The Gray-banded Kingsnake is a slender colubrid found in the Trans-Pecos/Chihuahuan Desert regions of West Texas and Northern Mexico. Dwelling mainly in the hills and mountains of this arid land, it is almost purely nocturnal. Collectors from around the world spend their nights in May and June wandering the hills and canyons of this darkened landscape, hoping for a glimpse of Day-Glo orange bands in the lamplight. Originally called the Davis Mountain Kingsnake, and the Blairs Kingsnake, they were once thought to be quite rare, but are now known to be one of the most common snakes in their range.
First described as Ophibolus alternus by Brown in 1902 the Type-locality animal was collected in the Davis Mountains in West Texas by E.Meyenberg in 1901. The holotype resides in the Academy of Natural Science collection in Philadelphia. The name L. alterna was described in 1917 by Stejneger and Barbour, but has undergone a number of revisions over the years before returning to the current L. alterna. In the 60's the "Blairi" and "Alterna" morphs were described as seperate sub-species until it was discovered in the 70's that both forms were different color/pattern types of the same animals.
L. alterna is a medium sized colubrid snake possessing a relatively wide head, large eyes and a sub-cylindrical body. Juveniles are 24cm. or longer at birth, with adults reaching 1 meter or more (averaging 80cm.), with animals from higher elevations being slightly smaller. Coloration is extremely variable throughout the range, there are two recognised color morphs. A typical "Blairi" morph can be charachterised as having between 12-15 wide red/orange saddles bordered by narrow black, which in turn is bordered by white, on a grey background. The typical "Alterna" morph has between 17-33 heavy black bands that may or may not be split with red/orange, alternating with between 10-25 broken black bands, on a gray background. The gray background on these animals can vary from an almost white to an almost black. This gray coloration is referred to as "light phase" , "medium phase", or "dark phase". Almost all these animals have a dark post-ocular stripe, and often display an elongated "nuchal" blotch behind head that can be up to 3 times the length as a standard saddle. Sometimes these animals will also have an elaborate speckling, though this trait is primarily confined to the "Alterna" morph. Generally speaking the "Blairi" form is found primarily in the eastern part of the range, while the "Alterna" form is found in the western part of the range ( though both can be found throughout the range).
Primarily a nocturnal animal, L. alterna feeds main on lizards and rodents, though occasionally it may also take frogs, birds, bats, and very rarely, other snakes. It inhabits the dry hillsides and mountain slopes of the Chihuahuan desert and eastward to the Edwards plateau. Specimens have been collected at elevations of 1500 feet to at least 7000 feet. The range approximates the northern limits of the Chihuahuan desert. Plant associations range from the acacia/lecheguilla/grama-grass in the Guadalupe, Eagle, and Hueco Mountains to the oak/juniper/grama-grass in the higher elevations of the Davis and Chisos mountains.
Almost all specimens of L. alterna have been found as or after they have attempted to cross roads after dark. Populations appear to become active at the surface in mid to late April, with a peak that tends to occur in late May or June with activity tapering off in the heat of July. Periods of activity may possibly be attributed to the rainy season which occurs in May or June. After this rainy season ends and the days become progressively warmer and drier the animals apparently estivate, with later activity only occuring after occasional summer rainstorms.