Earless monitor lizard

Source: Wikipedia, the free encyclopedia.

Earless monitor lizard
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Superfamily: Varanoidea
Family: Lanthanotidae
Steindachner, 1877
Genus: Lanthanotus
Steindachner, 1878
Species:
L. borneensis
Binomial name
Lanthanotus borneensis

The earless monitor lizard (Lanthanotus borneensis) is a

only living species in the family Lanthanotidae and it is related to the true monitor lizards.[3][4][5]

Taxonomy

The earless monitor lizard was

Shinisauridae; at a higher level the sister groups of these three are Helodermatidae and others families in Anguimorpha.[9][10] The most recent common ancestor diverged in the mid-Cretaceous.[5][12]

The extinct Cherminotus known from Late Cretaceous fossil remains in Mongolia has been considered a member of Lanthanotidae, but this is disputed.[13]

Distribution and habitat

The earless monitor lizard is endemic to the Southeast Asian island of Borneo, where it is known from Sarawak in East Malaysia, as well as West and North Kalimantan in Indonesia.[14][15][16] Until late 2012, its known range in North Kalimantan was a part of East Kalimantan.[17] It was also confirmed to be found in Brunei for the first time in 2022, in the country's Temburong District.[18] Prior to the discovery, it was believed that they may occur there and has been recorded c. 100 km (60 mi) from the border.[19] There are no records from Sabah, Central Kalimantan or South Kalimantan.[16][19]

It is found in lowlands at elevations below 300 m (1,000 ft) near streams and marshes.

rice paddies.[14][16][20] The streams it inhabits are often rocky.[14][16] Its habitat is tropical with air and water temperatures that generally are about 22–29 °C (72–84 °F),[15][16] and captives reportedly prefer 24–28 °C (75–82 °F).[22] At a site with a high density of earless monitor lizards the water was clear and had a neutral pH.[16] It is associated with the same microhabitat as Tropidophorus water skinks and in some places its range overlaps with T. brookei.[16]

Appearance

Earless monitor lizards have a cylindrical body, long neck, short limbs, long sharp claws, small eyes, semitransparent lower eyelids, and six longitudinal rows of strongly keeled scales.[20][23] Despite the name, they are capable of hearing, although lack a tympanum, an ear opening and other externally visible signs of ears.[4][24] The upperparts are orangish-brown, and the underside is mottled dark brown and whitish, pale yellowish, ochre or rusty.[7][14][20] The tail is prehensile and if it is lost, it is not regenerated.[23] The skin is shed infrequently, possibly less than once a year.[23] There are both reports of the skin shedding in one piece (similar to snakes),[23] or in smaller pieces (as typical of lizards).[25] Overall the sexes are alike, but males have a distinctly broader head and broader tail base than females.[16] The differences between the sexes are clearly noticeable from an age of about three years.[26] They sometimes oscillate the throat (similar to frogs) and the forked tongue is sometimes flicked (similar to snakes).[16] They can make a gentle, squeaky vocalization.[16]

Size

Adult earless monitor lizards typically have a snout-to-vent length (SVL) of about 20 cm (8 in),[20] and a total length of about 40 cm (16 in).[25] Eighteen wild individuals, six males and twelve females, ranged from 15.6 to 22 cm (6.1–8.7 in) in SVL, 17.4 to 22.1 cm (6.9–8.7 in) in tail length (disregarding one individual missing much of its tail), and 48 to 120 g (1.7–4.2 oz) in weight (disregarding one sickly and skinny individual).[16] Among these, the largest total length (SVL+tail) was a male that measured 44.1 cm (17.4 in), which also is the longest recorded in the wild.[16] A specimen collected in the 1960s has a total length of 51 cm (20 in),[7] and near the time of its death an individual kept at the Bronx Zoo from 1968 to 1976 had a total length of 47 cm (18.5 in) and weighed 209 g (7.4 oz), but it was highly obese.[27] When hatching the total length of the young is about 7–14 cm (3–6 in).[15][28][29] When one year old, their total length is about 23–25 cm (9–10 in).[30]

Behavior

Earless monitor lizards are generally strictly nocturnal animals, although exceptionally daytime observations in the open have been reported.[14][16] The day is usually spent near water in burrows that can be up to 30 cm (1 ft) long or under logs, rocks or vegetation.[5][20] They are generally quite inactive and not agile, but can make surprisingly fast spurts when startled,[16] and will rapidly catch prey items placed in front of them.[28] During one study where 19 individuals were located during the night, about half were in the water and the other half near water on land.[16] In captivity they sometimes remain virtually immobile underwater for hours, periodically lifting the nose above the water's surface to breathe.[31] When underwater, the semitransparent lower eyelids are generally closed, covering the eyes.[16] It has been speculated that the prehensile tail is wrapped around stones, roots and other things underwater to avoid being swept along during floods.[28]

