15 Most Dangerous (And Deadliest) Mammals In The World
When we think of dangerous animals in the wild, some of the first creatures that come to mind are sharks, crocodiles, venomous snakes, and poisonous spiders. Surprisingly, the most deadly animal in the world is one of the smallest: the mosquito! These annoying insects transmit diseases such as malaria and Dengue fever and, according to the U.S. Centers for Disease Control and Prevention, cause more than 700,000 deaths worldwide each year.
Beyond deadly insects, reptiles and fish, there are equally dangerous mammals of all sizes in the wilderness. While most of these animals avoid interactions with humans, some are known for being predatory and aggressive, especially if they are provoked or hungry. Many humans fail to understand that wild animals often behave unpredictably and deserve our respect by keeping our distance from their natural habitats.
Here are 15 dangerous wild — and domesticated — mammals that need cautious, gentle handling.
15. Slow Loris
Height/length: 7-15 in. long
Weight: 25 lbs.
Life expectancy: Up to 20 years
Why the Slow Loris Is So Dangerous
This nocturnal primate packs a powerful bite laced with toxic venom strong enough to rot flesh. The glands under the slow loris' armpits produce a smelly oil and once the animal licks the area, its salvia turns venomous. Although they rarely bother humans, at least one death has been attributed to the slow loris due to an extreme allergic reaction.
14. Mammal: Moose
Height/length: 6-7 ft. tall
Weight: 1,600-1,800 lbs.
Life expectancy: 15-25 years
Why the Moose Is So Dangerous
Known as the prince of the forest, moose attack humans more often than bears (roughly 5-10 people per year), but their attacks are less severe. Though they can be aggressive when provoked, what makes them so dangerous is their collisions with cars. There is a higher incidence of accidents with moose during the dark winter months when visibility is low and the animal wanders too close to the highway, especially in parts of Canada, Alaska and New England.
Due to their massive size, 20 percent of accidents with moose lead to injury, but less than 1 percent of moose-related deaths have resulted from these collisions.
13. Mammal: Horse
Height/length: 4.6-5.11 ft. tall
Weight: 900-1,200 lbs. (some are up to 2,000 lbs.)
Life expectancy: 25-30 years (domesticated)
Why the Horse Is So Dangerous
We don't usually think of horses as dangerous since they are considered a beloved part of the family. But horses kill roughly 100 people yearly in the U.S. in riding or equestrian-related accidents. However, with horse ridership at seven million plus, the risk of death is low. Always treat these magnificent creatures with the love and respect they deserve.
12. Mammal: Wolf
Height/length: 5 ft. long
Weight: 44-176 lbs.
Life expectancy: 13-15 years
Why the Wolf Is So Dangerous
There are more than 30 subspecies of wolves that roam all over Europe, North America, the Middle East and parts of Asia. Wolves in the wild do not usually pose a threat to humans unless they are provoked or have rabies. What makes them dangerous is their strength and sharp teeth, capable of shredding flesh. They also travel in packs and can easily outnumber their prey.
11. Mammal: Cougar
Height/length: 7-8 ft. long
Weight: 100-125 lbs.
Life expectancy: 8-13 years
Why the Cougar Is So Dangerous
Also known as puma or mountain lion, the cougar is the second largest cat in the Western Hemisphere after the jaguar. There have been 126 attacks (27 of which were fatal) in North America in the past 100 years. These big cats become extremely dangerous when cornered and will also attack a fleeing human or one who "plays dead," considering them easy prey. They have a strong hunting instinct and can kill creatures larger than themselves with their sharp claws and teeth.
10. Mammal: Polar Bear
Height/length: 7-10 ft. long
Weight: 1,760-3,530 lbs.
Life expectancy: 25-35 years
Why the Polar Bear Is So Dangerous
These powerful predators have a strong sense of smell that will draw them dangerously close to areas where humans are if food is nearby. They can easily outrun their prey or kill someone instantly with one swipe of their massive paws.
Unfortunately, global warming is melting the sea ice, which puts the polar bear population at a high risk of decline. The animal is now forced to spend more time hunting inland, bringing them closer to humans. Attacks are rare: Between 1870 and 2014, there were only 73 documented attacks. But a woman and her baby were mauled to death in a small Alaskan village in early 2023, so some think tragic incidents are becoming more common.
9. Mammal: Grizzly Bear
Height/length: 3-5 ft. tall (some can reach 9 ft.)
Weight: 290-790 lbs.
Life expectancy: 20-25 years
Why the Grizzly Bear Is So Dangerous
A subspecies of the brown bear, the grizzly is one of the most aggressive predators around. They have great strength and a bite force of 1,000 psi, capable of splitting a human body in half. Although extremely dangerous, most grizzlies will not attack unless they are startled or provoked — or if they have cubs nearby. There are roughly 44 grizzly bear attacks yearly worldwide and a documented eight deaths in North America from 2020-2022.
