Reproduction Usually only
the dominant pair breeds, however in areas where there is a high ratio
of prey per wolf, such as in Yellowstone National Park, there can be
multiple litters per pack. In the western Great Lakes area wolves breed
in February through March and after a gestation period of 63 days, four
to six pups are born in late-April or early-May. However, the higher
the latitude, the later the breeding. For instance, wolves in northern Canada living at a latitude of 71 degrees breed in late March through
April.
Pup Survival Pup
survival is directly related to prey availability. Prey availability is
generally higher in areas that are being newly colonized by wolves,
where wolves have been recently reintroduced, or where adult wolves are
harvested.
Adult Survival and Longevity The
overall survival of yearling and adult wolves in the western Great
Lakes area has been documented to vary between 60% and 80%. Gray wolves
are known to live up to 13 years in the wild and 16 years in
captivity. However, averages vary based on geographic location.
Pack and Territory Size The
number of individuals per pack can be highly variable, but averages
four to eight during winter in the western Great Lakes area with
records of up to 16. Pack size can be as high as 30 or more in parts of
Canada and Alaska. A wolf pack will roam and defend a territory of
between 42 and 100 miles2 in the western Great Lakes area. Territories
can reach hundreds of square miles where prey densities are in low
density such as in northwestern Canada.
Dispersal and Ability to Colonize New Areas Dispersal
is the primary way wolves colonize new areas and maintain genetic
diversity. Wolves have been known to disperse up to 550 miles, but more
commonly disperse 50 - 100 miles from their natal pack. Generally
wolves disperse when 1 - 2 years old as they reach sexual maturity
although some adults disperse also. At any one time 5 - 20% of the wolf
population may be dispersing individuals. Usually a wolf disperses to
find an individual of the opposite sex, find a territory, and start a
new pack. Some dispersers join packs that are already formed.
Habitat Requirements Wolves
can occur wherever there is a sufficient number of large ungulates such
as deer, moose, elk, caribou, bison, and musk ox. Wolves were once considered a
wilderness animal, however if human-caused mortality is kept below
certain levels, wolves can live in most areas. Historically, they once
occupied every habitat that had sufficient prey in North America from
mid Mexico to the polar ice pack.
Food Requirements Wolves
can survive on 2.5 pounds of food per day, but require about five
pounds per day to reproduce successfully. Wolves are estimated to eat
10 pounds of food per day on average. Wolves don't actually eat every
day, however as they live a feast or famine lifestyle. They may go
several days without a meal and them gorge on over 20 pounds of meat
when a kill is made. Wolves primarily feed oon prey animals larger than
themselves as this provides food for many individuals. However, wolves
will prey upon smaller mammals such as beaver and hare. Because wolves
as a species inhabit a much wider area than its prey species, different
populations of wolves prey upon different animals. Wolves located in
the Western Great Lakes region typically prey upon whitetail deer
whereas wolves located in central Canada prey primarily on caribou.
Impacts on Prey Wolf kill rates vary in relation
to winter severity. Young, old, and sick prey animals are often
nutritionally stressed and have difficulty traveling in deep snow. Wolf
kill rates are highest during severe winters and the following spring.
Sometimes wolf predation can keep prey populations at low levels for
extended periods, but habitat alterations like forest cutting or fire,
improved weather conditions, and human management practices allow prey
populations to quickly recover.
One example of the predator-prey
dynamic is that the reductions in ungulate herds caused by wolves increases
habitat quality and helps rid the herd of genetically unfit and
diseased individuals. This results in long term maintenance of a
healthier ungulate herd. For example, deer and wolves have evolved together and wolf
predation has played a crucial role in making the deer what it is today.
Population Cycles Wolf
density often changes with the density of their primary prey. For
example, in the northern Great Lakes region, the severe winters of
1995-96 and 1996-97 resulted in substantial numbers of deer being
stressed and many starved or were killed by wolves. This provided a
readily available food supply to wolves and increased their survival.
However, wolf numbers usually decline a year or two following the
decline of primary prey. In addition to other factors, the mild
winters since 1997 have been favorable to deer populations by
increasing the winter survival of deer and in turn increasing the
number of fawns being born.
Potential for Population Change With
abundant food and low human-caused mortality, wolves have a high
capacity for population growth. In fact, in the right conditions, wolf
populations can double in two to three years. From 1997 to 2000 the
wolf population in the Northern Rocky states doubled from 200 to 400.
Wolf populations can decline, however, if human caused mortality is
consistently greater than 28-50% of the fall wolf population.
Selected References Carbyn,
L.C. 1987. Gray wolf and Red wolf. Pages 361-376 in M. Novak, J.A.
Baker, M.E. Obbard, and B Malloch editors. Wild Furbearer Management
and Conservation in North America. Ontario Ministry of Natural
Resources, Ontario, Canada. 1150 pp.
Fuller, T.K. 1997.
Guidelines for gray wolf management in the northern Great Lakes region.
International Wolf Center, publication no. IWC97-271. 20pp.
Mech,
L.D. 1995. What do we know about wolves and what more do we need to
learn? Pages 537-545 in L.N. Carbyn, S.H. Fritts, and D.R. Seip
editors. Ecology and conservation of wolves in a changing world.
Canadian Circumpolar Institute, occasional publication no. 35. 642 pp.
Nowak,
R.M. 1995. Another look at wolf taxonomy. Pages 375-398 in L.N. Carbyn,
S.H. Fritts, and D.R. Seip editors. Ecology and conservation of wolves
in a changing world. Canadian Circumpolar Institute, occasional
publication no. 35. 642 pp.
