If they don't eat livestock, what do those wolves eat?

3-11-99, some revisions and update 3-27-99

Several days ago I wrote a story on wolf depredations in 1998 on livestock and dogs. In essence there were few. Since the wolves don't eat much lamb or beef, and no little girls yet (as Montana Senator Conrad Burns predicted would happen within a year back when the wolves were reintroduced), what do they eat?

"Too many elk," say some hunters, outfitters and guides.

I talked with Kerry Murphy, and later Doug Smith of the Yellowstone wolf team. They told me that their estimates were the Greater Yellowstone area wolves killed between 800 and 1200 elk a year. It is estimated there are about 30,000 to 40,000 elk in the Greater Yellowstone area occupied by wolves. Their data indicated that 87% of the animals killed were elk. Murphy also gave the following percentages for kills:

elk 87%
moose 2.5%
deer 1.5%
antelope 1%
bison 1%
coyote 1%
mountain goats 0.2%
beaver 0.2%
bighorn sheep none

~5% unknown

These data are based on all kills likely or observed, plus examination of carcasses. Caloric value is different. Obviously a moose or bison counts more than an elk. This is not a random sample of all kills. Obtained these data would be impossible.  The data overweigh the northern range of the Park where observers of wolves are more abundant.

Northern elk herd-
The highest concentration of wolves in Yellowstone is on the northern range of the Park where for the last two winters the elk population size has been stable at about 10,500 elk. Prior to the starvation winter of 1996-7, the northern elk herd population was 16,000 - 19,000.  Note: this year's winter census results were released on March 19, 1999. Officially the count of the northern range herd was 11,742 elk.

The sex ratio of elk in the northern herd is about equal. This means about 5000 cow elk   Approximately 65 calves per 100 cows are born a year (this is lower than most elk herds in the general area). Figure 3200-3300 new elk calves a year. To maintain a stable population, requires a one year elk calf survival rate of 25 calves per 100 cows. Elk calves are preyed on by not just by wolves, but coyotes, cougar, and for about a 2 week period, by bears, especially grizzly. The winter census just completed showed a calf to cow ratio of 34 calves to 100 cows.  So, I would conclude that for 1998-9 there was net recruitment into the herd. The National Park Service news release on the census stated "estimates of calf ratios have varied from 17 to 48 calves per 100 females since the mid-1970s and since 1995 have varied from 23 to 34 calves per 100 female elk."

Jackson elk herd-
There are a number of elk herds in the wolf area, but the other single largest herd is the Jackson elk herd, part of which summers in the southern portion of Yellowstone national park. So far this herd has not been much exploited by wolves, although the situation is changing. Wyoming Game and Fish has an exact goal for this herd's size (the herd is hunted much more than the northern herd) -- 11,000 elk. The herd has long been above this goal. It is presently estimated at about 15,000.

The National Elk Refuge-
Unlike the northern herd, which is naturally regulated, the Jackson (JH herd) is both hunted and fed in the winter. Because dwellings and agriculture long ago preempted much of the Jackson herd's winter range (southern end of Jackson Hole), the National Elk Refuge was created in 1912 and enlarged a number of times (presently 24,700 acres). Usually more than 50% of the Jackson herd winters on the Refuge. The rest winter nearby. In 1974 a goal of 7500 elk wintering on the Refuge was set. For the last 13 years actual numbers of the Refuge ranged from 7680 to 10,736. This winter the goal was reached for the first time -- 7400 elk.

This Refuge population goal was set by the general judgment of biologists. To some folks, however, there can't be enough elk. The arrival of wolves to the elk refuge this winter sent up cheers by most, but predictions of disaster by some. The publicly observed elk kills this winter spawned a rumor that briefly circulated in the Wyoming Legislature that the wolves (all 3 of them, plus the Soda Butte Pack for several weeks) had already killed 900 elk! Several thousand "missing" elk were soon found wintering on the Gros Ventre River and elsewhere.

The Jackson Hole Guide recently published elk population data for the herd:

Year Max number of elk on Refuge Total count JH Herd Est. Total JH Herd  
1991-2 8800 13,458 14,400
1992-3 8295 14,220   - - -
1993-4 8500 15,066 16,500
1994-5 9436 14,899 17,600
1995-6 10,004 14,700 18,000
1996-7 10,736 16,218 18,800
1997-8 8494 13,352 16,400
1998-9 7300 12,984 15,000

Elk in JH herd killed by hunters per year
1993         2648
1994         4322
1995         3079                   mean = 3233 elk harvested
1996         3029
1997         3290
1998         3029

What about bison?
Wolves don't kill very many bison, although there are indications that the number is increasing. The large Crystal Creek Pack winters and summers in the Pelican Valley of the Park. There are numerous elk in the summer, but in winter most elk leave. However, a number of moose and bison winter in the Pelican. The pack has killed both animals. Kerry Murphy reported that a double moose cow/calf kill was seen in Columbine Creek and shorter thereafter another moose kill in the Pelican. He had seen the wolves harassing bison several times.

The Nez Perce Pack killed a bison calf the other day on the Firehole River on the western side of Yellowstone Park. The calf would have been about 10 months old.

Somewhat over 400 bison winter in Jackson Hole. Official goals are to hold it to 400, but a lawsuit by the Fund for Animals stopped a planned bison hunt last fall just as the hunt began. Due to supplemental feeding on the Elk Refuge, the number of bison will increase unless a hunt is held. JH bison numbers are not constrained by the winter like the more natural Yellowstone Park bison are.

These data are not conclusive, but there is no evidence here that wolves are limiting the elk population, especially in view of the fact that they displace some other predators, mostly coyotes, but possibly cougar. The weather and, in the JH herd, hunting, are larger factors in the elk population size. Elk killed are a function of both Wyoming Game and Fish regulations and weather. The weather affects the number of elk born and the number that survive. It also affects hunting success.

3-27-99. Too early to tell if wolves impacting elk numbers. by Scott Mcmillion Bozeman Daily Chronicle. Mcmillion's article agrees with my conclusions. However, despite the lack of evidence that wolves are reducing the elk herd, the rumor mill is gearing up with die hard wolf opponents like T.R. Mader (opinion piece in the Jackson Hole Guide this week) and some outfitters talking about how wolves are killing all the elk.  My view is that, if anything, outfitters should welcome the wolves.  They do give them an excuse when their clients fail to get their prize -- "the damned federal wolves got all the elk."<g>

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