Skinks are a highly successful and diverse group of lizards that belong to the family Scincidae, representing nearly a quarter of all lizard species worldwide, with over 1,700 described species. This expansive family is found across most of the globe, inhabiting nearly every environment except the polar and boreal regions. They are frequently encountered in many natural and even suburban settings, often remaining hidden due to their secretive, ground-dwelling nature. Skinks have evolved a distinct and streamlined body plan that sets them apart from other lizards, contributing to their widespread ecological success.
Defining Physical Traits
Skinks possess a distinctive morphology that enables their ground-level and often burrowing lifestyle. Their scales are generally smooth, thin, and highly polished, often giving the animal a glossy or oiled appearance that reduces friction as they move through soil or dense leaf litter. The skink’s sleek body surface is a defining feature, unlike many other lizards with rough or spiny scales.
The body shape is typically cylindrical and elongated, with a small, mobile head that often appears to blend seamlessly into the body because many species lack a pronounced neck. Beneath the smooth outer scales are layers of bony plates, called osteoderms, which are embedded within the skin. These osteoderms act as internal armor, providing a protective, durable layer that reduces injury, especially when burrowing or encountering predators.
A characteristic of the skink family is the repeated evolutionary reduction or complete loss of limbs, observed in nearly one-quarter of all skink species. Where limbs are present, they are often relatively small, short, and positioned close to the body, further contributing to their streamlined form. This limb reduction facilitates movement through dense vegetation, sand, or soil, making some skinks appear snake-like.
Global Distribution and Preferred Environments
The family Scincidae has achieved a cosmopolitan distribution, meaning species are found on every continent except Antarctica, reflecting a strong adaptability to varied climates. Their centers of diversity are primarily located in the Southern Hemisphere, including Australia, New Guinea, Southeast Asia, and parts of Africa and Oceania. This wide geographical range encompasses ecosystems as varied as arid deserts, tropical rainforests, grasslands, and temperate forests.
Skinks are predominantly terrestrial and fossorial, meaning they spend most of their lives on or under the ground. They show a preference for microhabitats that offer cover and moisture, such as the areas under rocks, logs, bark, and within deep layers of leaf litter. This ground-level shelter provides protection from predators and helps them regulate their body temperature, which is necessary for these cold-blooded reptiles.
Diet and Feeding Strategies
Most skinks are primarily insectivorous, relying on a diet composed mainly of small invertebrates. Their typical prey includes a variety of arthropods such as crickets, flies, grasshoppers, beetles, spiders, and even snails and slugs. They are active foragers, constantly moving through their ground-level habitats and using their forked tongues to sample the air for chemical cues to track down prey.
While many species focus on insects, larger skinks often exhibit omnivorous tendencies, incorporating other food sources into their diet. These bigger species may consume small vertebrates, such as other lizards, or integrate plant matter like fruits, berries, and leafy greens. The ability to consume a varied diet contributes to their success in diverse environments.
Unique Survival Behaviors
A defining behavioral trait of many skinks is their strong propensity for burrowing and fossorial movement. Species that live in sand or loose soil, such as the sand skink, can effectively “swim” through the substrate using serpentine movements, aided by their streamlined bodies and reduced limbs. Other species create complex tunnel systems in the ground, which serve as long-term retreats for protection from predators and extreme temperatures.
When threatened by a predator, skinks will often utilize a defensive mechanism known as caudal autotomy, or tail dropping. They voluntarily sever a portion of their tail at a pre-formed fracture plane in the vertebrae. The detached tail continues to writhe and twitch for a period, creating a distraction that allows the skink to escape while the predator focuses on the decoy.
As ectotherms, skinks must regulate their body temperature externally, and they frequently engage in basking behavior to absorb solar energy. They will move between sun-exposed spots and the cool cover of their burrows or leaf litter to maintain an optimal internal temperature range. This regulation of body heat is directly linked to their ability to forage, digest food, and maintain necessary movements for survival.