Varanus indicus species-complex

Varanus indicus species-complex

Mangrove Monitor (Varanus indicus sensu stricto)

The 'mangrove monitor' (Varanus indicus) had historically been considered a very wide-spread species showing extensive geographical variation. In 1999, Philipp, Böhme & Ziegler redefined the species with the designation of a neotype. Varanus indicus is thus distinguished by a dark brown to blackish background color covered with numerous small whitish to yellow spots typically less that 5 scales in size, the absence of a postocular stripe, an unpatterned throat, and a solid dark purple tongue, as well as other morphological differences (i.e. genital structure or scalation).

Range

Varanus indicus occurs throughout the Moluccan Islands, possibly in Sulawesi (Böhme, Horn & Ziegler 1994, though this has been disputed), Timor, the Aru Islands, the Kei (Kai) Islands, New Guinea and its surrounding islands, the Bismarck Archipelago, the Solomon Islands, coastal portions of northern Australia (the Northern Territory and Queensland, absent from territory in between along the southern rim of the Gulf of Carpentaria), and (due to human introduction) in Micronesia. The neotype designated by Philipp, Böhme & Ziegler originated from Ambon in the Moluccas, also inhabited by the related Varanus cerambonensis. As the taxonomy of the indicus-complex remains to be resolved, it is likely that forms from many parts of this extensive range will eventually be given distinct taxonomic status.

Distinctive Features (Varanus indicus sensu stricto; from Philipp, Böhme & Ziegler 1999)

Background color: Dark brown to blackish

Dorsal pattern: White to yellowish small (typically one to three but up to five scales in size) spots, arranged irregularly

Tail pattern: Anterior third spotted as on the dorsal surface; posterior two-thirds banded (blue pigmentation absent)

Throat/ventral pattern: Underside light-colored (white to yellowish); throat unpatterned; ventral surface indistinctly banded

Post-ocular stripe: Absent

Tongue color: Dark (purplish)

Mangrove Monitor (Varanus c.f. indicus)

Despite the redefinition of indicus, the taxonomy of this species-complex is far from settled. Many 'mangrove monitor' forms exist from different localities whose true taxonomy is yet to be settled. These animals (Varanus c.f. indicus) commonly turn up the the reptile market labeled generically as 'mangrove monitors'.

Sprackland (2004) gave the following geographical variation:

  • Caroline and Marshall Islands - Body generally dark, covered with numerous, but not intense, single light scales. Specimens < 200 mm SVL with two distinct, light temporal streaks, separated by a black border. Larger specimens retain a single stripe, sometimes irregular in shape, but with a distinct light interior, extending to upper anterior surface of ear. Tail without conspicuous bands. Lips pink in most populations.
  • Irian Jaya, Halmahera, Seram, Aru and surrounding islands - Body dark, with light spots made of 2-6 scales in irregular pattern. Single light temporal streak present, becoming irregular and often interrupted in larger specimens. Tail with irregular bands made of light spots forming oval clusters, most hollow in the center. ----- Note: Sprackland mentions the presence of a temporal streak though Varanus indicus, as redefined, originates from this region and lacks a temporal streak. However, the stated region comprises a large land area which is known to contain at least two similar species, indicus and cerambonensis, and probably more.
  • Australia and Papua New Guinea - Similar to previous group, but body may be brown (instead of black), and light spots are intensely yellow (more rarely, lime green), giving dorsum a light appearance. Temporal stripe rare in young, rarer in adults. Tail with conspicuous bands, either solidly coloured, or made of well-defined oval clusters of light spots.
  • Bismarck Archipelago - Similar to previous, except light markings less intense, and dorsum darker in appearance. More likely than other populations to retain light gray ventral reticulations as adults.
  • Solomon Islands - Adults with sparsely patterned heads (i.e., they have the smallest and least conspicuous head spots). Body dark brown or olive green with 1-3 light scales per spot. No temporal streak in lizards > 170 mm SVL. Tails lack banding. Lips pink on some islands. (Note: Sprackland's description differs considerably from the appearance of many indicus which are imported or photographed in the Solomons - see below - but further details on this discrepancy are not available)

It should be noted that this is only a basic characterization of some geographical variants. Differences within these populations themselves may exist and numerous different color forms continue to be discovered as well.

