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The Solomon Islands skink (''Corucia zebrata''), also known as prehensile-tailed skink, monkey-tailed skink, giant skink, zebra skink, and monkey skink, is an
arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...
species of skink endemic to the
Solomon Islands archipelago The Solomon Islands (archipelago) is an island group in the western South Pacific Ocean, north-east of Australia. The archipelago is in the Melanesian subregion and bioregion of Oceania and forms the eastern boundary of the Solomon Sea ...
. It is the largest known extant species of skink. The Solomon Islands skink is completely herbivorous, eating many different fruits and vegetables including the pothos plant. It is one of the few species of reptile known to function within a social group or circulus. Both male and female specimens are known to be territorial and often hostile towards members not a part of their family group. ''Corucia'' is a monotypic genus, containing a single species. However, in 1997 it was determined that there are two subspecies of the Solomon Islands skink: the common monkey-tailed skink (''Corucia zebrata zebrata'') and the northern monkey-tailed skink (''Corucia zebrata alfredschmidti)''. Among other variances, the northern skink is smaller and has darker eyes with a black sclera. Extensive logging is a serious threat to the survival of this species. Consumption for food by indigenous Solomon Islanders and excessive pet trade exports have affected wild populations. Export of this species from the Solomon Islands is now restricted and the animal is protected under
CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
appendix II.


Taxonomy and etymology

The Solomon Islands skink was first described by John Edward Gray in 1855 as ''Corucia zebrata''. The
generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...
name ''Corucia'' derives from the Latin word ''coruscus'' meaning "shimmering". This is in reference to Gray's description of "a play of colors effect from the body scales". Its specific name ''zebrata'' is a Latinized form of the word
zebra Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. z ...
, in reference to the animal's zebra-like stripes. Some of its common names (prehensile-tailed skink, monkey-tailed skink, monkey skink) refer to its fully
prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely derived from a number of different orig ...
tail which the species uses as a fifth limb for climbing. Although appearances of Solomon Island skinks vary from island to island, only one subspecies, from the western islands of the Solomons Archipelago, was described by Dr. Gunther Köhler in 1996 as ''C. z. alfredschmidti'', the trinomial name of which is in honor of German amateur herpetologist Alfred A. Schmidt. (in German). The closest living relatives of ''C. zebrata'' are the blue-tongued skinks of the genus '' Tiliqua'' and skinks of the genus ''
Egernia ''Egernia'' is a genus of skinks (family Scincidae) that occurs in Australia. These skinks are ecologically diverse omnivores that inhabit a wide range of habitats. However, in the loose delimitation (which incorporates about 30 species) the ge ...
'' of Australia, New Guinea, and Indonesia, all of which are also assigned to the subfamily ''
Lygosominae Lygosominae is the largest subfamily of skinks in the family Scincidae. The subfamily can be divided into a number of genus groups. If the rarely used taxonomic rank of infrafamily is employed, the genus groups would be designated as such, but s ...
''.


Distribution and habitat

The Solomon Islands skink is native to Papua New Guinea, and the
Solomon Islands archipelago The Solomon Islands (archipelago) is an island group in the western South Pacific Ocean, north-east of Australia. The archipelago is in the Melanesian subregion and bioregion of Oceania and forms the eastern boundary of the Solomon Sea ...
, a group of islands in the south-west Pacific Ocean. The common subspecies (''C. z. zebrata'') is found on the islands of
Choiseul Island Choiseul Island, native name Lauru, is the largest island () of the Choiseul Province, Solomon Islands, at . The administrative headquarters of Choiseul Province is situated in the town of Taro, on Taro Island. History In 1768, the French explo ...
,
New Georgia New Georgia, with an area of , is the largest of the islands in Western Province, Solomon Islands, and the 200th-largest island in the world. Geography New Georgia island is located in the New Georgia Group, an archipelago including most o ...
,
Isabel Isabel is a female name of Spanish origin. Isabelle is a name that is similar, but it is of French origin. It originates as the medieval Spanish form of '' Elisabeth'' (ultimately Hebrew ''Elisheva''), Arising in the 12th century, it became popul ...
,
Guadalcanal Guadalcanal (; indigenous name: ''Isatabu'') is the principal island in Guadalcanal Province of Solomon Islands, located in the south-western Pacific, northeast of Australia. It is the largest island in the Solomon Islands by area, and the s ...
, Ngela, Malaita, Makira (Solomon Islands), Ugi and Santa Ana. The northern subspecies (''C. z. alfredschmidti)'' is known from the islands of Bougainville and Buka and the Shortland Island Group. Bougainville and Buka are geographically part of the Solomons Archipelago, though politically part of Papua New Guinea. Both subspecies of the Solomon Islands skink are strictly arboreal, usually inhabiting the upper
canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...
of forested areas throughout its range. It commonly occurs in the strangler fig tree (''Ficus sp.''), provided the epiphytic growth of its several food plants are present. It occurs in trees in semi-cleared areas and cultivated food gardens, again provided its food plants occur there.


