Herptiles.net - Mountain Horned Dragon Caresheet

Mountain Horned Dragons or Pricklenape Lizards
Acanthosaura sp.
Christina Miller

Last update: Friday, December 21, 2007.

This is a healthy female Acanthosaura capra. She is missing her eyebrow horns because of detrimental shipping and pet store conditions. Her bulging belly also suggests that she is probably gravid.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Subclass: Lepidosauria
Order: Squamata
Suborder: Sauria
Infraorder: Iguania
Family: Agamidae
Subfamily: Draconinae
Genus: Acanthosaura
Species: armata, capra, coronata, crucigera, lepidogaster, nataliae

Experience level: Intermediate (some lizard-keeping experience reccommended)

I. Introduction

Mountain horned dragons (also called pricklenape lizards), genus Acanthosaura, have recently gained popularity in the North American pet trade. Almost all “MHDs” are wild caught, there are currently few breeders producing captive born specimens in the United States and Canada. While these lizards have some very specific and maybe unexpected needs, they can be interesting pets.

All species are found in montane forests and rainforests at altitudes varying with the species. Several habitat descriptions from scientific journals quote that they are found in mixed coniferous, deciduous and bamboo forests.

Currently, almost all MHDs in the pet trade are wild caught. Please note that many wild caught dragons will be missing their eyebrow horns. This is caused by retained shed skin (dysecdysis) probably due to insufficient humidity while being shipped and/or while in the pet store. While the horns are not totally necessary to have a healthy dragon, it does indicate poor husbandry, so do not be duped into thinking that a dragon missing its eyebrow horns is normal. It is also impossible to know the age of a wild caught dragon, the best guess you can make is whether the animal is mature or not (based loosely on the lizard's size). Until more work has been done with captive MHDs, we will not know their lifespan, although similar agamids may live 10-20 years.

If you choose to keep a mountain horned dragon as a companion animal try to find a captive bred specimen. These individuals will do much better in captivity than wild caught animals. Wild caught animals are usually incredibly stressed by the transition to captivity, and stress can allow manifestation of many health problems. Acanthosaura capra is probably the best choice of species, as they are the most commonly bred in captivity and seem to be hardier than other species.

Distribution of Acanthosaura sp.

II. Taxonomy and Description

Acanthosaura is a genus of the family Agamidae, the Old World counterparts of Iguanidae. Other familiar species in Agamidae are the Inland Bearded Dragon (Amphibolurinae: Pogona vitticeps) and the Green (or Asian) Water Dragon (Amphibolurinae: Physignathus cocincinus). The subfamily Draconinae includes a huge variety of species, such as mountain and tree dragons, and the flying lizards, Draco sp. There are six speciescurrently recognized in the genus Acanthosaura:

Acanthosaura armata (Gray, 1827): The Armored Pricklenape is found through the Thai/Malaysian Peninsula, the Pinang and Tioman Islands and the Indonesian Anamba Islands.

Size (Manthey and Schuster, 1996):

Male Female

SVL 11.5-14.0 cm (4.5-5.5”) 11.0-12.0 cm (4.3-4.7")

STL 25.5-29.0 cm (10-11.4”) 25.0-27.0 cm (9.8-10.6")

Eyebrow spines are long and thin. The nuchal (nape) spines are thin and almost as tall as the eyebrow spine with definite gaps between them, and there may or may not be a gap between the nuchal and dorsal (back) spines. Both males and females have a small gular (throat) pouch.

A. armata tends to be very defensive and flighty, and is not shy to bite when provoked. It is uncommon in the North American pet trade.

Acanthosaura capra (Günther, 1861): The Two-horned Mountain Horned Dragon (capra meaning goat, a two-horned animal) or Green Pricklenape is native to Cambodia, Laos and Vietnam.

Size (Manthey and Schuster, 1996):

Male Female

SVL 13.0 cm (5.1”) 13.0 cm (5.1”)

STL 30.5 cm (12”) 30.5 cm (12”)

This species has spines on the eyebrows and is the only species that lacks spines on the occiput. The nuchal spines are described as lanceolate (lance-shaped: broad at the base and tapering to the tip) with no space between them. There is always a gap between the nuchal spines and the dorsal spines, which are much shorter. Males have a large gular pouch.

This species seems to be the most mellow and tolerant of handling compared to the other species. It appears to be the most common species in the North American pet trade.

Acanthosaura coronata (Günther, 1861): The Crowned Mountain Horned Dragon is poorly known or unknown in the pet trade. It is called a synonym of A. lepidogaster in some publications (Smith, 1935), however other authors disagree that they are the same species because of obvious differences in morphology.

This species possesses a prominent serrated edge on the upper eyelids, a short eyebrow spine, a short occipital spine, and one or two short spines on the back of the head between the tympanum and nuchal crest. There is no gap between the nuchal and dorsal crests.

