VULNERABLITY OF YEARLING AND 2-YEAR-OLD BULL MOOSE TO TWO ANTLER BASED HARVEST REGULATIONS IN BRITISH COLUMBIA

Abstract

A spike-fork (S/F) general open season (GOS) for bull moose (Alces alces) was introduced with a lottery draw, limited entry hunting (LEH) in the Omineca (1981), Thompson (1993), and Okanagan (1993) regions of British Columbia. The S/F regulation permitted harvest of a bull having no more than two tines on one antler, including the tines on the main antler and brow palms; the LEH controlled the harvest of bulls with antlers >S/F. In the Peace region, the S/F regulation was implemented (1996) as part of SOFT regulations which permitted harvest of bulls with spike, fork, or antlers with 3 or more points on either brow palm; in 2003, SOFT10 regulations permitted the harvest of bull moose with ≥10 points on one or both antlers. These combinations with the S/F regulation were meant to control annual harvest of bulls, maintain herd social structure, and maximize recreational opportunity. We used age and antler point data collected through a Voluntary Tooth Return Program (VTRP) from 1988 to 2003 (n = 39,325) to assess vulnerability of yearlings (n = 12,743) and 2-year-olds (n = 8,712) to the S/F regulation as well as a hypothetical spike-only regulation. For each age class, we defined potential vulnerability to the S/F regulation as the proportion of bulls in the harvest with S/F antlers when no antler-based restrictions were in place. We similarly defined potential vulnerability to the spike-only regulation as the proportion of bulls in the harvest with at least one spike antler. Potential vulnerability across British Columbia to the spike-fork regulation was 43% for yearlings and 10% for 2-year-old bulls, whereas potential vulnerability to the spike-only regulation was 8% for yearlings and 1% for 2-year-old bulls. Realized vulnerability to harvest of each age class was defined as the proportion of that age class with spike-fork antlers when there were spike-fork regulations combined with either LEH or other antler-based restrictions. Similarly, realized vulnerability to harvest for spike-only bulls in each age class was the proportion of harvested bulls with at least one spike antler when spike-fork regulations were combined with either LEH or as part of the SOFT or SOFT10 regulations. Realized vulnerability across British Columbia to the S/F regulation was 49% for yearlings and 7% for 2-year-old bulls; realized vulnerability to the spike-only regulation was 9% for yearlings and 1% for 2-year-old bulls. Potential vulnerabilities and realized vulnerabilities varied regionally and annually, which may reflect different subspecies of moose (A. a. shirasi, A. a. andersoni, A. a. gigas) with different antler architectures, but more likely, differences related to habitat quality across the latitudinal breadth of British Columbia. The S/F regulation provides hunting opportunity, but combined with other hunting seasons/regulations, may not provide adequate protection of yearling and 2-year-old bulls in some regions. The spike-only regulation exposes fewer yearling and 2-year-old bulls to harvest and offers an alternative to regulate bull harvests while maintaining hunter opportunity.