Varanus palawanensis, Koch, André, Gaulke, Maren & Böhme, Wolfgang, 2010

Koch, André, Gaulke, Maren & Böhme, Wolfgang, 2010, Unravelling the underestimated diversity of Philippine water monitor lizards (Squamata: Varanus salvator complex), with the description of two new species and a new subspecies, Zootaxa 2446, pp. 1-54 : 33-39

Varanus palawanensis sp. nov.

Figures 25–29

Holotype. SMF 73912 ( Figs. 25–27 ), adult male, Tabon, Palawan Island, Philippines, collected by M. Gaulke 19.I.1989, donated 6.IV.1989.

Paratypes. SMF 73914–15, 2 adults males, Tabon, Palawan Island, collected by M. Gaulke, I.1989, donated 6.IV.1989; BMNH 94.6.30.19, subadult, Palawan Island, collected by A. H. Everett, 1894; BMNH 94.6.30.20, adult ( Fig. 28 ), Palawan Island, collected by A. H. Everett, 1894; MNHN 1884-187, adult (mounted), “Ile Paragua ” (= Palawan), collected by A. Marché, ca. 1883; ZMUC E78, subadult, Dalawan Bay, Balabac Island, collected by the Noona Dan Expedition, 8.X.1961; ZFMK 89691 (formerly SMF 73913), adult male, Tabon, Palawan Island, collected by M. Gaulke, I.1989, donated 6.IV.1989.

Other material. See appendix.

Diagnosis. This new water monitor species is characterised by the following combination of characters that distinguishes V. palawanensis sp. nov. from all congeners: (1) relatively high scale counts around the head from rictus to rictus (character P = 53–65, mean = 56.64), (2) but low scale counts around the body (character S = 129–148, mean = 139.00), (3) and mean scale counts along the dorsal side (character XY = 116–145, mean = 128.27). For the remaining scalation features we refer to Table 3 . Moreover, (4) the salvator -typical colour pattern of dorsal transverse rows of big bright spots and a bright and dark banded tail is indistinct in V. palawanensis sp. nov., and replaced by a vague pattern of bright mottling consisting of many single or bright bordered scales. Instead, (5) specimens often exhibit white markings on the head, (6) but a bright lateral temporal streak extending between eye and ear opening is poorly defined. (7) The dark bluegreyish tongue is flesh-coloured only at its base. (8) Ventrally, the throat shows no dark lateral bars but is mottled with dark brown scales.

For details about scalation features and colour pattern of the remaining Philippine members of the V. salvator complex we refer to Tables 3 and 5 .

Description of the holotype. The holotype is an adult male with a slender habitus. The right hemipenis is partly everted. Total length 1174 mm (SVL = 441 mm, TaL = 733 mm, index 1 = 1.66), head length 80 mm, head width 39 mm (index 10 = 2.06), head height 28 mm (index 11 = 2.86). The distance from the anterior margin of the eye to the middle of the nostril is 27 mm, the distance from the middle of the nostril to the tip of the snout is 16 mm (index 2 = 1.69). The tympanum is oval-shaped. The tail is largely compressed laterally with a distinct dorsal double keel.

Scalation: The body scales are heterogeneous. The scales of the head are irregularly pentagonal to heptagonal; 56 scales across the head from rictus to rictus. The scales around the eye are granulous; 6 (right) and 6 (left) enlarged supraoculars; 60 (29 right/31 left) supralabials, plus one rostral. The scale covering the pineal organ is enlarged, irregularly pentagonal with a round whitish blotch in the centre. The scales of the nape are smooth, oval, slightly larger than dorsals; 32 scales from hind margin of the tympanum to opposite of the gular fold; 84 scales from opposite of the gular fold to insertion of the hind limbs. The limbs are covered with smooth, oval scales. The caudal scales are rectangular, above slightly keeled, below with prominent keels, twice as large as dorsally; 100 scales around base of tail and 53 around tail after approximately one third of its length. The two median rows of dorsal tail scales form a double crest starting from the base. The gular scales are smooth, slightly increasing in size toward the gular fold, 77 oval scales from the tip of the snout to the gular fold, and 93 scales around the neck anterior to the gular fold; 129 scales around the midbody. The ventrals are rectangular, arranged in 78 regular transverse rows from the gular fold to the insertion of the hind limbs. The scales around the cloaca, on the ventral side of the hind limbs, and first fifth of the tail bear an apical pit posteriorly.

