Aggression in Animal Species
It is very difficult to determine which is the most aggressive animal in the world, as every animal shows aggressive behavior at some point depending on the circumstances. While some species are quite aggressive during the mating season, others become aggressive when it comes to self-defense, or to protect their young ones. Every single member of kingdom Animalia shows aggression in varying degrees depending on what the provocation is, which makes it all the more difficult to find out which animals are dangerous.
In animals, aggressive behavior can be triggered by several factors: an offensive reaction to intruders, maternal instincts of protection, and sexual competition are just a few of them. Sometimes two members of the same species turn on each other, this is called combativeness. At other times, one species attacks another for food, which is called predation. Any physical behavior intended to cause pain or harm to others counts as aggression. One of the best examples of combative aggression is two bighorn rams clashing during the mating season. In contrast, one of the best examples of predatory aggression is a cheetah hunting an antelope for food.
Top 10 Most Aggressive Animals
How do you figure out which animals are the most dangerous or aggressive? There is no single measure for aggression, which makes ranking them tricky. Many people think that the number of fatalities caused by a species is a fair sign of its aggression, but that is not always true. While the great white shark is a fierce fish, it rarely comes into direct contact with humans, so it does not cause a huge number of deaths. That is one important fact to keep in mind when putting together a list of dangerous species. The animals below are all known for their aggressive nature.
African Elephant
Even though elephants are considered quite friendly, their aggressive behavior is something you need to watch out for, male elephants especially, who are quite aggressive during the mating season. With their strong tusks and long trunk, African elephants are known to kill 300-500 people every year.
Box Jellyfish
The box jellyfish is notorious for the fifteen-odd tentacles it sports, each of which has venom potent enough to kill 50 adult humans. That explains the significant number of human deaths linked to this marine creature.
Rhinoceros
A top contender for the most aggressive African animal, the rhino has earned a reputation for its unpredictable behavior. While it may look like a lazy animal, it can clock a speed of up to 30 mph when charging at an intruder.
Hippopotamus
Like the rhino, the hippo looks slow and lazy, but it is known as one of the most aggressive animals on the planet, especially when it comes to protecting its young ones. More importantly, it is quite fearless and won't hesitate to take on anyone that comes in its way.
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Cape Buffalo
Weighing 1.5 tons, the Cape buffalo (also called the African buffalo) is feared by lions and humans alike. It doesn't like intruders in its territory at all. The number of humans killed by Cape buffalo makes up a large share of all animal-attack deaths in Africa.

Polar Bear
If you don't hear about many polar bear attacks on humans, it's only because their habitat is far from where people live. Far from being a gentle species, these bears are quite aggressive in nature in the truest sense of the word.

Great White Shark
No other marine species can match the great white shark for sheer ferocity. Even though they don't often come into direct contact with humans, the great white shark, with its huge jaw and sharp teeth, is considered one of the most aggressive species on the planet.
Saltwater Crocodile
The saltwater crocodile is not just a threat for humans, it is dangerous to many other animals that share its habitat in the wild. With its enormous strength, this crocodile can bring down an animal as large as the water buffalo with ease.
Western Diamondback Rattlesnake
If you live in Mexico or the United States, you don't need an introduction to the western diamondback rattlesnake, or its aggression. It is responsible for a large share of snakebite deaths in these two countries every year.

Black Mamba
Beyond its amazing speed, the black mamba is also known for its ability to inject copious amounts of venom into its prey. These qualities make it the most aggressive snake in the world and place it right at the top of our list of aggressive species.
What About the Mosquito?
Quite a few names in this list may have surprised you, but there is little doubt about how dangerous these wild animals are. Many people think the mosquito, which causes 2-3 million deaths every year, is the most aggressive species on the planet. The mosquito should certainly be considered dangerous (thanks to its ability to spread diseases and contribute to so many deaths) but calling it "aggressive" wouldn't be technically accurate.
