The Round Island Boa also known as the Round Island Keel-scaled Boa, is a snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

 in the Bolyeriidae family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, in the monotypic

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Casarea. It is also the only extant member of the family Bolyeriidae, and is endemic to Round Island

Round Island (Mauritius)

Round Island is an uninhabited islet 22.5 kilometers north of Mauritius. It has an area of 1.69 square kilometers and a maximum elevation of 280 meters...

, Mauritius

Mauritius

Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

. No subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 are currently recognized.

Description

Adults are slender and reach a maximum length of 150 cm (5 ft). The males have slimmer, more pointed heads and have shorter bodies than the females. The body is covered in small keeled scales

Keeled scales

Keeled scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, making them rough to the touch...

 that give the species one of its common names. The genus is unique among extant vertebrates as it has a split jaw (intramaxilliary joint that separates anteria and posteria bones), an adaptation that may be advantageous in catching its main prey of gecko

Gecko

Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

s and skink

Skink

Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...

s.

The colour pattern is dark brown dorsally, the belly being lighter with dark spots. Over a 24 hour period the boa has a shift in colour, changing from 'dark' during its relatively inactive day time period to 'light' in the early evening through to dawn when it is most active. This effect is created through polychromatic

Polychromatic

The term polychromatic means having several colours.It is used to describe light that exhibits more than one color. In a technical respect, this can also mean that it contains radiation of more than one wavelength. The study of polychromatics is particularly useful in the production of diffraction...

 skin cells.

Geographic range

The boa is known only to survive on Round Island, but has been recorded on the islands of Gunner's Quoin, Flat Island, Ile de la Pas, and on mainland Mauritius (as subfossil remains). The type locality is "I'île ronde, près de Maurice" (Round Island, Mauritius).

Conservation status

The species is classified as Endangered (E) on the IUCN Red List for the following criteria: D (v2.3, 1994). This means that, although it is not critically endangered, for some time it has faced a very high risk of extinction in the wild. In 1996 the population was estimated to number less than 250 mature individuals.

Recent conservation efforts have seen an increase in the number of adult boas to around 1000. This has been achieved by eradicating goat

Goat

The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...

s and rabbit

Rabbit

Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...

s from the island and restoring natural habitat which has led to an increase of the boas’ natural prey, and it specializes in lizard hunting. In recent breeding efforts, Round Island Boas in captivity

Captivity (animal)

Animals that live under human care are in captivity. Captivity can be used as a generalizing term to describe the keeping of either domesticated animals or wild animals. This may include for example farms, private homes and zoos...

 have been fed by scenting small mice

MICE

-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...

 with chicken thigh meat.

Reproduction

Breeding begins during April, although young have been observed throughout the year. A clutch

Clutch (eggs)

A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...

 of up to 12 soft shelled eggs

Egg (biology)

An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

 can be laid amongst leaf litter or in hollow palm

Arecaceae

Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...

 trunks, and is sometimes attended by the female. Incubation is unusually long for a snake, lasting about 90 days. The young are bright orange

Orange (colour)

The colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 585–620 nm, and has a hue of 30° in HSV colour space. It is numerically halfway between red and yellow in a gamma-compressed RGB colour space, the expression of which is the RGB colour wheel. The...

 at birth and weigh less than 5 grams.

External links

• Round Island keel-scaled boa (Casarea dussumieri) at ARKive. Accessed 18 February 2008.
• Mascarene forests at National Geographic. Accessed on 18 February 2008.