Within the last couple of years, one species in particular has become increasingly popular-the spiny-tailed monitor Varanus acanthurus. In , Mertens placed the species in the subgenus Odatria along with most of the other small- to medium-sized Australian varanids. Two subspecies of spiny-tailed monitors may be found throughout much of the northern half of Australia, from the northern half of Western Australia, all of the Northern Territory except possibly where the closely related V. Animals from the northwest of the range are generally described as V. A third subspecies, V. Because the acanthurus group has such an incredibly large range, a great deal of morphological, color and ecological differences may be present.
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Within the last couple of years, one species in particular has become increasingly popular-the spiny-tailed monitor Varanus acanthurus. In , Mertens placed the species in the subgenus Odatria along with most of the other small- to medium-sized Australian varanids. Two subspecies of spiny-tailed monitors may be found throughout much of the northern half of Australia, from the northern half of Western Australia, all of the Northern Territory except possibly where the closely related V.
Animals from the northwest of the range are generally described as V. A third subspecies, V. Because the acanthurus group has such an incredibly large range, a great deal of morphological, color and ecological differences may be present.
Some northern animals may be jet black, while in other areas they may be yellow, brown, tan or red. Body size also varies greatly, with some animals reaching total lengths of 30 inches Ecology may even vary tremendously within the range.
Animals from tropical areas have been found in trees, while in drier areas they have been found in burrows, rock outcrops, or in spinifex grass Bennett, In addition, no true zones of segregation or overlap exist within the mainland forms, making the taxonomy of the species very confusing and in need of revision. Furthermore, species such as V. Together, these characters and habits are forcing researchers to believe a greater number of acanthurus subspecies exist than previously believed H.
DeLisle, B. Eidenmueller, D. King; pers. Two acanthurus forms are readily available in the hobbyist trade and are generally known as "red ackies" and "yellow ackies.
After a great deal of research and conversation with the leading experts, it has become apparent that these two color morphs are most likely the two mainland subspecies of acanthurus. The red form being V. Most books on varanids disagree about where the taxa are from and which color morphs come from what range, but the type specimen found by Gray was from the northwest coast and was named acanthurus, while the type brachyurus specimen was found in central Australia.
Recent field observations, along with morphological data such as tail length and size were also considered in confirming where each color form comes from. First, red specimens may have longer tails than yellows in some areas. Red ackies also grow larger than yellows and have a distinct cross and spot head pattern which is absent in the yellow ackie.
Further evidence that suggests the red ackie is, indeed, V. An enormous inch red was also found near Wyndham, an area also within the range of V. Yellow ackies were commonly found in the east, especially near Mt. Isa F. Retes, pers. In whatever microhabitat they exist, ackies generally prefer arid, flat terrain near rocky outcrops.
Rock crevices or burrows under large boulders serve as retreats and areas where animals may thermoregulate without being exposed to predators such as raptors, snakes and other monitors.
The flat body and spiny tail are perfectly evolved for living in burrows and cracks, as the animal is able to fill itself with air to avoid being extracted, while the spiny tail serves to cover the more vulnerable body parts that may be exposed at any given time.
The streamlined shape of the animal also makes living in burrows much easier, especially in group situations. Large monitor lizards are generally considered asocial, whereas acanthurus and other small monitors have been found living in underground colonies S. Irwin, pers. This interesting social behavior has also been noted in captivity, where alpha males and females rank the highest in group situations. Most small Australian monitors survive mainly on small lizards and insects, and V.
Losos and Greene found that in museum specimens, orthopterans, beetles, cockroaches and lizards were the main prey items. Lizards included agamids, geckoes and skinks. No relationship between monitor and prey size was found, but larger lizards usually contained more items in the stomach. A small ackie, weighing only grams, was found to contain seven large grasshoppers in its stomach.
Given the reproductive output seen in acanthurus in captivity, this is not surprising, because animals that produce multiple clutches of eggs require a great deal of food. Little information exists on reproduction in wild acanthurus; however, my friend and colleague Grant Husband examined a wild nest in the Northern Territory during the month of January Husband, It had been dug into a mound with an S-shaped tunnel underneath that consisted of a centimeter egg chamber.
The tunnel had been refilled and the eight young were found digging themselves out. From this and other data it has been reported that V. Clutch size in the wild is believed to range from two to 11 eggs and is dependent upon the size of the female. Hatchlings emerge during the wet season from December to March after a three- to four-month incubation period. Captive Husbandry and Reproduction Given the proper requirements, ackies will flourish in captivity.
In fact, they adjust so well to captive situations that they are commonly coined "the perfect beginner monitor. Of course, any monitor would benefit from a larger enclosure, especially a species as active and curious as acanthurus. Substrates commonly used are sand, dirt, or a mixture of the two, while the depth and substrate type depends on whether or not a nest box will be used during the breeding season. Because they come from hot environments, high temperatures are necessary to keep acanthurus healthy and fit.
A temperature gradient from one end of the cage to the other is effective in monitor husbandry. Ambient temperatures should range from degrees Fahrenheit A basking spot on the warm end, usually provided by a spotlight, should range anywhere from to degrees Fahrenheit 60 to 76 degrees Celsius on the substrate surface not air temperature. These temperatures may seem extremely high for any animal, but these temperatures are common on the surface of most substrates when the air temperature is greater than 85 degrees Fahrenheit 30 degrees Celsius.
As an example, on a degree Fahrenheit day in Southern California, the surface temperature of hard-packed dirt in the sun measures roughly degrees Fahrenheit 60 degrees Celsius , whereas on days that were hotter than 90 degrees Fahrenheit In ackie habitat in Australia, which gets as hot as degrees Fahrenheit I have yet to hear of or see a burn on an acanthurus.
