Hydrosaurus weberi, Weber’s Sailfin Lizard

Hydrosaurus weberi, Weber’s Sailfin Lizard 


Weber’s Sailfin Lizard (Hydrosaurus weberi), is an Agamid lizard found in Indonesia. Specifically, it is endemic to Halmahera and Ternate Islands of Maluku.[1][2] This species lives over 10 years

Varanus salvadorii, Salvadori’s monitor

Varanus salvadorii, Salvadori’s monitor


Varanus salvadorii is a monitor lizard found in New Guinea. It is also known by the common names Salvadori’s monitor, Crocodile monitor, Papua(n) monitor, and Artellia.[4] The largest monitor lizard in New Guinea, it is believed to be one of the longest lizards in the world, reaching up to 244 cm (8.01 ft). It is the sole member of the subgenus Papusaurus. V. salvadorii is an arboreal lizard with a dark green body and yellowish bands, a blunt snout and a very long tail. It lives in mangrove swamps and coastal rain forests in the southeastern part of the island, where it feeds on birds, small mammals, eggs, and carrion in the wild, using teeth that are better adapted than those of most monitors for seizing fast-moving prey. Like all monitors it has anatomical features that enable it to breathe more easily when running than other lizards can, and V. salvadorii is thought[by whom?] to have greater stamina than most monitors. Little is known about its reproduction and development, as the species is very difficult to breed in captivity.

V. salvadorii is threatened by deforestation and poaching, and is protected by the CITES agreement. The lizard is hunted and skinned alive by tribesmen to make drums, who describe the monitor as an evil spirit that “climbs trees, walks upright, breathes fire, and kills men”; yet the tribesman maintain that the monitor gives warnings if there are crocodiles nearby.

Taxonomy and etymology

V. salvadorii was first described as Monitor salvadorii by Wilhelm Peters and Giacomo Doria in 1878 from a female specimen with a snout-to-vent length of 48 cm (19 in) long and a tail measuring 114 cm (45 in) in length.[4]

The generic name Varanus is derived from the Arabic waral (ورل), meaning “Lizard”. The term “Monitor” is thought to have come about from confusion between waral and the German warnen, meaning “warning”. The term “Goanna” came about as a corruption of the name “Iguana”. The specific name is derived from a Latinization of Tommaso Salvadori, an Italian ornithologist who worked in New Guinea.[1] Later, in 1885, it was renamed Varanus salvadorii by George Albert Boulenger. The Papua monitor is occasionally confused for the Water monitor (V. salvator) because of their similar scientific names.[5]

Evolutionary development

The evolutionary development of V. salvadorii started with the Varanus genus, which originated in Asia about 40 million years ago and migrated to Australia. Around 15 million years ago, a collision between Australia and Southeast Asia allowed the varanids to move into what is now the Indonesian archipelago.[6]

V. salvadorii has been placed cladistically as part of a species cluster with the Lace monitor (V. varius) and the Komodo dragon (V. komodoensis). This study was based upon mitochondrial DNA and microcomplement fixation analysis. A theory has been put forth that the species diverged from a common ancestor, as the Torres Strait separating New Guinea from Australia is less than 90 km (56 mi) long, a distance that could have been covered fairly easily with island hopping. However, the similarities between V. salvadorii and V. varius may simply be an example of convergent evolution.[2] Another clade postulated by Eric Pianka places V. salvadorii in a larger “Australian” clade of large monitors, along with other species as the Komodo dragon, the Lace monitor, the Perentie (V. giganteus), the Argus monitor (V. panoptes), and the Sand goanna (V. gouldii).[7]


The largest of the seven species of monitors found on the island of New Guinea, V. salvadorii occurs in both the state Papua New Guinea and the Indonesian region of West Papua. It inhabits the high and low canopies of the lowland rainforests and coastal mangrove swamps, sometimes venturing out of these areas during floods in the rainy seasons. No detailed field investigation data is available for V. salvadorii, so the full extent of its range is unknown.[2][4] Its remote and generally inaccessible habitat is the main factor in preventing detailed study of this animal in its natural habitat.[2][4]

