Close your eyes and grab one of your forearms with the opposite hand. Now imagine that you hold a soft, wrinkly skinned, 400-gram gecko. Believe it or not, they get that large! Welcome to the world of the New Caledonian giant gecko (Rhacodactylus leachianus), also nicknamed a “leachie.” The first time I held one I was mesmerized, and my addiction began.
Rhacodactylus leachianus are currently recognized as the largest known living gecko in the world. Sometimes growing larger than (and out weighing) some miniature dog breeds, these geckos have evolved into one of the top predators in their environment.
Discovered by Georges Cuvier on the islands of New Caledonia in 1829, it wasn’t until the 1980s and 1990s that R. leachianus became commonly available to herpetoculturists. New Caledonia is located east of Australia and northwest of New Zealand, lying at the edge of the temperate zone, with temperatures ranging from 60 to 90 degrees Fahrenheit and humidity levels ranging from 65 to 80 percent.
New Caledonia consists of the main island, Grand Terre (literally meaning “large land”), and many offshore islands. To my knowledge, the following Grande Terre locale morphs are accurately represented in herpetoculture: Poindimie, Mount Koghis, Yate, Mount Humboldt and Riviere Bleue. Offshore island locales most accurately represented in herpetoculture are Pine Island, Bayonnaise, Borosse, Moro, Nuu Ana, Nuu Ami, Duu Ana, Koe and Caanawa. While others may exist, many have questionable origins.
The geckos from Grande Terre had been previously defined as Rhacodactylus leachianus leachianus, and the offshore island geckos were defined as Rhacodactylus leachianus henkeli. However, Aaron Bauer, Ph.D., presented information at the 2006 New Caledonian Gecko Symposium in Tinley Park, Ill., that brought into question the subspecies divisions of R. leachianus. The possible removal of subspecies status is based upon Dr. Bauer’s genetic comparisons between geckos from Moro, Bayonnaise and Grande Terre. Further studies are needed to define these geckos genetically, but due to morphological differences such as size and coloration, this division will remain important to herpetoculturists. Those holding geckos from the smaller locales compared to the large cousins from the mainland would recognize this importance.
Big and Beautiful
With regard to offshore island leachianus, those from smaller locales, such as Nuu Ana and Nuu Ami, are approximately 6 inches from snout to vent length, and those from larger locales, such as Pine Island and Moro, are approximately 8 inches in snout to vent length. The tail of these geckos, appearing visually distinct from the body, adds approximately 3 to 4 inches, bringing their total length up into the range of 9 to 12 inches. Weight varies from 120 grams up to more than 300 grams. Island geckos have a stout, cylindrical body with a head and neck that are clearly defined from their torso. Their base color is made up of browns, grays and greens. These geckos are more heavily patterned and tend to have more bulbous eyes along with a shorter snout. They are covered with blotches ranging from vivid white to black speckled white, while others have blotches that are pink to purple.
Conversely, animals found on Grande Terre can dwarf their island relatives. These geckos usually range from 8 to 10 inches in snout to vent length with some rare giants reaching a whopping 13 inches snout to vent length. The tails of the Grande Terre animals can vary in size, and tend to be more elongated than the tails of their island cousins, maxing out at around 5 inches. My longest leachie is 15.5 inches and weighs 365 grams and my heaviest is 14.5 inches and weighs in at an immense 415 grams.
Base colors of those found on Grande Terre range from golden yellow to green to brown to solid black. These geckos are patterned quite differently than their island cousins, with some animals having no pattern at all. Most that are patterned have markings ranging from white bands or blotches, usually along their sides, to thin white lines or simply white dots.
All leachies have loose fitting, velvety skin covering their body. Black longitudinal markings can be seen on many individuals, sometimes appearing almost netlike. Yellow spots or markings are commonly seen on mature animals. All leachies also have strong, well-developed limbs, a prehensile tale with a nuptial pad and large, round toe pads with a single curved claw on each. All of these traits are essential for their arboreal lifestyle.
In the Wild
During the day, R. leachianus can be found in tree hollows and on the underside of branches. Occasional basking in dappled sunlight has been observed, but these geckos are rarely found in direct sun. These nocturnal geckos become active at night and can be found either in search of food or interacting with each other on the sides of trees or on thick branches. Seasonal changes play an important part in their diet, behavior and activity. In the summer months ripe fruit makes up the bulk of their diet. In the winter months, when fruit is scarce, they feed on insects and anything else they can catch. In at least one recorded incident, bird parts were found in the stomach remains of an animal from Grande Terre. Their activity level decreases dramatically during the winter months, and cooler temperatures also signal the end of the breeding season.
Housing can be as simple as plastic storage containers or as complex as commercially available enclosures with a sliding front door. Adults should be housed individually in an enclosure about the size of a 20-gallon aquarium (24 inches long by 12 inches wide by 16 inches tall) or larger Take care that enclosures are made of a material that can be easily sterilized, such as plastic.
