Crotalus ornatus Hallowell, 1854

Taxonomic Identification

Crotalus ornatus Hallowell, 1854 is a medium-sized rattlesnake.

Adult Length Range

On average, adults of this species reach 76 to 107 cm (30 to 42 in) in length.

Recorded Maximum Lengths

Most large individuals are usually no longer than 100 cm (39 in), though maximum lengths of 125.0 cm (49.2 in), 125.7 cm (49.5 in), and 129.5 cm (51.0 in) have been documented in published records.

Sexual Size Dimorphism

Females of this species tend to grow larger than males.

Base Body Coloration

Body color ranges across yellows, olive greens, browns, and black.

Distinct Tail Feature

One of its most distinct features, consistent regardless of body color variation, is entirely black tail scales, which aligns with its common name.

Facial Markings

This rattlesnake often has a black facial mask: a band that crosses the eyes and extends diagonally downward to the corners of the mouth.

Tail Rattle Structure

Like all other rattlesnakes, this species has a keratin rattle at the tip of its tail.

Rattle Segment Growth

A new segment is added to the rattle each time the snake sheds its skin.

Rattle Age Limitation

Because snakes can shed multiple times per year, and the rattle is fragile and easily broken, rattle length cannot accurately indicate a snake's age unless the terminal end button remains intact.

Geographic Distribution

This species, commonly called the black-tailed rattlesnake, is distributed across the southwestern United States (Arizona, New Mexico, and west and central Texas), Mexico as far south as Oaxaca, and the Gulf of California islands of San Estéban and Tiburón.

Elevation Range

Its range reaches a maximum elevation of 2930 m; it has also been recorded at 6900 feet at McDonald Observatory in the Davis Mountains of west Texas.

Type Locality

Its official type locality is Fort Webster, Santa Rita del Cobre, Grant County, New Mexico, USA.

Diet Composition

All rattlesnakes are carnivorous, and this species feeds primarily on rodents, other small mammals, birds, and small reptiles such as small lizards.

Seasonal Activity Shifts

Its activity patterns change with the seasons. In spring and fall, it is mainly diurnal. In summer, it becomes nocturnal to avoid high summer heat.

Winter Hibernation Behavior

In winter, it hibernates in abandoned dens originally created by other animals, often sharing these dens with other snake species.

Locomotion Adaptations

Its locomotion adjusts to the surface it is crossing; it actively switches between sidewinding and rectilinear movement.

Habitat Preference

Although it is a capable climber and skilled swimmer, it is primarily a terrestrial species. It inhabits grasslands, desert areas, rocky and mountainous areas, and high-altitude forests.

Breeding Season Behavior

Breeding takes place in spring, when males follow the pheromone trails left by females. Copulation can last for hours and may happen multiple times across several days. After mating, the male typically remains near the female for several days to block other males from mating with her.

Reproductive Strategy

Females give birth to live young in summer.

Neonatal Dispersal

Newborns only stay with their mother until they disperse on their own, which usually happens within one to two days.

Breeding Frequency

Females are thought to breed annually.

Litter Size

Litter sizes can reach 10 to 12 young, but average four to six individuals.

Average Lifespan

The average lifespan of this species is 15–20 years.