DETECTION OF EARLY-PREGNANCY IN CARIBOU - EVIDENCE FOR EMBRYONIC MORTALITY

To investigate relations between body condition and fecundity we deter mined pregnancy status of arctic caribou (Rangifer tarandus granti) fr om presence or absence of pregnancy-specific protein B (PSPB) and prog esterone concentration in blood sera or plasma. We drew peripheral blo od samples from female caribou 3-5 (n = 142) and 20-23 (n = 44) weeks after the breeding season. We then weighed and estimated the fat conte nt of each caribou, and we radiocollared 115 of 184 individuals. We ve rified parturition status for 96 of these radiocollared females in Jun e. In addition. we determined presence of PSPB for captive caribou in autumn and early winter. Progesterone concentration was superior to PS PB as a predictor of pregnancy during early gestation, and a threshold value of 1.5 ng/mL was used to separate pregnant from nonpregnant fem ales in autumn and, winter Pregnancy status was strongly related to bo dy condition in both autumn and winter, and fatter or heavier caribou were more likely to be pregnant. Use of both PSPB and progesterone con centration allowed detection of early embryonic mortality among lactat ing caribou that were in poor condition.