Brachylophus gau

Fisher, Robert N., Niukula, Jone, Watling, Dick & Harlow, Peter S., 2017, A new species of iguana Brachylophus Cuvier 1829 (Sauria: Iguania: Iguanidae) from Gau Island, Fiji Islands, Zootaxa 4273 (3), pp. 407-422: 409-419

publication ID

publication LSID

persistent identifier

treatment provided by


scientific name

Brachylophus gau


Gau  Iguana (pronounced Ngau)

Figs. 2–7View FIGURE 2View FIGURE 3View FIGURE 4View FIGURE 5View FIGURE 6View FIGURE 7

Brachylophus fasciatus Gibbons 1984  (first map showing island record); Zug 1991; Morrison 2003 (on maps as literature record).

Brachylophus bulabula Fisher, Harlow, Edwards  , and Keogh 2008.

Holotype. SUVAAbout SUVA H 0264; collected in forest patch 1 km behind Nukuloa Village , Gau  Island, Republic of Fiji (18°2'46.68"S; 179°18'11.41"E, datum WGS84); 243 meters in elevation; collected by Robert Fisher, Peter Harlow, Tuverea Tuamotu, Joeli Vadada, Maleli Biciloa, Mark O’Brien, Poasa Qalo, 1 July 2013.GoogleMaps 

Paratypes. SUVAAbout SUVA H 0 265 female collected same date, collectors, and locality as holotype ( Figure 1 View Figure )  . SUVAAbout SUVA H 0266–0267 were collected at Nalaqere Creek (18°2'25.91"S; 179°17'12.05"E) on 2 July 2013, by the same collectors as the typeGoogleMaps  . SUVAAbout SUVA H 0 273 was collected at Waitabua Hill (18°2'S; 179°18'E, WGS84), Gau  Island, 439 meters in elevation, on 10 July 2013 by Mark Fraser and Poasa QaloGoogleMaps  . BMNH collected at Sawaieke (17°59'14"S; 179°15'12"E), Gau  Island, between 12 and 27 September 1854 by John MacGillivray.GoogleMaps 

Diagnosis. This species has a unique combination of color pattern characters that distinguish it from all other species of described Brachylophus  ( Figures 2–7View FIGURE 2View FIGURE 3View FIGURE 4View FIGURE 5View FIGURE 6View FIGURE 7, Table 1). It also does not match any museum specimens we have previously seen in collections, except two from the BMNH that previously lacked specific locality info. These specimens are included in the type series as we were able to determine their provenance as Gau  Island (see below in Provenance of Historic Specimens section). Although added to the type series, their measurements are left out of comparisons, but included in Table 2. We found that there are no locality specific museum vouchers that could represent extinct island populations of this species. Otherwise, this species differs from B. vitiensis  by having sexually dichromatism, with banded males and females that are either unicolor or with small spots, and a maximum snout vent length for both sexes of 153 mm, versus 255 mm for B. vitiensis  . It differs from B. bulabula  and fasciatus  in that males and females have green throats, whereas in these species males have white solid or white with green/grey spots or blotches, as do the females in most populations. Although in certain populations the females in B. bulabula  and fasciatus  the throat will be unicolor green, but never the males. It differs from the other three species by having a primarily green colored nasal scale. The mean snout vent length is 149.2 and max size for B. gau  is 153 mm (n = 7), versus adult B. fasciatus  with a mean 154.5 mm SVL and a maximum 176 mm SVL (n = 57) and B. bulabula  with a mean 156.6 mm and a maximum 195 mm SVL (n = 23) ( Table 1).

B. gau  B. vitiensis  B. bulabula  B. fasciatus 

Sexual ƇOlOľ paŧŧeľŊ dichromatism + - + + NuƇħal baŊđ pľe eŊŧ ỉŊ male paľŧỉal + + ‒ Female wỉŧħ đOľ al baŊđ ‒ + ‒ ‒ Male wỉŧħ wỉđe đOľ al baŊđ + ‒ + ‒ Max ỉze <154 mm + ‒ ‒ ‒ TħľOaŧ wħỉŧe Oľ wħỉŧe wỉŧħ pOŧ ‒ ‒ + + Eye ƇOlOľ ỉŊ lỉfe ƇOppeľy ŧaŊ‒gOlđ ľeđ gOlđ

gľeeŊ, ỉmỉlaľ ŧO

ađjaƇeŊŧ Ƈale, lỉgħŧ yellOw‒OľaŊge eŊŧỉľe

Na al Ƈale ƇOlOľ aŊđ ỉŊŧen ỉŧy (ee OľaŊge ỉŊ ỉđe ľỉm Ŋa al aŊđ exŧeŊđỉŊg yellOw fOľ eŊŧỉľe OľaŊge buŧ OŊly Fỉguľe 4 ỉŊ KeOgħ et al. 2008) Omeŧỉme ŧO ađjaƇeŊŧ Ƈale Ŋa al Ƈale aľOuŊđ ľỉm Of Ƈale Habỉŧaŧ Weŧ fOľe ŧ Dľy fOľe ŧ Weŧ fOľe ŧ Dľy fOľe ŧ SPRH 0 264 SPRH 0 265 RNF 13‒3‒3 RNF 13‒3‒4 SPRH 0 267 SPRH 0 266 SPRH 0 273 BMNH BMNH