Biology and morphology

The most characteristic feature of this monitor is its blunt bulbous snout, which makes this species look different than every other monitor on New Guinea and lends to its common name of tree crocodile.[4] The body of the lizard is dark green with rings of yellow spots.[8] The tail is banded yellow and black and is extremely long, being more than twice as long as the snout-to-vent length. It has long straight teeth and prominent curved claws. There is no external sexual dimorphism.[9]

Unique among living varanid species, the animal’s tail is two-thirds longer than the snout-to-vent length in both juveniles and adults.[4] Herpetologist Robert Sprackland gives the proportion as the tail being 210% of the animal’s body length.[10] At birth V. salvadorii is about 45 cm (18 in) long, while a sexually mature female may grow to 150 cm (4.9 ft).[11] This is possibly the longest living species of lizard, although considerably less massive and heavy than the Komodo Dragon.[12] Specimens are known to reach at least 244 cm (8.01 ft) in length.[13] but it has been speculated that it may grow longer.[10][14] A specimen reportedly measuring 323 cm (10.60 ft) was caught in Konedobu by Dr. F Barker.[12] Several reported specimens have been claimed to exceed 350 cm (11.5 ft), some even to 610 cm (20.0 ft), but most of these were second-hand reports and there are no museum specimens in this size range.[12] Weight in the species has been reported at up to 90 kg (200 lb), but a more typical specimen of under 200 cm (6.6 ft) will probably weigh a fifth or a sixth as much as this.[15][12]

Varanus salvadorii has what physiologists refer to as mammal-like aerobic abilities; this is accomplished by means of a positive pressure gular pump in the animal’s throat to assist lung ventilation.[2][16] The majority of lizards cannot run and breathe at the same time due to Carrier’s constraint, but monitor lizards are exceptions to this rule.[16][17] The development of this ventilatory pump is analogous to the evolution of the diaphragm in mammals, which ventilates the lung independently of locomotion; scientists place Varanus salvadorii as the species with the highest endurance in this regard.[2][16] This would suggest that the lizard is at an evolutionary midpoint, relying on both forms of breathing.[16]


V. salvadorii is an arboreal lizard. As such, it can hang onto branches with its rear legs and occasionally use its tail as a prehensile grip. The primary use of the tail, however, is to counterbalance its weight when leaping from one branch to another.[2] The tail may also be used for defense, as captive specimens have attempted to whip their keepers with their tails.[18] This species is occasionally seen in the pet trade, but has earned a reputation of being aggressive and unpredictable.[4] Although they are known to rest and bask in trees, they sleep on the ground or submerged in water.[2]

The monitors will rise up on their hind legs to check their surroundings, a behavior that has also been documented in Gould’s monitors (V. gouldii).[5] According to native belief, they will give a warning call if they see crocodiles.[5] In general V. salvadorii avoids human contact, but their bites are capable of causing infection, like the Komodo dragon’s.[5] One fatality is reported from a bite in 1983 when a Papuan woman was bitten and later died from an infection.[4]


The teeth of V. salvadorii do not resemble the teeth of other monitor species, which are typically blunt, peglike and face slightly rearward.[2] V. salvadorii’s upper teeth are long and fanglike standing vertical from the jawbone, designed to hook into fast-moving or feathered prey such as birds, bats, and rodents. Its lower teeth are housed in a fleshy sheath. In the wild it is the top predator in New Guinea, feeding on birds, eggs, small animals, and carrion.[9] There are reports from natives that it may take down pigs, deer, and hunting dogs, and that the monitor hauls its prey into the canopy to consume it.[2] Its only competition is the New Guinea Singing Dog. Captive specimens have been known to eat fish, frogs, rodents, chickens, and dog food.[4][19]

V. salvadorii has been observed hunting prey in a unique fashion for monitor lizards.[2] Rather than following its prey to ambush it from behind, V. salvadorii will stalk its prey and anticipate where it will run meeting it headlong.[2]


Reproduction has only been observed in captivity, so nothing is known about its reproduction in the wild. The egg clutches, comprising four to twelve eggs, are deposited around October to January, with the eggs showing a remarkable difference in dimensions, a phenomenon for which no explanation is known. Dimensions may vary from 7.5×3.4 cm (3.0×1.3 in) to 10×4.5 cm (3.9×1.8 in), while weight may vary from 43.3 to 60.8 grams (1.53 to 2.14 oz). Most clutches laid in captivity have been infertile, and there have only been four successful breedings documented thus far. Hatchlings are about 18 inches (45 cm) long and weigh around 56 grams (2.0 oz). Like that of many other monitors, the hatchlings of V. salvadorii are more colorful than adults and feed primarily on insects and small reptiles.[2][20]

