The black-palmed rock monitor (''Varanus glebopalma'') is a member of the

Varanidae The Varanidae are a family of lizards in the superfamily Varanoidea within the Anguimorpha group. The family, a group of carnivorous and frugivorous lizards, includes the living genus '' Varanus'' and a number of extinct genera more closely rel ...

family found in Australia. Also known as the twilight monitor or the long-tailed rock monitor, it is a member of the subgenus ''Odatria'', and is found in the northern part of Australia in the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Aust ...

and

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

, as well as

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , establishe ...

. Specifically, its distribution extends from

Mount Isa Mount Isa ( ) is a city in the Gulf Country region of Queensland, Australia. It came into existence because of the vast mineral deposits found in the area. Mount Isa Mines (MIM) is one of the most productive single mines in world history, base ...

in the east to the

Kimberleys The Kimberley is the northernmost of the nine regions of Western Australia. It is bordered on the west by the Indian Ocean, on the north by the Timor Sea, on the south by the Great Sandy and Tanami deserts in the region of the Pilbara, an ...

in the west. Its

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

is areas of rock escarpment, and large populations may be found in small areas.

Taxonomy

A species first described in 1955 by South Australian curator Francis John Mitchell, nominating the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

as a specimen obtained at Lake Hubert in the Northern Territory. Mitchell's specimen was the only example available, and was shot by R. R. Miller near a sandstone outcrop during the

1948 American-Australian Scientific Expedition to Arnhem Land In February 1948, a team of Australian and American researchers and support staff came together in northern Australia to begin, what was then, one of the largest scientific expeditions ever to have taken place in Australia—the American-Australia ...

. The new species was allied to the infrageneric classification ''Varanus'' (''Odatria''). Common names for the species include black-palmed and long-tailed rock monitor. The specific epithet ''glebopalma'' refers to the shiny black pads found on the undersides of their feet.

Description

The black-palmed rock monitor reaches a total length of just over 100 cm. The coloration of ''V. glebopalma'' on the back shows a black ground color with some light brown scales, overall the skin is reddish or gray brown. The scales form a "reticulated pattern at the sides or small

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

with a black central spot on top." Their tail is blackish for the first half of its length, becoming a creamy-yellow color. The top sides of the head and the limbs are black with small, light brown or cream-colored spots which "flow together". Their limbs have larger spots.

Behaviour

This varanid is secretive, eluding casual observers and poorly recorded in surveys. ''Varanus glebopalma'' is extremely timid and able to move quickly, usually hunting in daylight hours; although activity at dusk or night is noted in descriptions this is likely to be a response to disturbance by the observers. Their hunting mode is as an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey ...

. In the wild, black-palmed rock monitors prefer to eat

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

s, lizards, and other small

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

Orthopteran Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – grassho ...

s, species of grasshoppers, are sought in the dry season of Australia's north and skinks make up the majority of the diet during the wet, other prey captured and consumed includes frogs. Individual range may be from 1.25 to over 7 hectares, ambushing prey on the move or foraging at narrow hiding places. A report of males avoiding another male presence is assumed to be a demonstration of territoriality, a behaviour unknown in any other varanid species.

Distribution and habitat

The distribution range of the species extends from the Kimberley, across the

Top End The Top End of Australia's Northern Territory is a geographical region encompassing the northernmost section of the Northern Territory, which aside from the Cape York Peninsula is the northernmost part of the Australian continent. It covers a ra ...

and to the west of Queensland in the

districts. They occur from the coast to inland regions, with an offshore population recorded at

Adolphus Island Adolphus Island is an uninhabited island located in the Kimberley region of Western Australia. It is situated in Cambridge Gulf approximately north of Wyndham and covers an area of about . The island has a maximum height of approximately . T ...

. The habitat is complex rocky outcrops that provide crevices and boulders and only in association with open woodlands; despite the presence of trees in the local environment the species is not known to be arboreal. In the Yarrangguljna region of the Northern Territory the population's strongly preferred vegetation type is woodland dominated by ''

Allosyncarpia ternata ''Allosyncarpia ternata'', commonly known as ''an-binik'', is a species of rainforest trees constituting part of the botanical family Myrtaceae and included in the eucalypts group. The only species in its genus, it was described in 1981 by Stan ...

''. This same habitat is occupied by another long-tailed monitor '' Varanus glauerti'', and while the two species are closely sympatric they occupy distinct niches within this ecology. The range of habitat includes arid woodland and monsoonal forest near their strongly preferred refuge within crevices and boulders at the outskirts of sandstone escarpments and outcrops. The assessment of the IUCN work group, published in 2017, listed this species as least concern, with a population that is assumed to be stable. As a consumer of amphibians, the species is assumed to be susceptible to the advance of ''

Rhinella marina The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...

'', a poisonous introduced species known in Australia as the cane toad.

References

{{Taxonbar, from=Q2713666 Varanus Monitor lizards of Australia Endemic fauna of Australia Reptiles described in 1955 Taxa named by Francis John Mitchell