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The Rosy Boa (Lichanura trivirgata) is a small ground boa found in the desert and chaparral zones of the Southwestern United States, Baja California, and Sonoran Desert of Mexico. The Rosy Boa operates within a narrow temperature range, restricting its geographic range. The range map provided herein reflects the three geographic clusters of rosy boas in the United States. The clusters do not necessarily imply taxonomical differences. This range map is the first of its kind to report the northern extend of the Mojave population of Lichanura. There are also reported sightings of the Rosy Boa in extreme southern Nevada, however an established population has yet to be verified at this time.
The Rosy Boa is predominately a crepuscular species with periods of nocturnal activity observed in late spring through the summer months, and diurnal activity in late winter through early spring. The Rosy Boa emerges from hibernation usually in late-February to early March, depending of the specific locality and seasonal conditions. Lichanura enters the active season by warming itself under sunlit rocks and rock fragments, or conceals itself under the shadows of shrubs. This behavior usually occurs mid-February through late March. By April, the surface activity of Lichanura increases and the Rosy Boa may be found during daytime or early evening hours. This period is usually characterized by heavy feeding in preparation for the upcoming breeding season. As the seasonal conditions become warmer and drier, Lichanura exhibits more crepuscular behavior. This behavior addresses two considerations: the need for adequate heat while minimizing predatory risk, and conserving water (loss) by restricting activity to periods of higher relative humidity. Mating occurs anytime from May to July
in the wild. By November, Rosy Boa activity is uncommon and most have retreated to hibernaculum for the winter. Hibernaculum include underground burrows, dens within rock structures, rat nests, and caves. In any event, these structures likely provide cooling between 55oF-65oF for 2-3 months. The Rosy Boa feeds primarily on rodents, though birds, bats, and possibly lizards may also be eaten. Most Rosy Boas in captivity "ambush" their prey. Some captive Lichanura will burrow themselves under loose soil with only their nostrils protruding, awaiting the unsuspecting prey. By occupying rodent burrows and dens, the Rosy Boa can enjoy a "Bed and Breakfast" lifestyle, expending little energy to acquire an adequate food source. The Rosy Boa will also stalk its prey. The Rosy Boa at maturity is approximately 32"-38" for males and 34"-40" for females. Heavily nourished captive specimen of the California Coastal region have attained sizes of up to 50 inches in length. Males are identified by the presence of rudimentary legs or spurs on each side of the vent. The Rosy Boa can live up to 30 years in captivity, with a current living record at ~ 27 years. Record longevity will no doubt be redefined with the vast number of captive bred Rosy Boas in collections today. Taxonomy and Species Identification For complete information about Lichanura
species and subspecies identification, taxonomy, and range distribution
by ssp.,
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Within its geographic range, Lichanura
prefers a habitat in association with rock outcroppings or a ground
composition of granitic rock, and high annual sun explosure (90% or
greater). Such climatic conditions have enabled the Rosy Boa to
utilize its adaptive traits of nocturnal behavior, low metabolic rate,
and heat sensing predatory capabilities (common to most boas).
Granitic rock outcroppings, rock piles, and ground borrows in areas of
high sun exposure create a natural thermal gradient for Lichanura
while allowing it conceal itself from potential predators. This
microhabitat also can provide a moisture trap, improving moist
conditions during much of the year. Specific habitat forms
include boulder piles with cap rocks, fissures, base fragments, or
talus; smaller rock piles in bajadas, alluvial fans, washes and canyons;
desert scrub or coastal sage-scrub (chaparral) habitat with a granitic
base suitable for burrowing. Lichanura is most likely to be
found in these micro habitats with southern exposure and the presence of
permanent or intermittent water. Evidence of rodent nests or
activity is usually present.
The breeding frequency of females in the wild is not
well documented, and is likely influenced by the available food supply
and seasonal conditions. However, it is generally thought that
most females will breed every other year under normal circumstances.
Gestation typically requires 115-140 days for full term. Offspring
are live born live and are in evidence anytime from August to November.
Litter size varies from 3-8 in most wild populations.