Lampropholis delicata

Species of lizard

Lampropholis delicata, the delicate skink, dark flecked garden sun skink, garden skink, delicate garden skink, rainbow skink or plague skink, or the metallic skink is native to Australia and invasive in New Zealand and Hawaii where it is commonly found in gardens. Lampropholis delicata were accidentally introduced into Lord Howe Island, a remote oceanic island between Australia and New Zealand, in the 1980s and subsequently introduced into the Hawaiian islands. Upon introduction, these lizards have rapidly spread themselves across the islands. On Lord Howe Island specifically, they reside in low elevation vegetation communities. They are a diurnal species whose activity varies seasonally, in which activity peaks during the months of November and December. Sexual dimorphism is present in L. delicata, in which males have broader, longer heads and females have larger abdomen and body sizes. Female reproduction takes place in the spring season and more commonly in the late summer, ranging between the months of September and February. A positive correlation exists between the clutch size and body size of the female, and although it is common for clutch sizes to vary between 1 and 7 eggs, the average clutch size is between 2 and 4. Communal egg nests are also common, with anywhere between 11 and over 200 eggs. Tail loss and subsequent regeneration occurs frequently with these lizards but is observed most commonly in females and adults.

Lampropholis delicata can be classified as diurnal, terrestrial, arthropod feeders, and they consume a wide range of prey. An in depth analysis of L. delicata gut samples—taken from their foregut, hindgut, and stomach—reveals the wide variety of prey taxa and size classes incorporated into their diets. These gut samples are taken from L. delicata that reside in the Mumbulla State Forest, a region with a vast history of fires and logging. As a result of intense fires, several canopies and ground vegetation have ceased to sustain the lizard population, resulting in a primarily carnivorous diet. L. delicata primarily consumes spiders, insects, snails, and crustaceans. Gut analysis after a major fire in 1980 reveals that these lizards ate limited amounts of invertebrates, and they had a preference for bees, wasps, and springtails over beetles, termites, and ants relative to their related species L. guichenoti, which also reside in the Mumbulla State Forest. L. delicata are characterized as general feeders, and their prey can be described as aerial and arboreal (i. e. bugs, beetles), slow moving (i. e. larvae), concentrated (i. e. termites, ants), concealed (i. e. crickets, cockroaches), and active (i. e. spiders). These lizards demonstrate foraging behavior and employ “active foraging” and “sit and wait” strategies to capture their prey. Because their environment is prone to fires and droughts, L. delicata have adapted flexibility into their foraging ecology. They practice opportunistic foraging in that they consume a wide variety of prey and adapt to whatever food becomes available, rather than following a foraging pattern and consuming similar prey. As a result of droughts, arthropods become less abundant; however, L. delicata are not dependent on resident invertebrates, like those that reside in litters, and instead forage after a broader range of insects spanning both aerial arboreal invertebrates and ground dwelling invertebrates.