Bite

See also: Toxicofera

Although generally docile and inactive when handled, males are usually more aggressive than females when caught.

blood clotting reportedly being slower than in normal wounds.[25] Recent studies have found both venom glands,[32] and toxic compounds in the bite of this species.[33] The main components are kallikreins (to a lesser degree CRiSP) with the primary effect being the cleaving of fibrinogen, which is important for blood clotting.[33] However, this effect is quite weak in the venom of the earless monitor lizard compared to that of many other venomous reptiles, including some of the true monitor lizards.[34]

Feeding

They typically feed on earthworms, crustaceans and fish.[20] In captivity, they will eat fish (both whole and pieces), earthworms, squid, shrimp, tadpoles, yolk from green sea turtle eggs, pieces of pig and chicken liver, baby mice and mussels, but refuse to take bird eggs and legs of frog.[16][27][29][31] In captivity adults typically eat once or twice per week, but sometimes enter longer periods where they do not feed.[31] Unusually for a lizard, they can swallow prey while submerged underwater.[27] They appear to be able to do this by draining water from their nostrils, similar to turtles.[28]

Breeding and life cycle

Like their closest relatives, they are

oviparous, although little is known about their reproduction.[4] Based on captive observations a pair will mate repeatedly over a period of a few months, with each session lasting for hours.[35] In one case, a single mating lasted 44 hours.[28] They mate in the water.[35][36] In the wild mating has been seen in February,[5] and a female caught in April was likely gravid.[16] The 2–12 (average 8) oval eggs measure about 3 cm (1.2 in) long and have a leathery white shell.[7][20][28][37] They are deposited on land.[37] In captivity the eggs hatch after about three months at a temperature of 27 °C (81 °F).[28][29] Adult males are likely territorially aggressive, as a survey of a locality found twice as many females as males, and most of the males (but no females) had various injuries, such as loss of toes or tail, and scarring on the head or neck.[16] In captivity, young up to 6 months old have been kept in groups, and adults have been kept singly, as pairs or a single male with several females; more than one adult male causes problems.[31] The lifespan is unknown, but—despite the very limited knowledge of reptile keeping at the time—an individual that entered captivity as a young adult in the 1960s lived for more than 7.5 years after its capture (growing from 38.2 to 47 cm or 15.0 to 18.5 in in total length),[27] and others have reportedly surpassed a decade in captivity.[7]

Status and conservation

The earless monitor lizard has been rated by the

IUCN as endangered (its range covers less than 500 km2 or 190 sq mi).[21] The species is usually considered very rare, but it is easily overlooked and as recently as 1999 the only published confirmed records were from Sarawak.[7] Confirmation from Kalimantan only appeared later.[16] In some areas locals are unaware of its presence or consider it rare, but in others it may be common. At one site in West Kalimantan, 17 of 21 locals asked were aware of its presence and most of these considered it common.[14] At three other sites in the region the majority asked were aware of its presence, but less than half considered it common.[14] Elsewhere in West Kalimantan, a three-night survey of a 400 m (1,300 ft) long section of a stream, as well as two adjacent streams, located 19 earless monitor lizards, representing an unusually high density for a lizard of this size.[16] Despite this high density in a stream used by locals for washing, fishing and as a source of drinking water, they only reported seeing the species very rarely and some had never seen it.[16] Nevertheless, at present the earless monitor lizard is only known for certain from a relatively small number of sites.[19][21]

About 100 museum specimens are known and most major

Appendix II (export quota is zero for wild individuals for commercial purposes).[41]

The first confirmed captive breeding was at a zoo in Japan in 2014.[27][28] A couple of years later a few European zoos initiated a breeding program; in 2017 it was bred at Schönbrunn Zoo in Austria, and in 2018 it was bred a Prague Zoo in the Czech Republic and Moscow Zoo in Russia.[29][42][43][44] There have been other breeding reports by private keepers and captive bred individuals have been offered for sale, but some of these may not involve genuine cases of captive breeding.[21]

Habitat loss represents another serious threat, as forests in Borneo rapidly are being replaced by oil palm plantations.[16][23][38] However, the earless monitor lizard can survive in high densities in areas surrounded by degraded habitats (including oil palm plantations), and rocky streams, possibly its preferred habitat, are relatively unaffected by humans.[16]

