Text 23276, 104 rader
Skriven 2007-11-22 22:49:00 av JIM WELLER (1:123/140)
     Kommentar till en text av CAROL SHENKENBERGER
Ärende: Caribou
===============
-=> Quoting Carol Shenkenberger to Glen Jamieson <=-

 GJ> I have read of those enormous herds of bison and caribou across North
 GJ> America, now gone forever.

 CS> Not sure Caribou were ever that big in herd size but bigger probably
 CS> than they are now.

They are numerous but herds are shrinking and the species is at risk
in some areas. Some factoids from the Canadian Wildlife Service at
www.hww.ca

Caribou are unusual among deer family members in that females, as
well as males, carry antlers.
 
They use lichens as a primary winter food, which enables it to
survive on harsh northern rangeland

Caribou are similar to and belong to the same species as the wild
and domesticated reindeer of Eurasia.

There are more than 2.4 million caribou in Canada.

The woodland caribou is the largest and darkest of the caribou
subspecies.

About half of all caribou in Canada are barren-ground caribou. They
are somewhat smaller and lighter coloured than woodland caribou.
They spend much or all of the year on the tundra from Alaska to
Baffin Island. Most, or about 1.2 million, of the barren-ground
caribou in Canada live in eight large migratory herds, which migrate
seasonally from the tundra to the taiga, sparsely treed coniferous
forests south of the tundra. (That's the kind I see; we are 200
miles south of that tree-line and they come down to with 20 miles of
Yellowknife in the winter.)

Population status

Despite the large number of caribou in Canada, some subspecies or
populations have been determined to be at risk

The Queen Charlotte Islands population of woodland caribou, found
only on Graham Island, British Columbia are extinct.

Woodland caribou became extirpated from (no longer exist in) Prince
Edward Island before 1873 and from New Brunswick and Nova Scotia by
the 1920s. Only a small, relic herd on the Gaspe Peninsula remains
of the maritime woodland caribou population. It is endangered.

The widespread Boreal population of woodland caribou, which occurs
in the Northwest Territories, British Columbia, Alberta,
Saskatchewan, Manitoba, Ontario, Quebec, and Newfoundland and
Labrador, has been assessed as threatened.

Recovery measures

Caribou are susceptible to and recover slowly from population
declines because of their low rate of reproduction. The main factors
leading to caribou declines are habitat loss, degradation, and
fragmentation, as well as predation. Loss of caribou habitat, which
is permanent, occurs when forest is cleared for agriculture, for
example. Habitat degradation means a reduction in the amount or
quality of caribou habitat, as happens following such events as
wildfires or timber harvesting, or through human disturbance.
Habitat fragmentation is the breaking up of habitat areas by roads,
timber harvest cut-blocks, pipelines, oil and gas well sites,
geophysical exploration lines, and other developments.

Caribou in the boreal forest require large tracts of relatively
undisturbed, older forest habitat in order to spread out so they are
harder for predators and hunters to find, and to avoid the linear
corridors that predators and hunters use to gain easier access to
their prey. Older forests tend to be richer than younger forests in
the lichens caribou depend on. They are also less favoured by moose
and deer, which as prey species of the wolf, attract this primary
predator of caribou.

A wolf eats a variety of prey but requires food equivalent to 11 to
14 caribou a year. Some wolf packs will follow migrating herds of
caribou from summer to winter range and back. Other predators of
caribou include grizzly and black bears, cougars, wolverines, lynx,
coyotes, and golden eagles.

Partly as a result of habitat changes caused by humans, white-tailed
deer have expanded into caribou areas from Manitoba to Quebec,
transmitting meningeal brain worm, which is fatal to caribou,
although it does not harm the deer. (We now have deer on the north
side of Great Slave Lake for the first time ever.)

Recently there has also been a lot of concern about the potential
impact of climate change on caribou, especially in the north. Deeper
snow, faster spring melt, warmer summers, freezing rain, and the
high annual variability of all these factors will have an impact on
the ability of the species to thrive in its environment.


Cheers

YK Jim


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