Gray wolves (Canis lupus) are the largest wild members
of the dog family
(Canidae). Adult gray wolves range from 40–175 pounds,
depending upon sex and region. In the Northern Rocky Mountains,
adult male gray wolves average over 100 pounds, but may
weigh up to 130 pounds. Females weigh slightly less than
males. Wolves have a wide range of fur color, frequently
a grizzled gray, but it can vary from pure white to black.
Gray wolves have a circumpolar range including North America,
Asia. As Europeans began settling the United States, they
poisoned, trapped, and shot wolves, causing this once-
widespread species to be eradicated from most of its range
in the 48 conterminous states.
Wolves primarily prey on medium and large mammals. Wolves
have a social structure, normally living in packs of two
to 12 animals. In the Northern Rocky Mountains, pack sizes
average about 10 wolves in protected areas, but a few complex
packs have been substantially bigger in some areas of Yellowstone
National Park. Packs typically occupy large distinct territories
(200–500 square miles) and defend these areas from
other wolves or packs.
Once a given area is occupied by resident wolf packs,
it becomes saturated and wolf numbers become regulated
the amount of available prey, intraspecies conflict,
other forms of mortality, and dispersal.
Dispersing wolves may cover large areas as lone animals
as they try to join other packs or attempt to form
their own pack in unoccupied habitat. Dispersal distances
the Northern Rockies average about 60 miles, but dispersals
over 500 miles have been documented.
Females and males typically begin breeding as two-year-olds
and may annually produce young until they are over
10 years old. Litters are typically born in April
one to 11 pups, but average around five pups. Most
years, four of these five pups survive until winter.
can live 13 years but the average lifespan in the
Northern Rockies is less than four years. Pup production
survival can increase when wolf density is lower
and food availability
per wolf increases. Breeding members also can be
quickly replaced either from within or outside the
wolf populations can rapidly recover from severe
disruptions, such as very high levels of human-caused
After severe declines, wolf populations can more
than double in just two years if mortality is reduced;
nearly 100 percent per year have been documented
in low-density suitable habitat.
Source: U.S. Fish and Wildlife Service