Natural History

Rosy Boas are small ground boas that inhabit the Mojave, Colorado, and Sonora Deserts of southern California, western Arizona, Baja California, and mainland Mexico. They also inhabit the coastal scrub areas of southern California and northwest Baja California. Rosy Boas exist within a variable temperature range, manipulated by natural land barriers. Provided is a range map that illustrates their verified geographical range. Historically their taxonomy has been an argument for many herpetologists as well as hobbyists, making educating the masses somewhat of a challenge. Illustrated on the range map, as well as throughout this website, is what is most commonly recognized and used for referencing sub species as well as “localities”. It’s my opinion that only DNA analysis will determine and recognize different sub species, or if they are in fact different (other than color and pattern) at all. It is also my opinion that their geographical differences create recognizable differences in terms of their “in the wild” behaviors (i.e. breeding, feeding, activity, longevity, and population density). Again, my opinions are based on my personal observations and feedback from fellow long term Rosy Boa enthusiasts.

Rosy Boas are diurnal during winter months in the areas consisting of moderate temperatures (i.e. from San Diego County south throughout the Baja peninsula, as well as the lower elevation localities of Arizona). Rosy Boas are crepuscular through spring time. As summer brings on higher temperatures, Rosys become nocturnal, commonly seen crossing roads from sun set on. It has been an ongoing argument with hobbyist as to whether Rosy Boas hibernate or not. In the wild, Rosy activity begins to increase in February (referenced from field observations by very reputable sources) as they try to build fat reserves for the coming breeding season. They can be observed under rocks being warmed by the sun, crawling at the base of rock outcroppings, semi-exposed in rock fissures, and even crawling out in the open. As the season progresses and the temperatures increase, Rosys are observed more in the early morning and then later in the early evening. Once the day time temps reach the 90’s, Rosys are usually only observed at night when the temperature has dropped. This is directly manipulated by their geographic origin.

Mating occurs anytime from April through June in the wild. Again, this variable is related to their geographic origin. Year after year, their frequency of breeding in the wild is only a guess. There is no hard data to support what promotes a successful breeding season. Most rosy enthusiasts agree their geographic origin, available food supply, and seasonal conditions directly affect their frequency and success. In general, it is thought that most females breed every two years. Gestation is usually 130 days for full term. Rosys give live birth of up to 8 neonates from late August to late October.

Rosy Boas primarily feed on rodents. In the wild they will also prey upon birds, bats, and lizards. Rosy Boas are very opportunistic feeders in the wild. They are very patient, and can lay in wait for very long periods of time to ambush their prey, and will occasionally stalk their prey if necessary.

Mature wild adult male Rosys reach approximately 36" and females reach 40" or more. Commonly, the larger animals are found with heavy scaring and even stub tails. Coastal localities are among the largest, but the high elevation Arizona localities are as equal. Males are identified by the presence of spurs (rudimentary legs) on each side of their vent. Rosy Boas can live up to 30 + years in captivity. I personally know of an animal that was captive born in 1971 that is still alive and well.