Colour pattern (in preservative): The dorsal side is dark brown. Dorsum, neck, and base of tail are strongly mottled with single partly bright scales and bright interspaces between the dorsal scales. The tail shows a very indistinctive pattern of black and white bars only on its second half, where the white parts are interspersed with numerous dark scales. The hind limbs are spotted with single bright scales; the forelimbs are covered with many scales which exhibit a bright dot. Towards the lateral side of the limbs these bright spots increase in size until the entire scales are bright ventrally. The dark digits are dotted with single bright scales; the first scale after each claw has a white dot. The head is dark brown, bright crossbands on the snout are absent. An ill-defined bright temporal streak extends from the eye to the tympanum, which is encircled by a row of bright scales posteriorly. The tongue is dark bluish-grey dorsally and ventrally. The granular scales below the eyes are cream-coloured. The ventral side is cream-coloured; the chin exhibits three dark crossbands. The bright throat is heavily mottled with dark scales. The breast exhibits three faded dark crossbands, while the belly shows ill-defined dark V-shaped markings laterally. The tail is bright on the first two thirds of its length becoming darker towards the end.

Genital morphology: The right hemipenis is party everted in the male holotype. In this state, the copulatory organ is about 30 mm long and apically broadened. As far as visible, only the pedicel and the truncus are dark pigmented at its basal smooth paryphasman-free parts. The remaining parts are fleshcoloured. The sulcus spermaticus is basally oblique, mesially running straight to the apex. The sulcus is largely open from the pedicel toward the apex. The paryphasman rows (‘frills’) are strongly developed, asymmetrically arranged, and enter the sulcus spermaticus only at the proximal asulcal side. Eight paryphasman rows are visible starting from the proximal asulcal side of the truncus. The lower truncus and pedicel are unornamented.

Intraspecific variation. With a maximum total length of about 200 cm, V. palawanensis sp. nov. is the largest of the Philippine water monitor species ( Horn & Gaulke 2004). These authors referred to a specimen (there allocated to V. s. marmoratus ) from Calauit. For a summary of main morphometrics and scalation features of this monitor species we refer to Table 3 .

The best studied water monitor population of the Philippines is that of Calauit ( Gaulke 1989), a small islet belonging to the Calamian Island Group at the north-easterly margin of Palawan Province. Gaulke (1989) provided morphological data for 167 specimens. The longest specimen had a total length of 1880 mm with parts of its tail missing. The smallest specimen measured only 390 mm from the tip of the tail to the tip of the snout. Latter specimen had a snout-vent length of 14 cm, while the largest measured 78.8 cm. The mean snout-vent length was 54.77 cm. Only two voucher specimens from Calauit, SMF 73907 and SMF 73908, exist. The latter exhibits an extraordinary high number of scales around midbody (S = 178). Another aberrant specimen from Busuanga, SMF 73909, stands out of the other V. palawanensis sp. nov. specimens examined for this study due to its unusual short-snouted head resulting in significantly low values for proportion indices 10 (1.60) and 11 (2.09). This deviation, however, may be explained due to pathological deformation as a consequence of inappropriate conditions while this specimen was kept as pet for several months (see above). The average scale counts of ventrals between the gular fold and the insertion of the hind limbs was given by Gaulke (1989) as 90 (min = 81, max = 98), thus slightly exceeding the mean value reported in this study (see Table 3 ).

In colour pattern, V. palawanensis sp. nov. shows some considerable variation ( Tab. 5 ). Gaulke (1989) observed that the dimension of bright parts and patterns of the head and dorsal side strongly varies among individuals of the population from Calauit Island. Accordingly, specimens with predominantly dark heads dominated with 54.9%, followed by 33.5% which had about equally distributed bright and dark parts of the head, and only 11.6% showed predominantly bright heads. Specimen BMHN 94.6.30.20 from Palawan ( Fig.