Biology

The Solomon Islands skink is the world's largest species of
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extin ...
skink; adults can reach a total length (including tail) of when fully grown, with the tail accounting for more than half this length. The Solomon Islands skink has a long, slender body, strong, short legs, and a triangular shaped head with small round eyes. The skink has a strong crushing jaw but the teeth are small and used for eating plant material. Its prehensile tail helps it maneuver from branch to branch with ease and gives the skink its more common names: monkey-tailed skink, prehensile-tailed skink, or monkey skink. Male Solomon Islands skinks tend to have a broader head and a more slender body shape than do female skinks. Males have a V-shaped pattern of scales just aft of the
cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, an ...
l opening, which is not present in female skinks. The scales of Solomon Islands skinks are a dark green but are often speckled with light brown or black. The scales on the underside vary from light yellow to different shades of green. The toes on all four legs have thick, curved nails used for climbing and gripping tree limbs. As a
crepuscular In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylig ...
animal, it is most active during the dusk and dawn hours, feeding primarily at dusk. it also is active and eats during the hours of dawn, though to a lesser extent. It has quite good eyesight and relies upon it to identify threats, as well as potential food. It relies heavily on its sense of smell and uses it to identify its territory and other members of its group, called a circulus. Like snakes, the skink "smells" by flicking its tongue to gather scents and when the tongue is retracted, it touches it to the opening of a
Jacobson's organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapods. T ...
at the roof of its mouth.


Subspecies

The common Solomon Islands skink (''C. z. zebrata'') has a white sclera with its eyes while the northern Solomon Islands skink (''C. z. alfredschmidti)'' has a black sclera. The iris of the northern Solomon Islands skink is a mix of green and yellow whereas the iris of the common Solomon Islands skink can vary from several different shades of green to orange to a dark black. According to Dr. Gunther Köhler, who described the northern subspecies, this subspecies possesses "larger dorsal and ventral scales" and has "seven instead of usually five parietal scales". The northern Solomon Islands skink is the shorter of the two subspecies with males averaging and females averaging in total length. The common Solomon Islands skinks are slightly longer with the males averaging and the females averaging in total length. The common Solomon Islands skink, at , weighs more than the northern Solomon Islands skink, which weighs closer to .


Diet

Solomon Islands skinks are
herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...
s, feeding on the leaves, flowers, fruit, and growing shoots of several different species of plants. This includes the somewhat toxic (due to high concentrations of
calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydrate ...
) '' Epipremnum pinnatum (cf. E. aureum)'' plant, which the lizard eats without ill-effect. Juvenile skinks often eat feces from adults in order to acquire the essential
microflora Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found to ...
to digest their food. Newborn skinks have been observed consuming their placental sac after birth and will not feed on other food for the first two days.


