Wisconsin Wolf Recovery Exceeding Expectations

By Dick Thiel, TWIN member, DNR biologist

The decade of the 1990’s has been an extremely important one in terms of wolf recovery in the upper Great Lakes states. Wisconsin’s wolf population has experienced rapid expansion in both numbers and distribution. The forty or so wolves counted in 1990 has expanded to a population of 180 (1998). In the early years of the 1990’s, wolves colonized the Central Forest region between Black River Falls and Wisconsin Rapids. By 1998 this area consisted of 24 wolves in 6 packs. Within this decade the species has rapidly filled the void between the few founding packs scattered across northwestern and north-central Wisconsin. The only region of suitable habitat that remains devoid of wolf packs is northeastern Wisconsin.

Similar trends have been noted in neighboring Minnesota, and in the Upper Peninsula of Michigan. No resident wolves were known to exist in the UP until 1990. By 1998, around 120 wolves were present.

What has spurned this remarkable turn-around? The rebound in wolves witnessed during the decade of the 1990’s in the three upper Great Lakes states can be traced back in part to stringent adherence to federal and state endangered species protection and population management programs. These programs’ roots extend back to the mid 1970’s. The thrust of established recovery goals (1) ensure survival of wolves in their forested northern Minnesota habitats, and (2) reestablishment of modest-sized wolf populations in both Wisconsin and in upper Michigan.

Public attitudes towards wolves have steadily improved since the 1970’s, helped along by cooperative educational efforts on the part of private organizations (such as TWIN), government agencies, and individuals.

The real recovery work was actually performed by the wolves. After all, the forces the drive increases in a population -reproduction and survival tactics- have been left up to them. So what in particular is it about wolves that has led to this endangered species success story?

Wolves are prolific. Each breeding pair mates annually, and a litter of 5-6 pups is born each spring.

Wolves are also inherently social beings, living in families called packs. Both parents tend to the needs of the pups, and when they are away hunting, yearlings (the pups’ older sib generation) take over baby-sitting duties. Sexual maturity is delayed until the second year, affording one-year olds the opportunity to acquire an extra amount of learning under the tutelage of parents before they strike out on their own.

Thus survivorship of offspring is enhanced. One out of three pups (33 percent) reaches its second birthday, or maturity. This means on average, two individuals from each litter of six, or an average of two wolves per pack each year become young adults. Those wolves that make it to adulthood have a high life expectancy. Mortality rates drop to 10 or 20 percent for wolves older than two. Survival is very good among adults, and a few Wisconsin wolves manage to make it to the ripe old age of ten or twelve years.

Wolves are territorial, meaning the pack defends their space (in Wisconsin, each pack occupies a discrete territory of 50 to 75 square miles) against others of their own kind. This compels sexually mature wolves to leave their natal pack in order to search for unoccupied space, and a potential mate. In the late 1970’s and 1980’s (the early phase of recovery in Wisconsin), most suitable habitat in the state was unoccupied. Dispersing Wisconsin wolves move an average of 70 miles away from their source location. One Wisconsin wolf moved 250 miles into Ontario, Canada, and the species is know to move as much as 500 miles. Thus, the species’ practice of territoriality facilitates rapid recolonization of even scattered habitats because young’uns are nearly all destined to leave, and to search for that unoccupied space.

High reproductive rates, delayed maturity, good adult longevity/survival skills, and territoriality enhance the proliferation of this species which is probably why they are one of the most successful carnivores on Earth in recent times.

As we approach the end of the decade and the millennia, most of Wisconsin’s suitable wolf habitat will be filling up. Active population management will become necessary as we approach saturation, the point at which nearly all available suitable habitat is occupied by territorial packs. And that is the topic of another article.