Nile monitor

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Nile monitor
Nile monitor (Varanus niloticus) 2.jpg
Botswana
Nile monitor lizard (Varanus niloticus) head.jpg
Lake Baringo, Kenya
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Varanidae
Genus: Varanus
Subgenus: Polydaedalus
Species:
V. niloticus
Binomial name
Varanus niloticus
(Linnaeus, 1758)
Nile monitor (varanus niloticus) distribution map.png
Nile monitor's native range (including West Africa Nile monitor, now often recognized as a separate species)
Synonyms
List
  • Lacerta monitor Linnaeus, 1758 — nomen rejectum
  • Lacertus tupinambisLacépède, 1788
  • Lacerta capensisSparrman, 1783
  • Lacerta nilotica Linnaeus, 1766
  • Tupinambis elegansDaudin, 1802
  • Tupinambus ornatusDaudin, 1803
  • Monitor niloticusLichtenstein, 1818
  • Monitor pulcherLeach, 1819
  • Stellio saurusLaurenti, 1768
  • Varanus niloticusMertens, 1942
  • Varanus (Polydaedalus) niloticus ornatusMertens, 1942
  • Varanus (Polydaedalus) ornatusBöhme & Ziegler, 1997

The Nile monitor (Varanus niloticus) is a large member of the monitor family (Varanidae) found throughout most of Sub-Saharan Africa, particularly in drier regions, and along the Nile River and its tributaries in East Africa. Additionally, there are modern, invasive populations in North America. The population found in West African forests and savannahs is sometimes recognized as a separate species, the West African Nile monitor (V. stellatus). [2] While it is dwarfed by its larger relatives, such as the Komodo dragon, the Asian water monitor or the crocodile monitor, it is still one of the largest lizards in the world, reaching (and even surpassing) Australia’s perentie in size. Other common names include the African small-grain lizard, [3] as well as iguana and various forms derived from it, [4] such as guana, water leguaan [5] or river leguaan (leguan, leguaan, and likkewaan mean monitor lizard in South African English, and can be used interchangeably). [6]

Contents

A feral population of Nile monitors (descended from escaped or intentionally-released pets) has become established in several locations in South Florida. [7] In addition to any illegally-released animals, it is speculated that during particularly intense hurricane seasons in Florida, many reptiles potentially escape when their enclosures are damaged or inadvertently unlocked; as Florida has a semi-tropical to tropical climate, many reptiles are housed outdoors, and poorly-secured enclosures may become damaged during bad storms. Along with Nile monitors, Florida is infamous for its feral populations of agamas, Argentine black and white tegus, Burmese pythons, green iguanas, Madagascar giant day geckos, and panther and veiled chameleons, among others. Many of these species are thought to be descendants of hurricane escapees.

Taxonomy

Members of the Nile monitor species group were already well known to Africans in ancient times. For example, they were commonly caught, likely as food, in the Djenné-Djenno culture at least a millennium ago. [8]

The Nile monitor twice was given a scientific name by Carl Linnaeus: First as Lacerta monitor in 1758 in the 10th edition of Systema Naturae, the starting point of zoological nomenclature. He described it again in 1766 as Lacerta nilotica. Despite being older, the name proposed in 1758 is invalid because it was rejected in ICZN opinion 540, making the name of 1766 valid. [5] [9] The genus Varanus was coined in 1820 by Blasius Merrem. Six years later Leopold Fitzinger moved the Nile monitor into this genus as Varanus niloticus, [10] the currently accepted scientific name for the species. [5]

Species complex

As traditionally defined, the Nile monitor is a species complex. [2] The ornate monitor (V. ornatus) and West African Nile monitor (V. stellatus) were described as species in 1802 and 1803 by François Marie Daudin. In 1942, Robert Mertens moved them both into the Nile monitor (V. niloticus); as synonyms or as a valid subspecies. [11] This was the standard treatment until 1997, when a taxonomic review based on color and morphology indicated that the ornate monitor is distinctive and revalidated it as a separate species from rainforests of West and Central Africa. [12] In 2016, a review based primarily on genetics came to another result. They found that monitors from West African forests and adjacent savannah are distinctive and worthy of recognition as a separate species: the West African Nile monitor (V. stellatus). [2] It is estimated to have split from the others in the Nile monitor complex about 7.7 million years ago, making it older than the split between humans and chimpanzees. [8] In contrast, those in the Central African rainforests are genetically similar to the Nile monitor. This essentially splits the ornate monitor—as defined in 1997—into two: the western being the West African Nile monitor and the eastern (of Central African rainforests) being moved back into the Nile monitor. As the type locality for the ornate monitor is in the Central African country of Cameroon, the scientific name V. ornatus becomes a synonym of V. niloticus. Individuals with the "ornate color pattern" and individuals with the "Nile color pattern" occur in both the West African Nile monitor and the Nile monitor, with the "ornate" appearing to be more frequent in densely forested habitats. [2]

