The Most Dangerous Animals in Yellowstone National Park

Yellowstone National Park is home to an array of iconic animals, which are among the main attractions for the millions of visitors who visit the region every year.

Some of these animals can be dangerous, however, and are capable of causing severe injury and death. As a result visitors must take great care to follow park guidelines during their trip in order to stay safe.

The National Park Service (NPS) recommends staying more than 25 yards away from all large animals—such as bison, elk, deer, and moose—and at least 100 yards away from bears and wolves.

But which species that live in the park pose the highest risk to humans?

Yellowstone's Most Dangerous Animal

A Yellowstone National Park spokesperson told Newsweek that bison have injured more people in the park than any other animal.

Figures from a 2019 report published in the journal Human–Wildlife Interactions showed that 25 people were injured by bison in Yellowstone between 2000 and 2015. Meanwhile, between 1978 and 1992, bison injured 56 people and killed two in the park.

According to Brad Bulin—a wildlife biologist, Yellowstone guide and author—among the main issues with bison is that they are fairly tolerant of people and typically appear to be relatively tame and docile, while also being unpredictable.

This mix of traits can create the perfect conditions for injuries to occur if visitors don't follow park guidelines and approach too close.

A bison in Yellowstone National Park
Stock image: A bison in Yellowstone National Park. Bison have caused more injuries in Yellowstone than any other animal. iStock

"[Bison] sometimes hang out pretty close to and even on the roads, they're walking through parking lots, they're in close proximity to people and become accustomed to them," Bulin told Newsweek.

"Sometimes people will go way too close, not realizing they are dangerous and not realizing how fast and agile they are."

So far this year, three people have been gored by bison in the park.

How Many Bison Are In Yellowstone?

Around 5,450 bison were counted in Yellowstone in the summer of 2021. These included 4,100 in the northern herd and 1,300 in the central herd.

The species was almost wiped out in the 1900s after hunting and poaching saw numbers fall to just two dozen bison.

Animals from private herds were used to boost numbers and the species was given special protection so numbers could rebound to the figures we see today.

These giants are the largest mammals in North America, with males weighing up to 2,000 pounds. Despite their immense size, bison can run three times faster than humans.

"They are amazing athletes," Bulin said. "Some predators can get out the way because they're fast enough, but we can't. Bison can run 35 miles per hour. And they can get to that pace in a very short distance. They can jump a six-foot fence from a standstill.

"Their front end is heavier than their back end, so they can spin around really quickly by shifting that weight to the front and swinging their tail around. All of a sudden, they've done a 180 on you. They're also very used to defending themselves. Very few predators kill healthy, adult bison, especially bulls, which are too aggressive and dangerous for even a pack of wolves to take on."

If a bison does decide to charge at someone, it won't chase them for long distances in an attempt to kill them, according to Bulin. More likely is that the bison will make a quick charge in order to make contact with the individual.

Most of the injuries are puncture wounds from horns, because they put their head down and try to gore you and then toss you up in the air. That's the typical pattern," Bulin said.

"They can stomp on you too."

Grizzly Bears and Black Bears

The park's bears can also pose a danger to humans, particularly the grizzlies, according to Bulin. "Bears can be a big threat because they can hurt people very badly, very quickly," he said. "It can be far more serious if a grizzly bear attacks you very quickly than even a bison, sometimes."

As a predator, a bear that is attacking you may try to cause injuries to your head or neck, which can lead to severe trauma.

Despite the potential threat posed by bears in the park, predatory attacks on humans by these animals are extremely rare, according to the NPS.

As of 2019, there are estimated to be around 150 grizzly bears in the park proper, according to the NPS. Meanwhile, there are thought to be between 500-650 black bears, figures from the Yellowstone Wildlife Sanctaury show.

Black and brown bears are omnivorous, meaning they eat plants and animals. The black bear diet consists mostly of berries, fruit, and insects, although they will also eat other animals. Grizzly bears will also eat a wide variety of plants, as well as preying on animals such as elk, trout and other creatures.

"Most bear encounters end without contact or injury," the spokesperson said. "When bears do attack, it is usually during a surprise encounter and the bear is reacting defensively to protect itself from a perceived threat to itself, its cubs or its food."

A grizzly bear in Yellowstone
Stock image: A grizzly bear in Yellowstone. Bears have the potential to cause severe trauma. iStock

Since the park was established in 1872, eight people have been killed by bears in the park. In the 1960s, bears injured 45 people per year on average in the park. Then in the 1970s, officials implemented a new bear management plan to restore the animal's natural diet and to reduce property damage, as well as human injuries.

