Harmless · Native to the mountains of southern California

Southern rubber boa

Charina umbratica

Threatened in California since 1971
Data updated November 2026

Southern rubber boa coiled on pine needles, showing smooth plain brown skin and a blunt tail
Fig. 1 — Adult on forest litter. The plain brown skin and blunt, head-like tail are typical.
Southern rubber boa curled into a loose ball on a mossy log
Fig. 2 — Docile when handled, it often curls into a ball.

At a glance

A small, secretive burrowing boa found only in the high pine and oak forests of southern California’s mountains, chiefly the San Bernardino and San Jacinto ranges. It is harmless, slow and rarely seen, and it is listed as threatened by the state of California.

01

Identification

The southern rubber boa is a small, stout snake with smooth, shiny skin that looks and feels like rubber. It is a plain, uniform olive green, reddish brown, tan or chocolate brown, with no stripes or blotches. The head is short and broad with large scales on top and small eyes, and the short, blunt tail is shaped so much like the head that the snake can look two-headed.

  1. 01Rubbery look. Small, smooth scales and loose skin give a soft, rubber-toy appearance.
  2. 02Plain color. Uniform olive, tan or brown above with no pattern.
  3. 03Head-like tail. The short, blunt tail is used to fend off attackers, such as a mother mouse defending her nest.

Commonly confused with

The southern rubber boa was long treated as a subspecies of the northern rubber boa, and some researchers have proposed raising it to a full species; checklists still differ, but California recognizes it as a distinct, protected taxon. The two look nearly the same and are hard to tell apart without counting scales in the hand. The southern form is smaller, and range is the best guide: in southern California, rubber boas in the San Bernardino and San Jacinto mountains are this species, while boas around Mount Pinos and the Tehachapi Mountains appear to be intergrades with the northern form. Rosy boas share the blunt, glossy look but have stripes and live in lower, drier, rockier country.

02

Size

01 ft2 ft3 ft4 ft Typical adult · about 18 in (46 cm)

This is a small boa. The body alone (snout to vent) reaches about 15 inches (38 cm), and most adults are well under 2 feet in total length, smaller than the northern rubber boa. Newborns are about 7 inches (18 cm) long.

03

Range & habitat

Mixed conifer and black oak forest floor in the San Bernardino Mountains with fallen logs
Fig. 3 — Moist pine–oak forest with rotting logs and deep leaf litter.

The southern rubber boa is found only in California, in the San Bernardino Mountains (San Bernardino County) and the San Jacinto Mountains near Idyllwild (Riverside County). Over 40 sites are known in the San Bernardino Mountains, 26 of them in a 10-mile strip between Twin Peaks and Green Valley, and about 8 in the San Jacinto Mountains. Boas on Mount Pinos and in the Tehachapi Mountains are sometimes assigned to this species, but their identity is unsettled. In the San Bernardino National Forest it has been found at about 5,050 to 8,070 feet in moist pine–oak and conifer forest of Jeffrey, yellow and sugar pine, white fir and black oak, where deep soil, rock outcrops, large fallen logs and a thick layer of leaf litter keep the ground damp. In summer it is usually found in moist draws near springs, seeps and streams.

04

Diet & predators

Rubber boas hunt underground and in burrows. In feeding trials southern rubber boas ate nestling deer mice, nestling shrews and lizard eggs most often; they also take lizards and, now and then, small snakes, salamanders and birds. When a boa finds a nest of baby mice it tries to eat the whole litter, fending off the mother by jabbing its blunt tail at her.

Feeds on

  • Nestling deer mice
  • Nestling shrews
  • Lizards and lizard eggs
  • Small snakes and salamanders (occasionally)

Preyed on by

  • Hawks and owls
  • Skunks
  • Raccoons
  • Domestic cats
Deer mouse on a forest floor
Prey — nestling deer mice.
Raccoon walking along a fallen log
Predator — raccoon.

05

Behavior & seasons

Southern rubber boas are very secretive and spend most of their lives burrowing in damp soil, rotting logs, leaf litter and under rocks. They come out at dusk, at night or on overcast, humid days and prefer cool air of about 60–70°F (15–21°C). They swim well and climb shrubs and small trees with the help of a prehensile tail. They are docile and usually curl into a ball when picked up.

They hibernate from about November until February or March, often in rock outcrops or rotting stumps. In spring adults are found under rocks and logs. Individuals tend to stay in a small area; most recaptured snakes were found within about 25 feet of where they were first caught, though one snake moved about 900 feet in a season.

06

Reproduction

Females come out of hibernation around April, and courtship runs through mid-May. Southern rubber boas give birth to live young, usually between late August and the third week of September, in loose soil, under surface objects or inside rotting logs. Litters hold about 2 to 8 young. The snakes are long-lived: one captive female first caught in 1971 was estimated to be 50 to 70 years old.

07

Conservation

The southern rubber boa was listed as threatened by the state of California in 1971 and is a U.S. Forest Service Sensitive species in the region. It has no federal Endangered Species Act listing.

Its small mountain range overlaps resort towns such as Lake Arrowhead and Idyllwild, so private land development is the main threat. Others include water diversion that dries out springs and seeps, ground disturbance from large fuel-reduction projects after drought and tree die-off, logging, unauthorized off-road driving and firewood cutting, and new mountain-bike trails. Keeping fallen logs, snags, rock outcrops and streamside areas intact protects its habitat. Browse protected reptiles

Keep reading

Sources

Data updated November 2026 · How we build these pages