Acanthosaura crucigera (Boulenger, 1885): The Cross-bearing Mountain Horned Dragon or Boulenger's Pricklenape is so named because of the cross-shaped dark colouration over its shoulders. They range thoughout Myanmar (formerly Burma), Thailand, the northern Malaysian Peninsula, Cambodia and southern Vietnam.

Size (Manthey and Schuster, 1996):

Male Female

SVL 9.7-10.0 cm (3.8-3.9”) 25.9-26.2 cm (10.2-10.3”)

STL 9.0-9.7 cm (3.5-3.8”) 21-24 cm (8.3-9.5”)

Spines on the eyebrows, neck and occiput are short and triangular in shape. The nuchal spines are separated from each other by a space of one scale, and the entire crest is distinctly separated from the shorter dorsal spines.

This species is rarely seen (if not absent) from the North American pet trade, and is reportedly the most aggressive of the genus. A. lepidogaster are often mislabelled as A. crucigera.

Acanthosaura lepidogaster (Cuvier, 1829): The Rough-bellied Mountain Horned Dragon or Brown Pricklenape is so named because of its keeled ventral scales. It is found throughout Myanmar (formerly Burma), northern Thailand, Cambodia, Laos, Vietnam, southern China and the island of Hainan.

Size (Manthey and Schuster, 1996):

Male Female

SVL 7.2-11.1 cm (2.8-4.4”) 19-27.6 cm (7.3-10.9”)

STL 8.5-10.7 cm (3.3-4.2”) 19.5-26.4 cm (7.8-10.3”)

The spines on the eyebrows and occiput are short. Nuchal spines are short and broad with no gaps between them. The nuchal and dorsal spines are not separated by a gap, but the dorsal spines are distinctly shorter.

A. lepidogaster are typically nervous in captivity. They are uncommon in the North American pet trade.

Acanthosaura nataliae (Orlov, 2006): The newest member of the genus, this species was discovered in central Vietnam and southern Laos in 2006. It lacks the occipital spine, the nuchal and dorsal spines are long and lanceolate. It lacks a dark marking on the nape and appears to be sexually dichromatic.

This species, only recently discovered, is still poorly known in the pet trade.

III. Behaviour

These lizards are diurnal and arboreal. They are ambush predators, sitting and waiting for prey to walk by. This makes them rather sedentary lizards, you will often see them just hanging out on branches in their enclosure, motionless for hours at a time. Once they spot prey, however, they enthusiastically lunge at it. These lizards will also visit a moving water source almost daily, where they will splash around and usually defecate.

Temperament varies between species. As previously mentioned, A. capra seems to be the most mellow of the three commonly kept species, whereas A. armata and A. lepidogaster are either more nervous or more eager to bite. A MHD that feels threatened will often gape, hiss and extend its gular pouch in an attempt to scare you or another lizard away.

When seized, they may either struggle to escape or bite, or remain almost completely motionless (tonic immobility). I have personally noticed that If they go limp, they tend to wiggle and twirl the tip of their tail, probably to distract the predator from the rest of the lizard. Unlike most lizards (but like most other agamids), they may not perform caudal autotomy. However, one might wonder if the tail would break off easily as a defensive mechanism, considering they seem to try to use it to distract you (the "predator") when being held.

These animals are not social and do not appreciate each other's company. To reptiles, other animals are seen as either predators, or competitors for the best food, heat and hiding spots. Because of this, they are best kept in singly-housed enclosures. Enclosures with multiple animals that are not large enough or are poorly-designed will result in one or more stressed out lizards. Stress is a leading factor in the poor health of captive reptiles and amphibians. Territorial displays include gular pouch inflation, head bobs and pushups.

IV. Diet

These lizards will thrive on a varied diet of invertebrates. Crickets, cockroaches, superworms and mealworms should be part of the diet to provide roughage, and adding soft prey like earthworms (nightcrawlers and red wigglers), hornworms, butterworms, and silk worms adds more variety (and the lizards seem to love them!). All prey should be gut-loaded on a nutritious diet 24-36 hours before being fed to the lizards. This is to ensure that the prey you are feeding contains a variety of nutrients, as most prey is poorly fed at the pet store.

Other prey can occasionally be added to the diet, like wax worms, pinky mice, and feeder guppies (all prey from reputable sources). These prey items are nice supplements, but because of their high fat and/or calorie content should be fed sparingly to avoid having an overweight lizard.

These lizards have a pretty voracious appetite; it is surprising how much they will eat. Young dragons should have food available daily (preferably confined to a dish so that the prey is easy to find). Adults can be fed every 2-5 days, as much as they will eat in about 10 minutes is a good way to find out how much your dragon will normally take. Remove uneaten food from the enclosure.

