Crotalus molossus - Black-tailed rattlesnake

Meaning
Molossus comes from the Greek, molossos, which refers to the Molossos Hound which is a breed of dog.
Estebanensis referring to the name of the island San Esteban
Nigrescens derived from two words niger, meaning black and escens stand for "state of beginning" in other words beginning to turn black.
Oaxacus comes from the area where the snake is found Oaxaca, Mexico.

English name
Crotalus molossus estebanensis - San Esteban Island black-tailed rattlesnake
Crotalus molossus molossus - Northern black-tailed rattlesnake
Crotalus molossus nigrescens - Mexican black-tailed rattlesnake
Crotalus molossus oaxacus - Oaxacan black-tailed rattlesnake

Distribution
This snake is found in northern Arizona down to the Mexican Plateau and eastwards to the Edwards Plateau in central Texas, but also on islands in the Gulf of California. Their elevation ranges from sea level upwards to almost 3750 meters.

Habitat
This species can be found in a wide variety of habitats grasslands, desert areas but is commonly found in rocky and mountainous areas.

Description
This medium to large rattlesnake has an average size that ranges between 70 - 130cm. C. m. estebanensis appears to be the smallest of this species. They can have a tremendous variety of ground colors ranging from brown, gray, yellow, red, green often depending on location. A dark band runs between the eyes as a diagonal stripe from the eye to the corner of the mouth. The large black or brown blotches tend to have appeared jagged-edged with a few light patches in the interior of each dorsal blotch. The main characteristic of this species is the black tail, sometimes with muted, dark, gray-brown rings. The females tend to be larger than the males and have larger and thicker tails.
The determination of the species is difficult and is usually done by location and scalation. Not all species can be assigned as some populations naturally have overlapping ranges where they intergrade.

Diet
C. molossus tend to feed on mice, rats, rabbits and other small mammals but also lizards, frogs birds and even bird eggs. There is even a report that a C. m. molossus regurgitated a Heloderma.

Venom
The venom of C. molossus is basic and "mildly toxic" compared to that of other Crotalinae venoms but bites in a human can have significant effects. The venom often causes hemorrhaging, swelling, ecchymosis and thrombocytopenia.

Extra
Radio telemetry studies show that females protect their new born babies until their first shed.
It is said that this snake prefers sleeping above ground and they have been found 2.5-2.7m height up.
C. m. molossus is known to crossbreed with C. basiliscus.