Identifying high residency areas of the threatened St. Lawrence beluga whale from fine-scale movements of individuals and coarse-scale movements of herds

Abstract

The development of high-performance tracking and analytical tools has greatly facilitated the study of animal movements, which, in turn, are increasingly employed to study habitat use. However, data on individual movements are rarely available at both broad spatial and temporal scales, limiting their utility for the study of habitat use at population levels. In this study, we propose a novel approach to investigate habitat profitability and population residency patterns by combining the analysis of fine-scale tracking data from individual animals with coarser, short-term movement patterns of herds. We used this approach to identify areas of high residency (AHR) for the St. Lawrence beluga whale Delphinapterus leucas, a population classified as 'threatened' under the Canadian Species At Risk Act. We used radio telemetry and a first passage time approach to study the fine-scale daily movements of 30 belugas. Information obtained from these animals on variation of search effort during displacements, scales at which area-restricted search (ARS) occurred, and associated swimming speeds was used to grid our study area and define a criterion for high residency of beluga herds. The beluga herd database used to identify AHR was composed of 772 visual 'herd follows' covering a large portion of the beluga population summer distribution. Thirty-three ARS zones were identified at 2 different spatial scales (∼500 m and ∼1500 m). Using these scales and the swimming speeds associated with ARS to study the r esidency of herds resulted in the identification of 28 AHRs used by beluga within their summer distribution. © Inter-Research 2012.