Introduction to the New Caledonian Giant Geckos

New Caledonia is a biodiversity hotspot located in the Southwest Pacific Ocean and is composed by three land formations: Grande Terre (mainland), Pine Islands, and the Loyalty Islands. New Caledonia broke off from present-day Australia 60-85 million years ago, and then was submerged for 20 million years before resurfacing 37 million years ago. Thus, all terrestrial life colonized New Caledonia via overwater dispersal, including geckos which arrived from Australia 30 million years ago. The mainland Grande Terre is mountainous and roughly one third is covered in metallic or “ultramafic” substrate, the climate is semitropical and there are a variety of unique habitats.

Species: Rhacodactylus auriculatus (Gargoyle Gecko or Knob-headed Giant Gecko) [Discovered in 1869]

Conservation Status: Species of Least Concern per 2009 IUCN Red List Assessment.

Description: Colorful species of gecko reaching snout-to-vent (SVL) lengths of 110 to 130 mm. Many different color types and patterns exist, ranging from black and white to bright red or even pink.

Distribution: Found in the humid forests, montane forests, and maquis throughout Grande Terre at elevations up to 1,100 meters.

Behavior: Solitary species with the most diverse diet of any gecko. They are known to consume fruit, nectar, flower parts, snails, insects, spiders, skinks, and other geckos (they are highly cannibalistic). They are considered semi-arboreal because they tend to spend the most time on shrubs and small trees. Compared to the other New Caledonia giant geckos this species is the most adapted for running on the ground, they are fast sprinters and good jumpers. They are oviparous (egg-laying), their eggs are laid in tree cracks or buried underground.

Species: Rhacodactylus leachianus (New Caledonia Giant Gecko or Leachie Gecko) [Discovered in 1829]

Conservation Status: Species of Least Concern per IUCN Red List Assessment.

Description: This is the largest gecko in the world reaching snout-to-vent lengths of up to 300 mm, but the insular localities can be as small as 150 mm SVL. The northern populations have well developed and long tails that are semi-prehensile, in contrast, much of the southern insular population have poorly developed and short tails that do not offer much advantage. Morphology is regionally-variable, some populations are black or melanistic, while others are lime-green with pink and purple blotching.

Distribution: Found in low to mid-level canopy of humid forests, coastal forests, and rainforests up to 1100 meters with a wide distribution throughout Grande Terre and the Pine Islands.

Behavior: Known to consume fruit, other lizards, insects, and birds. Leachies are social species that will form life-long pair bonds and lay their eggs inside of tree hollows which they will fiercely defend. The Pine Island and islet localities are known to sometimes engage in communal egg laying at dune sites. They are very noisy, and their sounds can be as loud as a jet at take-off.

Species: Rhacodactylus trachycephalus (lesser rough-snouted gecko) [Discovered in 1878]

Conservation Status: Critically Endangered species per IUCN Red List Assessment.

Description: Previously considered a subspecies of Rhacodactylus trachyrhynchus but is now designated as its own species (Aaron Bauer 2012). They have large eyes and reach lengths of 140 mm from snout-to-vent.

Distribution: Highly restricted range, only found on Ilot Moro and the western half of Pine Island.

Behavior: Ovoviviparous gecko species that gives live birth to two offspring annually.

Species: Rhacodactylus trachyrhynchus (greater rough-snouted gecko) [Discovered in 1873]

Conservation Status: Endangered species per 2009 IUCN Red List Assessment.

Description: This is the second largest of the New Caledonian geckos, reaching lengths of up to 190 mm snout-to-vent, they are further distinguished by their long tail.

Distribution: Found at elevations between 5 to 500 meters in the low to mid elevation canopy of sclerophyll forests, humid forests, and maquis of Grande Terre.

Behavior: Highly social species that is known to congregate in groups. They are ovoviviparous and give birth to twins once per year after a six-month gestation period.

Species: Mniarogekko chahoua (mossy prehensile-tail gecko) [Discovered in 1882]

Conservation Status: Vulnerable species per 2010 IUCN Red List Assessment.

Description: Covered in brown, red, white, and green colors with mossy patterns, reaching lengths of 115 to 145 mm snout-to-vent length. Their tail is completely prehensile, which means that it acts as a sort of fifth limb. They are great climbers and can be seen at heights of 80+ feet in the trees.

Distribution: Distributed throughout Grande Terre and Pine Island in the forests of low-elevation valleys on non-ultramafic substrate.

Behavior: Known locally as “tree devils” because they are usually found “barking” from within tree hollows. They will curl their tail into a ball when they feel threatened. Mniarogekko species have the lowest reproductive output of the egg-laying giant geckos because their eggs are so highly mineralized and require a lot of energy to produce. One special feature of their eggs is that they can be glued to surfaces above or near the ground.

Species: Mniarogekko jalu [Discovered in 2012]

Conservation Status: Endangered species per IUCN Red List Assessment.

Description: Visually they are very similar to M. chahoua, reaching lengths of 100 to 140 mm snout-to-vent, with colors ranging from yellow green to gray, brown to brick red with mottled mossy patterns. Their tails are completely prehensile and help them climb with great agility.

Distribution: Found in the forests on ultramafic substrate of northern Grand Terre and the Belep Group Islands.

Behavior: They will curl their tail into a ball when they feel threatened. Mniarogekko species have the lowest reproductive output of the egg-laying giant geckos because their eggs are so highly mineralized and require a lot of energy to produce. One special feature of their eggs is that they can be glued to surfaces above or near the ground.

Species: Correlophus belepensis [Discovered in 2012]

Conservation Status: Critically Endangered species per IUCN Red List Assessment.

Description: The smallest of the “giant geckos” with a snout-to-vent length of 90 to 100 mm. They have a mostly uniform dark brown color.

Distribution: Only found on Belep Island (which is north of Grande Terre) in closed forests with ultramafic substrate.

Behavior: Not much is known about the behavior of this newly discovered species, but they are very active and will occupy all layers of the canopy from the lowest part of the sub-canopy to the upper canopy.

Species: Correlophus ciliatus (crested gecko or eyelash gecko) [Discovered in 1866]

Conservation Status: Vulnerable species per 2010 IUCN Red List Assessment. Previously believed to be extinct from 1870s to 1993, rediscovered in the 1990s on the Pine Island and then later in scatter populations throughout Grande Terre.

Description: Second smallest of the “giant geckos” reaching snout-to-vent lengths from 95 to 115 mm. They are named for the projections of skin above their eyes and on their heads, some geckos have this pattern extend along their dorsal area.

Distribution: Scattered on Grande Terre (mostly in the southern province) and Pine Island. They are found in coastal forests, closed humid forests, and montane forests at elevations between 150 and 1000 meters.

Behavior: They feed mostly on fruit, nectar, flower parts, and insects. These geckos are excellent jumpers and travel throughout the canopy with ease, they have been spotted at heights between 10 and 100+ feet in the canopy. Another distinguishing feature is that they cannot regrow their tails after dropping them. They lay clutches of two eggs up to ten times per year.