Overview

Brief Summary

Vavanus bitatawa is a 6 foot (2 meters), brightly colored monitor lizard that was hidden from science in the heavily deforested island of Luzon in the Philippines until 2009. Large terrestrial lizards rarely go unnoticed, and with its black and gold patterned scales, V. bitatawa is relatively conspicuous (Welton, et al. 2010).

It may be big, colorful, and inhabit a heavily populated area--Luzon is host to the three largest cities in the Philippines, including Manila, Quezon City, and Caloocan City--but V. bitatawa was unknown to scientists until 2009. The scientists who first recorded seeing the species suspect V. bitatawa, like its close relative V. olivaceous, is secretive and "hides" in trees (Welton, et al. 2010) (Read more: Behavior).

While the lizard was still absent from scientists' biodiversity register, it was well known to the indigenous Agta and Ilongot tribespeople, who regard it as a rich source of protein. In fact, the name Bitatawa is derived from the Agta tribe's common name for the species.(Welton, et al. 2010)

Despite its elusive nature, V. bitatawa cannot hide from the deforestation activity that is threatening its habitat in the northern Sierra Madre mountains. Locals are tearing down the forests for logging, both legal and illegal, and small-scale subsistence agriculture. The Philippines were thought to be nearly completely covered in primary forest, but in the late 1990s, studies showed less than 6 percent of the land cover retained intact lowland forest. Since then, reports show more forests are being cleared. Scientists say they hope charismatic species like V. bitatawa can become effective flagship species for conservation efforts for Luzon's forests (McGinely and WWF 2008) (Read more: Trends and Threats).

  • McGinely, Mark, and WWF. Luzon rain forests. Edited by Cutler J. (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment) Cleveland. August 22, 2008. www.eoearth.org/article/Luzon_rain_forests (accessed August 2010).

    Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.

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Comprehensive Description

Etymology

The specific epithet for this species is derived from bitatawa, the Agta tribespeoples' common name for this species throughout much of its distribution.

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Biology

Varanus bitatawa is one of three species of primarily frugivorous monitor lizards (Subgenus: Philippinosaurus), all of which are endemic to the Philippines. This species exhibits a dark gray dorsal ground color overlain with bright yellow-gold dorsal bands, comprised of transverse series of ocelli. Tail with unbroken dorsal bands.

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Distribution

Faunal Affinity

Luzon Pleistocene Aggregate Island Complex

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Varanus bitatawa is known only from central and northern portions of the Sierra Madre mountains of northern Luzon Island, Philippines. Based on the localities of the type series and photographic accounts, this species is expected to inhabit suitable habitat from the San Ildefonso Peninsula (Aurora Province), north through Isabela and Cagayan provinces to Peñablanca and Baggao municipalities.

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Continent: Asia
Distribution: Philippines (Luzon)  
Type locality: San Ildefonso Peninsula, Sitio Casapsipan, Barangay Casiguran, Municipality of Casiguran, Aurora Province, Luzon Island, Philippines (16.286667° N, 122.185833° E, WGS-84; 1 m elevation.
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V. bitatawa are found in central and northern Sierra Madres in Luzon in the Philippines (Welton, et al. 2010).

  • Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.
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Physical Description

Size

V. bitatawa has a large, robust body. Its dorsal side is black and golden, and the head is black speckled with yellow. The forelimbs are more yellow than black, while the hind limbs are black with large yellow spots. The tail is striped with black and yellow. Its nares, or nostrils, are anteriorly directed. Like other members of its genus, V. bitatawa displays hemipenal morphology (Welton, et al. 2010).

  • Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.
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Diagnostic Description

Varanus bitatawa generally exhibits a dark gray to black dorsal ground color, overlain by highly contrasting bright yellow or golden yellow blotches and spots. Head and neck with irregularly arranged bright gold blotches ususally consisting of 1-8 scales, density of brightly colored scales incresing anterolaterally on head. Trunk generally patterned with a series of transverse bands comprised of variably-sized yellow to gold oscelli; bands may be interspersed with smaller irregular blotches; limbs colored similar to body, but often with less discernable bands, and gold coloration becoming more prominent distally; hands and feet primarily golden yellow, with irregular aggregations of black scales; digits variably banded golden-yellow, often with single enlarged yellow terminal scale sheathing the claw; tail with regular golden-yellow bands from insertion to terminus, with alternating black bands containing small irregular yellow blotches. Ventral coloration less variable, bright yellow; gular and nuchal regions slightly darker; limbs similar to body; hands and feet black, except for a variable number of golden-yellow terminal scale rows; tail uniform yellow ventrally. Tongue is pinkish gray, and the iris is brick red.

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V. bitatawa has a large, robust body. Its dorsal side is black and golden, and the head is black speckled with yellow. The forelimbs are more yellow than black, while the hindlimbs are black with large yellow spots. The tail is striped with black and yellow. Its nares, or nostrils, are anteriorly directed. Like other members of its genus, V. bitatawa displays hemipenal morphology (Welton, et al. 2010).

  • Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.
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Look Alikes

Superficially, Varanus bitatawa may be confused with species of Philippine water monitors (V. marmoratus, V. cumingi, or V. palawanensis) based on the presence of golden-yellow dorsal patterning, but can easily be distinguished from those species by characteristics of body size, behavior, and dietary preference.

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Ecology

Habitat

Varanus bitatawa is assumed to be a forest obligate (as has been documented with its closest relatives V. mabitang and V. olivaceus), and is heavily dependent upon unfragmented lowland and mid-elevation forests with sufficient stands of fruiting Pandanus, Canrium, or Ficus trees.

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V. bitatawa inhabits the northern forests in the Sierra Madre Range on Luzon Island in the Philippines (Welton, et al. 2010).

  • Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.
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General Ecology

Ecology

As with the other two species of frugivorous monitors, Varanus bitatawa is a predominately arboreal species, spending vast amounts of time in the canopies of fruiting trees. During dry periods, it can be expected to transition to a more terrestrial lifestyle in search of a preferred secondary food source, snails.

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Life History and Behavior

Behavior

Behaviour

Although no behavioral studies have been on this species, it is assumed to be very similar to its closest relative, Varanus olivaceus. All frugivorous monitors are highly secretive, and rarely seen through chance encounters. Gray's monitor has been documented spending several days at a time in the tops of fruiting trees, decending to the ground only to move to the next tree.

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V. bitatawa is suspected of being a secretive species like its closest relative, Varanus olivaceus, meaning it never leaves the forests to traverse open areas. (Welton, et al., 2010)

  • Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.
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Conservation

Conservation Status

Varanus bitatawa is designated as a CITES Appendix II species. This taxon is not currently threatened by extinction, but may become so unless trade or other factors are closely monitored.

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Conservation

Varanus bitatawa has only recently been introduced to the scientific community, and consequently must be considered data-defficient when assessing its conservation. This species is targeted as a bush meat delicacy by local tribespeoples, and despite a relatively wide distribution, is likely highly impacted by harvest and habitat degradation.

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V. bitatawa is not yet included in the IUCN Red List of Threatened Species. Its closest relative, Varanus olivaceus is listed as Vulnerable (IUCN, 2010).

  • IUCN. (2010). IUCN Red List of Threatened Species, 2010.2. Retrieved August 2010, from www.iucnredlist.org
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The habitat of V. bitatawa is highly deforested. Scientists hope large vertebrate species like V. bitatawa will act as flagship species for conserving the forests in Luzon (Welton, et al. 2010).

The island's mountain ranges and river valleys create disparate habitats allowing for differential evolution of related taxa. This means the biodiversity in the region may be richer than previously thought, and the Philippines may be well on their way to being listed as a biodiversity hotspot. Threats to V. varanus's habitat include legal and illegal logging, unsustainable hunting and the construction of roads that transect the forests (Lamoreux, 2001).

  • Lamoreux, J. (2001). Luzon Rain Forests. In E. Wikramanayake, E. Dinerstein, & C. Loucks, Terrestrial ecosystems of the Indo-Pacific: a conservation assessment. Washington, D.C.: Island Press.

