Rhacodactylus ciliatus

Geographic Range

Crested geckos are endemic to the islands of Grand Terre (Provence Sud), and the Isle of Pines, New Caledonia. There are unconfirmed reports of these geckos from Kôtomo Island, New Caledonia.

• Biogeographic Regions
• australian australian
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

There are three distinct and disjunct populations of crested geckos: one on the Isle of Pines, and two on Grand Terre. The southeastern rainforests of Grand Terre, the main island of New Caledonia where crested geckos are primarily found, are divided by the highest peak on the island, Mont Paniė (1628 meters above sea level). This greatly influences climate and soil type in the region. High and low temperatures can range from 11.1-27.8°C, though temperatures typically range from 22.2-23.9°C. This area is tropical rainforest with precipitation levels potentially as high as 400 cm per year. They are most typically found at elevations from 150-1000 meters above sea level. Crested geckos spend daytime hours resting in thick vegetation near the forest floor, where it is cooler and less sunny. At night they spend much of their time foraging in shrubs and lower portions of the canopy, rarely traveling much higher than 3 m from the forest floor.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

Physical Description

Crested geckos have a relatively large, triangular head, with two large eyes and two relatively large ear openings on either side of the head. Very fine light tan, peach, or reddish brown-colored granular scales cover their long bodies. They have moderately thick, prehensile tails. The back typically has a pattern of lateral, darker stripes. Thin, continuous, calcareous crest, project along either side of the back and also above the eyes and portions of the limbs. Above the eyes, these crests seem to serve primarily to keep dust and other particles out, but it is unknown what purpose is served by the dorsal and limb crests; they may be used in discriminating between potential mates. There are three color morphs that appear in wild crested geckos: patternless, tiger, and white-fringed. Patternless crested geckos are more or less solid in color, ranging from yellow, green, brown, red, to gray, and have very faint or no pattern present on the back. Tiger crested geckos have a light colored background with deep, dark, contrasting stripes and a patterned belly. White-fringed crested geckos are characterized by white or yellow coloration on all or a portion of the calcareous crest. In addition to these three patterns, there are many other variations that are distinct in captive bred individuals but are not found in the wild.

Crested geckos have four limbs, each ending in four fingers; at the bottom of each finger is a network of hairs (setae) which allow them to walk on very smooth vertical surfaces. These pads are especially important in tree climbing. Crested geckos also have a prehensile tail with setae at the tip, adding extra support when hanging from tree branches or trying to regain balance; unlike many species, these geckos can not re-grow their tails if lost. Adult crested geckos typically average 20.3 centimeters in total length and 10.2-11.9 centimeteres snout-to-vent length (SVL). These geckos lack eyelids, though they do have a clear protective covering over each eye. They must lick their eyes with their tongues periodically in order to keep them clean and moist. Crested geckos have a small opening, covered in a tympanic membrane, on each side of side of the head, which acts as an ear.

• Sexual Dimorphism
• sexes alike

Development

Information regarding development in this species has not been gathered in the wild, but has been extensively recorded in captivity. It has been found that temperature is a determining factor on rate of development, offspring size, and sex. In particular, sex is not determined genetically but after egg laying, by environmental temperature. Evidence suggests that warmer incubation temperatures lead to higher proportions of males and colder incubation temperatures lead to higher proportions of females. It has also been observed that crested gecko eggs kept at higher temperatures during incubation develop faster than eggs kept at lower temperatures.

After hatching, young crested geckos will not eat for 3-5 days (until they shed their skins for the first time), using stored yolk remains for sustenance. After this period of time, hatchlings will begin searching for food such as nectar, fruits, and small insects.

• Development - Life Cycle
• temperature sex determination
• indeterminate growth indeterminate growth

Reproduction

Mating behaviors have yet to be observed in the wild. Captive males have been known to fight violently if forced into contact with each other, especially during breeding season, and so multiple breeding females are kept with one male. A male will approach a female with jerky movements and, if she is willing, she will remain still while he climbs on her back and bites her neck as copulation begins.

• Mating System
• polygynous polygynous

Males become sexually mature between 9-12 months of age and females typically become mature at 12 months at a weight of 30-35 gm. At 3-4 months old, an external hemipenal bulge becomes visible in males, located at the base of the tail near the vent. In contrast, females are flat at the base of their tails, with much smaller bulges. Females are capable of laying 2 eggs every 4-6 weeks and do so 30-40 days after copulation; they retain sperm and may lay up to 4 eggs before copulating again. Breeding and egg laying takes place 8-10 months of the year, with a shift to lower temperatures halting egg production. If this resting period does not occur, females may lay eggs year round and are at risk of suffering severe calcium deficiencies. Eggs can be as large as 11x24 mm and 1.2-2.8 gm, and hatch 60-150 days after being laid. Young are independent at hatching.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• sexual sexual
• fertilization fertilization
• oviparous oviparous
• sperm-storing sperm-storing

Males exhibit no parental investment beyond fertilization. Females allocate nutrients to their eggs (moreso because of their small clutches) and lay their eggs in a hole a few inches deep, safe from predators, and within an appropriate proper temperature range and soil moisture, allowing for gas exchange through the egg membrane. After laying her eggs, the female does not provide any additional parental care to her developing offspring.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • provisioning

Lifespan/Longevity

Crested geckos are thought to be able to live for over 20 years in captivity, though there is some uncertainty; they have only recently been reintroduced to science and the pet trade (1994) after having been assumed extinct. No information regarding lifespan in the wild is currently available.