Dietary supplement powders are a controversial topic as we are uncertain of exactly how much is needed. We cannot possibly provide the same type of nutrition that these animals have in the wild, so their use is not unfounded. Vitamin and minerals overdoses are possible, so they should be used sparingly, and gut-loading should never be replaced by supplements. Because most invertebrate prey has an inverse calcium to phosphorus ratio, consider dusting most invertebrate prey with calcium powder. Multivitamin and mineral supplements can be used less often. Gravid females should be provided more calcium in their diet to make up for calcium lost to eggshell and yolk production. My personal supplementing schedule for all of my insectivorous herps includes calcium every 1-2 meals, and a multivitamin and mineral supplement every 4-5 meals.

V. Housing

Fake rock walls add a lot of vertical climbing space to the enclosure. Plenty of fake or live plants are suggested to let the dragon feel secure, and reduce stress. Can you spot the dragons in this custom enclosure made out of an old wall unit?

Size and build: These lizards need a surprisingly large enclosure for their size. Minimum suggested dimensions for a single dragon are 100-130 cm (3-4') tall, 100 cm (3') long and 50 cm (1.5') wide. Height is very important because of their arboreal nature.

Dragons kept in smaller enclosures tend to develop stereotypic escape behaviours like scratching and face rubbing on cage walls. These are indicators of environmental stress, and can lead to both physical wounds and secondary stress-related health problems.

The enclosure may be screen, wooden or glass, as long as humidity and temperature requirements are met. Completely transparent enclosures are discouraged. As with most lizards, MHDs are prey animals and opaque walls can help their sense of security and reduce stress. They also have a poor perception of transparent barriers, making them more prone to scratching and face rubbing behaviours on transparent walls.

Cage furniture: Vertical climbing space and plenty of plant cover are key with MHDs. Branches placed vertically, diagonally and horizontally provide climbing and resting spots. Live or fake plants may be used. Fake plants are less work to maintain than live plants, but live plants provide more humid microhabitats and can help to raise relative humidity.

Not all live plants are suitable as some are too delicate to withstand a dragon's abuse and are a waste of money to keep replacing. Others may grow too large for the average enclosure. Tough and hardy plants that appreciate warm, humid conditions like pothos, philodendrons, dracaenae (like the Madagascar dragon tree and corn plant dracaena), hibiscus, some bromeliads, spider plants and sansvierias (snake plants) have been used with success in MHD enclosures. All plants to be used in the enclosure should be repotted into a sterile, plain potting soil free of fertilizers, pesticides, vermiculite and perlite (small Styrofoam balls). The entire plant should be rinsed several times in lukewarm water to remove any pesticide residue from the nursery. Inspect the plants before purchase for pests like slugs, aphids and others. Once in the enclosure, maintain the plants according to their appropriate needs. Even tough plants like the ones above might need replacing after a dragon has romped around on them for a while! See Plants for the Tropical Terrarium for more information.

Substrate: As substrate, plain potting earth is relatively safe, simple and cheap. Be sure to select soil with no additives such as fertilizers, vermiculite or perlite. Appropriate forest soil mixes including soil, woodchips, sand and decomposing leaves are also suitable. Substrate consisting of loose chunks of material such as woodchips, crushed walnut shell and crushed corncob should be avoided, as these are generally unsuitable for lizards for various reasons.

VI. Water

This water dish has a submerged filter with a tube attached to create a tiny waterfall.

Water is a very important topic with mountain horned dragons because of their particular needs. These lizards absolutely need their water to be moving, or they will not recognize it. This is possibly because they always live near moving streams in the wild.

There are several ways to create movement in a water dish. An aquarium air stone (with an air pump attached) to create bubbles or a drip bottle to create movement in the water are cheap and effective. A submersible filter can be used to make water movement, as well. Premade waterfall systems found at the pet store can also work, however I have found that they tend to accumulate dirt and debris and the water fouls quickly without frequent cleaning.

The water dish should be large enough for the lizard to fit most of its body; dishes can be a bit deeper for adults as long as there are rocks or branches positioned so that the dragon can exit the water or sit comfortably half-submerged. They do seem to appreciate dishes deep enough so that they are submerged chest-deep.

Keep the water source clean and fresh by changing it frequently: Every few days if there is no filtration system, or whenever the lizard defecates in it. If you have a particularly large water area with a filter, follow the filter's suggested maintenance schedule but do not forget to spot clean the water of feces, and do a partial water change weekly.

VII. Heating

One of the biggest mistakes new owners (and pet stores) make is providing a small enclosure with no place to escape from a hot heat lamp. These lizards appreciate a warm hot spot at 32 °C (90 °F), but they absolutely need an enclosure large enough to escape the heat. A difference of at least 8-10 °C (14-18 °F) between the hot spot and cooler region is suggested. Excess heat can debilitate reptiles by suppressing their immune system and appetite, which can lead to disease. A general drop in temperature by a few degrees is expected at night- no night time heat source is suggested.