28) closely resembles the only voucher specimen (SMF 74295) from Sibutu Island, Sulu Islands. The bright markings of the head form two pairs of outwards pointing half-moon shaped curves, the first encircling the supraocular region and the second the occipital region. The dorsal colour pattern in 78.5% of the Calauit specimens examined consisted of merely single bright scales or spots, which form strongly reduced transverse rows. Only the remaining specimens showed more-or-less distinct transverse rows of larger bright spots. Ventrally, most specimens (94.3%) exhibited more-or-less distinctive dark bars laterally on a whitish background. In 18.5% of the specimens the bars formed continuous crossbands, while in 45.6% the bars extend only over half the belly ( Gaulke 1989). In addition, the amount of mottling on the throat may vary from single dark scales on a whitish background to a dark background colouration mottled with few bright scales.

Comparisons with other Philippine Varanus taxa. V. palawanensis sp. nov. is distinguished from the remaining Philippine members of the V. salvator complex by its reduced dorsal colour pattern. Only V. rasmusseni sp. nov. and V. marmoratus show the same tendency in adult specimens. However, latter species are either characterized by an increase ( V. rasmusseni sp. nov.) or a reduction ( V. marmoratus ) of dorsal transverse rows of bright spots in juveniles. In addition, whitish markings of varying extent on the head are only known from V. nuchalis , which, however, is clearly differentiated by enlarged nuchal scales (character XY = 94–138, mean = 109.45 vs. 116–145, mean 12.14 in V. palawanensis sp. nov.). Note that at present due to the small sample size it cannot be excluded that V. rasmusseni sp. nov. also may show white blotches on the head. In tongue colouration, V. palawanensis sp. nov. resembles V. s. macromaculatus from Borneo which also exhibits dark blue-greyish pigmentation on the dorsal side and below, while the remaining Philippine water monitor populations have a flesh-coloured ventral side of the tongue.

Compared to V. marmoratus , V. palawanensis sp. nov. exhibits significantly more scales around the base of the tail (character Q = 98–119, mean = 105, vs. 85–107, mean = 94.73), and along the dorsal side (character XY = 116–145, mean = 127.14, vs. 101–123, mean = 110.80).

Compared to V. s. macromaculatus from Borneo, V. palawanensis sp. nov. has the nostrils on average further apart from the tip of the snout (index 2 = 1.69–2.20, mean = 1.90, vs. 2.00–2.80, mean 2.16; P = 0.018). It has fewer scales around the tail after one third of its length (character R = 48–70, mean = 56, vs. 53– 70, mean = 61.15; P = 0.014), around midbody (character S = 129–178, mean = 141.93, vs. 142–170, mean = 152.05; P = 0.029), on the dorsal side (character XY = 116–145, mean = 127.14, vs. 125–172, mean = 151.20; P <0.0001), fewer supraoculars (character U = 10–14, mean 12, n = 14, vs. 12–19, mean = 14.33, n = 9; P = 0.006), and fewer supralabials (character c = 59–63, mean = 60.64, n = 14, vs. 58–70, mean = 65.25, n = 20; P <0.0001). In addition, the salvator -typical colour pattern is only rarely expressed in V. palawanensis sp. nov.

Despite a similarity in colour pattern of adult specimens between V. rasmusseni sp. nov. and V. palawanensis sp. nov., the latter species has larger and, therefore, fewer scales on the dorsal side (character TN = 155–176, mean = 169.50, vs. 183–187, mean = 185), and around the neck (character m = 93–116, mean = 101.15, vs. 120–129, mean = 124.50).

Distribution. At present, V. palawanensis sp. nov. shows a disjunct distribution. With certainty it is only known from the islands of Greater Palawan (Balabac and the Calamian Island group including Calauit and Busuanga), and Sibutu Island within the Sulu Archipelago. Moreover, photographic evidence suggests that V. palawanensis sp. nov. also inhabits islands of the Sulu group within the Sulu Archipelago, and thus, may live in sympatry with V. rasmusseni sp. nov. ( Fig. 34 ).

Due to the close distance to Borneo it is very likely that V. palawanensis sp. nov. might also inhabit the northern part of Borneo (the natural range of V. s. macromaculatus ) and Banggi Island which is located between the Bornean mainland and Greater Palawan. Gaulke (1996) predicted that the same monitor species from Sibutu Island, Philippines, should also occur on North Borneo. Further investigations are needed to confirm this assertion which would close the present gap in the disjunct distribution of V. palawanensis sp. nov.

Etymology. The specific epithet palawanensis refers to the type locality Palawan Island, Philippines.