Conservation status

V. salvadorii is currently protected under the Convention on International Trade of Endangered Species (CITES) Appendix II,[21] which requires an exportation permit for international trade. It is not listed on the IUCN Red List or the Endangered Species Act.[11] It faces threats from deforestation and poaching as it is hunted and skinned alive by native peoples to make drums, who consider the monitor an evil spirit that “climbs trees, walks upright, breathes fire, and kills men”.[4][9] The species is maintained at 17 zoological parks worldwide. The total U.S. captive zoo population totals 52 individuals and an unknown number in private collections

Varanus prasinus. Emerald Tree monitor

Varanus prasinus. Emerald Tree monitor 


The Emerald Tree monitor (Varanus prasinus), or the Green Tree monitor, is a small-to-medium-sized arboreal monitor lizard. It is known for its unusual coloration, which consists of shades from green to turquoise, topped with dark, transverse dorsal banding. This coloration helps camouflage it in its arboreal habitat.[2] It also makes the Emerald Tree monitor highly coveted by private collectors and zoos alike.[3]


Varanus prasinus was first described as Monitor viridis by John Edward Gray in 1831; however, Gray’s original holotype (RMNH 4812 in the National Natural History Museum in Leiden) was lost and the species was redescribed by Schlegel eight years later as V. prasinus using the found specimen.[4] The generic name Varanus is derived from the Arabic word waral (ورل), which translates to English as “monitor”.[5] Its specific name, prasinus, is Latin for the color green.

V. prasinus is a member of the Euprepiosaurus subgenus. It is closely related to several other arboreal species and when combined these are often referred to as the V. prasinus species group. In addition to V. prasinus itself, this species group, whose members are all allopatric, includes V. beccarii (Aru Islands), V. boehmei (Waigeo Island), V. bogerti (D’Entrecasteaux Archipelago), V. keithhornei (Cape York Peninsula), V. kordensis (Biak Island), V. macraei (Batanta Island), V. reisingeri (Misool Island) and V. telenesetes (Rossel Island).[6][7]

Evolutionary development

The evolutionary development of V. prasinus started with the Varanus genus, which originated in Asia about 40 million years ago and migrated to Australia and the Indonesian archipelago around 15 million years ago.[8]


Emerald tree monitors and their close relatives can be found in New Guinea, as well as several adjacent islands,[9] and the northern Torres Strait Islands.[10] The green tree monitor is reported to thrive in lowland environments including tropical evergreen forests, palm swamps and cocoa plantations.[10]


The emerald tree monitor is about 75–100 centimetres (30–39 in) long with a slender body that helps it support itself on narrow branches. It also has a prehensile tail and long claws that it uses to grip branches.[2][11][12] Unlike other varanids this monitor defends its tail rather than lashing with it for defense when threatened.[13] The soles of the feet of the emerald tree monitor have enlarged scales which aid the lizard when climbing.[12]


When threatened, the emerald tree monitor will flee through vegetation or bite if cornered. It is one of the few social monitors, living in small groups made up of a dominant male, several females, and a few other males and juveniles.[2]


The emerald tree monitor’s diet consists of large tree dwelling insects such as katydids, stick insects, cockroaches, beetles, centipedes, spiders, crabs, birds, and small mammals. Before swallowing stick insects, the lizards tear off the legs.[9] Captive specimens tear off the limbs of rodents prior to eating them and as a result they are capable of swallowing mammals of a considerable size: A 135-gram (4.8 oz) lizard was documented as eating a 40-gram (1.4 oz) rodent, an animal almost one-third its size. Paleontologist and Biology Professor at Temple University, Michael Balsai has observed V. prasinus eating fruit(bananas) in captivity as has herpetologist and author, Robert G. Sprackland.[14][13]


Clutches consist of up to five eggs, each weighing 10.5–11.5 grams (0.37–0.41 oz) and measuring about 2 by 4.5 centimetres (0.79 in × 1.8 in). As many as three clutches are laid throughout the year; captive clutches have been laid in January, March, April, November, and December. The female emerald tree monitor lays her eggs in arboreal termite nests.[12] The eggs hatch between 160–190 days, typically from June to November after which the young eat the termites and the termite’s eggs within minutes of hatching.[12] Sexual maturity is reached in about two years

