Sunday, July 3, 2011

Varanus Rainerguentheri With Varanus Indicus

Varanus rainerguentheri was described as a cryptic species within the V. indicus complex based on molecular and morphological evidence (Ziegler et al., 2007a). Unfortunately, the genetic comparison of the new species with Varanus indicus in that paper was restricted to a single sequence of mt DNA from a Varanus indicus specimen without specific locality data. Additionally, the type locality of Varanus rainerguentheri (Jailolo, Halmahera) is disputed by the original collector (L. Wagner, pers. comm. November 2008), making the genetic and morphological argumentation a comparison between two unknown localities.

Varanus Rainerguentheri

Two of the characteristic morphological features of the holotype were the blunt snout and occurrence of a light postocular stripe. The blunt snout was never observed in the field and appears to be unique to that particular specimen. Field investigations of larger sample sizes also show that the postocular stripe is variable among Halmaheran and north Moluccan populations of V. rainerguentheri, and usually fades with age.  For example, the two specimens depicted in Setiadi and Hamidy (2006) as Varanus indicus and Varanus rainerguentheri appear to only show intraspecific variation, and cannot be allocated to different species based solely on the occurrence of a temporal stripe.

Varanus Rainerguentheri

The temporal stripe is usually less pronounced on specimens from Obi and Gebe compared to Halmahera and Morotai, though based on external features, the populations on these islands are very difficult to distinguish. Specimens from Obi do appear to have dark pigmentation further back on the tongue.

Despite the potential weaknesses in the original description, I have opted to use the name Varanus rainerguentheri for populations of the Varanus indicus-type monitors in the northern Moluccas included in this paper. A more detailed taxonomic investigation of animals from verifiable localities and with larger sample sizes is much needed to confirm the taxonomy and specific characteristics of this species, particularly since the description of Varanus rainerguentheri failed to make a comparison with the very similar animals of nearby Waigeo, which were described as Varanus chlorostigma by Gray (1831).

Varanus indicus

This name was synonymized with V. indicus by Böhme et al. (1994) and earlier authors, but the subsequent redefinition of V. indicus (Philipp et al. 1999) excludes animals from Waigeo on several characteristics (such as throat markings, tongue color and scalation). The redefinition of V. indicus invalidates this earlier synonymization, and makes V. chlorostigma a potentially available name for V. rainerguentheri.

Varanus Rainerguentheri Distribution
Varanus rainerguentheri is widely distributed, particularly around the coastlines, on Halmahera, Ternate (RMNH voucher), Tidore (MZB voucher), Morotai, Bacan, Kasiruta, Gebe and Obi (and probably on many of the smaller islands of this region).

Varanus Rainerguentheri Ecology
One hundred and twelve (112) observations were made during the course of fieldwork. On all islands except Gebe, they are mostly restricted to coastal areas and mangrove swamps High densities are also reached in brackish water river deltas and Nypa swamps. Occasionally, individuals are found further inland along freshwater streams, lakes and smaller swamps where they occur syntopically with V. caerulivirens. One individual on Bacan was encountered at an elevation of more than 200 m in a small mountain swamp. This species was only once (on Gebe) encountered in sago swamps, despite several searches in that habitat. They heavily utilize trees for basking and nighttime refuges.

Diet consists of crabs (Tanner, 1950) as well as other suitable aquatic and terrestrial prey and carrion. One individual was seen chasing aquatic prey in a small stream, while another individual was observed digging for food in a steep riverbank. On Obi and Gebe, they were also frequently seen foraging around human waste heaps at the margins of villages. The ecology of V. rainerguentheri appears to be more generalized on Gebe, where it occurs alone, from that of Halmahera and Obi where they face competition from other monitor species, probably indicating niche release (Weijola, in prep.). The largest specimen measured was 133 cm in total length, however, animals estimated to be nearer to 150 cm were observed on Obi.


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