They seem to prefer opaque surfaces rather than clear surfaces. A mulch substrate can be used for non-breeding animals. However, if it used with breeding animals, gravid females may deposit their eggs in the substrate, risking egg dehydration. Adequate humidity can be easily maintained by using substrate at a depth of 1 to 2 inches. Regular moistening of substrate is necessary due to the low humidity levels in most home environments. These geckos require a humidity of 50 to 80 percent. A fresh water source at one end of the enclosure is important and helps maintain high humidity levels. I find it best to stay away from screen or screen top enclosures because they are difficult to keep humid. Care must be taken to maintain humidity levels without over-saturating the substrate. This over-saturation may cause serious skin infections that can quickly lead to the death of a leachie. In this cool humid environment, fecal matter and uneaten food must be removed promptly to avoid bacterial or fungal growth.
Cage furnishings can vary from wrist-thick branches to cork flats and hollows. Live plants can be added for aesthetics. A hide box with a moist, peat-type mixture can be added as a humidity and egg-laying chamber. This hide box can also be used as a refuge and can aid in shedding.
When setting up an enclosure, give the geckos plenty of places to hide and branches to climb. Maintaining these geckos at temperatures from the mid to upper 70s year round is acceptable for non-breeding animals; however, breeding animals produce best with a natural seasonal fluctuation. Most R. leachianus, especially gravid females, will make use of and benefit from a basking site, but this is not mandatory. A 15 watt incandescent bulb or fluorescent fixture can be used for plant growth and/or a basking site, but full spectrum lighting is not necessary.
Most young leachies have a tendency to be flighty when first handled, but with frequent gentle handling, they can become quite calm. Do not grasp your leachie tightly, as this will only frighten it, causing a predator-to-prey response (a sure way to get bitten). Let the leachie hold on to you, as you will become a moving branch in its eyes. I find the hand-to-hand technique works best. Hold the gecko in one hand, and if it tries to jump put your other hand in front of it so it has somewhere to land. It will soon get tired and relax. In addition, when removing your gecko from its enclosure, try to do so swiftly and almost catch it off guard. If it sees you coming in slowly, it may lunge and bite, chasing you from its territory. For safety reasons, an animal with this behavior is best removed from its enclosure with gloves. Once out, even the most aggressive leachies usually calm down, and do not attempt to bite. As they mature, most locales become calmer and are less resistant to being handled. However, some Grande Terre individuals always seem defensive, and are quick to lunge and bite.
In captivity the majority of their diet consists of commercially produced powdered diets made specifically for Rhacodactylus geckos. Baby food should never be used as a substitute for these commercial diets. The majority of leachies that I have seen fed baby food regularly develop deformities as they mature due to nutritional deficiencies. Proper food should be fed two to three times per week in the summer when temperatures are warm, and one to two times in the winter. A varied diet of size-appropriate insects (no longer than the geckos’ head is wide) should be offered weekly. Offer as many as the gecko can consume in one sitting, and dust the insects with a calcium and multivitamin supplement. Crickets, wax worms, mealworms and roaches are readily accepted, but uneaten insects should be removed promptly. Pinky mice can be fed periodically, but should not be offered more than one to two times per month to avoid obesity issues.
Studies done on the island of Bayonnaise showed that the average age of leachies in the wild is somewhere around 8 years. No other longevity information is available on other locales of leaches, but it could be speculated that the average age of animals on the mainland might be longer due to a larger habitat. Fighting to the death is quite common, and only the strongest animals survive to breed. In captivity, with proper care and nutrition, they are known to be a very long-lived species. One animal, brought in as an adult, was recorded living at least 30 years in captivity. Only time will tell what “old age” is for R. leachianus.
One common problem seen in captive leachies is Metabolic Bone Disease (MBD). It is usually the result of improper diet, such as baby food concoctions, or improper supplementation. Proper diets formulated for Rhacodactylus geckos can be used on their own with great success.
Obesity has been seen in animals that are overfed diet or fed pinky mice regularly. Growth problems have been seen in animals kept too dry. When kept too dry, they also seem unable to find their food and stunting and or deformities are commonly seen, due to malnutrition.
Skin infection, due to wet and improperly sterilized caging, is also a problem that can set in very quickly. This almost always ends in death. If it is caught early enough, removing the gecko from its enclosure, cleaning and sterilizing the enclosure immediately, and setting the gecko back up on sterilized paper towels seems to greatly increase the geckos chance of survival. The gecko should then be taken to a qualified reptile veterinarian immediately.
A Growing Obsession
Given the many different natural color variations, ease of care, calm temperament and impressive size of these geckos, it is easy to see why leachies have become a favorite to many reptile enthusiasts. That said, I caution the new enthusiasts: If you acquire one, it is difficult to stop there. For me, the obsession has grown to a quest to have representative pairs from each locale. I have embarked in a species-specific breeding program to insure the purity of the different morphs for future herpetoculturists. And I continue to learn more about these great animals every year.
Learn about breeding leachies in our Breeding Leachies article.
Stephen Cemelli has cared for reptiles for more than 30 years and has bred many types for more than 20 years. He maintains one of the largest and most complete collections of locale specific Rhacodactylus leachianus in the world. Visit him on the Web at leapinleachies.com.