This winter, almost a fifth of our nation’s pure-bred bison herd in Yellowstone National Park will be culled. ©Henry H. Holdsworth

As many as 900 Yellowstone National Park American bison may be exterminated in winter 2014-2015. It’s estimated that our nation’s last, pure herd of free-ranging bison that have managed to continuously live on their native grounds currently numbers at 4,900. That means that a fifth of this near-threatened species is soon to be killed.

On the state level, I see a similar prospect for this winter regarding gray wolves. In Wisconsin, where I live, the natural resources board has recently approved a wolf quota of 156 animals for the 2014 hunting season. It’s part of Wisconsin’s wolf management plan, which calls for reducing the state’s wolf population by about 45 percent, from approximately 800 wolves to 350 in a three-year span.

Less than only three years ago, on January 27, 2012, the gray wolf was removed from the federal endangered species list in the Western Great Lakes area following a decades-long federal government effort to repopulate the animals after they were nearly wiped out in the early 20th century.

When once-threatened species have only recently recovered enough to be delisted, should we be so quick to institute culling measures?

Wisconsin’s 800 wolves will be cut back to 350 in three years. ©Henry H. Holdsworth

Worries about land and livestock

Once, 30 million Bison bison roamed the plains west of the Mississippi River. But systematic hunting after European settlement drove their numbers down to fewer than 50. Those remaining animals found refuge in Yellowstone in the early 1900s. Today, the population has recovered to almost 5,000, a number that is above the 3,000 to 3,500 goal set in a management plan hammered out among federal and state agricultural and wildlife agencies.

Agreeing to keep bison numbers that low is in part a response to fears among ranchers in Idaho, Montana and Wyoming that bison migrating each winter from Yellowstone to historic grazing grounds could spread the bacterial disease brucellosis to livestock. Roughly half of Yellowstone’s bison have been exposed to the disease, most likely brought to the park by cattle that once grazed there. Brucellosis, which can cause cows to miscarry, has been virtually eradicated from Montana livestock; and the state’s brucellosis-free status allows ranchers to sell and ship cattle across state lines without expensive quarantines, tests and vaccinations.

According to the National Park Service, bison are also prolific when environmental conditions are favorable and have high survival rates, soon filling what available habitat there is for them and out-pacing the acquisition of additional habitat. While the carrying capacity of the land inside the park could be as high as 5,500 to 7,500 bison during winter, lower-elevation habitat for bison is limited by mountains in the park and by competition with agriculture, development and transportation systems outside the park’s boundaries.

In Wisconsin, a similar reasoning is used to support wolf culling. Gray wolves, which have lived in the state since the glaciers retreated 10,000 years ago, were driven to extinction here in 1960 after a century of elimination efforts. They began to make a comeback along the Minnesota border in 1975. In 1989, the Wisconsin Department of Natural Resources launched a plan to recover the species. Wolves were reclassified on the state level from “threatened” to “protected wild animal” in 2004 when the population passed 350.

Proponents of reducing the population back down to 350 say that 800 wolves is far too many for the habitat the state currently has for them and that drastically reducing their numbers would decrease wolf depredations on livestock, deer, hunting hounds and, occasionally, pets.

Pressure from special interest groups

The number of bison culled from Yellowstone National Park has varied widely from year to year, but the 900 slated for this winter represents the largest slaughter in seven years.

Yellowstone’s elk—which also carry brucellosis—are not culled. ©Henry H. Holdsworth

Those who oppose the culling have argued that no other wildlife in the national park, including elk—which also carry brucellosis—is killed while following an ancient winter migration route (although wolves choose elk over bison). A state veterinarian in Montana, Marty Zaluski, has suggested a plan to shoot bison with “biobullets,” absorbable projectiles containing a vaccine against brucellosis. Yellowstone managers, however, rejected that plan because of its cost of $9 million and questions about its ultimate effectiveness.

According to sustained yield theory (the ecological yield that can be extracted without reducing the base of the capital itself)—a prominent approach for managing wildlife—a species’ population numbers should be at no less than half of its habitat’s total carrying capacity to ensure long-term stability. Above that level, a population can naturally rebound from environmental variations and harvest seasons. Experts have estimated that the carrying capacity for wolves in Wisconsin is 900. But at 350, small mistakes in management would no longer be self-correcting and could lead to instability.

Surprisingly, the Wisconsin Wolf Advisory Committee does not allow members who are University of Wisconsin biologists, UW faculty or representatives from wolf advocacy groups. The recently revamped committee now has more representation from members who belong to special interest groups, including sportsmen from hunting and trapping organizations and hunting hound enthusiasts.

This year’s planned large cull of bison comes at the same time that there is a call to declare Bison bison as our national mammal. Unlike the grizzly bear that appears on the California state flag, I hope that once designated as such, there will be enough real bison left in our nation for future generations to see in the flesh.

Do you think culling recently threatened or near-threatened species can be done without placing such animals in serious danger of extinction, or should longer periods of recovery and a higher population minimum be mandated before any population reduction measures are taken?

Here’s to finding your true places and natural habitats,

Candy