The bright yellow coloring of this frog makes it easy to pick out among the Colombian wilderness, but as nature often tells us, bright coloring means danger. It might come as a surprise, but this animal is one of the most toxic found on Earth (toxic: don’t eat it). It packs enough potency to kill ten fully-grown adults, but we don’t have any information about how many have succumbed to this powerful creature.
The indigenous people of Colombia use the venom of the golden poison frog to tip blowgun darts before going hunting. The frog might not be able to utilize the toxin for offense, but any creature that takes a nibble is going to have a bad time.
Army Ants
Just look at those ferocious snappers. Thinking of an army of those is enough to send anyone running for the hills. For such a tiny insect, their bites are anything but small.
One bite can affect your circulatory system, and they’ll eat just about anything. An army ant colony never stops moving over the time it exists. Are they about to take over the world? Who knows? Are we about to stay close and find out? Heck no!
Moray Eel
Hanging out mainly in tropical seas, a moray eel doesn't really have much of a body count (an average of zero human deaths per year), but that doesn't mean they aren't dangerous. Their sharp teeth are perfect for puncturing through skin, and their thick, scaleless skin is difficult to penetrate in turn.
When disturbed, they're all too willing to take the fight to whatever is bothering them. If a human does manage to win the fight, they can't even enjoy the spoils of the battle – moray eel flesh can be toxic, causing illness or even death if it isn't prepared properly. If you're swimming in the warm waters of the Atlantic, Pacific, or Indian Oceans, watch out.
Grizzly Bear
If you've ever gone hiking in the wilderness of North America, you know to watch out for these big beasts. While grizzly bears (or brown bears) are the cause of 1.6 human deaths per year (using recent numbers, at least), they have the potential to be much higher. There's a reason bear mace is a thing. People who like to enjoy the great outdoors need to keep an eye open for them.
They might look cuddly, and they don't seem to move that fast, but they're almost half a ton of muscle and sharp claws. You can't beat them in a fight, and you can't run from them – give these austere beasts a wide berth.
Horse
Horses are an animal that humans have been using for their betterment for thousands of years – maybe even tens of thousands. We love them, they often love us, and this symbiotic relationship has produced plenty of great things, like the movie “Black Beauty.” But horses are still plenty dangerous, especially since humans spend so much time around them.
At least a hundred deaths per year are due to horses, though very few of them are because of aggression on the horse's part. Most of them are because of equestrian activities and head injuries. There are also thousands of minor injuries humans get while riding.