The black widow spider got its name because the female supposedly consumes her mate after breeding, but this generally occurs only in captive situations when the unlucky male has little room for retreat. Nearly 1,000 species of fish are venomous, including species of stingrays, sharks, catfish, weeverfishes, and scorpionfishes. Of the 3,000 species of snakes worldwide, only about 300 are venomous.
Venomous animals are immune to their own venom.
If two rattlesnakes of the same species fight, neither will be harmed by the venom they inject. The venom of the tiny Blue-ringed Octopus contains tetrodotoxin, one of the most potent neurotoxins known. Human death from heart and respiratory failure can occur within minutes. An adult rattlesnake can rattle at a rate of 50 times per second. A snake would rather frighten away a predator with a harmless strike than deplete its store of venom.