When these gentle animals are stepped on or threatened, they will strike out with a sharp, serrated barb — about the thickness of a golf pencil — located at the base of the tail.
"The physical wound can be pretty intense," said Jon Hoech, director of husbandry operations at the Monterey Bay Aquarium. "It's extremely painful, like getting punctured with an eight-penny nail. Also, it's like a cat scratch, it can carry a lot of bacteria."
On top of the sizeable puncture wound comes a dose of toxins that cause instantaneous pain.
Stingrays only use their venomous barbs as a defense, not for hunting or attacking. As many marine biologists, scuba divers and snorkelers know, the animals are the ocean's pussycats.
"I work with rays on a regular basis," said Hoech. "I swim with them, I feed them by hand, and they're very benign." Just be sure to look where you step.
There are thousands of scorpion species, all of them equipped with stings. Many species' stings aren't much worse than a bee or hornet; but a select few can be a serious source of suffering.
"There are scorpions in the Old World that have extremely painful stings," said Don Boyer. "It gets worse and worse and worse."
These types of scorpions — found in Africa and Asia — can be dangerous as well as painful. However, in the Southwestern United States, the Arizona Bark Scorpion doesn't pose much of a threat to healthy adults. It just means extreme pain.
"If you're an adult and you get the poison in your finger, it just stays, and fires your pain nerve," said Dr. Leslie Boyer — no relation to Don Boyer. "It locks the nerve in the on position."
Leslie Boyer, who is medical director of the Arizona Poison and Drug Information Center, said that the tiny sting will "send shooting sensations up your arm." If you're clumsy enough to tap or bump that finger on anything, the pain instantly amplifies.
"You just give it a tap and you're screaming in pain," said Leslie Boyer. "Just that one little spot hurts like heck, it radiates up to your arm pit with this throbbing pain — but there's nothing to see."
Boyer says that since her practice sees so many painful stings and bites, "I tend to give out morphine like it's candy."
While this reptile has a poisonous bite, it doesn't actually induce much pain. Sure, it stops you from breathing, but for the venom to really make you scream, it needs to get into your eyes.
Spitting cobras have perfected the art of defense by shooting venom into an attacker's eyes, which creates a blinding, burning pain. Like many other pain-inducing animals, the reason for the agony is to keep attackers away, rather than to stage an offensive.
Van Wallach was unfortunate enough to get the spitting treatment from a cobra in the Philippines.
"It is excruciating," he said. "The only way I could relieve it was to pour milk into my eye about every 15 minutes. I was blind for about four to six hours."
The cobra's venom contains a mix of nerve poisons, tissue-destroying chemicals and other nasty compounds designed to elicit severe stinging. In worst case scenarios, it can lead to permanent blindness.
Should you ever encounter a spitting cobra — which is unlikely as they are fairly rare — make sure to keep a good 10-foot distance away from it. Their venom can shoot about four to eight feet.