Midget Faded Rattlesnake

Crotalus oreganus concolor (Crotalus viridis concolor)

Midget Faded Rattlesnake

Distribution in Wyoming

 

 

 

 

 

 

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The distribution of the Midget Faded Rattlesnake extends from the tri-border area in southwestern Wyoming south along western Colorado and eastern Utah to just north of Arizona and New Mexico. In Wyoming it resides in a corridor along both sides of the lower Green River Valley and eastwardly a bit toward Kinney Rim, from approximately I-80 south to the Colorado and Utah state line in Sweetwater County. It inhabits the sagebrush, shrub, and juniper woodland communities of the desert life zone where it prefers the habitat of brush covered hillsides terraced with rock outcrops.

Midget Faded Rattlesnake Midget Faded Rattlesnake

These venomous snakes are active from May through September and are primarily diurnal, tending to be more active in mid morning and early evening. They prey on lizards and small mammals such as mice and chipmunks—using the heat-sensing organ within the pit (found between the nostril and the eye) to help locate warm blooded animals in the darkness of their burrows. They employ a strike-and-release method to inject the venom (rather than a bite-and-hold method) which helps to prevent the snake from being injured by the prey before the toxin takes effect. The snake searches for the envenomated prey using its forked tongue to collect and pass air borne chemicals to sensory receptors located on the roof of the mouth (known as the vomeronasal organ) to follow the trail of chemical clues left by the dying animal.

Midget Faded Rattlesnake Midget Faded Rattlesnake

They are medium sized snakes with a maximum length (TL) of about 24 inches. Their dorsal scales are keeled and the anal plate is entire. They have a wide, triangular shaped head, narrow neck, and vertically elliptical pupils. The belly is white and unmarked. The dorsal background is a light brown with a series of about 40 oval to rectangular, darker brown blotches running along the body; these blotches are bordered with a black margin and form rings near the end of the tail. The tail ends in a rattle.

This species is distinguished from the Prairie Rattlesnake by its smaller size and by the black, not white, edging around the dorsal blotches. In addition, the white stripe extending from the front of the eye to the rear of the jaw is much wider (3-4 scales) when compared to the narrower (1-2 scales) stripe of the Prairie Rattlesnake. The ranges of these two species come very close to each other but do not overlap in Wyoming, a type of ecological distribution known as parapatric overlap.

Midget Faded Rattlesnake Midget Faded Rattlesnake

The young of this rattlesnake, with a litter size of 2-7, are born alive in late summer or early fall. Mating may occur at the den on emergence but also occurs in midsummer after migrating away from the den site. Ovulation occurs in early spring with fertilization taking place using sperm stored overwinter and from the mating of the previous year. Females probably reproduce every 2nd or 3rd year. Gravid females may be found alone or in communal areas known as rookeries.