Varanus melinus, quince monitor

Varanus melinus, quince monitor 


The quince monitor (Varanus melinus) is a species of monitor lizard, endemic to Indonesia. It is very closely related to the mangrove monitor (Varanus indicus), with both belonging to the subgenus Euprepiosaurus.[1]


The quince monitor has a bright yellow head, legs, back and tail. Varanus melinus has a black reticulation on the lower part of its neck. The tail has alternating bands of yellow and black which get pale toward the last third. Its tongue is light pink in color with little variation. The quince monitor’s nostril is situated closer to the tip of its snout than to its eye. This species can reach 80–120 cm in total length.[1]


Varanus melinus is likely endemic to the Sula Islands in Indonesia, but there are also reports that it may occur in Banggai.[4] Initially it was reported to originate from the Obi Islands, but this was only an intermediate wildlife trade station.[4] It is threatened by habitat loss and collection for the wildlife trade

Varanus macraei, Blue Spotted Tree Monitor

Varanus macraei, Blue Spotted Tree Monitor


The Blue Spotted Tree Monitor, Varanus macraei, is a species of Monitor lizard found on the island of Batanta in Indonesia. It is named after Duncan MacRae, founder of the reptile park “Rimba” on Bali. [1]


Varanus macraei is black with scattered blue scales, forming spots that may in turn form bands across the back. The tip of the snout is light blue and the lower jaw, white. The underside of the legs is uniformly pale turquoise.

The tail is prehensile and about twice the snout-to-vent length (SVL).

V. macraei can grow to an SVL of 35 centimetres (14 in) and total length of 100 centimetres (39 in).[2]

The blue tree monitor can vary from blue to black to gray, and it can have spots or stripes.


Distribution of V. macraei is limited to the island of Batanta, off the northwest coast of Irian Jaya.

Varanus gouldii, Gould’s monitor

Varanus gouldii, Gould’s monitor


The Sand goanna is a large Australian monitor lizard – also known as Gould’s monitor, the Sand monitor, or Racehorse goanna.[1]

In some Aboriginal languages, the sand goanna is called Bungarra,[2] a term commonly used by non-aboriginal people in Western Australia, too.

The name sand monitor can be used to describe various other species. The Gould’s monitor is a terrestrial or “ground-dwelling” reptile that excavates large burrows for shelter. Rock escarpments and tree hollows are also suitable dwellings. Varanus gouldii inhabits a vast range throughout Australia. The Gould’s monitor reaches an average length of 140 cm (4.6 ft) and can weigh as much as 6 kg (13 lb). They can be found in Northern and Eastern Australia where they inhabit open woodlands and grasslands. Varanus flavirufus, a subspecies resides in Australia’s interior. There are some places however where the ranges of Gould’s, Flavirufus and Argus monitors overlap. The similarities between the species and their close proximity frequently cause confusion.

The Sand monitor is a relentless forager. It is diurnal meaning most of its activities take place during the day. Anything smaller than itself will be eagerly devoured. The diet of hatchlings and juveniles often consists mostly of insects and small lizards but generally varies more with age. Adult monitors will prey on mice, large insects, small agamids and geckoes, smaller varanids, snakes, and carrion. Gould’s monitor does consume smaller species of monitor. Ackies, Rock Monitors and other dwarf species are often found and eaten. It is common to see a Gould’s disturbing rock piles in an attempt to flush out any odatria. It lays it eggs in termite mounds to protect it eggs from the harsh desert climate.

