What Yellowstone Wolves Eat

Their menu varies by season and size

Wolves kill for three reasons: to fill their stomachs, feed their young, or eliminate competitors. The Yellowstone Wolf Project keeps close tabs on what the park’s wolves kill. They send teams to study specific wolf packs for set periods of time. These technicians may be lucky enough to see wolves in action or may investigate carcasses that wolves leave behind. Other technicians go out and investigate sites where the Wolf Project thinks there may be a kill. And there are the many wolf watchers glued to spotting scopes and happy to report what they observe. 

All in all, Yellowstone’s wolves may be the most watched in the world. The Wolf Project keeps track of information from numerous sources, and in each annual report they summarize their findings. 

I spent a bunch of hours recently analyzing all the annual reports released since the 1995 reintroduction of wolves. While the Wolf Project doesn’t find or investigate every wolf kill in the park, their findings provide a solid picture of what wolves eat and the relative frequency of each type of meal. That data allows me to imagine a wolf menu. 

On the right side of the menu in large font would be—THE BIG MEALS. First, of course, is elk. At 500 pounds for a female and 700 pounds for a male, an elk makes a satisfying meal for nine to ten wolves, the typical size of a Yellowstone pack. In 2020 elk made up 60% of wolf kills analyzed, according to the Wolf Project annual report. In 1995, on the other hoof, elk accounted for 86% of wolf kills. 

That decrease in the number of elk taken coincides with the decrease in the total number of elk running around the northeastern corner of Yellowstone—the area called the Northern Range. In 1995 when wolves were reintroduced, there were perhaps 17,000 elk overrunning the Northern Range. Wolves were reintroduced, in part, to help reduce that number and the damage the elk were doing to park vegetation. Those thousands of elk had never seen a wolf, had not yet learned that ignoring a pack can be fatal. Wolves ate elk for most meals.

Fast forward to today: The elk count has stabilized at 6,000 to 7,000 on the Northern Range, where wolves, black bears, grizzly bears, coyotes, and cougars prey on elk—and, don’t forget, people hunt elk outside the park. Today’s elk have grown up in herds that are experienced in dealing with predators. Wolves take fewer of these experienced elk.

But enough about elk, let’s get back to the menu. Next under THE BIG MEALS heading would be bison. Though challenging to bring down, bison have become an increasing part of wolves’ diet since wolf reintroduction. In 1995 the Wolf Project found no evidence of wolves taking bison; wolves were satiated with naive elk. But by 2020 (latest data available), bison made up 17% of wolf kills studied.

One large pack in particular, the Mollie’s pack, made its name early on bringing down bison, 1,000 pound females or 2,000 pound males, in Yellowstone’s interior. In 2020 the large Junction Butte Pack with five adult males accounted for the majority of bison killed by park wolves. 

Next in terms of popularity would be deer. At just 200 or so pounds, one deer may feed four to six wolves. As the number of elk on the Northern Range has fallen, the number of deer consumed—like the number of bison—has risen. In 1995 there was no evidence that wolves took deer. But by 2020, deer made up 5% of wolf kills studied.

Next in the list of favorites would be pronghorn, an even small grazer at about 100 pounds. The Wolf Project has found evidence of wolves taking a couple each year. Since pronghorn are built for speed and can outrun a wolf, the few who end up being dispatched are probably calves or ailing older animals. 

Rounding out THE BIG MEAL list would be moose, bighorn sheep, and mountain goats. A moose, at about 1,000 pounds, could be a feast for a pack of fifteen or more wolves. But the Wolf Project finds evidence of wolves on average consuming only a couple per year. I can imagine that bringing down a huge animal with big hooves and broad antlers would not be attractive. Few bighorns and even fewer mountain goats are taken since both tend to hang on steep and rocky cliffs where a wolf is at a distinct disadvantage when it comes to chasing.

The Wolf Project also lists other animals wolves take. These animals are so small and so few that we would have to list them as SNACKS on the left side of our imaginary menu. A partial list would include (starting with largest number of remains studied) badgers, ravens, golden eagles, otters, rabbits, and beavers. 

Now, on to the other reason wolves kill: to cut competition. The Wolf Project also keeps track of the predators they find eliminated by wolves. Topping that list would be coyotes, with 115 found killed since 1995. At least one researcher has watched a wolf pack attack coyotes at their den and kill pups. But for the most part, coyotes die when they are careless while scavenging at a wolf kill. 

Next on the competitor list are other wolves, with the Wolf Project finding 89 killed by their own kind since 1995. These kills could be made in battles over territory or while protecting a meal that one pack brought down and another wants to consume. Only three wolves were found killed between 1995 and 2001. But wolves killing wolves reached a peak with the Wolf Project finding eleven remains in 2008. Since then the number has fallen, with only three wolves found killed by wolves in 2020.

The third Yellowstone canid, the red fox, almost escaped unscathed; only six have made the “killed by wolves” list since 1995. 

Wolves have also killed a smattering of other competitors including cougars, black bears, grizzly bears, and grizzly cubs.

A wolf’s diet varies with the seasons. Winter, with its deep snow and cold temperatures is a satisfying time for wolves. Almost all winter diet is elk; wolves take down adult males and females as well as calves. Summer, on the other hand, is a harder time for a wolf to bring down elk that are in good shape from eating lots of vegetation. And there’s little to get in the way of an elk outrunning a wolf pack. So in summer wolves bring down fewer elk and more deer and rodents.

So there you have it, a menu for wolves. The meals vary by season and size, from rodents to bison and elk. Wolves have adjusted their diet as the size and diversity of the park’s prey population has changed over the years since reintroduction.

Of course, there are some anti-wolf folks that swear too many wolves eat too many elk—and wolves should be eliminated. I’ll look at this controversy in an upcoming Save the Wild. 

To Learn More:

Read the annual Yellowstone Wolf Project Reports

Read the NPS account of wolf reintroduction into Yellowstone.

To Speak for Wolves:

Ask for wolves in the Northern Rockies to be relisted under the ESA.

Join a Wolf Protectors Group.

Photo credit: wolf, ravens, and magpies at carcass by Jim Peaco, NPS

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My bestselling In the Temple of Wolves; its sequel, Deep into Yellowstone; and its prequel, The Wilds of Aging are available signed. My books are also available on Amazon unsigned or as eBook or audiobook.