Serpent in Lincoln park zoo

Photographed by CHA

Most snake skin colors result from pigments, although Asian sunbeam snakes (Xenopeltis) and some other species have microscopic structures that make their scales iridescent. Some boas, colubrids, and vipers become lighter at night and darken during the day. With age, melanin deposits in the skin often obscure the bright patterns of juvenile snakes; examples of such ontogenetic color shifts include several pitvipers and colubrids that are blotched or bright red as juveniles, then uniformly dark-colored as adults. Color changes sometimes vary geographically within a species, perhaps associated with changes in habitat and defensive responses: As adults, Black Ratsnakes (Elaphe o. obsoleta) are uniformly dark and Yellow Ratsnakes (E. o. quadrivittata) have black stripes on a light background, whereas all juveniles of that species are light brown or gray with a dorsal pattern of dark blotches. Adult Western Rattlesnakes (Crotalus viridis) are contrastingly blotched like their young over most of the range of that species, but some full-grown Arizona Black Rattlesnakes (C. v. cerberus) are sooty black with small golden flecks.

Adult color patterns are constant in most snake species, at least within a population. Well-known polymorphisms, however, include striped versus banded Common Kingsnakes (Lampropeltis getula); striped, banded, and unicolored Prairie Groundsnakes (Sonora semiannulata); and red versus gray or brown estuarine species in Asia (Dog-faced Watersnake [Cerberus rynchops]) and the United States (Salt Marsh Watersnake [Nerodia clarkii]). Although popular with hobbyists, free-living snakes with truly aberrant colors and patterns are easily visible to predators and thus rare. At least in Brazil, most naturally occurring albino snakes are either nocturnal or burrowers, therefore less likely to be seen by enemies, or are venomous and thus especially capable of defense.

Molting (shedding, ecdysis) in reptiles results from cyclical changes in the underlying skin structure; the end result--a shiny new skin--might facilitate growth, renew tissue abraded during locomotion or otherwise damaged, remove ectoparasites, and maximize chemical communication. Most squamates molt in small, ragged pieces over a period of days or weeks, but alligator lizards, amphisbaenians, and snakes typically shed their skins in one piece. Intervals between ecdysis range from a few weeks to several months and vary with temperature, health, growth, and feeding. For several days prior to molting the eyes are clouded gray or blue by fluid between the old and newly formed spectacles; snakes in that condition are usually inactive and sometimes remain hidden. Among those I found "in the blue," a Northern Cat-eyed Snake (Leptodeira septentrionalis) was hidden in a bromeliad, two Terciopelos (Bothrops asper) remained in burrows, several Bushmasters (Lachesis muta) were coiled on the forest floor, and a Lowland Bush Viper (Atheris squamiger) was resting on a branch.

word source : www.nytimes.com

SNAKES: The evolution of mystery in nature by Harry W. Greene, University of California Press