With the West African Nile monitor as a separate species, there are two main clades in the Nile monitor: A widespread clade found throughout much of Southern, Central and East Africa, as well as more locally in coastal West Africa. The other clade includes the monitors of the Sahel (Mali to Ethiopia) and Nile regions. [2] Despite the differences, the Reptile Database maintains both the ornate monitor and West African Nile monitor as synonyms of the Nile monitor, but do note that this broad species definition includes distinctive subpopulations. [5]

Description

Nile monitor eating crocodile egg, Katavi National Park Monitor lizard eating crocodile egg, Katavi National Park.jpg
Nile monitor eating crocodile egg, Katavi National Park

The Nile monitor is Africa's longest lizard. [13] They grow from about 120 to 220 cm (3 ft 11 in to 7 ft 3 in) in length, with the largest specimens attaining 244 cm (8 ft). [14] [15] In an average-sized specimen, the snout-to-vent length will be around 50 cm (1 ft 8 in). [16] In body mass, adults have been reported to vary widely, one study claiming only 0.8 to 1.7 kg (1.8 to 3.7 lb), others state weights ranging from 5.9 to 15 kg (13 to 33 lb) in big monitors. Variations may be due to age or environmental conditions. [17] [18] [19] Exceptionally large specimens may scale as much as 20 kg (44 lb), but this species weighs somewhat less on average than the bulkier rock monitor. [20] They have muscular bodies, strong legs, and powerful jaws. Their teeth are sharp and pointed in juvenile animals and become blunt and peg-like in adults. They also possess sharp claws used for climbing, digging, defense, or tearing at their prey. Like all monitors, they have forked tongues, with highly developed olfactory properties. The Nile monitor has quite striking, but variable, skin patterns, as they are greyish-brown above with greenish-yellow barring on the tail and large, greenish-yellow rosette-like spots on their backs with a blackish tiny spot in the middle. Their throats and undersides are an ochre-yellow to a creamy-yellow, often with faint barring. [20]

Their nostrils are placed high on their snouts, indicating these animals are very well adapted for an aquatic lifestyle. They are also excellent climbers and quick runners on land. Nile monitors feed on a wide variety of prey items, including fish, frogs, toads (even poisonous ones of the genera Breviceps and Sclerophrys ), [21] small reptiles (such as turtles, snakes, lizards, and young crocodiles), [22] birds, rodents, [23] other small mammals (up to domestic cats and young antelopes [ Raphicerus ]), [24] [25] eggs (including those of crocodiles, agamids, other monitor lizards, and birds), [22] invertebrates (such as beetles, termites, orthopterans, crabs, caterpillars, spiders, millipedes, earthworms, snails, and slugs), [23] [22] carrion, human wastes, and feces. [22]

Distribution and habitat

Nile monitors are native to Sub-Saharan Africa and along the Nile. [26] They are not found in any of the desert regions of Africa (notably Sahara, Kalahari and much of the Horn of Africa), however, they thrive around rivers. [27] [28] Nile monitors were reported to live in and around the Jordan River, Dead Sea, and wadis of the Judaean Desert in Israel until the late 19th century, though they are now extinct in the region. [29]

Invasive species

In Florida in the United States, established breeding populations of Nile monitors have been known to exist in different parts of the state since at least 1990. [30] Genetic studies have shown that these introduced animals are part of the subpopulation that originates from West Africa, and now often is recognized as its own species, the West African Nile monitor. [8] The vast majority of the established breeding population is in Lee County, particularly in the Cape Coral and surrounding regions, including the nearby barrier islands (Sanibel, Captiva, and North Captiva), Pine Island, Fort Myers, and Punta Rassa. Established populations also exist in adjacent Charlotte County, especially on Gasparilla Island. [28] Other areas in Florida with a sizeable number of Nile monitor sightings include Palm Beach County just southwest of West Palm Beach along State Road 80. [31] In July 2008, a Nile monitor was spotted in Homestead, a small city southwest of Miami. [32] Other sightings have been reported near Hollywood, Naranja, and as far south as Key Largo in the Florida Keys. [31] The potential for the established population of Nile monitors in Lee, Charlotte, and other counties in Florida, to negatively impact indigenous crocodilians, such as American alligators (Alligator mississippiensis), and American crocodiles (Crocodylus acutus), is enormous, given that they normally raid crocodile nests, eat eggs, and prey on small crocodiles in Africa. Anecdotal evidence indicates a high rate of disappearance of domestic pets and feral cats in Cape Coral.

