The Round Island boa (''Casarea dussumieri''), also known commonly as the Round Island keel-scaled boa and the Round Island ground boa, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of non

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

ous

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

''Casarea'' in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Bolyeriidae :''Common names: Mauritius snakes, Round Island boas, splitjaw snakes.'' The Bolyeriidae are a family of snakes native to Mauritius and a few islands around it, especially Round Island. They also used to be found on the island of Mauritius, but ...

. The species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to Round Island,

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label=Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It incl ...

. No

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

are currently recognized.

Etymology

The specific name, ''dussumieri'', is in honor of

Jean-Jacques Dussumier Jean-Jacques Dussumier (1792–1883) was a French voyager and merchant from Bordeaux. He is known as a collector of zoological species from southern Asia and regions around the Indian Ocean between 1816 and 1840. These collections were later studied ...

, a French merchant, ship owner, and collector of

zoological Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and dis ...

specimens.

Description

Adults of ''C. dussumieri'' are slender and reach a maximum total length (including tail) 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 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, Campbell, J. A., Lamar, W. W. (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithac ...

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 anterior and posterior bones), an adaptation that may be advantageous in catching its main

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos ar ...

s and

skink Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Ski ...

s. The colour pattern is dark brown

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...

ly, 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 skin cells.

Geographic range

''C. dussumieri'' is known 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

remains). The type locality is "''I'île ronde, près de Maurice'' " (Round Island, Mauritius). Between 11 and 31 October 2012 the boa was reintroduced into Gunner's Quoin as part of a joint collaborative project involving the

Durrell Wildlife Conservation Trust Durrell Wildlife Conservation Trust is a conservation organization with a mission to save species from extinction. Gerald Durrell founded the Jersey Wildlife Preservation Trust as a charitable institution in 1963 with the dodo as its symbol. T ...

, the

Mauritian Wildlife Foundation The Mauritian Wildlife Foundation (MWF) is an independent, non-governmental, non-profit conservation agency working in Mauritius to save threatened endemic local flora and fauna. History The Mauritian Wildlife Appeal Fund was established in 19 ...

, and the National Parks and Conservation Service of Mauritius.

Conservation status

The species ''C. dussumieri'' is classified as Endangered (E) on the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

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.1994 Categories & Criteria (version 2.3)
http://www.iucnredlist.org/ IUCN Red List]. Accessed 16 August 2007. Recent conservation efforts have seen an increase in the number of adult Round Island boas to around 1,000. This has been achieved by eradicating

goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...

s and

rabbit Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...

s from the island and restoring natural habitat, which has led to an increase of the Round Island boas’ natural prey, lizards. In recent breeding efforts, Round Island boas in

captivity Captivity, or being held captive, is a state wherein humans or other animals are confined to a particular space and prevented from leaving or moving freely. An example in humans is imprisonment. Prisoners of war are usually held in captivity by a ...

have been fed by scenting small

mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

with chicken thigh meat.

Reproduction

In ''C. dussumieri'', breeding begins during April, although young have been observed throughout the year. A

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

of up to 12 soft-shelled

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

may be laid amongst leaf litter or in hollow

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae **List of Arecaceae genera * Several other plants known as "palm" Palm or Palms may also refer to: Music * Palm (ba ...

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 most often refers to: *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Orange (colour), from the color of an orange, occurs between red and yellow in the visible spectrum * ...

at birth and weigh less than 5 grams.

References

External links

*
Round Island keel-scaled boa (''Casarea dussumieri'' )
a
ARKive
Accessed 18 February 2008. * {{Taxonbar, from=Q1066530 Bolyeriidae Taxa named by Hermann Schlegel Reptiles described in 1837 Reptiles of Mauritius Endemic fauna of Mauritius Taxonomy articles created by Polbot Monotypic reptile genera