The coral snake found in Texas (Micrurus fulvius tenere) is the only black, red, and yellow crossbanded serpent whose red and yellow bands touch: "Red against yellow kills a fellow." Its uncommon look-alikes, the milk and scarlet snakes, have red and yellow bands separated by narrow black rings: "Red against black, poison lack." The coral's black bands, in contrast, are as broad as its red ones and are separated by bright sulfur rings; the head and tail are marked only with black and yellow, and, unlike those of nonvenomous snakes, the coral's body bands continue uninterrupted across its belly. The bright colors of the coral snake may serve both as a warning signal and as camouflage, for at night, when red appears as gray, on the dappled forest floor its alternating light and dark make the snake's shape less discernible to owls and other predators. The bold contrast between the bands of M. fulvius seems to deter small mammalian carnivores. In defense against them the coral may tuck its foreparts under its trunk while waving its elevated yellow and black banded tail tip back and forth in imitation of its head threatening to strike.
Coral snake venom is largely composed of neurotoxically destructive peptides and is, therefore, more deadly than the venom of most other North American reptiles. A lethal dose for an adult human being is as small as five to ten milligrams, dry weight—several times more virulent than the venom of the western diamondback rattler (see RATTLESNAKES). Since its toxic peptides spread rapidly through the blood stream, the application of a tourniquet and immediate hospital administration of antivenin are probably appropriate in cases of severe poisoning. Although intense pain usually accompanies a bite, heavy envenomation is often difficult to determine because the central nervous system may not manifest symptoms for several hours. Still, few people are harmed by coral snakes: only 1 percent of all snake bites are by coral snakes, and fewer than 10 percent of these are fatal. Though locally common in suburban neighborhoods throughout all of the state but far West Texas, M. fulvius is so secretive and nonaggressive toward human beings that only those who handle the snake are often bitten. The rigid fangs, which are longitudinally grooved pegs rather than hollow hypodermic tubes, are less than one-eighth inch in length and are unlikely to penetrate shoes or even most clothing, although corals can pierce a pinch of skin anywhere on the body. If molested, the coral snake is a quite determined biter that flips its head from side to side and snaps sharply.
Texas coral snakes average about two feet in length. The record is nearly twice the average. They are most often seen in spring and fall, when they forage abroad on cool, sunny mornings; during hot weather their activity is mostly crepuscular or nocturnal. Their prey is chiefly other snakes, some as big as the coral itself, which are overcome by means of the potent venom. M. fulvius has an extended reproductive season, perhaps because of its small home range; because of the low sensory perception in males, which sometimes makes it difficult for them to find a mate; and because the larger of a pair of introduced corals, usually the female, sometimes tries to eat its prospective mate. The coral snake breeds from late summer to late spring and lays its clutches in midsummer. The three to five eggs, one and three-eighths inches in length by three-eighths inch in diameter, are deposited beneath loose ground cover or a layer of soil to prevent their drying; they hatch after some two months into young 6½ to 7½ inches long, which resemble adults. See also REPTILES.