Reproduction

The Solomon Islands skink is one of the few species of reptile that lives in a communal group known as a circulus. The Solomon Islands skink reproduces by viviparous
matrotrophy Matrotrophy is a form of maternal care during organism development, associated with live birth (viviparity), in which the embryo of an animal or flowering plant is supplied with additional nutrition from the mother (e.g. through a placenta). This ...
: the female provides a placenta for its young, which are born after a gestation period of six to eight months; this is a rare trait among reptiles. The newborn skink is of a large size compared to its mother; the northern Solomon Islands skinks are approximately in length and weigh , whereas the common Solomon Islands skinks are and when they are born. This reduced size disparity led the former curator of reptiles at the
Philadelphia Zoo The Philadelphia Zoo, located in the Centennial District of Philadelphia on the west bank of the Schuylkill River, is the first true zoo in the United States. It was chartered by the Commonwealth of Pennsylvania on March 21, 1859, but its openin ...
, Dr. Kevin Wright, to compare it to "a human mother giving birth to a six year–old". Almost all births are single babies, but occasionally twins will be born. At least one instance of
triplets A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such ...
has occurred according to
herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and rept ...
Bert Langerwerf. The newborn skink will stay within its circulus for six to twelve months during which time it will be protected by not only its parents but other unrelated adult skinks within the group. Around one year of age, sometimes earlier, the juvenile will move off to form a new family group. Individuals have been documented to stay within the group for several births without being expelled, however. Females exhibit fierce protective behavior around the time of birth; this protectiveness of young is a rare occurrence in reptiles but is shorter in duration when compared to the protective behavior exhibited by a typical mammal.


Conservation


Threats

Extensive logging is a serious ongoing threat to the survival of this species, as is consumption for food by native people, and export demand for the pet trade. Because of the large numbers of lizards that were being exported for the pet trade, the small region to which the skink is native, and its low reproductive rate, in 1992 ''Corucia zebrata'' was listed as a
CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
Appendix II animal, which allows limits to be placed on the number of animals in commercial trade between countries. Since there is no regulation on the rapid deforestation occurring in the Solomon Islands, limited export to recognized institutions may be needed to aid this species in genetic diversity for its survival via '' ex situ'' breeding programs. According to herpetologists who study the Solomon Islands skink, such as Dr. David Kirkpatrick and the late Dr. Kevin Wright, captive breeding alone is not practical as a sole method of species survival due to the limited number of offspring and long gestation periods.


In captivity

The Solomon Islands skink is represented in both public and private collections. The
Philadelphia Zoo The Philadelphia Zoo, located in the Centennial District of Philadelphia on the west bank of the Schuylkill River, is the first true zoo in the United States. It was chartered by the Commonwealth of Pennsylvania on March 21, 1859, but its openin ...
has bred this species of skink over multiple generations for the past 40 years. The keeping of the Solomon Islands skink in captivity is not without its challenges: as it is a large arboreal tropical animal. It requires a large arboreal enclosure, with a constant temperature between 75–80 degrees Fahrenheit (24–27 degrees Celsius), with heat being provided from above as well as below, allowing the skink to bask in the heat from above as it would during dusk, while providing a radiant heat from below to aid digestion. The dynamics of the skink's circulus means that not all groups do well when new animals are introduced. Despite successful breeding programs, its somewhat unusual nature of single births and slow growth has made these programs challenging. Biologist Michael Balsai of
Temple University Temple University (Temple or TU) is a public state-related research university in Philadelphia, Pennsylvania. It was founded in 1884 by the Baptist minister Russell Conwell and his congregation Grace Baptist Church of Philadelphia then called ...
has noted a significant number of breedings between skinks from different islands has resulted in non-productive unions. Balsai's theory is that there are enough differences between animals from different islands that pairing of lizards from different locales will be unproductive, further frustrating many captive breeding attempts.


Footnotes


References


Further reading

* Boulenger GA (1887). ''Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume III. ... Scincidæ ...'' London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xii + 575 pp. + Plates I-XL. (''Corucia zebrata'', p. 142). * Goin CJ, Goin OB, Zug GR (1978). ''Introduction to Herpetology, Third Edition''. San Francisco: W.H. Freeman and Company. xi + 378 pp. . (''Corucia zebrata'', p. 301). * * Parker F (1983). "The prehensile-tailed skink (''Corucia zebrata'') on Bougainville Island, Papua New Guinea". pp. 435–440. ''In'': Rhodin AGJ, Miyata K (editors) (1983). ''Advances in Herpetology and Evolutionary Biology: Essays in Honor of Ernest E. Williams''. Cambridge, Massachusetts: Harvard University Press. xix + 725 pp. . *


External links

*
Honolulu Zoo Species ProfileSanta Barbara Zoo Species ProfileISIS Abstract
{{Taxonbar, from=Q591268 Skinks Coprophagous animals Reptiles described in 1855 Taxa named by John Edward Gray Reptiles of the Solomon Islands Endemic fauna of the Solomon Islands