The Two Most Aggressive Bears: Grizzlies and Polar Bears

The most aggressive and dangerous bears are the grizzly and polar bear. But, there are also reports of other bears like the Eurasian brown bear, the sloth bear, and the Asiatic black bear showing substantial amounts of aggression.

The American black bear is considered much more shy and more tolerant of humans than other bear species, which is also believed to have helped it throughout the centuries to survive from other predators.

Regardless, all bears are apex predators and opportunistic feeders that won’t think twice to attack if they feel threatened or if a mom bear is protecting her cubs.

Most Aggressive Bears

This is why proper behavior in bear country is pivotal, although bears don’t normally hunt humans or feed on them. Attacks happen when bears defend themselves, their cubs, their food, or their range. 

This article explores the aggressive traits of three of the most common bear species: Polar bears, Grizzly bears, and Black bears.

How Dangerous Is a Polar Bear?

Polar bears are one of the most aggressive and dangerous bear species! They’re curious, strong, and must never be approached or surprised, but rather admired for afar. 

Polar bears have long been feared because of their impressive predatory skills and because they’re big enough to perceive humans as a potential source of food.

They’re much faster than humans and humans can never outrun them, they have one of the deadliest bites, and their strong and massive paws can easily crack a spine. 

According to USGS data from 2017, there were 73 recorded attacks by polar bears on humans from 1870 until 2014 throughout the five polar bear range states (Greenland, Norway, Canada, US, and Russia). Of these attacks, 20 were fatal and 63 humans were injured. 

Adult male polar bears, especially when they’re starving, may hunt humans for food. Attacks by female polar bears on humans are rarer though. 

Unfortunately, according to Yale School of the Environment, the rise of attacks on humans by polar bears is a result of the retreating of the sea ice. Polar bears now spend more time on land. 

With their natural food sources lacking, they’re hungrier and may encroach urban areas, increasing the risk of conflicts and fatalities on both sides.

Related Article: Polar Bear vs Grizzly Bear

How Dangerous Is a Grizzly?

Humans have long been afraid of grizzlies, mostly because, when compared to the more timid black bear, the attacks by grizzlies on humans usually end up fatally. Grizzlies have a deadly bite with a force that exceeds 8 mega-pascals. 

Grizzlies are bad tree climbers, unlike black bears that weigh two to three times less than them and are excellent climbers. 

Read More: Which Bears can Climb Trees?

Therefore, when threatened, a grizzly can’t climb a tree like a black bear can so it has to stand its ground and attack first to ward off wolves, dogs, and other potential attackers, including humans. 

Richard H. Yahner, a professor of wildlife conservation notes another reason why grizzlies are more aggressive than black bears.

It has to do with reproduction. A female black bear may raise up to 13 cubs during her lifetime whereas a grizzly will only have around six to eight cubs. Their aggressiveness, notes Yahner, may be an extra effort to ensure their offspring survives and reaches reproductive age.

Read More: How Many Cubs Do Bears Have?

Although a 2019 report found a rise in bear attacks in recent years, it also concluded that only 24 individuals were killed by grizzlies in North America during the period from 2000 and 2005, that is, 1.6 people yearly. 

Related Article: Bear vs Tiger

How Dangerous Is a Black Bear? 

The American Black bear is a relatively shy bear that will act viciously only as a last resort, according to Tree Hugger. However, just because a black bear is less dangerous than the polar bear and the grizzly, it doesn’t mean that fatal attacks don’t happen or that they haven’t happened.

One of the best methods to prevent bear attacks is to reduce encounters and keep a safe distance from bear areas, especially if the bear is female with cubs. They’re known to be very protective of their young ones and may attack if threatened.

Read More: Do Bears Attack Camping Tents?

Plenty of black bears live near urban areas and therefore, they’ve developed a certain amount of tolerance to humans. On the other hand, grizzlies tend to stay far from human areas and aren’t comfortable near heavily populated areas.

Black bear attacks on humans that end fatally are rare, more so than those by any other bear species. The average occurrence is once per year in North America and around one black bear from million black bears will attack humans in predatory behavior. 

The apprehensive nature of the black bear is believed to have developed during the Ice Age when they had rivals like wolves, huge lions, and short-faced bears that had potent jaws and were fast runners. 

Since the black bear stood no chance competing against them, it kept its distance and resorted to tree climbing.

Read More: Bear vs Wolf Pack (Who Would Win?)


The polar bear and the grizzly are considered to be the two most aggressive bears, although there have been reports of other attacks on humans by bears such as the Eurasian brown bear, the Asiatic black bear, and even the black bear which is considered to be the most timid bear and the least likely to attack humans. 

Since bears are apex predators with enhanced predatory skills, any encounter with them, no matter the species, is unpredictable!

The best way to prevent an attack that could easily be fatal considering their immense strength and survival skills is to stay at a safe distance and understand that bears are wild animals that must never be underestimated. 

Bears are majestic creatures that deserve the utmost respect. By realizing their power and behavior, people can take the right precautionary measures to reduce aggression, fatal conflict, and property damage.

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