Sidewinders are named for their unusual method of locomotion, in which they move sideways across loose ground, such as sand. Many snakes that live in similar habitats also "sidewind". This involves a wave-like undulation of the snake's body, so that only two points are in contact with the ground at any given moment. The snake progresses in a sideways direction across the ground (compared to the orientation of the body), leaving parallel S-shaped tracks in the sand.
Sidewinders have wide bodies so that they do not sink into sand. Their tails are tipped with rattles that increase in length as the snakes age. Their heads are flattened and triangular.
Sidewinders are desert rattlesnakes that lie under shrubs and ambush small animal prey at night, using sensory pits below their eyes to detect their victims' body heat. They strike with lightning speed, injecting venom from glands in their upper jaws through their hollow fangs.
If the prey escapes a short distance before being overcome, the snake soon locates the corpse with its heat-sensitive pits.
Distribution: South-western United States and northwestern Mexico.
Food: Lizards and rodents.
Size: 45 - 80 cm (18 - 32 in).
Maturity: Not known.
Breeding: Live young born in late summer.
Life span: Unknown.