(HOlOŧype) (Paľaŧype) (Relea eđ) (Relea eđ) (Paľaŧype) (Paľaŧype) (Paľaŧype)

(Paľaŧype) (Paľaŧype)

Sex M F F M M M F M F SVL 150 122 153 108 152 153 145 113 127 TL ľegeŊeľaŧeđ 370 440 325 483 510 414 320 412 Ma(gm) 80 55 118 36 92 ‒ ‒ ‒ ‒ TOŧalpOľe 31 26 30 31 28 40 28 23 29 DOľalCľeŧpỉŊe 67 71 77 68 67 82 71 86 73 Max pỉŊe ħỉgħŧ 1.6 1.6 1.7 1.6 1.5 1.8 1.3 1.1 1.9

fu eđ OŊ OŊe

ỉđe, eŊlaľgeđ fu eđ OŊ bOŧħ fu eđ OŊ bOŧħ fu eđ OŊ bOŧħ eŊlaľgeđ OŊ

SubOƇulaľ Ƈale OŊ Oŧħeľ ỉđe ‒ ‒ ỉđe ỉđe bOŧħ ỉđe ‒ ‒ HW 19.3 15.2 17.9 15.1 19.4 20.1 19.6 16 19 HL 31.4 26 31.5 24.3 32.2 32.4 29.9 25.9 30 HH 18.1 14.7 17.4 13.6 20 19.4 18.7 16.6 19.6 TľuŊk leŊgŧħ 62.5 65.8 74 48.4 70.7 77.5 81 59 68 FOľeaľm leŊgŧħ 24.7 24.5 27.5 18 27.7 26.8 29.2 21.7 26.2 Cľu ‒kŊee ŧO ħeel 29 26 30.1 22.3 32.1 29.8 29.6 25.3 30.6 SŊOuŧ leŊgŧħ 14.2 11.9 13.3 10.6 14.3 13.4 13.3 11 13.5 Description of holotype. Holotype is an adult male ( Figure 2–3View FIGURE 2View FIGURE 3). Meristics are as follows: snout vent length 150 mm, tail length regenerated, live weight 80 gm, head length 31.4 mm, head width 19.3 mm, head height 18.1 mm, and jaw length 24.4 mm. It has 16 elongated/enlarged upper labials (9 left, 7 right) and 17 elongated/enlarged lower labials (8 left, 9 right). Rostral enlarged and triangular wide at base, apparently split on the left side and contacts with nasal scale only on the right side. Mental is incised half way anteriorly, with three postmental scales between the labial scales. Tympanum is translucent and unpigmented, vertical and oval in shape with less height (5 mm) then the eye is wide (6.4 mm). Nostril scale squarish with egg shaped opening raised dorsally within the scale, pale orange in color within the opening, fades to light-green over the rest of the scale. Parietal eye small and scale containing parietal eye similar in size to surrounding parietal. Supraocular head scales smallest, other head scales larger and polygonal shaped, a fused subocular scale on the right side, enlarged subocular scales on the left side. Dewlap is small in size, slightly rounded and unicolor with the throat. Poorly defined gular pouch covered with smaller scales.

Two nuchal bands on right side, one originating at tympanum and continuing posteriorly, reaching nuchal crest, the other above shoulder, left side contains one band with some spotting; two dorsal body bands, both with a dorsal bifurcation leading to green infusion within the bands similar to a saddle at the dorsum, one axial band, and all bands not completely colored, with some background diffusion. Tail regenerated and three tail bands, banding fades posteriorly into background tail coloration. Nuchal crest poorly defined, 67 modified scales, up to 1.6 mm in height and 2.3 mm in width on the nuchal region. Dorsal scales small and conical shaped. Ventral scales much larger then dorsal ones, elongated and strongly keeled, with posterior ends pointed and elevated.

Limbs long and thin covered with keeled scales similar in size to ventral ones; forearm length 24.7 mm, crusknee to heal 29 mm. Digits elongated, palms covered with small keeled scales. Third digit of hind feet contains a denticulate comb on proximate phalynx with some fusion of scales. Toenails very long and not worn. Total of 28 enlarged exuding femoral pores (15 left; 13 right). Tail laterally compressed in cross section, weakly crested for first 30% then undifferentiated. Anterior dorsal scales on tail smaller than ventral ones. All tail scales keeled and posteriorly all scales become similar in size and larger.

