Common Death Adder

The common death adder has independently evolved almost the entire viper body plan, a short thick body, a broad triangular head set off by a narrow neck, small keeled scales, vertical pupils, and a sit-and-wait ambush hunting style, despite belonging to the elapid family of front-fanged snakes that otherwise contains slender, active hunters like cobras, mambas, and taipans. This is a textbook case of convergent evolution, where an unrelated lineage arrives at the same solution because it faces the same problem, in this case the challenge of being a heavy-bodied ambush predator that relies on camouflage and a fast strike rather than pursuit, which favours the same set of physical traits regardless of ancestry.

The very tip of a death adder's tail is thin, often paler than the rest of the body, and soft, and when the snake is lying concealed and motionless in leaf litter with prey nearby, it twitches and wriggles just this tail tip so that it looks like a small grub, caterpillar, or worm moving on the ground. A lizard, frog, or bird that approaches to investigate this apparent easy meal is drawn within range of the snake's head, at which point the death adder strikes. This behaviour, called caudal luring, is used by a number of ambush snakes around the world, but the death adder is one of the best-known practitioners.

Studies filming death adder strikes with high-speed cameras have found that the snake can launch from a fully at-rest position, seize or envenomate its target, and return its head to a resting posture in a total time well under two-tenths of a second, making the complete strike-and-recoil one of the fastest recorded for any snake. This extreme speed is essential to the death adder's whole strategy, since as a slow-moving ambush predator it gets only a single chance at prey that has been lured close, and it must connect and withdraw before the prey can react or before a larger, dangerous prey animal can retaliate.

The death adder has highly potent venom that acts on the nervous system and, before antivenom became available, its bites had a high fatality rate, so it is considered a genuinely dangerous snake, though bites are now uncommon because the snake is not aggressive and its habit of freezing rather than fleeing means people usually pass by without being bitten unless they tread on one. Separately, in northern Australia the death adder faces its own serious threat from the introduced cane toad, because a death adder that strikes and swallows a toad is poisoned by the toad's powerful skin toxins, to which the snake has no resistance, and local death adder populations have collapsed as the toads have spread.