Sorong, West Papua

Photo courtesy of Frank B. Yuwono.

Waigeo

Photo courtesy of Jody Pieper.

Aru Islands

Photo courtesy of Jody Pieper. Note: The mangrove monitors from the Aru Islands were originally described as a distinct subspecies, Varanus indicus rouxi (Mertens 1926), a name which is now considered a junior synonym of Varanus indicus.

Solomon Islands

The Solomon Islands have been a large source of mangrove monitors seen in the pet trade. Specimens from these islands are often highly patterned wioth considerable dorsal spotting and a well-banded tail. Their appearance does not align with the redefinition of Varanus indicus as given by Philipp et al (1999) and so with future research should prove to be taxonomically distinct. Other phenotypes possessing reduced pattern are known from the Solomons, though the considerable degree of ontogenetic changes seen in indicus-complex pattern may explain these.

Photo courtesy of Kenneth Jensen. Note: this specimen possesses a pink tongue, a feature distinguishing it from Varanus indicus sensu stricto.

Mariana Islands

Mangrove monitors are present in the Mariana Islands, though it is widely accepted that their presence here is due to human - most likely recent - introduction (Cota 2008). The population on Saipan was once described as a distinct species (Varanus tsukamotoi Kashida 1929), though this form is no longer recognized.Locality: Saipan.

Kei Islands

Photos courtesy of Jody Pieper. Note: The above two specimens certainly do not correspond to Varanus indicus as now defined. They are similar in pattern to the Varanus c.f. finschi discussed separately, with which they occur on the same islands. The two do differ in other respects, such as the yellow (vs. white) underside of these animals.

Status in Captivity

Varanus indicus has long been available in the pet trade. However, given the changes to the taxonomy of this group of monitors, many of the ‘indicus’ which were available both in the past and currently are members of different species. Given the continued basket-case that is indicus-complex taxonomy, ‘mangrove monitor’ is often a generic catch-all term for any indicus-like thing which gets imported. Most of these specimens are similar to indicus or some other species but not enough to assign taxonomy with certainty while others are wildly different (see Mystery Monitors). All that being said, most ‘mangrove monitors’ imported for the pet trade come from three main locations: the Moluccas, West Papua, and the Solomon Islands. It is in the first of these that Varanus indicus sensu stricto is found and they certainly turn up for sale, though few dealers bother to notice. Mangrove monitors have been bred in captivity though infrequently and nearly all available species are imported. This is partly due to the general unsuitability that most of these species show towards captivity as well as the fact that imports are available so cheaply.

Sources

Böhme, W.; Horn, H. & T. Ziegler (1994): On the taxonomy of the Pacific monitor lizards (Varanus indicus complex): Resurrection of Varanus doreanus (A.B. MEYER, 1874) and description of a new subspecies. Salamandra 30 (2): 119-142.

Cota, M. (2008): Varanus indicus and its presence on the Mariana Islands: natural geographic distribution vs. introduction. Biawak 2 (1): 18-27. (http://www.varanidae.org/Vol_2_No_1.pdf)

Kishida, K. 1929. A new Monitor from the island of Saipan, South Sea Islands. Lansania. 1(1): 13-16.

Mertens, R. (1926): Uber die Rassen einiger indo – australischer Reptilien. Senckenbergiana 8: 272-279. 

Philipp, K. M.; Böhme, W. & T. Ziegler (1999): The identity of Varanus indicus: Redefinition and description of a sibling species coexisting at the type locality (Sauria: Varanidae: Varanus indicus group). Spixiana 22 (3): 273-287.

Sprackland, R. G. (2004): Evolution, Systematics, and Variation of Pacific Mangrove Monitor Lizards. Lizard Biology 2 (1): art. 1 (http://www.curator.org/legacyvmnh/VMNH_Publications/MuseumJournals/Lizard%20Biology/new_page_2.htm)