Introduction
The wolverine’s habitat is spread across northern and western Canada, Alaska and the mainland USA. However, the historical wolverine population is decreasing, due to unknown reasons although causes could include the changing environment, changing food resources, human activity and settlement, harvest and persecution. They are considered a Species of Special Concern. Wolverines on mainland British Columbia are blue-listed, however, the populations on Vancouver Island are red-listed to a point where their state of existence is unknown.
Background of the Research Project
Wolverine populations have low densities, they inhabit large home ranges and their reproduction is quite low making them susceptible to added outside pressure. Knowing the effects of harvest on wolverines is important to understanding the effects of one external stressor. Males also have a higher mortality rate than females in harvested areas, which makes proper planning and evaluation important to sustainable harvest. The aim is to conserve the populations in their historic and present range and ensure to provide a sustainable harvest for hunters and trappers. Trapping and hunting is regulated with bag limits and seasons throughout almost all of British Columbia.
Methods, Material and Study Area
British Columbia with its area of 980,000 km2 served as the study area. 74 population units were created throughout British Columbia based on a former study about grizzly bear populations. The units were about 12,800 km2 big, however, units in the south tended to be smaller than in the north as there were more potential human-caused threats in those parts. Estimates were used regarding survival rates, reproductive rates and age of first reproduction. More data on harvest and sex of harvested wolverines were acquired from the years of 1985 to 2004.
Results of the Study
For the population estimates in individual units the results were between 0 and 268 individuals. The units with an estimate of zero for harvest and population were Queen Charlotte Island, Arrow Lakes and Kootenay Lakes which were all excluded from further analyses leaving 71 units. Mean population growth rate was calculated to be 1.06, the recruitment for the population units was between 0.02 and 15.71 wolverines and for the whole province it was 195.93 individuals. 16% of the individual units had a recruitment of less than zero. In total 3,496 wolverines were calculated to have been harvested for the time period of 1985 to 2004. Out of these, 97% were harvested through trapping. Within the individual units the total harvest ranged from 0 to 280. The mean annual net recruitment in the whole province was 20.73 wolverines and in the individual units the median net recruitment ranged from -3.05 to 6.00. Fifteen population units might not have sustainable harvest of wolverines as they had a mean and median net recruitment of below zero, and these units make up 40.2% of all wolverine harvest in British Columbia. Five units had a negative mean net recruitment but a positive median net recruitment making it unclear if they were harvested sustainably or not. Less than 50% of the mandatory reporting was made up by female wolverines except for in the units of Lower Stikine, North Coast and West Chilcotin.
Discussion
Throughout most of British Columbia the wolverine harvest has been sustainable. Only 15 population units were estimated to be harvested unsustainably during the time period of 1985 to 2004. Five units were determined to need more management attention. In order to have more valuable data it needs to be ensured that the compulsory harvest data collection and other data collections are consistent. When calculating the net recruitment rates it is important to do both median and mean net recruitment rates. Median net recruitment can be used as an indicator of how likely unsustainable harvest is practised in an area and the mean net recruitment rate can show instances of unsustainable harvest.
The population units are still connected with each other making dispersal possible. For example the data might show an area to be overharvested, however, the population was only a small number to begin with and those might have come from another unit located adjacent or next to it. It would be possible to improve the whole evaluation by including empirical density estimates and local vital rates.
Not all harvest is included in the data as First Nations trappers do not have to report their harvest and poaching and unreported legal harvest are missing as well. For individual units it is possible to sustain 15% more unreported harvest in 51 units, however, the other units cannot sustain more unreported harvest.
Suggested Action
The probability for a change in the wolverine harvest management is small as only 20 out of all the population units had sustainability issues. The issue could be solved by reducing the mean annual harvest by three wolverines in areas with such sustainability problems. Southern and eastern areas of British Columbia should be focused on as they are important to the wolverine populations of Alberta and the rest of Canada and the United States. Closed seasons should be considered and the harvest of consecutive years should be focused on when it exceeds the mean harvest and recruitment rate for a unit. The monitoring of female harvest needs to be improved in order to get better data.
Conclusion
As the wolverine population is decreasing it is important to look at different external stressors which might be the cause. Next to changing environment, food resources and human activity, harvest is also a big stressor. It is important to ensure sustainable harvest and therefore data from 1985 to 2004 was collected and evaluated for individual population units. In the results only 20 out of the 71 analyzed units had unsustainable harvest or other sustainability issues. The compulsory harvest data collection needs to be better monitored as well as the monitoring on female harvest as it may lead to more valuable data. Regarding net recruitment rate the median and mean number should be calculated. In areas with sustainability issues the mean annual harvest should be reduced by three wolverines. These few changes can help with keeping the harvest sustainable in all the population units.
Wolverines in:
- Evergreen Stewardship Plan for Lillooet Sub Region
- Evergreen Stewardship Plan for South Chilcotin Sub Region
- Source Eric C. Lorfroth, Peter K. Ott. December 2010. Journal of Wildlife Management. Assessment of the Sustainability of Wolverine Harvest in British Columbia, Canada. DOI: 10.2193/2007-095 Available at : https://www.researchgate.net/publication/229642518_Assessment_of_the_Sustainability_of_Wolverine_Harvest_in_British_Columbia_Canada [Accessed 03/2021].