As a result of these actions, the number of people injured by bears fell to an average of around one injury per year in the 2000s, according to the NPS.

Most of the injures caused by bears in the park result from people not taking proper precautions, particularly in the backcountry, according to Bulin.

"A lot of times, someone's just not paying attention to their surroundings. They're not making noise. They're not carrying bear spray. In bear country, you want to make noise and don't sneak up on things. You want to hike in groups," Bulin said.

"In the front country, the problem is people getting way too close. We've had people take selfies with grizzly bears and cubs, we have had people trying to pet bears, we've had people getting between cubs and their moms."

Encounters with grizzly bears in the park tend to be more dangerous than those with black bears, because the latter are usually much less aggressive, according to the NPS.

The majority of bear-inflicted human injuries inside Yellowstone are caused by grizzlies, which rely on their large size and aggressiveness to protect themselves from perceived threats.

Black bears, meanwhile, are smaller and are more likely to run away—often up a tree—when they feel threatened.

Moose

Moose will usually flee when they feel threatened but they can be unpredictable and become aggressive in certain contexts.

Being the largest member of the deer family, adult males can weigh close to 1,000 pounds and can run at high speeds, meaning they are capable of doing serious damage. They can injure people in a variety of ways—by charging, stomping or kicking, for example.

A cow moose with a young calf may act aggressively if they feel the juvenile is under threat. Meanwhile, bull moose can also become "very aggressive" toward humans in late September and October during the rut, or mating season, according to Bulin.

A moose bull in Yellowstone
Stock image: A moose bull in Yellowstone. Moose can be unpredictable and become aggressive in certain situations. iStock

Moose in Yellowstone have been known to chase people before but incidents involving these animals in the park are rare, in part, because humans don't encounter them very often. The population of moose in the park numbers fewer than 200, according to the NPS.

"We don't get an opportunity to get up close enough to them, but they are probably the most aggressive of what we have," Bulin said.

Elk

Elk are the most abundant large mammal in Yellowstone, with an estimated 10,000-20,000 spending time in the park during the summer.

Like moose, male bull elk—which can weigh 700 pounds—are easily agitated during the September-October mating season and may become very aggressive towards humans.

During the rut, males compete for females by fighting other males using their large antlers and making loud, wailing "bugle" sounds.

An elk
Stock image: An elk in Yellowstone. Elk bulls are easily agitated during the mating season. iStock

One of the reasons elk are so dangerous, according to Bulin, is that during the mating season, they often gather around Mammoth Hot Springs, which is one of the most popular destinations in Yellowstone.

"[This] creates big problems because there are so many people coming and going in Mammoth Hot Springs that the park has to bring in a lot of staff at that time of year to prevent people getting too close to these aggressive bulls, which can smash into their cars or chase people, or gore people.

"That's a limited window of just a few weeks. But it's a pretty serious time in one or two locations," Bulin said.

Elk also gather at the same hot springs in the spring and early summer after cow elk have given birth to their calves. Like moose, cow elk are particularly protective of their young at this time of year and may act aggressively if they feel they are threatened.

In 2019, a concession employee at Yellowstone was injured by a cow elk in late May at Mammoth Hot Springs. The previous spring, two other individuals also suffered injuries after being attacked by a cow elk in the same location.

"Anecdotally, elk injuries are not common, although elk charging people seems to happen each year. Not all of those instances are formally reported to us," a park spokesman, Jacob Frank, previously told the Mountain Journal.

Wolves

When Yellowstone National Park was established in 1872, wolves were present in Montana, Wyoming and Idaho but their numbers were already declining. By the early 20th century, wolves had been virtually wiped out from the park with the help of government predator control programs.

But in in the 1990s, wolves were reintroduced in a program that has now been hailed as a success in many quarters.

There are no records of wolves attacking a human in Yellowstone over the course of its modern history, according to the NPS. These animals are not normally a danger to us unless we habituate them by giving them food, in which case they may lose their fear of humans.

In such cases, the animals have the potential to be dangerous. In 2005, a 22-year-old male was killed near a remote mining camp in Canada where wolves often visited a garbage dump, for example, according to the International Wolf Center.

In very rare cases, predatory attacks have also occurred where human feeding has not been a factor, as occurred in 2010 when a 32-year-old female was killed in Alaska by a pack of wolves.

yellowstone wolf
Stock image shows a wolf in Yellowstone National Park. The last fatal attack on a human by a wolf in North America was in 2010 when a a 32-year-old woman was killed in a predatory attack. Getty Images