Crotalus aquilus - Querétaro dusky rattlesnake

Meaning
In Latin aquilus means dark colored, dun or swarthy.

English name
Querétaro dusky rattlesnake

Other names
Vibora de cascabel

Distribution
In the southern part of the Mexican Plateau from northwestern Veracruz, and southern San Luis Potosí, southward and westward through northern Hidalgo, Querétaro, Guanajuato and northwestern Michoacan to the Chapala region of Jalisco.

Habitat
They are usually found in open grassy rocky habitats, pine-oak forest, open karstic areas, grassy montane meadows and stone mesquite grassland. This species normally is found between the altitudes 1600 to 3110 meters.

Description
This small heavy-bodied snake reaches an average length of about 50cm. The maximum length recorded is 67.8 cm. There is a lot of color variations within the species, adult males normally have a greenish or yellowish cast, whereas females are brownish or grayish. Many of the populations are sexually dimorphic.
A pair of dark brown nape blotches, usually covering 5 to 7 scales, is followed by 21-41 middorsal blotches and 3-8 bands on the tail. Many of the animals have a yellow/pinkish postocular stripe extending under the eye towards the preoculars.
The species has often been confused with and has even carried the name C. triseriatus, Klauber 1972 noted the species as C. triseriatus aquilus. Dorcas in 1992 showed several differences which made it a full species and even suggested that C. aquilus may be even more closely related to C. lepidus then to C. triseriatus. Some of the differences can be found in the shape of the nasal, tendency towards sexual dimorphism, osteology, the eyes, rattle size and differences in the hemipenialspines.

Diet
Their diet mainly consists of small mammals and lizards but juveniles may also eat insects.

Venom
The venom appears to act mainly on the blood cells, producing localized pain and swelling.