Harmless · Native to the United States

Northern rubber boa

Charina bottae (Blainville, 1835)

Also called rubber boa, two-headed snake
Data updated October 2026

Northern rubber boa coiled on forest soil, showing a plain olive-brown body with smooth, shiny scales
Fig. 1 — Adult on forest soil. The skin looks and feels like rubber.
Close view of a northern rubber boa’s blunt tail, which looks similar to its small head
Fig. 2 — The short, blunt tail looks like a second head.

At a glance

A small, stout boa of western mountains and forests, rarely over 2 feet long. It is slow, gentle and mostly active at night. It kills small prey by constriction and is one of the most cold-tolerant snakes in North America.

01

Identification

The northern rubber boa is short and thick, with small eyes, tiny smooth scales and loose skin that gives it a rubbery look and feel. The back is a single plain color: tan, brown, olive, gray, charcoal or sometimes rosy. The belly is yellow or cream, sometimes flecked with dark spots. Pupils are vertical. The tail is short and blunt and looks much like the head. Young are pinkish and almost see-through.

  1. 01Blunt, head-like tail. The short, rounded tail is easy to mistake for the head.
  2. 02Rubbery skin. Small, smooth, shiny scales on loose, wrinkled-looking skin.
  3. 03Plain color. No pattern on the back; brown to olive above, yellow or cream below.

Commonly confused with

02

Size

01 ft2 ft3 ft4 ft Typical adult · about 22 in (56 cm)

Adults are usually 14 to 33 inches (36–84 cm) long, and in the Northwest they rarely pass about 2 feet. Females grow larger than males: in one Oregon study males averaged about 21 inches and females about 26 inches. Newborns are about 10 inches long.

03

Range & habitat

Open conifer forest with rocks, fallen logs and woody debris on the ground
Fig. 3 — Rock outcrops, talus and rotting logs in open forest make good boa habitat.

The northern rubber boa is the most northerly boa in the world. It ranges from southern British Columbia south through Washington and Oregon to northern California, and east through Idaho to western Montana, Wyoming and Utah, from sea level up to about 10,000 feet. It lives in grassland, shrubland, woodland and forest, often near water. Rock outcrops, talus slopes, loose rock and fallen logs are important cover, and in forests it favors openings. A separate species, the southern rubber boa, lives in a few mountain ranges of southern California.

04

Diet & predators

Rubber boas are constrictors that wrap around prey and squeeze it. About two thirds of the diet is small mammals, mainly nestling mice, voles and shrews taken from burrows. Lizards, small birds, salamanders and the eggs of lizards and snakes make up most of the rest. Smaller boas take more eggs and lizards. Adults often carry scars on the tail from mother rodents defending their nests.

Feeds on

  • Nestling mice and voles
  • Lizards and lizard eggs
  • Small birds
  • Salamanders and small snakes

Preyed on by

  • Red-tailed hawks
  • Common ravens
  • Raccoons and house cats
  • Night snakes (young boas)
Deer mouse at a burrow entrance
Prey — nestling rodents.
Red-tailed hawk perched on a branch
Predator — red-tailed hawk.

05

Behavior & seasons

Rubber boas are slow, secretive and gentle, and they rarely if ever bite. They spend much of their time underground or under logs, bark and rocks, and come out mostly at night and dusk, sometimes by day in mild, cloudy weather. When threatened a boa may hide its head under its coils and raise its blunt tail, which draws attacks away from the head, and it can also release a strong odor.

They are unusually tolerant of cold and can be active at body temperatures around 57°F (14°C). They emerge from winter shelter in March and spend the winter in rock outcrops, talus or forest soil, often in small groups. Individual boas return to the same sites year after year.

06

Reproduction

Rubber boas give birth to live young. Mating takes place soon after spring emergence, into mid-May, and young are born from late July to November. Litters hold 1 to 8 young, averaging about 4. Most females breed only every 2 to 5 years. Males mature at about 3 to 4 years and females at 4 to 5. They are long-lived: wild boas have been recaptured at 10 to 24 years old, and captives have passed 30.

07

Conservation

The northern rubber boa is not listed under the US Endangered Species Act and is considered secure across its range as a whole. In Canada, where it is found only in southern British Columbia, it is listed as a species of Special Concern. Habitat loss and fragmentation, roads and development are the main local threats. Because the species breeds slowly, losing adults can take a long time to recover.

Keep reading

Sources

Data updated October 2026 · How we build these pages