Fossil record. Fossil remains of monitor lizards referred to as V. cf. salvator and Varanus sp., respectively, have recently been recovered in 9,000–12,000 years old deposits on Palawan ( Reis & Garong 2001, Piper et al. 2008).

Biology. In the mid 1980s a comprehensive study on the biology of V. palawanensis sp. nov. (then regarded as V. s. marmoratus ) was conducted on Calauit Island, northern part of the Palawan Province ( Gaulke 1989). This species is widespread throughout its range. Its preferred habitats are mangrove swamps and other coastal areas, and riparian habitats. But it is also found in primary and secondary lowland forests, in coconut groves, and other agricultural areas. The highest point on Calauit is about 160 m asl, while on Palawan mainland the monitor occurs at least up to about 700 m asl (M. Gaulke own observ.). While most individuals are residents, others are transients. The activity areas of residents are highly overlapping. Individuals do not defend specific territories. Activity areas of three adults were 4.0, 8.2, and 8.7 ha (markrecapture method) during a one-year period. During the dry season first activities start at sunrise (around 5 a.m.), during the rainy season activities start about one hour later.

Digging nesting holes was observed in February, August, and November, and courtship behaviour in November. Preferred oviposition sites were termite mounds and sandy soil. A wildlife guard from Calauit Island discovered 60– 70 eggs of V. palawanensis sp. nov., at a depth of around 50 cm in the nest mound of the megapodiid bird Megapodius freycinet cumingi .

V. palawanensis sp. nov. are generalist carnivores. They spend a big part of their day actively searching for prey, especially crabs, but also other arthropods and vertebrates including fish (which is captured while diving), anurans, reptiles, birds, rodents, and macaques. They are also scavengers. Large carcasses (wild boars, dead dolphins at the coast, etc.) may attract several individuals. Interactions within feeding aggregations include ritualistic combat fights with bipedal clinch phases. Even though V. palawanensis sp. nov. are typically diurnal, nocturnal activities by at least two individuals were observed around the carcass of a wild boar (all data from Gaulke 1989).

Conservation status. Calauit Island has been a wildlife sanctuary since 1976. During the time of the survey (1984–1985) the water monitor population of this small Island (3760 ha) was calculated to be 913 (+/- 131; capture/recapture method) adults. During this time only few people lived on this island, and no wildlife was hunted or trapped. Later on, people started to invade the island illegally, destroying the natural vegetation and hunting and trapping wildlife. During visits in the late 1990s, the number of water monitors had decreased markedly, based on comparisons of sightings within specific areas in a certain time span (M. Gaulke unpubl. observ.). On Palawan the monitor lizard population seems to be rather high, based on own observations (M. Gaulke) and the observations of other visitors. This might be due to the protection of the Palawan wildlife, which is much more actively pursued compared with many other areas of the Philippines. The population of V. palawanensis sp. nov. can presently be considered as stable.

Figures

FIGURE 25. Dorsal view of the holotype (SMF 73912) of V. palawanensis sp. nov. Photo by André Koch.

FIGURE 26. Ventral view of the holotype (SMF 73912) of V. palawanensis sp. nov. Photo by André Koch.

FIGURE 27. Portrait of the holotype (SMF 73912) of V. palawanensis sp. nov. Note the ill-defined temporal stripe and the dark pigmentation on the dorsal and ventral side of the tongue. Photo by André Koch.

FIGURE 28. Adult paratype (BMNH 94.6.390.20) of V. palawanensis sp. nov. with bright marking on the head. Photo by André Koch.

FIGURE 29. Adult V. palawanensis sp. nov. from Palawan. Photo courtesy of Ingo Langlotz.

FIGURE 34. Distribution ranges of the Philippine species of the V. s a l va t o r complex according to the morphological investigations presented here: V. marmoratus = red; V. nuchalis = blue; V. palawanensis sp. nov. = green; V. rasmusseni sp. nov. = black; V. c. cumingi = yellow; and V. c. s a m a re n s i s ssp. nov. = purple. Question marks denote the water monitor populations from Mindoro, Basilan, and northern Borneo of unknown taxonomic status. The grey shaded areas indicate the paleo-shorelines of several Pleistocene aggregate island complexes, which today, form biogeographic subregions of the Philippines: I = Greater Palawan; II = Greater Luzon; III = Greater Negros – Panay; IV = Greater Mindanao; and V = Greater Sulu. Map modified after Gaulke (in press).