The proper way to ensure that an animal will not be burned is to make sure the ambient cage temperature stays warm. Provide multiple hide areas throughout the temperature gradient, especially if more than one animal inhabits the enclosure. A hide area is very important under the spotlight, because acanthurus and other Odatria monitors prefer to thermoregulate under cover.
A method that proves very effective is a stack of plywood boards, separated just enough for the animals to squeeze between them. This method, developed by Frank Retes, simulates a burrow or caprocks with a vertical temperature gradient within which the animals may be found thermoregulating in the wild.
A heating pad situated under the substrate at the bottom of the woodpile ensures the animals will not only stay warm at night, but that they will use the entire woodpile to thermoregulate. As with any diurnal, basking animal, providing ultraviolet light is important.
Although it is still uncertain whether monitors can acquire enough vitamin D and calcium from their diet to remain healthy, most keepers provide full-spectrum lighting to be safe.
Provide basking areas within 6 to 10 inches Finally, provide a water bowl at all times, while under some of the hide areas the substrate should be lightly sprayed a couple of times per week. Although they come from hot areas, humidity in much of northern Australia is very high, as is the humidity in any subterranean burrow. Proper humidity levels for acanthurus enclosures should range from roughly 65 to 85 percent.
Because of the speedy metabolism associated with high temperatures, acanthurus should be fed five to seven times per week, with younger animals being fed daily. Insects such as crickets, wax worms, mealworms and roaches make up most of the diet of captives, but pink mice and frozen-thawed ground turkey are also readily taken-especially during the breeding season. Adults have been known to become obese when fed pinkies more than three or four times per week, but if kept on an insect diet they may be fed every day.
Live insects and pinkies are grabbed swiftly at mid-body and then brought to "killing stations. Ground turkey or frozen-thawed pinkies may be offered on rocks or small dishes near hide areas.
The spiny-tailed monitor has been bred in captivity for years, with some successful breeding taking place in Europe as long as 25 years ago H. Horn, pers. Multiple clutching, believed to be a fairly new concept to captive reproduction of monitors, also occurred over a decade ago in private collections Erdfelder, In the last five years, however, breeding success of many monitors has been tremendous and captive-produced animals have been bred to at least the fourth generation.
When planning to raise ackies for reproductive purposes, one of the most important things is to purchase a group of hatchlings that hatched together or are the same size and age, and raise them together from as early an age as possible. Not only males fight, but the social system of ackies also seems to include an alpha female who will not only attack other females, but smaller males, too.
Females raised together may be introduced to a larger single male raised separately, but the animals should be observed for the first few days to make sure they are compatible J. Lemm, pers. Like most other varanid species, ackies are difficult to sex, and hatchlings are next to impossible to sex, although the well-trained eye can ascertain gender at four or five months of age.
Males develop clusters of enlarged scales on either side, and just below, the vent. Females may have slightly enlarged scales, but they are much smaller. Male ackies also have a more developed, muscular neck region with a wider head, whereas females have a more slender head that may be more pointed.
I have noticed that females of both subspecies in my collection also tend to be less shy towards their keepers than males, although both male and female reds can be snappier than yellows, which never seem to bite. One interesting behavior common to immature animals, even hatchlings, is they may show mating behavior, but this does not mean they are a certain gender. Female ackies will "mate" other females as well as males, and males may mate other males, although this behavior seems to decrease with maturity.
Ackies reach sexual maturity very quickly and have been known to lay fertile clutches at as little as 5 or 6 months of age. King and Rhodes discovered that females with a snout-to-vent SVL between 10 to 12 centimeters 3. Basking temperatures are very important during breeding, and copulation may cease if the basking site dips below surface temperatures of degrees Fahrenheit If kept warm and fed daily, spiny-tailed monitors will begin to copulate many times a day, usually in the spring and summer months, and ending around October; although this pattern differs greatly depending on temperatures, food and light cycles, as well as where the animals are geographically located.
Animals seem to suddenly "turn off" even when kept warm and well fed, and will show no interest in one another until the start of the next breeding cycle. At this time, I normally reduce temperatures by roughly 20 degrees Fahrenheit and shut off one of two basking lights. Light cycles are reduced to 10 hours of light and the animals are only fed two to four times per week. This will last until the animals show signs of restless activity, usually one to three months later.
Ackie Monitors (Varanus acanthurus) Care Sheet
Ackie Monitor Pictures 2 Overview The varanus acanthurus is a medium sized member of the subgenera Odatria. The Red Ackie acanthurus acanthurus can reach lengths of 24 to 30 inches. It usually has a longer tail and is a reddish brown color. While the Yellow acanthurus brachyurus is usually 15 to 24 inches in length, is a yellowish brown color and has a more slender body compared to the Reds.
Like bearded dragons, Ackies are from the dryer regions of Australia and need similar but not the same conditions. They get a little larger well longer at least and so will need a large enclosure. They should also be quite active, making a larger enclosure essential. Due to their relatively small size for monitors and generally good temperment, Ackies make a good starter monitor but are attractive enough to appeal to more experienced keepers too. Enclosure Akies get to around 2 feet in length males slightly larger. They are a very active lizard and like to burrow in the substrate. This, coupled to the fact that they like it very hot in the basking area degrees centigrade means that they need a large vivarium.
Spiny-Tail Monitor Ackie (Varanus acanthurus) Care Sheet
They are found in arid dry regions or scrubland environments throughout Western Australia, Northern Territory, and parts of Queensland. Living near rocky outcroppings, they will retreat into crevices and puff up their bodies to wedge themselves between the rocks when frightened. They live in humid burrows, which are dug deep to escape the midday heat and control their hydration and temperature levels. Ackies Monitors are a popular monitor species to own because they are inquisitive, active, and have great colors and patterns, and relatively small size.