Post-calving photo-census of the Rivière George caribou herd in July 1993

Abstract

A photographie census of the Rivière George caribou herd in Quebec and Labrador was conducted between 4-23 July 1993 during the post-calving period. The primary objective of the study was to obtain an accurate estimate of the current size of the herd to permit the monitoring of population trends and effective management of the herd. The census procedure consisted of (1) use of satellite and conventional radio-telemetry to locate and photograph post-calving aggregations during the period of optimal aggregation, (2) determination of the minimum population size by direct counts from photographs, and (3) estimation of the total population size using the Petersen Index method. This method allowed extrapolation of the data to caribou that were either not photographed or that were not aggregated at the time of the census. The minimum count indicates that the Rivière George caribou herd consisted of at least 358 460 adults (older than calves) at the time of the census. This count underestimates the total population size but is useful because it is virtually free of error. The total size of the Rivière George herd in July 1993 was estimated to be 540 040 adults within 90% confidence limits of + 12.8%. Comparisons with previous estimates indicate that the size of the herd continues to be large, but that its growth has probably ceased. This study demonstrates that a photographic survey of post-calving aggregations is an effective method to census the Rivière George herd and possibly other large migratory caribou herds that are monitored by telemetry.

Evaluation of satellite collar sample size requirements for mitigation of low-level military jet disturbance of the George River caribou herd

“…The number of caribou locations in each distance class was determined for each caribou season by extrapolating the proportion of locations to the esti¬ mate of herd size (700 000, Russell et al, 1996;Couturier et al, 1996). We converted the distance class measure to caribou group size by using the equation: Y=mX+b, where, Y=caribou group size and X=distance class.…”

Predation risk and optimal foraging trade-off in the demography and spacing of the George River Herd, 1958 to 1993

“…We argue that the censuses in 1993 Russell et al, 1996) were too high to represent internal growth of the George River Herd and that animals from the Leaf River Herd were present and counted in these estimates; we did not include these counts in our equations of population growth of the herd. In both 1988 and 1993 Leaf River ani¬ mals were associated with George River calving females (Bergerud, 1996).…”

Population Estimate for the Bluenose-East Caribou Herd Using Post-calving Photography

“…Calving-ground photo surveys, although an improvement, also often produce highly variable results (Crête et al, 1986;Sutherland and Gunn, 1996;Gunn and Sutherland, 1997;. Although the technique is not reliable for all herds during all years, postcalving photography is the method of choice for surveying the Porcupine and other Alaskan herds, as well as the George River herd in Quebec and Labrador (Russell et al, 1996). Our method of digitally counting caribou provides a significant improvement over previous methods in that it requires no manual tallying of caribou numbers, and it is much easier for several people to verify a single count of each group (three observers verified our counts).…”

“…We estimated the total population size using two published methods. The first was presented by Russell et al (1996) and is based on the Lincoln-Petersen Index as applied to radio-telemetry data by White and Garrott (1990). By this method, …”

“…However, because not all collared caribou are associated with aggregations and not all aggregations always contain a collared caribou, total herd size will always be larger than the minimum count obtained during a photo census (Russell et al, 1996). We estimated the total population size using two published methods.…”