Goannas, like snakes, have forked tongues which they regularly flick side to side near the ground or amongst leaf litter and are thought to looking for olfactory clues to prey.[3]


  • Gould’s Goanna (V. g. gouldi)
  • Desert Sand Monitor (V. g. flavirufus)

Varanus jobiensis, Peach Throat Monitor

Varanus jobiensis, Peach Throat Monitor 


The Peach Throat Monitor (Varanus jobiensis) is a species of Monitor lizard, native to New Guinea. It belongs to the subgenus group Euprepiosaurus along with the Ceram Mangrove monitor and Finsch’s Monitor.[2] They grow up to 120 cm long. The colour of the throat, for which they are named, is white-yellow to red. They eat insects, frogs, freshwater fish and small mammals

Varanus indicus, Mangrove Monitor

Varanus indicus, Mangrove Monitor


Varanus indicus, also known as the Mangrove Monitor[2], Mangrove Goanna, or the Western Pacific monitor lizard, is a member of the monitor lizard family with an enormous distribution from northern Australia and New Guinea to the Solomon Islands, Marshall Islands, Caroline Islands, and Marianas Islands. It grows to lengths of 3.5 to 4 feet (1.1 to 1.2 m).


Varanus indicus was first described by the French herpetologist François Marie Daudin in 1802.[1] Daudin’s original holotype of a subadult specimen was collected on Ambon, Indonesia, and has since disappeared from the museum in Paris. Daudin’s original name for the species was Tupinambis indicus, an appellation it would carry for 75 years until being renamed as a Varanus.[3]

The generic name Varanus is derived from the Arabic word waral (ورل), which translates to English as “monitor.”[4] Its specific name, indicus, is Latin for the country of India, however, in this instance it relates to Indonesia or the East Indies, where the animal was first described.[3]

Due to its large geographic range, Varanus indicus is considered a cryptic species complex of at least four species: Varanus indicus, Varanus doreanus,Varanus spinulosus, and Varanus jobiensis.[5] More research is being done on possible future species within this complex, not surprising since it has had over 25 different scientific names since it was first described.[3]

Distribution and habitat

The Mangrove monitor’s range extends throughout Australia, New Guinea, the Solomon Islands, the Marshall Islands, the Caroline Islands and the Marianas Islands, where it inhabits damp forests near coastal rivers, mangroves, and permanent inland lakes. It also occurs on the Moluccan islands of Morotai, Ternate, Halmahera, Obi, Buru, Ambon, Haruku, and Seram. Within this range of thousands of miles across hundreds of islands there is a huge amount of variation in size, pattern and scalation.[3] The monitors have also been introduced to Japan since the 1940s.[6] Like the introduction to Japan, some herpetologists believe this animal’s dispersal from the East Indies to smaller Pacific islands was facilitated by Polynesians in order to provide a meat supply. However, other scientists maintain this is not likely as the monitors would compete with man for food, grow slowly, and yield little meat.[7]

Anatomy and morphology

The monitor’s body is dark green or black in color and covered with golden yellow spots, with light coloration on the top of the head and a solid, cream colored belly lacking dark markings.[3] It has a distinct dark purple tongue and serrated teeth.[3][8] The mangrove monitor attains different sizes in different parts of its range, but seldom if ever exceeds 1.5 meters in total length.[3] Australian herpetologist Harold Cogger gives a total length of 100 cm for Australian specimens.[9] The tail is almost two times the length of the body and laterally compressed to aid in swimming. Like the rest of the lizard’s body it is covered with small, oval, keeled scales.[8]

This monitor has the ability to increase the size of the mouth by spreading the hyoid apparatus and dropping the lower jaw in order to eat large prey, a process similar in appearance to that of snakes, although the jaw of the mangrove monitor remains rigid.[10] Mangrove monitors possess a Jacobson’s organ which they use to detect prey, sticking their tongue out to gather scents and touching it to the opening of the organ when the tongue is retracted.[8]

The mangrove monitor is one of only two species of monitor lizard, the other being Varanus semiremex, that possess salt-excreting nasal glands, which enable them to survive in saltwater conditions and to consume marine prey.[7] The presence of this gland probably enabled the monitors to reach new islands and aid in its dispersal throughout the Pacific.[8]


The Mangrove monitor is an opportunistic carnivore feeding on the eggs of reptiles and birds, mollusks, rodents, insects, crabs, smaller lizards, fish, and carrion.[9][11][12] Mangrove monitors are the only monitor capable of catching fish in deep water.[13] In some parts of its range it is known to eat juvenile crocodiles.[3]

A study done in 1993 showed that mangrove monitors in the Southern Mariana Islands shifted major prey classes when their regular prey began declining.[6] The monitors were known for eating shrews on Guam,[4] but the introduction of the brown tree snake (Boiga irregularis) led to decreased shrew numbers, prompting the monitors to switch to eating invertebrates and foraging through human garbage.[4][6]


