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Gunn, Farnell,
Adamczewski, Dragon, & Laberge. 2002. Census For The South Nahanni
Mountain Caribou Herd, September 2001. 37 pp.
Abstract
The
Nahanni herd of woodland caribou has a main wintering area largely within
Nahanni National Park and a cross-border summer-fall range near the
Tungsten mine in the southern Mackenzie Mountains.
Studies by Parks Canada biologists had defined the herd’s
seasonal ranges from standard VHF radio-collars and fall composition
surveys in the mid to late 1990’s, but the herd’s size had not been
previously estimated.
Relatively low fall calf:cow ratios and increased hunter access had
led to concerns about the sustainability of the harvest from both sides of
the territorial border.
In late September 2001, we carried out a helicopter-based
census-survey of this caribou herd, with joint funding from the NWT, Parks
Canada and Yukon.
We counted 781 caribou and estimated herd size as 940 –1140
caribou based on a sightability correction derived from radio-collared
caribou. Some questions remain about how distinct this herd’s
distribution is as overlap with neighbouring herds occurs in winter. The
calf:cow ratio was 10:100, well below recruitment needed to balance
natural mortality.
However the survey was during the rut when the radio-collared cows
showed high fidelity to the mountain plateaux, which increases the
repeatability of the census.
Hunter harvests (outfitters, licensed residents, and First Nations)
were estimated at 36-44 caribou/year, or 4-5 % of the herd annually.
Yukon Management Guidelines for woodland caribou indicate a
sustainable harvest as 1-3% of a herd’s size annually, from a stable
herd.
Given this harvest rate and increased access from the upgrading in
2001 of the road to the Tungsten mine, NWT and Yukon wildlife managers
should work together to continue monitoring this herd’s demographics,
and to manage the harvest within sustainable limits. |