In captivity

Nile monitors are often found in the pet trade despite their highly aggressive demeanor and resistance to taming. Juvenile monitors will tail whip as a defensive measure, and as adults, they are capable of inflicting moderate to serious wounds from biting and scratching. Nile monitors require a large cage as juveniles quickly grow when fed a varied diet, and large adults often require custom-built quarters.

"There are few lizards less suited to life in captivity than the Nile monitor. Buffrenil (1992) considered that, when fighting for its life, a Nile monitor was a more dangerous adversary than a crocodile of a similar size. Their care presents particular problems on account of the lizards' enormous size and lively dispositions. Very few of the people who buy brightly-coloured baby Nile monitors can be aware that, within a couple of years, their purchase will have turned into an enormous, ferocious carnivore, quite capable of breaking the family cat's neck with a single snap and swallowing it whole." [33]

Related Research Articles

<span class="mw-page-title-main">Varanidae</span> Family of lizards

The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). Varanus includes the Komodo dragon, crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the earless monitor lizard and chinese crocodile lizard. The oldest members of the family are known from the Late Cretaceous of Mongolia.

<span class="mw-page-title-main">Monitor lizard</span> Genus of reptiles

Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recognized.

<span class="mw-page-title-main">Megalania</span> Largest species of lizard (extinct)

Megalania is an extinct species of giant monitor lizard, part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, reaching an estimated length of 3.5 to 7 metres, and weighing between 97–1,940 kg (214–4,277 lb), but the fragmentary nature of known remains make estimates highly uncertain.

<span class="mw-page-title-main">Nile crocodile</span> Reptile of Africa

The Nile crocodile is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed in sub-Saharan Africa, occurring mostly in the eastern, southern, and central regions of the continent, and lives in different types of aquatic environments such as lakes, rivers, swamps, and marshlands. Although capable of living in saline environments, this species is rarely found in saltwater, but occasionally inhabits deltas and brackish lakes. The range of this species once stretched northward throughout the Nile River, as far north as the Nile Delta. Generally, the adult male Nile crocodile is between 3.5 and 5 m in length and weighs 225 to 750 kg. However, specimens exceeding 6.1 m (20 ft) in length and 1,000 kg (2,200 lb) in weight have been recorded. It is the largest freshwater predator in Africa, and may be considered the second-largest extant reptile in the world, after the saltwater crocodile. Size is sexually dimorphic, with females usually about 30% smaller than males. The crocodile has thick, scaly, heavily armoured skin.

<span class="mw-page-title-main">Bengal monitor</span> Species of lizard

The Bengal monitor, also called the common Indian monitor, is a monitor lizard distributed widely in the Indian Subcontinent, as well as parts of Southeast Asia and West Asia. This large lizard is mainly a terrestrial animal, and its length ranges from about 61 to 175 cm from the tip of the snout to the end of the tail. Young monitors may be more arboreal, but adults mainly hunt on the ground, preying mainly on arthropods, but also taking small terrestrial vertebrates, ground birds, eggs and fish. Although large Bengal monitors have few predators apart from humans who hunt them for meat, younger individuals are hunted by many predators.

<span class="mw-page-title-main">Asian water monitor</span> Species of lizard

The Asian water monitor is a large varanid lizard native to South and Southeast Asia. It is one of the most common monitor lizards in Asia, ranging from coastal northeast India, Bangladesh, Sri Lanka, mainland Southeast Asia, and southern China to Indonesian islands where it lives close to water. It is listed as Least Concern on the IUCN Red List. It was described by Laurenti in 1768 and is among the largest squamates in the world.

<span class="mw-page-title-main">Lace monitor</span> Species of lizard

The lace monitor, also known as the tree goanna, is a member of the monitor lizard family native to eastern Australia. A large lizard, it can reach 2 metres (6.6 ft) in total length and 14 kilograms (31 lb) in weight. The lace monitor is considered to be a least-concern species according to the International Union for Conservation of Nature.