    Welton, L., Siler, C., Bennett, D., Diesmos, A., Duya, M., Ruday, R., et al. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biol. Lett. Published online: April 7, 2010. DOI: http://dx.doi.org/10.1098/rsbl.2010.0119.

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Threats

The most severe threat to this species is likely habitat loss or degradation. Assessing the full impact of bush meat harvesting on V. bitatawa requires future investigations.

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Management

Varanus bitatawa is likely a forest obligate, requiring relatively large tracts of intact habitat. Specifically, the protection of habitat which includes dense populations of this species' prefered fruiting trees (Pandanus, Canarium, and Ficus) will be essential for maintaining this species in the future.

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Wikipedia

Northern Sierra Madre forest monitor

The Northern Sierra Madre forest monitor, Varanus bitatawa, also known by the local names bitatawa, baritatawa, and butikaw, is a large, arboreal, frugivorous lizard of the genus Varanus.[1][2] The lizard is a staple food of the Aeta and Ilongot indigenous people of the Philippines.[3]

Physical description[edit]

A dorsal view of Varanus bitatawa with inset showing a lateral view of the head

The forest monitor lizard can grow to more than 2 m (6.6 ft) in length, but weighs only about 10 kg (22 lb). "Its scaly body and legs are a blue-black mottled with pale yellow-green dots, while its tail is marked in alternating segments of black and green."[4] Dorsal ground coloration is black, "accentuated with bright golden yellow in life, while the dorsum is golden yellow spots and flecks.[1]

News reports emphasized that males have hemipenes, paired penis-like organs.[4][5] However, all male lizards and snakes have hemipenes.[6]

Behavior[edit]

V. batawaka is one of only three frugivorous lizards in the Varanidae family Along with V. olivaceus One of only three frugivorous monitor lizards in the world,.[1]

The forest monitor specializes in eating the fruit of Pandan palm trees.[7] They spend most of their time in trees, more than 20 meters above the ground; similar species spend less than 20 minutes on the ground per week.[8]

Taxonomy and distribution[edit]

V. bitatawa is closely related to the Komodo dragon of Indonesia. It was confirmed as a new species in April 2010 by biologists from the University of Kansas. DNA analysis has revealed a deep genetic divergence between this species and its closest relative, Gray's Monitor (Varanus olivaceus), which is also a fruit-eater, but lives on the southern end of Luzon, rather than the northern end where the forest monitor lizard lives.[1]

The lizard's known range is currently limited to the Sierra Madre Forest, in the northeastern coast of the island of Luzon, Philippines.

References[edit]

  1. ^ a b c d Welton, L. J.; Siler, C. D.; Bennett, D.; Diesmos, A.; Duya, M. R.; Dugay, R.; Rico, E. L. B.; Van Weerd, M.; Brown, R. M. (2010). "A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation". Biology Letters 6 (5): 654–658. doi:10.1098/rsbl.2010.0119. ISSN 1744-9561. PMC 2936141. PMID 20375042. 
  2. ^ "Third Quarter Topical Issue – Philippine Endemic Lizards". PHLPOST. Philippine Postal Corporation. 20 July 2011. Retrieved 11 December 2013. 
  3. ^ Milius, S. (6 April 2010). Scientists Name Large But Elusive Lizard. Science News. Retrieved 6 April 2010{{inconsistent citations}} 
  4. ^ a b AFP (7 April 2010). "New giant, double-penis lizard - Varanus bitatawa or monitor lizard - found on Luzon Island in the Philippines". Herald Sun. Retrieved 11 April 2013. 
  5. ^ Liyu, Lin (7 April 2010). "Lizard with 2 penises found in Philippines". Xinhuanet.com. Retrieved 7 April 2010{{inconsistent citations}} .
  6. ^ "Hemipenes"{{inconsistent citations}} 
  7. ^ "New Lizard Species Discovered in Philippines". Leiden University Research Portal News. Retrieved 11 December 2013. 
  8. ^ Owen, James (7 April 2010). "New Giant Lizard Discovery "an Unprecedented Surprise"". National Geographic News (National Geographic). Retrieved 11 December 2013. 
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