Behavior

Crested geckos are typically solitary, nocturnal animals. which tend to hide in thick vegetation during the day and emerge into the lower canopy at night (usually no higher than 3 m) to search for food. They are also semi-arboreal, very agile, and stealthy. They can jump short distances, from branch to branch, and they are able to hold on to tree branches easily using the adhesive pads on their feet and their adhesive, prehensile tails.

• Key Behaviors
• arboreal arboreal
• scansorial
• terricolous
• nocturnal nocturnal
• daily torpor
• solitary solitary

Home Range

There is no data currently available regarding a particular home range or territory for these geckos. In captivity, it is not recommended to keep more than one male in an enclosure as they may be aggressive to each other, suggesting that males could be territorial in the wild.

Communication and Perception

Crested geckos use a high pitched chirping sound that is primarily used to call for a mate and as a defense mechanism to frighten a predator in an attempt to escape. They also use visual cues; if startled, crested geckos have been known to rise up on their hind legs and open their mouths wide in a threatening posture, and mating involves jerky body motions from the male.

Crested geckos have specialized eyes for seeing in the dark. Like other gekkonid species, crested geckos have what has been referred to as Gehyra pupils; instead of having vertical, slit-shaped pupils with smooth edges, geckos have vertical, slit-shaped pupils with slightly lobed edges. They have color vision, as their retinas contain only cones. Nocturnal geckos such as these have larger apertures and cones, in addition to a shorter viewing length, than diurnal reptiles. This allows them to absorb as much light and see as much as possible in the dark.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Crested geckos are omnivores, feeding primarily on insects, nectar, and fruits, hunting and feeding at night. Calcium and Vitamin D3 are vital for the proper growth and development of crested geckos, especially for young individuals. Deficiencies can result in metabolic bone diseases, which can be fatal, so they have endolymphatic sacs on the roofs of their mouths for calcium storage.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
• herbivore herbivore
  • frugivore frugivore
  • nectarivore nectarivore
  • eats sap or other plant foods
• omnivore omnivore

• Animal Foods
• insects

• Plant Foods
• fruit
• nectar
• sap or other plant fluids

Predation

One of the main predators of crested geckos are little fire ants, which have been introduced to New Caldonia and will swarm and bite the geckos. Other predators include dogs, cats, rats, snakes, and other geckos, many of which are introduced species as well. Crested geckos exhibit caudal autotomy and can drop their tails if in danger from a predator. Vasoconstrictor mechanisms prevent the tail from bleeding and small fractures in the tail bone allow the tail to break off at predetermined segments. After being dropped, the tail will continue to move for 3-5 minutes, distracting the predator as the gecko escapes. These geckos can not re-grow their tails, which can cause them to become less agile.

Ecosystem Roles

Very little is known of the role that crested geckos have in their ecosystem. One reason for this is that, for more than a century, crested geckos were believed to be extinct. In 1994 they were rediscovered and most of the studies and observations carried out following their rediscovery were on captive bred individuals. Crested geckos are likely important in the distribution of pollen for various nectar and fruiting plants. These geckos have been found to host parasitic amoebas and protozoans.

• Ecosystem Impact
• pollinates

Economic Importance for Humans: Positive

Crested geckos are a favorite in the pet trade because they are very docile and are easy to maintain. The wide availability of crested geckos may help to draw attention to the 41 regionally endemic species of reptiles present on New Caledonia and the importance of protecting them. An interest in preserving these habitats could then play some role in increasing wildlife research and conservation efforts on these islands.

• Positive Impacts
• pet trade pet trade
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of crested geckos on humans.

Conservation Status

Little is known about crested geckos in their natural environments, and even less in known about the impact of human activities on their populations. Slash and burn agriculture, deforestation, and mining (nickel, cobalt and chromium), as well as the introduction of non-native species are all believed to be threats to crested geckos and they are classified by The IUCN Red List as "Vulnerable", with a downward population trend. The primary indigenous conservation organization on New Caledonia, the Association pour la Savvegarde de la Nature NėoCalėdonienne (ASNNC) is currently working with the government to protect more land and habitat and raise awareness about the reptilian fauna of the islands. The other organization working to protect this environment is the Center of Initiation of the New Caledonia Environment. The hope is that laws will eventually be passed to protect the terrestrial reptilian fauna there.

Other Comments

In 1866, Crested geckos were described by Alphone Guichenot. After this, the species was not observed again for over a century. In 1994 this species was rediscovered by Robert Seipp and Phillippe de Vosjoli. Upon being rediscovered, live specimens were collected for research and the pet trade. Today, crested geckos are becoming increasingly common in captivity.

New Caledonia’s large diversity of climate, soils, and geography (especially topographical diversity) has resulted in a large array of biological variation. The genus Rhacodactylus contains five endemic New Caledonian species of gecko in addition to this one ( R. auriculatus , R. chahoua , R. leachianus , R. sarasinorum , and R. trachyrhynchus ). In addition to these closely related species, three species of Rhacodactylus exist outside of the island and are endemic to northern Australia.

Additional Links

Encyclopedia of Life

Contributors

Kristin Brusso (author), Michigan Technological University, Amy Schrank (editor), Michigan Technological University, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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