(unedited) by helado on iNaturalist
Midget Faded Rattlesnake
Crotalus oreganus concolor
Least Concern (Crotalus oreganus)
Federal and State Protections
Special Concern - Colorado
Sensitive Species (S1) - Wyoming
Countries of Occurrence
50cm (19.7in) - 65cm (29.5in)
States or Providence
Wyoming, Colorado, Utah, possible extreme NW Arizona
This relatively small-sized rattlesnake is only found in the Colorado and Green River basins of Wyoming, Utah, and Colorado in the United States. It requires rocky hillsides, cliff-faces and slopes with an abundance of crevices & rock cover and sage-brush thickets. Gravid (pregnant) females practice communal thermoregulation, where multiple females use the same spot to sun and give birth.
This species generally stays under 3 ft long. Juveniles of the midget faded rattlesnake are typically distinctly patterned, and the pattern tends to fade to a silver or gray as the snakes age.
Midget faded rattlesnakes are threatened by habitat loss due to infrastructure development (roads, oil & natural gas pipelines, etc.) and by human collection/poaching of individuals and destruction of their hibernacula. Destruction of communal denning (over-wintering) and pregnancy sites can lead to local extirpation (extinction) of populations. It is listed as a Sensitive Species with an S1 rank (high likelihood of extirpation) in Wyoming, and a Species of Concern in Colorado. Both states restrict the collection of this subspecies to permit-only, however, little other action is taken.
The midget faded rattlesnake possesses venom more toxic than most other rattlesnakes and any other subspecies under Crotalus oreganus. This is due to a neurotoxin, concolor toxin, as well as a potent mytotoxin. This species exhibits an ontogenetic shift in prey type (favoring lizards or shews over larger rodents) but not a shift in toxicity; venom of juvenile midget faded rattlesnakes are just as toxic as adults of this species.