Asked by: Jordan Shemilt, Midsomer Norton
Snakes don’t have claws or powerful jaws to pin down their prey. If the venom doesn’t kill quickly enough, the victim may escape into a burrow or up a tree and die out of reach of the snake – or, worse, injure the snake in its death throes.
Snakes are in an evolutionary arms race with their prey, which are evolving ever-greater resistance to snake venom. Snakes have adapted to this by evolving venoms that contain a cocktail of several hundred different enzymes and proteins. Some block nerve transmission, others interfere with the beating rhythm of the heart, some break down muscle tissue or cause blood vessels to suddenly become leaky.
Snakes can control how much venom they inject with a single bite and generally use far more than the lethal dose. The black mamba, for example, injects up to 12 times the lethal dose for humans in each bite and may bite as many as 12 times in a single attack. This mamba has the fastest-acting venom of any snake, but humans are much larger than its usual prey so it still takes 20 minutes for you to die.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.