7 Otters

Otters appear sweet and playable but can be violent when necessary. They have robust teeth and a powerful bite with sharp claws that can harm anyone who appears threatening. Their scratches and bites can even transmit rabies.

Otters are adapted for both land and water and weigh up to 30 pounds. They have a heavy, muscular body that can deliver lethal wounds. Otters are generally harmless, but they really get violent when protecting their territory, and especially when they sense a threat to their babies.

Several cases have been recorded when otters attacked humans. An eight-year-old nearly was killed, and in another case, two teenage boys were severely wounded on their legs by three otters. 

It is suggested that we must maintain a safe distance of at least 50 yards from the animal and never try to feed them. (1, 2, 3)

8 Deer

Deer are usually gentle, docile, and easy-tempered, but they do attack in situations when they are cornered, feel their young ones are not safe, and especially when they perceive someone as their mating rival in the rutting period. Deer attacks can inflict permanent damage. They deliver strong kicks and stomp with their hooves on the torso, limbs, or head, and their antlers’ attack can lead to bruising, puncture wounds, and skin lacerations.

When it comes to choosing between flight and fight, deer are the animals that will generally choose to run away – but not always. When they do attack, they do so with their strong kicks, sharp hooves, and antlers in certain situations. 

Female deer are always on alert near their young ones, and they will attack humans with their hooves if they fear them to be potential predators.

Confronting deer during the rutting season must be avoided since their urge for mating is at its peak, and the males will attack perceived rivals with all their might. 

When deer tighten their tail and hold their head erect, it’s a sign they are ready to go on a rampage, so one must retreat silently in such cases. (Source)

9 Raccoons

Raccoons are one of the “rabies vector species,” or the primary carriers of rabies. A raccoon may attack in the process of defending her young ones by lunging forward and biting with a “whoof” sound. Additionally, a rabies-infected raccoon is more likely to attack.

It is perfectly normal for raccoons to wander in the daylight and look for food, but deviated behavior, as a result of rabies infection, can make them aggressive. 

Raccoons don’t chase after the perceived threats, but they will not hesitate to bite humans if they feel their young ones are threatened. The female will make a growl, arch her back, and bite the perceived threat. 

Other than rabies, an aggressive and ill raccoon may be infected with canine distemper or feline parvovirus as well. (1, 2)

10 Koalas

Nearly half of the koalas in Australia are infected with chlamydia, and the disease can be transmitted to humans easily just with contact with their urine. They may also attack humans with their jaws if they feel unsafe.

The cuddly animals may seem friendly and show that they want to hug you, but it’s better to keep your distance from them. They can transmit chlamydia and potentially cause STI through their urine. Also, there have been enough instances of koalas directly urinating on visitors. 

They are very quarrelsome when someone seems to breach their safety. One South Australian woman was attacked by a koala that left her bloodied and bruised. After the koala grabbed her leg with its jaws, it was just not ready to let go. She received a swollen foot with 12 stitches. (1, 2)

11 Slow Loris

If the adorable, nocturnal primate bites you, it can literally rot your flesh because of the deadly venom they deliver with the bite. The slow loris is the only venomous primate in the world.

The slow loris is a wide-eyed, harmless-looking nocturnal primate generally found in small groups in South and Southeast Asia. Underneath their armpits, they have glands that ooze noxious oil, and when they lick it, their saliva combines with it to produce the flesh-rotting venom. 

The slow loris rarely attacks humans but has the capacity to deliver a fatal anaphylactic shock if they release their venom through a bite. Other effects of their venom have been noticed, including loss of mobility, permanent disfigurement, and near-death in their bite victims. 

It is not just about the biting. Slow lorises have been found rubbing the venom on their fur to protect themselves from predators. Close contact with a slow loris in the wild should certainly be avoided at any cost. (1, 2)

12 Platypuses 

Platypuses are among the rare, venom-secreting mammals. The males secrete the most venom in the mating season to compete. This venom, when in contact with humans, is not life-threatening but causes swelling and “excruciating pain,” the kind that will make you want to die. 

Platypuses are one of a kind; they look extremely unusual. They have a tail like a beaver, a body like an otter, feet like a duck, and also secrete venom.

Males secrete venom during the mating season to compete with their rivals. They have spurs on the back of their hind legs that are connected to glands that secrete the venom. 

The venom paralyzes smaller animals, but on humans, it is not as lethal. However, the venom is still intense enough to incapacitate. The wound will leave severe swelling and pain that can last for months. This condition of long-lasting sensitivity to pain is called “hyperalgesia.”

One of the former members of the Australian Army who was struck by a platypus on the hand described the pain as worse than being struck by shrapnel. He said he still experienced the same intensity of pain after a month. (1, 2)