VIII. Humidity

These lizards live in very humid habitats, and a relative humidity over 80% should be provided at all times. Moving water sources, regular misting and a natural, moisture-holding substrate can all help increase relative humidity. Various humid microhabitats up to 100% humidity can be provided by using live plants, slabs of bark and moist sphagnum moss.

IX. Lighting

Light quality is often overlooked in reptiles and amphibians. Broad-spectrum lighting (including UV-A and UV-B wavelengths, which are naturally found in sunlight) is suggested for these lizards. Most domestic lightbulbs produce these wavelengths in negligable quantities, or not at all. Specially made bulbs for use with herps and/or birds are required, and they must be replaced every 6-10 months depending on their usage and the manufacturer's suggestions. These bulbs should not be placed further than 38 cm (15")from the closest basking spot, as the amount of UV reaching the animal decreases significantly with distance. Plastic and glass completely filter UV, and mesh or screen filters a noticeable amount.

Ultraviolet B may not be necessary for vitamin D metabolism, as many owners have kept these lizards with no UV-B lighting, providing well-rounded diets and good husbandry without any calcium-related health problems developing. Providing it is not harmful, and may still help the lizard's calcium balance stay within normal limits.

A source of light that provides UV-A is necessary because of the behavioural implications that UV-A has. Ultraviolet A is important when considering reptile vision as they can see certain wavelengths that we cannot. Not providing this wavelength has behavioural implications as it may be rendering them colour-blind to an extent.

Provide a photoperiod of 12-14 hours, varying with the seasons. A proper day/night cycle can be achieved by using an electrical timer.

X. Sexing

Sexing these lizards is easy. The female on the left has a narrow tail base. The male on the right has a distinct hemipenile bulge.

The presence of hemipenile bulges in males is the most reliable method of sexing these lizards. This feature should be evident at sexual maturity.

There appears to be some variable sexual dichromatism in some species, but it may not always be reliable for sexing. These lizards do display colour changes in colour intensity, and there is a lack of documentation on the colour differences between sexes.

Acanthosaura lepidogaster appears to be sexually dichromatic. The male (left) is more brilliantly coloured than the female.

XI. Health

Proper husbandry is the key to good health in all reptiles. If you provide good basic care, then you will avoid most health problems that reptiles can encounter in captivity.

There are some important health concerns with mountain horned dragons because of the poor condition that wild caught animals arrive to pet stores in. Most are dehydrated, and it should be assumed that all are parasitized. A parasite "profile" including a fecal exam is strongly reccommended for all newly-acquired lizards. This can be performed by an experienced herp veterinarian. If a severe parasite imbalance is discovered, then treatment may be necessary.

Parasites like Capillaria are very common in wild caught MHDs. A fecal exam should be part of your to-do list for a newly acquired dragon, especially if it is wild caught.

Anorexia is a common problem in mountain horned dragons, and is often attributable to poor environmental conditions (too hot, too cold or too stressful) or a heavy parasite load.

Gravid females will also have a decrease in appetite, however they are prone to many health problems if husbandry is inadequate. Calcium deficiencies can result in egg-binding (dystocia), which is fatal if left untreated. Females that have a poor body condition and are bred may develop various other illnesses due to the energy invested in developing eggs. Females with a poor muscle mass may also have difficulties laying their eggs (also dystocia).

When in doubt about a health issue with your pet, do not hesitate to contact a knowledgeable reptile and amphibian veterinarian. To find a vet in your area, see the directory at the Association of Reptile and Amphibian Veterinarians website.

Glossary:


STL: "Snout to tail length," the length of the animal from the tip of its snout to the tip of its tail. SVL: "Snout to vent length," the length of the animal from the tip of its snout to the vent, i.e. the length of the animal not including the tail.

Sources:

Bradley, MB. 2002. FroggieB Dragons. <http://www.froggieb.com/MHDHome.html>
Bradley, MB. 2003. The New Dragon On the Horizon. REPTILES. 11:10 (October, 2003), 76-84.
Manthey U and N Schuster. 1996. Agamid Lizards. New Jersey: T.F.H Publications.
Orlov, NL, TQ Nguyen and SV Nguyen. 2006. A New Acanthosaura Allied to A. capra Günther, 1861 (Agamidae, Sauria) from Central Vietnam and Southern Lao. Russian Journal of Herpetology. 13(1): 61-67.
Smith, MA. 1935. The Fauna of British India, including Ceylon and Burma. Reptilia and Amphibia. Vol. II.-Sauria. London: Taylor and Francis.
Stuart, BL, K Sok and T Neang. 2006. A collection of amphibians and reptiles from hilly eastern Cambodia. Raffles Bulletin of Zoology. 54(1): 129-155.

Further Reading: