PRODUCTIVITY AND EARLY CALF SURVIVAL IN THE PORCUPINE CARIBOU HERD

Concerns have been raised that displacement from traditional calving and postcalving areas by petroleum exploration may cause increased calf mortality in the Porcupine Caribou (Rangifer tarandus) Herd. Consequently, we determined productivity and early calf survival by frequently locating 23-53 radio-collared cows and 59-61 radio-collared calves from 1983 to 1985. Seventy-nine to 87% of the adult females gave birth each year, and 68-90% of calves were born within, or adjacent to, a coastal plain area proposed for petroleum leasing and development. Sixteen to 35% of the calves died by 25 June. Fifty-nine to 74% of calf mortality occurred within 48 hours of birth and involved a number of causes in addition to predation. Predation was the major cause of death after the first 48 hours, and mortality increased toward higher terrain away from the coastal plain. Additional data from carcasses of unmarked calves corroborated the trends noted for radio-collared cows and calves. We conclude that if petroleum development displaces calving from the coastal plain, calf mortality likely will increase.