With selecting a habitat, animals must consider the cost and benefit trade offs of acquiring shelter and food while evading competitors and predators. Because lizards are ectothermic, thermal conditions and subsequent impacts on physiological performance must also be taken into consideration for habitat selection. Thus deciding the degree of exposure or insulation, canopy or ground cover, structure of litter layer, or amount of grasses, forbs, rocks, and woody debris within the shelter remain prevalent considerations for lizard habitats. For small lizards like L. delicata, the structure of the leaf litter layer influences thermoregulation, feeding, and refuge seeking, making it an influential factor in microhabitat selection. Experimental evidence suggests that L. delicata prefer leaf litters to bare substrate, with more nuanced preferences for different types of leaves, as they adjust the structure, depth, and distribution of their litter layer accordingly. Generally, these lizards select more open structures. Such open structure makes thermoregulation more effective, as lizard individuals can move into different positions within their habitat to avoid overheating or raise their temperature to more optimal levels. Achieving optimum temperature levels influences their efficiency in avoiding predators and capturing prey, thus making open habitats conducive to many other behavioral characteristics. Furthermore, open litters allow for more effective foraging movements and also provide lizards with more access points and space to move, which is necessary when accessing refuge for predator avoidance. The abundance of L. delicata in an area may also be influenced by habitat modifications that vary the structure of their litter layers. In females, the autumn and winter months between February and July are defined by quiescent ovaries, and only during the late winter and spring months between August and October, follicles begin growing into notable sizes. In October or November, one or two follicles per ovary become vitellogenic and ovulated. After ovulation, the corpora lutea forms and maintains until oviposition occurs about a month later. Following ovulation, many other growing follicles become vitellogenic, although they may not ovulate and may regress after the mating period during the late summer. In females, many of these ovarian events parallel ovarian weights. Although growing oocytes are not commonly found in young adult females, young adult males of all ages undergo spermatogenesis. Observation of L. delicata suggests that they produce no more than one clutch per season; however, some evidence suggests that young female lizards may produce a clutch in the season following their birth, which aligns with male lizards’ ability to mate during both the spring and late summer. Though temperature and photoperiod are hypothesized to induce reproductive activity in lizards, more evidence suggests the influence of rain patterns on lizard reproduction cycles. With lower annual rainfall, annual vegetation productivity, and arthropod availability, food becomes relatively scarce for these lizards. As a result, it may influence the follicular development in female lizards, in particular the vitellogenesis cycle, although decreased rainfall may be insufficient to influence male testicular patterns. Female Lampropholis delicata lizards tend to reproduce in the spring and summer seasons (September–February). It was found that there is a positive relationship between body size and clutch size. Clutch size typically ranges between 1 and 7 (mean 3.4). Communal egg nests (11–200+ eggs) are common. Environmental factors greatly influence the change within the Lampropholis delicata species and continue to preserve each distinct variation. These polymorphisms have the potential to greatly affect survival in each niche, especially because the Lampropholis delicata is an invasive species, creating more need for adaptations.

The predation of small reptiles and amphibians by terrestrial arthropods is very common in Australia, more so than other continents. More specifically, small lizards and snakes commonly become entangled in webs of female red back spiders, or Latrodectus hasseltii. A typical account of predation involves a dead adult L. delicata entangled in the usually irregular web of a mature adult female L. hasseltii. If the lizards’ tails are not autotomised, an angular point in the curved tail may suggest a partial break around the mid tail level. Commonly, rigor mortis is present in these lizards.

Known in New Zealand as "rainbow skink", or more recently "plague skink", it was accidentally introduced in the early 1960s presumably as eggs in garden plant potting mix and is extremely common in the top third of the North Island, found in several other parts of the North Island, and also in the top of the South Island around Blenheim. Considered an invasive species as it competes with native lizards for food and habitat. It is reportedly now the most numerous skink on the main Hawaiian Islands. It was accidentally introduced to Lord Howe Island in the 80s, where it quickly colonised the whole island.

Lampropholis delicata was accidentally imported to the Hawaiian islands from Australia around the 1900s via shipments of plant materials and lumber. It was noted as an unreported specimen taken on the Oahu island and identified as a Lipinia noctua at that time, then later reclassified as Lygosomoa metallicum (the metallic skink) because of its physical appearance. L. Metallicum does not occur in Hawaii, however, and is instead a misidentification of L. delicata. L. delicata are most common on the Oahu island but are also present on other islands in Hawaii, including the main island and Kauai. These lizards bear great importance in Hawaiian zoogeography because they have established high altitude records amidst all the Hawaiian reptiles at 1220 meters on the Kauai island and 1130 meters on the main island. In fact, these lizards prefer and thrive at much higher and wetter altitudes in Hawaii and other species of lizards. Because these lizards are semi mountainous and found in dry to wet sclerophyll forests, they are distributed throughout the dry lowland and wet upland. The three populations of L. delicata found on the main island, Oahu, and Kauai differ with respect to their average body length and in the numbers of eggs they produce. Female lizards at a sexually mature age are larger on the big island and Kauai relative to those on Oahu. The Oahu females average about 38.6 millimeters in body length while those from the main island and Kauai average a length of 41.2 millimeters and 41.8 millimeters respectively. It is theorized that Oahu females grow to a relatively smaller body size because of their higher population densities, thus creating competition amongst individuals for food and space availability. Competition against other species might also be a possibility, and the inter and intraspecific competition experienced by Oahu females may also serve to explain the reduced egg production, as generally body size correlates to clutch size (smaller individuals with less internal body capacity lay fewer eggs than larger individuals). As such, Oahu females have a lower average number of eggs per clutch relative to the sexually mature female lizards on the main island and Kauai. Female lizards from Oahu have an average of 2.9 eggs, while the main island females average 4.7 eggs per clutch and Kauai females average 4.1 eggs per clutch.