food is unpredictable.