Wolves repopulated in the United States at an incredible rate, especially for an endangered species.

Norbert Rosing/Getty Images

Wolf Repopulation in the United States

The wolf's classification as an endangered species sparked a tug-of-war between conservationists wanting to restore balance in nature and the livestock industry looking to protect its livelihood. Despite fierce opposition from the latter, the U.S. government ruled in nature's favor.

It all started when specialists relocated 29 wolves from Alberta, Canada, to Yellowstone National Park in 1995. Officials from the U.S. Fish and Wildlife Service caught the wolves by using tracking collars and transplanted these animals to their new homes [source: Bangs]. After rehabilitating the wolves in pens at the park, the officials released them into the wild. The following year, 37 more wolves were brought into the wilderness of central Idaho.

Wolves don't reproduce like the clichéd rabbit. Many times, only the alpha female in the pack will bear offspring. Nevertheless, the gray wolf has repopulated at a faster rate than almost any other endangered species, chugging along at around 30 percent growth each year [source: Robbins].

But this environmental success hasn't come without a price. From 1987 to 2002, wolves slaughtered a documented 200 head of cattle, 600 sheep, 50 dogs, nine llamas and one horse [source: Robbins]. People have also reported instances of surplus killings, when packs attack more prey than they can consume, which is out of the ordinary for the normally economical eaters [source: Robbins].

Because of this mixed bag of effects, wolves have been simultaneously protected as an endangered and threatened species and managed when they get too close to homes or farms. To ensure survival of the transplants, the federal government stipulated that people could shoot the wolves only if they attacked [source: Bangs]. Also, many of the packs contain at least one wolf with a tracking collar that allows wildlife officials to quickly pinpoint the pack's location if any of the members are causing problems [source: Robbins]. To curb livestock predation, entire packs were taken out in Idaho and Montana, mollifying the ranchers and angering conservationists [source: Wilkinson].

What about their effects on wild animals? Remember those elk we discussed on the previous page? Big game hunters have been in quite a huff since the wolves have sliced the Yellowstone elk population in half [source: Robbins]. In Idaho, wolves have killed as much as 70 percent of the elk­ [source: Berg].

The gray wolf population has boomed since the reintroduction, and evidence exists of the wolves expanding their territory into north-central Washington [source: Cornwall]. Once its numbers crested above 1,500 in the United States, the federal government removed them from the endangered species list in March 2008.

The debate raged on, however, when Montana, Idaho and Wyoming passed laws to allow wolf hunting outside of national park grounds [source: Ewers]. In response, groups including the Sierra Club and National Resources Defense Council filed joint lawsuits to reclassify the wolf as endangered because of these hunting permissions [source: ­Berg]. In July 2008, a federal judge restored protection for gray wolves living in the northern Rockies under the U.S. Endangered Species Act [source: Brown]. Government officials could file an appeal to this ruling, continuing the back-and-forth dispute.

For more information about lobos and canines, check out the links on the next page.

­­