The species lacks distinct sexual dimorphism, however mature male monitors on Guam have been reported to be three times the mass of mature females.[4] Males fight for females and in one observation, after mounting the female, the male used his chin to rub the dorsum of the female’s head and forequarters.[6] It was also observed that while mounted and oriented head to head, the male and female slowly rotated in a clock-wise direction through 360 degrees with the male remaining superior.[6]

Female mangrove monitors lay 2-12 eggs that measure 3.5 to 5 cm in length. The oblong eggs are white, and hatch in about 7–8 months.[8]

The first successful captive breeding of this species was at the Philadelphia Zoo in 1993.

The Reptilian Zoo in Vlissingen, the Netherlands [14], reports that they have successfully hatched eggs by a female animal that was not in any contact with a male of the same species.

Contact with humans

Humans have introduced the mangrove monitor to a number of Pacific Islands since the 1930s.[12][15] They have been present on Ifaluk in the western Caroline Islands since the Second World War.[15] The Japanese introduced the lizards to the Marshall Islands prior to World War 2 to eliminate rats; the lizards flourished and soon began to raid the local chicken houses.[12] When American troops arrived, the locals asked them for help in getting rid of the mangrove monitors. The US response was to introduce the marine toad (Bufo marinus) which proved toxic to the lizards.[12] As the monitor population dropped, however, the rat population began to rise.[12] Marine toads were introduced to the Palau Islands for a similar reason, and the demise of the mangrove monitors led to an increase in numbers of beetles known to be harmful to coconuts.[15]

The mangrove monitor is hunted in many places for its skin which is used for leather in making drum heads.[16][17] Although international trade in this species is small, Mertens referred to it as one of the most heavily exploited monitor lizards.[17] In 1980 trade in over 13,000 monitors was declared. However in many remote places they are used as a food source and are killed because of their reputation for preying on domestic animals.[8] There is an ethnic group on Guam that eats the monitors as a traditional food and a business exists there that sells monitors for food.[6]

The United States Department of Agriculture’s Animal and Plant Inspection Service division, announced that it will use a combination of two poisons, diphacinone and brodifacoum, to kill off the rodents on Cocos Island. They will also attempt to lower the mangrove monitor population on Cocos Island by 80%, using a myriad of trapping methods proposed by herpetologist Seamus Ehrhard, as the lizard is believed to prey upon the endangered Guam Rail (Gallirallus owstoni). Most locals, however, do not see the monitor as an invasive species and a few activists are opposed to the attempt to lower the population on Cocos Island.

Mangrove monitors are often kept in zoos and private collections as they are an active and alert animal that generally can be handled if tamed properly.[11] Most specimens defecate on their handlers when stressed.[8] With proper care they can live up to 20 years in captivity.

Varanus dumerilii, Dumeril’s monitor

Varanus dumerilii, Dumeril’s monitor 


Dumeril’s monitor (Varanus dumerilii)[3] is a member of the Varanidae family found in Southeast Asia. It is found in southern Burma and north of the Isthmus of Kra to Kanchanaburi Province in Thailand.[4] Varanus dumerilii is also found in peninsular Malaysia, throughout Borneo, Sumatra, Riou and other smaller islands of Indonesia.[5] Their habitat is dense evergreen forests with high humidity [6] and mangrove swamps.[7] They were more common in the pet trade in the 20th century, but are rarer now.

Dumeril’s monitors is a crab specialist; however, they will also eat snails, insects, molluscs, fish, frogs, and smaller rodents.[7] Little is known overall about this species compared to other monitor lizards.[10]


Adult Dumeril’s monitors are largely dark coffee-brown in colour, with occasional brighter indistinct crossways bars. For juveniles the colors and patterns are quite different. “The major color is a dark varnish black which is interrupted by several yellow crossways bars on the back.” Juveniles have shiny orange red or, sometimes yellow heads. This youth coloration disappears again after only 4–8 weeks.[10]


There are two subspecies:

  • Varanus dumerilii dumerilii (Schlegel, 1839)
  • Varanus dumerilii heteropholis (Boulenger, 1892)[2]

Note: Sprackland made V. d. heteropholis a synonym of V. d. dumerilii