Here is an example of just how these types of management programs can work. A Yukon Study:
In response to declining numbers of the Aishihik Caribou Herd and adjacent moose populations in that area, a Recovery Program was undertaken through the '90's and into 2000. That program was initiated with a complete closure for the licensed hunting season for Aishihik Caribou in 1991 and placing moose on permit in 1993 followed by full closure in 1994. To limit predation on the caribou and moose, the Yukon government then led an experimental program to reduce the number of wolves through lethal and non-lethal methods in the region of study.
Wolf numbers were manipulated in three phases:
· They were shot from helicopters each winter from 1993-1997;
· Surgical sterilizations occurred between 1993 and 1997 (14 wolves from 7 packs);
· An experimental immune-contraceptive vaccine was applied to 11 females between 2000 and 2003.
These methods resulted in a reduction of wolf numbers by 80% -- from 28 wolf packs in 1992 to 7-20 packs during the reduction period. A total of 157 wolves were killed over the period 1993-1998 in the Aishihik caribou herd’s range. As well, 32 wolves were trapped during this period.
The Aishihik caribou herd’s adult sex ratio changed from 29 bulls for every 100 cows (pre-1993) to 52 bulls/100 cows by 1997. Increased recruitment rates (calf:cow ratio) during wolf control compared to before was not observed in control populations. However, Aishihik was the only herd that showed a sustained increase in annual recruitment during treatment.
Overall it was concluded that the Aishihik caribou population was positively affected by the removal of wolves from the system.
Moose numbers stopped declining and rapidly increased between 1992 and 1998. The change in moose numbers was explained through adult survival rates
that increased from 80% to 98% in the treatment area between the two survey periods.
The Aishihik herd size was estimated to be 2044 caribou in 2009. It has increased by approximately 5% per year since 1997. This increase has occurred in the presence of a recovering wolf population, an increasing wood bison population, and a modest bull-only harvest by licensed hunters which began in 2002.
Lessons Learned
Lowered wolf predation was more important than reducing hunting to increase moose numbers.
Predation limits ungulate populations below their range carrying capacity in the Yukon.
Wolf predation can be reduced using a combination of lethal and non-lethal techniques.
The Aishihik area represents a multi-predator prey system. However, even with bears in the area, wolf reduction resulted in an increase in prey numbers.
This is but one case that the outcome was Successful, in fact
Very Beneficial to the dwindling caribou and moose populations in the area of study. Wolf populations rebounded (as they almost always do) however given the "
boost" in numbers prior to that development, the caribou and moose populations continued to CLIMB as the wolves' number increased alongside them. It very much appears that both populations of predator and prey are still increasing.
No matter how you slice it, this particular program must be viewed as a potentially long-lasting
Success.
http://www.yfwcm.ca/YukonWolfPlanRe..._recovery_program_summary_FINALApr_11_204.pdf
