Meeting Abstract

29.1  Jan. 5  Timing of birth affects body protein dynamics of mothers in an arctic mammal BARBOZA, P.S.*; PARKER, K.L.; Univ. of Alaska, Fairbanks; Univ. of Northern British Columbia ffpsb@uaf.edu

Rapid changes in climate are altering the timing and abundance of food for seasonal reproduction in arctic animals. Reindeer and caribou typically form large herds throughout the circumpolar north. Timing of birth is separated by one month for these two subspecies of Rangifer tarandus under similar conditions. Reindeer (R. t. tarandus) lose more body mass during pregnancy than caribou (R. t. granti) because they complete pregnancy in late winter when food intakes are still low. We used isotopically labeled diets to demonstrate that maternal protein stored from early winter is used for 96% of fetal protein in reindeer and only 84% of fetal growth in caribou. Both subspecies rely on maternal body protein for 87-94% of the protein deposited in the growing calf. Successful calving by caribou is most vulnerable to delays in spring plant growth at the end of pregnancy, whereas reproduction by reindeer is more vulnerable to short summers and reduced food supplies in early pregnancy. The response of Rangifer herds to environmental change therefore will depend on reproductive strategies for timing of birth and the use of body stores to support pregnancy and milk production.