Aerial Surveys of the Wolverine and Chase Woodland Caribou Herds in North-central British Columbia
Our goal was continued implementation of an adaptive management project which is focused on mitigating risk of predation for woodland caribou (Rangifer tarandus caribou). Completed surveys from annual work contribute to the required baseline information for the project where our specific emphasis was on surveying caribou population status incorporating assessments of recruitment and mortality, as well as completing an assessment wolf movements based on downloaded GPS collar information. We updated population summaries for caribou in the Wolverine and Chase recovery plan areas by conducting aerial surveys to estimate post-neonatal calf survival (July), post-summer calf survival (November), potential late winter juvenile recruitment (March), and a total count of animals (March). We authoritatively sampled seasonal ranges based on outputs of the Caribou Habitat Assessment and Supply Estimator (CHASE) surveying areas that we knew had a high likelihood of being occupied by caribou relative to the seasonal timing of the sampling period. We supplemented the evaluations of the range types by surveying as much open alpine habitat as our budget would allow.
During the post neonatal survey we accounted for 64 of 67 collared caribou and 12 of 15 collared wolves (Canis lupus). All collared caribou were accounted for during the post summer survey (65/65) but only 10 of 15 collared wolves were accounted for. During the late winter survey we accounted for 61 of 64 collared caribou and 10 of 13 collared wolves. During the late winter survey we observed 36 groups of caribou in the Wolverine herd area and 37 groups in the Chase herd area. The total number of caribou counted in the Wolverine was 230 corresponding to a population estimated of 341 animals. The total count for the Chase herd was 292 animals corresponding with a population estimate of 347. For the Wolverine and Chase areas, calf recruitment was estimated in late winter to be 13 and 14%, respectively. Estimates of calf recruitment from the June and November calf recruitment surveys indicated that most mortality of calves occurred during the summer months for both herd areas. Calves appeared to remain relatively free of mortality during winter months.
Through the year (i.e. for all survey sessions) 23 mortality investigations were completed which were located by: 1) analyzing wolf collar data, and 2) visual observations of sites found during census or telemetry surveys. Five of these mortalities were moose (Alces alces), 11 were caribou, three were wolves, two could not be classified, and two were locations identified using GPS collar data but no mortality was found. All survey data: telemetry, census, collar relocations, and mortality site investigations were entered into the Wildlife Information Management System, a data based specifically designed for this purpose to ensure the long-term accessibility of the data as a baseline dataset for the adaptive management project.