8. Mammal: Cape Buffalo
Height/length: 51-59 in. tall
Weight: 937-1,918 lbs.
Life expectancy: 15-25 years
Why the Cape Buffalo Is So Dangerous
Considered one of the most dangerous mammals in Africa, the Cape Buffalo is a large mammal with massive horns that likes to travel in herds. If a buffalo feels threatened, the entire herd will likely charge the predator. They are considered very aggressive animals and responsible for 200 yearly deaths.
7. Mammal: Deer
Height/length: 6 ft. long, 3 ft. tall
Weight: 80-160 lbs. (up to 300 lbs)
Life expectancy: 3-6 in the wild, 15-20 in captivity
Why the Deer Is So Dangerous
Native to all continents except Australia and Antarctica, deer have become familiar residents in the suburbs and cities of North America and Canada. Although we often think of these animals as gentle forest creatures, they are dangerous when they venture into the streets. An unwary deer darting across the highway can cause severe automobile accidents.
Some insurance companies show documented cases of hundreds of thousands of deer-vehicle accidents yearly in the U.S., resulting in 200 human fatalities annually.
6. Mammal: Lion
Height/length: 9-10 ft. long
Weight: 265-550 lbs.
Life expectancy: 12-16 in the wild, 25 in captivity
Why the Lion Is So Dangerous
The stealthy lion usually attacks at night, capturing its unsuspecting prey with sharp claws and teeth capable of cracking its victim's bones in one bite. Males can consume up to 75 pounds of meat in one meal!
The most dangerous times to be around lions are when they are in courtship or with cubs. There are at least 200 deaths recorded each year from lion attacks.
5. Mammal: Tiger
Height/length: 6-10 ft. long
Weight: 220-660 lbs.
Life expectancy: 10-15 in the wild, 20 years in captivity
Why the Tiger Is So Dangerous
Known for their strength and agility, these apex predators are as deadly as bears, alligators or any other major predators. They are considered one of the top five deadliest mammals on the planet. Although tigers are aggressive animals, they only attack humans when they are provoked, surprised, feeling threatened or unable to find other prey. They have incredible hunting skills and kill 250 humans each year on average.
4. Mammal: Dogs (in the wild or untrained)
Height/length: Highly dependent on breed. A medium-sized dog averages 27 in.
Weight: Varies. 22-55 lbs. for medium-sized breeds, but Mastiffs can weigh as much as 230 lbs.
Life expectancy: 10-13 years
Why the Dog Is So Dangerous
When we think of dogs, we think of our domesticated, furry companions as family members. While dog attacks in North America are rare, human deaths from rabies transmitted by dog bites are far more common in less developed countries. Rabies are transmitted by saliva from a dog bite, scratch or contact with an infected area on the animal.
Rabies caused by dog attacks contributes to approximately 59,000 deaths worldwide per year.
3. Mammal: Hippopotamus
Height/length: 10.8-16.5 ft. long
Weight: 1,760-3,530 lbs.
Life expectancy: 40-50 years
Why the Hippopotamus Is So Dangerous
The hippopotamus is one of the deadliest large land animals on the planet because they are fiercely protective of their habitat. There are conflicting opinions on the nature of the hippo's aggressiveness, but the large mammal accounts for 500 to 3,000 human deaths per year.
Most hippo attacks on humans occur when someone approaches or threatens their habitat. These mammals' sharp teeth have a bite force of 1,800 psi, enabling them to cut a human in half with one bite.
2. Mammal: Elephant
Height/length: 8.2-13 ft. tall
Weight: 12,000 lbs.
Life expectancy: 60-70 years in the wild, 40 in captivity
Why the Elephant Is So Dangerous
Elephants are peaceful, social creatures that form strong bonds with members of their herd. Although they can be gentle with humans at times, they are wild animals and should be respected as such. These mammals become aggressive when stressed, sick, provoked or threatened. Due to their sheer size and strength, they can easily overpower a human and kill with one strike. Roughly 100-600 deaths occur yearly from attacks by elephants.
1. Mammal: Humans
Life expectancy: 76 years
Why Humans Are So Dangerous
Humans are by far the deadliest mammals on the planet and are responsible for an estimated 431,000 to 526,000 deaths yearly. Armed violence, vehicular accidents and medical malpractice all contribute to the rising death toll, but our ability to create complex weapons of mass destruction is our biggest downfall. The human impact on the environment is also a reason to consider ourselves the biggest threat to the planet and the most dangerous mammal of all.