<P> Rattlesnake fangs are connected by venom ducts to large venom glands near the outer edge of the upper jaw, towards the rear of the head . When the rattlesnake bites, muscles on the sides of the venom glands contract, which squeezes the venom through the ducts and into the fangs . When the fangs are not in use, they remain folded against the palate . </P> <P> Rattlesnakes are born with fully functioning fangs and venom, and are capable of killing prey at birth . Adult rattlesnakes shed their fangs every 6--10 weeks . At least three pairs of replacement fangs lie behind the functional pair . </P> <P> The venom is hemotoxic, destroying tissue, causing necrosis and coagulopathy (disrupted blood clotting). In the U.S., the tiger rattlesnake (C. tigris) and some varieties of the Mojave rattlesnake (C. scutulatus) also have a presynaptic neurotoxic venom component known as Mojave type A toxin, which can cause severe paralysis . Although it has a comparatively low venom yield, the venom toxicity of C. tigris is considered to be among the highest of all rattlesnake venoms, and among the highest of all snakes in the Western Hemisphere based on LD studies conducted on laboratory mice . C. scutulatus is also widely regarded as producing one of the most toxic snake venoms in the Americas, based on LD studies in laboratory mice . </P> <P> Rattlesnake venom is a mixture of five to 15 enzymes, various metal ions, biogenic amines, lipids, free amino acids, proteins, and polypeptides . It contains components designed to immobilize and disable the prey, as well as digestive enzymes which break down tissue to prepare for later ingestion . The venom is very stable, and retains its toxicity for many years in storage . </P>

What type of venom does a rattlesnake have
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