<i>Varanus salvadorii</i> Species of lizard

The crocodile monitor, also known as the Papuan monitor or Salvadori's monitor, is a species of monitor lizard endemic to New Guinea. It is the largest monitor lizard in New Guinea and is one of the longest lizards, verified at up to 255 cm (100 in). Its tail is exceptionally long, with some specimens having been claimed to exceed the length of the Komodo dragon, however less massive.

<span class="mw-page-title-main">Rock monitor</span> Species of reptile

The rock monitor is a species of monitor lizard in the family Varanidae. The species is endemic to Sub-Saharan Africa. It is on average the largest lizard found on the continent, and is locally called leguaan or likkewaan.

<span class="mw-page-title-main">Peach-throated monitor</span> Species of lizard

The peach-throated monitor, also known commonly as the Sepik monitor, is a species of monitor lizard in the family Varanidae. The species is native to New Guinea.

<span class="mw-page-title-main">Ornate monitor</span> Species of lizard

The ornate monitor is a monitor lizard that is native to West and Middle Africa. Comprehensive molecular analyses of the group have demonstrated that animals previously assigned to "Varanus ornatus" do not constitute a valid taxon and are actually polymorphisms of two different species; Varanus stellatus and Varanus niloticus. Consequently, Varanus ornatus is considered a synonym of Varanus niloticus and "ornate monitor" is an informal term for forest forms of either species . Until 1997, the ornate monitor was considered a subspecies of the Nile monitor. It was subsequently described as a separate species on the basis of reduced number of ocelli rows on the body, a light coloured tongue and a more massive build. More recent work based on a large sample size using mitochondrial and nuclear DNA sequences indicates that Varanus ornatus is not a valid species and that animals with the diagnostic appearance belong either of two sister species of Nile monitor. Animals described as ornate monitor lizards are native to closed canopy forests in West and Middle Africa.

<span class="mw-page-title-main">Dumeril's monitor</span> Species of lizard

Dumeril's monitor is a species of lizard in the family Varanidae. The species is endemic to Southeast Asia.

Finsch's monitor is a species of monitor lizard in the family Varanidae. The species is native to New Guinea and Australia.

<span class="mw-page-title-main">Mitchell's water monitor</span> Species of lizard

Mitchell's water monitor is a semiaquatic species of monitor lizard in the family Varanidae. The species is native to Australia. The species is native to the Northern regions of Australia, and is on IUCN's Red List as a critically endangered species. They can be distinguished by the orange or yellow stripes along their neck and dark spots along their back. They are mainly carnivorous, and eat small prey such as lizard, birds, and insects.

<span class="mw-page-title-main">West African Nile monitor</span> Species of reptile

The West African Nile monitor is a subspecies of monitor lizard that is native to West African forests and adjacent savannah. It has also been introduced to Florida, United States, where it is considered invasive.

Amblyomma gervaisi is a hard-bodied tick of the genus Amblyomma. The tick is a parasite of snakes, such as Naja naja, Python molurus species and monitor species such as Varanus ocellatus, Varanus yemenensis, Varanus benghalensis, Varanus griseus and many other Varanus species in southeastern Asia and Asia-minor. They exhibit sexual dimorphism. They can be found in Sri Lanka, India, Yemen, Saudi Arabia. It is a potential vector for Coxiella burnetii.

