By Nancy Warren
Science shows that the Michigan wolf population has remained stable within a range of 600-700 animals for the past 12 years, with wolf packs remaining constant with an average of 4-5 animals.
The reason: biology.
Wolves have low reproductive rates. Within a pack, typically only the dominant pair breeds and reproduces. Breeding among others within the pack is suppressed by the dominant male and female.
If one or both members of the breeding pair are killed, the remaining members of the pack may disperse, starve, or remain in the territory until an unrelated dispersing wolf arrives and mates with one of the remaining pack members to begin a new pack.
The biology of wolves has been researched and documented extensively, and can be found at www.wolfplanning.org (Comprehensive Resource Guide Chapter 8) and in the 2015 Michigan Department of Natural Resources Wolf Management Plan, which is in the process of being updated with the latest scientific data.
Wolves are also subject to diseases. Research published in 2009 by Dr. David Mech, senior research scientist who specializes in studying wolves with the Biological Resources Division of the U.S. Geological Survey, revealed that disease has been a threat to the wolf population for a long time. Wolves are particularly susceptible to parvovirus, distemper, blastymycosis, and lyme disease.
Pups, which are born in the spring, average 4-6 litter mates but aren’t likely to survive. Pups are susceptible to and often succumb to disease and malnutrition during their first six months of life, and may even be killed by predators such as bears. Mech and others have documented pup mortality at 60%.
Adult mortality is also high, and the average life expectancy of an adult Michigan wolf is four years. Mange, which can be transmitted by body contact among pack members, may increase susceptibility to other diseases and tick-borne diseases such as anaplasmosis and ehrlichiosis. A 2016 peer-reviewed report published in the Public Library of Science found that 9.2% of Wisconsin wolves were exposed to heartworm, and records show Michigan wolves have also been exposed.
There’s also the human factor: Illegal killing of wolves, car collisions, and wolves killed in territorial disputes or those who die when bringing down prey, also contributes to low survival rates for wolves.
Individual wolves rarely assume a breeding position within their natal packs. While some animals will remain within the pack, content with their low ranking, others will disperse in search of a mate and their own territory. But life is not easy for a lone wolf who must find food, cross unfamiliar roads, and often trespass into another pack’s territory – where it will either be accepted, or killed.
Attempts to count wolves in each state vary somewhat, but all states use some common standards. Surveys are done in the winter. Finding wolf tracks is best done after two or three days of snowfall. Snow tracking also makes it easier to find territorial markings, like raised leg urinations by the dominate male and female, and squat urinations by subordinate male and females of the pack.
The track surveys combined with data obtained from collared animals, howling surveys, visual observations, and trail camera photos help determine the number of wolves within a pack, the county and the state.
At the Michigan Wolf Advisory meeting, DNR biologist Brian Roell explained the methodology used to determine the wolf population. You can view his presentation at the DNR Website Michigan.gov/dnr then click public input and scroll down and click Wolf Management Advisory Council.
Managing wolves is a controversial topic, and it is important to use the best scientific data, research, and facts during the discussion.