References

  1. doi:10.2305/IUCN.UK.2021-2.RLTS.T102342572A102342580.en
    . Retrieved 21 January 2022.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ^ Lanthanotidae at the Reptarium.cz Reptile Database. Accessed 19 January 2021.
  4. ^
    ISBN 0-12-178560-2
    .
  5. ^ a b c d Das, I. (2013). "Lanthanotus borneensis, the Bornean Earless Monitor" (PDF). Herpetological Review. 44 (4): 553.
  6. ^ a b Lanthanotus borneensis at the Reptarium.cz Reptile Database. Accessed 19 January 2021.
  7. ^ a b c d e f g h i j k Sprackland, R.G. (1999). "Sarawak's Earless Monitor Lizard (Lanthanotus borneensis)". Reptiles (March): 72–79.
  8. S2CID 53623809
    .
  9. ^
    PMID 22993238
    .
  10. ^
    PMID 23627680
    .
  11. S2CID 83550662
    .
  12. PMID 20006722
    .
  13. S2CID 129367764
    .
  14. ^
    S2CID 52023963
    .
  15. ^ a b c d Vergner, I. (2013). "První nález varanovce bornejského ve Východním Kalimantanu a další setkání se vzácným ještěrem [First Discovery of the Earless Monitor Lizard in Eastern Kalimantan]". Živa (in Czech) (March): 131–133.
  16. ^
    doi:10.30906/1026-2296-2019-24-1-1-10
    .
  17. ^ "House agrees on creation of Indonesia's 34th province: 'North Kalimantan'". The Borneo Post. 23 October 2012. Retrieved 26 June 2017.
  18. ^ "Treasured find in Green Jewel » Borneo Bulletin Online". Treasured find in Green Jewel. 2022-10-22. Retrieved 2022-10-22.
  19. ^
    Convention on International Trade in Endangered Species of Wild Fauna and Flora
    , Seventeenth meeting of the Conference of the Parties Johannesburg (South Africa): 1–9. 5 October 2016. Retrieved 25 June 2017.
  20. ^
    ISBN 978-1-84773-347-4
    .
  21. ^ a b c d Stoner, S.S.; V. Nijman (2015). "The case for CITES Appendix I-listing of Earless Monitor Lizards Lanthanotus borneensis". TRAFFIC Bulletin. 27 (2): 55–58.
  22. ISBN 0-253-34366-6
    .
  23. ^
    ISBN 978-0520248472
    .
  24. JSTOR 1442189
    .
  25. ^ a b c "Lanthanotus borneensis – Description". borneo-taubwaran.de. Retrieved 27 July 2019.
  26. ^ "Geschlechtsunterschiede" (in German). borneo-taubwaran.de. Archived from the original on 13 August 2018. Retrieved 13 July 2018.
  27. ^ a b c d e f Mendyk; Shuter; Kathriner (2015). "Historical notes on a living specimen of Lanthanotus borneensis (Squamata: Sauria: Lanthanotidae) maintained at the Bronx Zoo from 1968 to 1976". Biawak. 9 (2): 44–49.
  28. ^ a b c d e f g h i Shirawa, T.; S. Bacchini (2015). "Captive Maintenance and the First Reproduction of Borneo Earless Monitors (Lanthanotus borneensis)". Herp Nation. 18.
  29. ^ a b c d "Taubwarane: Tiergarten Schönbrunn verzeichnet seltenen Zuchterfolg" (in German). Vienna Online. 7 March 2017. Retrieved 25 June 2017.
  30. ^ "Aufzucht" (in German). borneo-taubwaran.de. Archived from the original on 13 August 2018. Retrieved 13 July 2018.
  31. ^ a b c d "Verhalten im Terrarium" (in German). borneo-taubwaran.de. Archived from the original on 13 August 2018. Retrieved 13 July 2018.
  32. PMID 20631207
    .
  33. ^
    PMID 28783084
    .
  34. PMID 31067768
    .
  35. ^ a b Reising, M. "Lanthanotus borneensis" (in German). Heloderma. Retrieved 26 June 2017.
  36. ^ "Paarung" (in German). borneo-taubwaran.de. Archived from the original on 13 August 2018. Retrieved 13 July 2018.
  37. ^ a b "Eiablage, Inkubation und Schlupf" (in German). borneo-taubwaran.de. Archived from the original on 13 August 2018. Retrieved 13 July 2018.
  38. ^ a b c d e "Malaysia goes to battle for Godzilla-like lizard". Today Online. 5 August 2016. Retrieved 25 June 2017.
  39. ^
    ISBN 978-983-3393-41-1
    .
  40. ^ Neslen, A. (11 November 2015). "Lizard traffickers exploit legal loopholes to trade at world's biggest fair". The Guardian. Retrieved 25 June 2017.
  41. ^ "Appendices I, II and III". CITES. 4 April 2017. Retrieved 25 June 2017.
  42. ^ Archived at Ghostarchive and the Wayback Machine: "Seltener Zuchterfolg: Taubwarane im Tiergarten Schönbrunn" (in German). Zoovienna Tiergarten Schönbrunn. 7 March 2017. Retrieved 25 June 2017.
  43. ^ ""Holy Grail" of lizard species born in Prague Zoo". Reuters. 16 October 2018. Retrieved 27 July 2019.
  44. S2CID 214465130
    .

External links

Wikispecies has information related to Lanthanotus borneensis.
Wikimedia Commons has media related to Lanthanotus borneensis.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Earless_monitor_lizard&oldid=1215486724"