|Eastern blue-tongued lizard|
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae (the "true" or wall lizards), they comprise the superfamily or infraorder Scincomorpha. With more than 1500 described species, the Scincidae are the most diverse family of lizards.
Skinks look roughly like true lizards, but most species have no pronounced neck and their legs are relatively small; several genera (e.g., Typhlosaurus) have no limbs at all. Some other genera, such as Neoseps, have reduced limbs, lacking fore legs, and with fewer than five toes (digits) on each foot. In such species, their locomotion resembles that of snakes more than that of lizards with well-developed limbs. As a general rule, the longer the digits, the more arboreal the species is likely to be. A biological ratio can determine the ecological niche of a given skink species. The Scincidae ecological niche index is a ratio based on anterior foot length at the junction of the ulna/radius-carpal bones to the longest digit divided by the snout-to-vent length.
Most species of skinks have long, tapering tails they can shed if predators grab them. Such species generally can regenerate the lost part of a tail, though imperfectly. Species with stumpy tails have no special regenerative abilities.
Some species of skinks are quite small; Scincella lateralis typically ranges from 7.5 to 14.5 cm (3.0 to 5.7 in), more than half of which is tail. Most skinks, though, are medium-sized, with snout-to-vent lengths of about 12 cm (4.7 in), although some grow larger; the Solomon Islands skink, (Corucia zebrata), is the largest known extant species and may attain a snout-to-vent length of some 35 cm (14 in).
Skinks are generally carnivorous and in particular insectivorous. Typical prey includes flies, crickets, grasshoppers, beetles, and caterpillars. Various species also eat earthworms, millipedes, snails, slugs, isopods, other lizards, and small rodents. Some species, particularly those favored as home pets, have more varied diets and can be maintained on a regimen of roughly 60% vegetables/leaves/fruit and 40% meat (insects and rodents).
A trait that is apparent in nearly all species of Skink is a love of digging and burrowing. Most spend their time underground where they are mostly safe from predators, sometimes even digging out tunnels for easy navigation. They also use their tongues to sniff the air and track their prey. When they encounter their prey they chase it down until they corner or manage to land a bite and then swallow it whole.
As a family, skinks are cosmopolitan; species occur in a variety of habitats worldwide, apart from boreal and polar regions. Various species occur in ecosystems ranging from deserts and mountains to grasslands. Some species are endangered, such as the androgynous skink in New Zealand, with less than 100 reports since first being identified at Molesworth Station, South Island, by Keith Frankum.
Many species are good burrowers. More species are terrestrial or fossorial (burrowing) than arboreal (tree-climbing) or aquatic species. Some are "sand swimmers", especially the desert species, such as the mole skink in Florida. Some use a very similar action in moving through grass tussocks. Most skinks are diurnal (day-active) and typically bask on rocks or logs during the day.
About 45% of skink species are viviparous. Many are ovoviviparous (hatching eggs internally and giving birth to live offspring). Some, such as the genera Tiliqua and Corucia, give birth to live young that develop internally, deriving their nourishment from a mammal-like placenta attached to the female – viviparous matrotrophy. However, a recently described example occurring in Trachylepis ivensi is the most extreme to date, of a purely reptilian placenta directly comparable in structure and function, to a eutherian placenta. In skinks, though, placental development of whatever degree is of course phylogenetically analogous, rather than homologous to functionally similar processes in mammals.
Skinks typically seek out sheltered environments out of the elements such as thick foliage, underneath man-made structures, and ground-level buildings such as garages and first-floor apartments. When two or more skinks are seen in a small area, it is typical to find a nest nearby. Skinks are considered to be territorial and often are seen standing in front of or "guarding" their nest area. If a nest is nearby, one can expect to see 10-30 lizards within a month period. In parts of the Southern United States, it is quite common to find nests within houses and apartments, especially along the coast.
Raccoons, foxes, possums, snakes, coatis, crows, cats, dogs, herons, hawks, lizards, and other predators of small land vertebrates also prey on various skinks. This can be troublesome given the long gestation period for some skinks making them an easy target to predators like the mongoose which often threaten the species to at least near extinction, such as the Anguilla Bank Skink Lizard.
Many large genera, Mabuya for example, are still insufficiently studied, and their systematics is at times controversial, see for example the taxonomy of the western skink, Eumeces skiltonianus. Mabuya in particular is being split, many species being allocated to new genera such as Trachylepis, Chioninia, and Eutropis.
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- Mecke, Doughty & Donnellan (2013). "Redescription of Eremiascincus fasciolatus (Günther, 1867) (Reptilia: Squamata: Scincidae) with clarification of its synonyms and the description of a new species". Zootaxa 3701 (5): 473–517.
- Schnirel, Brian (2004) SENI biometric analysis on the extinct Scincidae species: Macroscincus coctei. Polyphemos, Volume 1, Issue 2, May, Florence, South Carolina, U.S.A. pp. 12-22.
- McLeod, Lianne. "Keeping Blue Tongued Skinks as Pets". Retrieved 2006-08-27.
- Blackburn, D. G. and Flemming, A. F. (2011), Invasive implantation and intimate placental associations in a placentotrophic african lizard, Trachylepis ivensi (scincidae) Journal of Morphology. doi:10.1002/jmor.11011
- De Vosjoli, Philippe (1993) Prehensile-Tailed Skinks. Advanced Vivarium Systems. ISBN 1-882770-24-2
- Hedges, S. Blair and Caitlin E. Conn. 2012. A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae). Zootaxa 3288.