References

  1. ↑ Wilms, T.; Wagner, P.; Luiselli, L.; Branch, W.R.; Penner, J.; Baha El Din, S.; Beraduccii, J.; Msuya, C.A.; Howell, K.; Ngalason, W. (2021). "Varanus niloticus". IUCN Red List of Threatened Species . 2021: e.T198539A2531945. doi: 10.2305/IUCN.UK.2021-2.RLTS.T198539A2531945.en . Retrieved 18 February 2022.
  2. 1 2 3 4 5 Dowell, S.A, D.M. Portik, V. de Buffrenil, I Ineich, E Greenbaum, S.O. Kolokotronis and E.R. Hekkala. 2016. Molecular data from contemporary and historical collections reveal a complex story of cryptic diversification in the Varanus (Polydaedalus) niloticus Species Group. Molecular Phylogenetics and Evolution 94(Part B): 591-604. doi : 10.1016/j.ympev.2015.10.004
  3. ↑ "Synonyms of Nile Monitor (Veranus niloticus)". Encyclopedia of Life. Retrieved 15 December 2013.
  4. ↑ "iguana" . Oxford English Dictionary (Online ed.). Oxford University Press.(Subscription or participating institution membership required.)
  5. 1 2 3 4 Varanus niloticus at the Reptarium.cz Reptile Database . Accessed 15 September 2019.
  6. ↑ "leguan - definition". Oxford Dictionaries. Oxford University Press. Archived from the original on December 17, 2013. Retrieved 17 December 2013.
  7. ↑ "Nile Monitor". Florida Fish And Wildlife Conservation Commission. Retrieved 24 October 2022.
  8. 1 2 3 Yong, Ed (20 April 2016). Florida’s Dragon Problem. The Atlantic. Retrieved 15 September 2019.
  9. ↑ ICZN (1959). Opinion 540. Protection under the plenary power of the specific names bengalensis Daudin, 1802, as published in the combination Tupinambis bengalensis, and salvator Laurenti 1768, as published in the combination Stellio salvator. Opin. Declar. intern. Com. zool. Nom. 20: 77-85.
  10. ↑ Fitzinger, L. (1826). Neue Classification der Reptilien nach ihren natürlichen Verwandtschaften nebst einer Verwandschafts-Tafel und einem Verzeichnisse der Reptilien-Sammlung des K. K. Zoologischen Museums zu Wien. Wien.
  11. ↑ Mertens, R. (1942). Die Familie der Warane (Varanidae), 1. Teil: Allgemeines. Abh. Senckenb. naturf. Ges. 462: 1-116.
  12. ↑ Böhme, W., and T. Ziegler (1997). A taxonomic review of the Varanus (Polydaedalus) niloticus (Linnaeus, 1766) species complex. The Herpetological Journal 7: 155-162.
  13. ↑ "5 Fascinating Facts About the Nile Monitor – SafariBookings".
  14. ↑ Nile Monitor Care Sheet
  15. ↑ Enge, K. M., Krysko, K. L., Hankins, K. R., Campbell, T. S., & King, F. W. (2004). Status of the Nile monitor (Varanus niloticus) in southwestern Florida. Southeastern Naturalist, 3(4), 571-582.
  16. ↑ "Varanus niloticus". Monitor Lizards – Captive Husbandry. Monitor-Lizards.net. Archived from the original on 25 October 2012. Retrieved 15 December 2013.
  17. ↑ Condon, K. (1987). A kinematic analysis of mesokinesis in the Nile monitor (Varanus niloticus). Experimental biology, 47(2), 73.
  18. ↑ Hirth & Latif 1979
  19. ↑ "ANIMALS - Varanus niloticus". Dr. Giuseppe Mazza's Photomazza. Retrieved 2013-06-06.
  20. 1 2 "Nile Monitors". L. Campbell's Herp Page. Retrieved 2013-06-06.
  21. ↑ Dalhuijsen,Kim et al:"A comparative analysis of the diets of Varanus albigularis and Varanus niloticus in South Africa. African Zoology 49(1): 83–93 (April 2014)
  22. 1 2 3 4 "Varanus Nilotlcus".
  23. 1 2 "Varanus niloticus (Nile Monitor, Water Leguaan)". Animal Diversity Web .
  24. ↑ Daniel Bennett, Brian Basuglo (1999-04-01). University of Aberdeen Black Volta Expedition 1997 Final Report. Viper Press. p. 138. ISBN   9780952663232.
  25. ↑ François Odendaal, Claudio Velásquez Rojas (2007-01-01). Richtersveld: The Land and Its People. Struik. p. 176. ISBN   9781770073418.
  26. ↑ (Schleich et al., 1996; Spawls et al., 2002).
  27. ↑ Reptile Specialists (Nile monitor)
  28. 1 2 "NAS - Invasive Species FactSheet: Varanus niloticus (Nile monitor)". Nonindenous Aquatic Species. USGS Nonindigenous Aquatic Species Database. Gainesville, FL: United States Geological Survey. Archived from the original on 2009-05-09.
  29. ↑ Baker., Tristram, Henry (2013). The Fauna and Flora of Palestine. Cambridge: Cambridge University Press. p. 148. ISBN   9781108042048. OCLC   889948524.{{cite book}}: CS1 maint: multiple names: authors list (link)
  30. ↑ (Campbell, 2003; Enge et al. 2004).
  31. 1 2 "Everglades CISMA". Archived from the original on 2012-01-25. Retrieved 2011-10-11.
  32. ↑ Hofmeyer, Erik (10 June 2008). "Homestead ARB home to diverse array of wildlife". Homestead Air Reserve Base News. Homestead Air Reserve Base. Archived from the original on 17 May 2009. Retrieved 15 December 2013.
  33. ↑ Bennett, Daniel (1998). Monitor Lizards: Natural History, Biology & Husbandry. Edition Chimaira. ISBN   3-930612-10-0.
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