Sonoran whipsnake (Coluber bilineatus)

The Sonoran whipsnake (Coluber bilineatus) can be identified by its elongated, slender body, measuring between 24 – 67 inches (61 – 170 cm) in total length. Its coloration is a distinctive blend of blue-gray to gray-green hues around the neck, transitioning to yellow-green mid-body, and finally gray-brown towards the tail. Notably, two to three thin, white stripes adorn each side of its body, extending from the neck to about mid-body before rapidly fading and merging with the background color. Additionally, on the mid-section, a pair of light dots mark the anterior edge of each dorsal scale. The underside of the Sonoran whipsnake is white to cream, fading to a pale yellow beneath the tail.

This species boasts large, round-pupiled eyes and smooth scales, contributing to its sleek appearance. Unlike its similar-looking counterpart, the Striped Whipsnake, the Sonoran whipsnake lacks side stripes on the posterior portion of its body.

In terms of distribution, the Sonoran whipsnake primarily inhabits the sub-Mogollon Rim mountain ranges of south-central and southeastern Arizona, spanning elevations from near sea level to approximately 7,500 feet (2,290m).

Its habitat range extends from semiarid lower mountain slopes to pine-oak belts in the mountains, with a preference for rocky stream courses. More specifically, this species across a range of biotic communities such as Arizona Upland Sonoran Desertscrub, Semidesert Grassland, Interior Chaparral, Madrean Evergreen Woodland, and the lower regions of Great Basin Conifer Woodland. It is frequently sighted on mountain slopes, in canyons, foothills, along ridges, and on steep rocky bajadas, with a preference for elevated areas over flat terrain.

The Sonoran whipsnake exhibits a dynamic range of behaviors reflective of its adaptable nature. It is characterized as a diurnal, very fast-moving and alert predator, typically active during the day. Often seen basking in the mid-morning sun, this snake demonstrates a unique behavior of elevating its head high off the ground, possibly to survey its surroundings for prey. Its agility and speed make it a proficient predator, primarily preying on lizards, snakes, bats, mice, rats, other small mammals, birds, and amphibians. Its hunting strategy involves seizing prey without necessarily killing them first.

While primarily a ground-dweller, it exhibits both terrestrial and arboreal habits, gracefully climbing bushes and trees when necessary especially when it feels threatened, as it can swiftly escape into the high branches and out of reach of terrestrial predators.

During warm, humid nights, this species occasionally takes refuge in trees for sleeping. However, during the cold months of late fall and winter, the Sonoran whipsnake enters a period of hibernation, or brumation.

Mating occurs during spring, with 6 – 13 eggs laid in June and July.

The Sonoran whipsnake displays a notable defensive behavior; when handled, it readily bites. 

References:

Stebbins, R. C., & McGinnis, S. M. (2018). Peterson Field Guide to Western Reptiles and Amphibians (4th ed.). Houghton Mifflin Harcourt.

Brennan, T. C. (n.d.-b). Sonoran whipsnake. The reptiles and amphibians of Arizona. https://reptilesofaz.org/snakes-subpages/h-c-bilineatus/

Sonoran whipsnake (Masticophis bilineatus). Arizona-Sonora Desert Museum. (n.d.-b). https://www.desertmuseum.org/books/nhsd_whipsnake.php