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Varanus salvadorii

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Varanus salvadorii
Varanus salvadorii at the Cincinnati Zoo
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Order:
Squamata
Suborder:
Lacertilia
Family:
Varanidae
Genus:
Varanus
Subgenus:
Papusaurus
Species:
V. salvadorii
Binomial name
Varanus salvadorii
Peters and Doria, 1878[1]
Estimated range of V. salvadorii, indicated by green.[2]

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.[3] 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 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.[3]

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.[4]

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.[5]

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).[6]

Distribution

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 northern region of the Indonesian Province of Irian Jaya. 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.[3][2] Its remote and generally inaccessible habitat is the main factor in preventing detailed study of this animal in its natural habitat.[3][2]

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.[3] The body of the lizard is dark green with rings of yellow spots.[7] The tail is banded yellow and black. It has long straight teeth and prominent curved claws. There is no external sexual dimorphism.[8]

Unique among living varanid species, the animal's tail is two-thirds longer than the snout-to-vent length in both juveniles and adults.[3] Herpetologist Robert Sprackland gives the proportion as the tail being 210% of the animal's body length.[9] At birth V. salvadorii is about 45 cm (18 in) long, while a sexually mature female may grow to 150 cm (4.9 ft).[10] The longest recorded specimen is 244 cm (8.01 ft) in length,[11] but it has been speculated that it may grow longer.[9][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][13] 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.[13][14] 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][13] This would suggest that the lizard is at an evolutionary midpoint, relying on both forms of breathing.[13]

Behavior

A specimen of V. salvadorii at the Oklahoma City Zoo.

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.[15] This species is occasionally seen in the pet trade, but has earned a reputation of being aggressive and unpredictable.[3] 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).[4] According to native belief, they will give a warning call if they see crocodiles.[4] In general V. salvadorii avoids human contact, but their bites are capable of causing infection, like the Komodo dragon's.[4] One fatality is reported from a bite in 1983 when a Papuan woman was bitten and later died from an infection.[3]

Diet

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.[8] 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", a feral dingo. Captive specimens have been known to eat fish, frogs, rodents, chickens, and dog food.[3][16]

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

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 7.5x3.4 cm (3.0x1.3 in) to 10x4.5 cm (3.9x1.8 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][17]

Conservation status

V. salvadorii is currently protected under the Convention on International Trade of Endangered Species (CITES) Appendix II,[18] which requires an exportation permit for international trade. It is not listed on the IUCN Red List or the Endangered Species Act.[10] It faces threats from deforestation and poaching as it is hunted and skinned alive by tribesmen to make drums, who consider the monitor an evil spirit that "climbs trees, walks upright, breathes fire, and kills men".[3][8] 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.[7]

References

  1. ^ a b Klipfel, Meghan; Peters, Wilhelm C. H.; Bauer, Aaron M.; Günther, Rainer (1995). The herpetological contributions of Wilhelm C. H. Peters (1815-1883). Ithaca, N.Y., USA: Society for the Study of Amphibians and Reptiles in cooperation with Deutsche Gesellschaft für Herp. ISBN 0-916984-35-4.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ a b c d e f g h i j k l m Horn, H-G. (2004). "Varanus salvadorii". In Pianka, E.R., King, D., and King, R.A. (ed.). Varanoid Lizards of the World. Indiana University Press. pp. 234–244. ISBN 0253343666. Retrieved 2008-11-24.{{cite book}}: CS1 maint: multiple names: editors list (link)
  3. ^ a b c d e f g h i j Bayless, Mark K. (June 1, 1998). "The Artellia: Dragons of the Trees". Reptiles. 6 (6). Mission Viejo, California: Norman Ridker: 32–47. {{cite journal}}: |access-date= requires |url= (help)
  4. ^ a b c d Netherton, John; Badger, David P. (2002). Lizards: A Natural History of Some Uncommon Creatures--Extraordinary Chameleons, Iguanas, Geckos, and More. Stillwater, MN: Voyageur Press. pp. 140–141. ISBN 0-7603-2579-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  5. ^ Ciofi, Claudio. "The Komodo Dragon". Scientific American. Retrieved 2006-12-21.
  6. ^ Pianka, Eric. "Evolution of Varanid Lizards". Retrieved 2008-12-07.
  7. ^ a b "New Guinea Crocodile Monitor". Central Florida Zoo and Botanial Gardens. Retrieved 2008-08-21.
  8. ^ a b c "Crocodile Monitor". Leeward Community College's Zoology 101. Honolulu Zoo. Retrieved 2008-08-21.
  9. ^ a b Robert George Sprackland (1992). Giant lizards. Neptune, NJ: T.F.H. Publications. ISBN 0-86622-634-6.
  10. ^ a b "Crocodile Monitor". Retrieved 2008-12-07.
  11. ^ "Varanus salvadorii". Retrieved 2008-10-31.
  12. ^ Folkard, Claire (2003). Guinness World Records 2003. Guinness World Records Ltd. p. 87. ISBN 1-892051-17-6.
  13. ^ a b c d Owerkowicz, Tomasz (4 June 1999). "Contribution of Gular Pumping to Lung Ventilation in Monitor Lizards". Science. 284. www.sciencemag.org: 1661–1663. doi:10.1126/science.284.5420.1661. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); line feed character in |coauthors= at position 37 (help)
  14. ^ Brainerd, Elizabeth (1999). "Research by UMass Amherst Biologist Suggests that Lizards Offer Evolutionary Freeze-Frame". UMass Amherst. Retrieved 19 December 2008. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help)
  15. ^ Stafford, Grey. "Aloha to three crocodile monitors". Wildlife World Zoo. Retrieved 2008-08-21.
  16. ^ McDade, Melissa C.; Grzimek, Bernhard; Schlager, Neil; Hutchins, Michael; Trumpey, Joseph E.; Olendorf, Donna (2004). Grzimek's Animal Life Encyclopedia. Detroit: Thomson/Gale. p. 368. ISBN 0-7876-5362-4.{{cite book}}: CS1 maint: multiple names: authors list (link)
  17. ^ Gressitt, J. Linsley (1982). Biogeography and Ecology of New Guinea. Vol. 2. Hague: W. Junk. pp. 803–813. ISBN 90-6193-094-4.
  18. ^ "Appendices I, II and III". Retrieved 2008-11-08.
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