Color in life. Head is emerald green with a white stripe lining the lower jaw just at margin. No blue on face. Eye is copper or coppery brown, and a light orange rim around the interior of the nostril. Throat color is unicolor green but hints of some grey bars. No color break but a subtle transition between throat and venter. Dorsal body background color is an avocado green and transitions to a sulfurous green ventrally. There are two wide bands across the back of a blue/grey green color, but diffused with background color and head color via individual scales. The bands do not cross to the ventral side and break into saddles at dorsal crest. Tail with three bands colored as body, but the last two very faded, this is first third of tail then brown bands towards the anterior. The tail maintains a white lateral border. Hindlimbs with striking recurved bars colored as with body stripes. Forelimbs are unicolor. Dorsal crest scales are green and become less distinctive towards anterior.

Color in alcohol. Overall dorsal color is greatly darkened with banding less distinctive but still present. Ventral maintains light-green to blue-grey coloration. Dewlap remains unicolor and not distinctive from ventral coloration. Striking leg banding is obscured. Nasal scale retains light orange color within rim. Parietal eye relatively obscure. Tympanum translucent. Tail becomes brownish and bands become less obvious towards tip.

Variation. The diagnosis above describes some of the variability in this species for the main characteristics that distinguish it from the other living forms ( Table 1). Variability in scalation and measurements for B. gau  are reported in Table 2. Overall it’s a gracile species with long legs and tail. Additional variability in this species is described here and includes either fused or elongated subocular scales in all of the paratypes. Relatively high femoral pore counts. Short dorsal crest height, but high number of dorsal crest scales. Males with two wide dorsal bands, a pelvic band, and a partial nuchal band. Background color of males and females the same lime green. Females have small blue spots anteriorly when looked at closely.

Etymology. The specific epithet is for the only island where the species is known to occur, Gau  .

Comparisons. Table 1 reports the most important characters that distinguish between B. gau  and the other three living Brachylophus  species. One important difference is that this species has fused or elongated subocular scales, and these scales are as long or longer as the eye, this condition is rare in Brachylophus  , and absent in most populations. Dorsal crest scales average 53.2 with a range of 45–60 (n = 50) for B. vitiensis  and for B. bulabula  dorsal crest scales vary in number between 55–88 with an average of 66.2 (n = 14). B. gau  has a greater count than these two species with an average of 71.8 and a range of 67–82 (n = 7), and a lower count than B. fasciatus  which averages 74.6 with a range of 52–94 (n = 48). It also has the shortest dorsal crest scales of any species, with a maximum height of 1.8 mm (n = 7). So comparing it to B. vitiensis  , it is much shorter, with longer legs and tail, thinner build with fewer dorsal crest spines. Its nasal is mostly the same color as the head with a slight orange tinge on the rim. It has unicolor females, versus the banded females of B. vitiensis  . When compared to B. bulabula  , this species is shorter by almost 25%, it has a uniform lime green throat, with few black spots, versus white throat in males that may have grey/green or black barring. It lacks a strong nuchal band in males, and has very little orange on the nasal scale. Finally comparing B. gau  to B. fasciatus  , it has much wider dorsal bands in males, and a more coppery eye, versus the gold eye of B. fasciatus  . It lacks the pastel light blue that B. fasciatus  tends to have on the anterior of the face, and instead has unicolor lime green head color.

Distribution. Brachylophus gau  appears restricted to the large inland forest patches on Gau  Island ( Figure 1 View Figure ). Iguanas were reported from Gau  by Watling (1986), but no specimens were collected or described. It continues to be widespread in high quality forest habitat in the interior of Gau  Island ( Figure 8 View Figure ), with some individuals also in degraded forest closer to the coast ( Figure 9 View Figure ). Gau  is about 136 sq. km. in size and is the fifth largest island in Fiji.

Provenance of historic specimens. The two specimens at the Natural History Museum, London ( BMNH were obviously Brachylophus gau  based on morphology, but lacked specific locality information except that they were submitted by John MacGillivray, esq. and from H.M.S. Herald. A more complete log of the overall expedition of the Herald within Fiji is presented by David (1995). By examining his expedition notes we were able to determine that John MacGillivray directly discusses finding and collecting an iguana on Gau  Island (as he spells it Ngau) on page 55, on line 4 ( Figure 10 View Figure ; MacGillivray 1855):

In the wood behind the beach I shot but lost a large parrot, and a singular chameleon—like green + variegated lizard with extremely long tail among the foliage of an ivi (Tahitian Chestnut) tree to which it closely assimilated in colour.

Later he summarizes his reptile samples from Gau  Island collected between September 12th and 27th, 1854, and highlights the Brachylophus  , and accurately points out that as of this time there were no samples yet in the British Museum ( MacGillivray 1855). Additionally he discusses/collected Gehyra vorax  , Laticauda  sp. and Candoia bibroni  from Gau  Island. This is from page 59 of his notes ( Figure 11 View Figure ):

Reptiles. Perhaps the most remarkable reptile of Ngau is a very handsome tree lizard reminding one of a chameleon. In colour it is a yellowish green (matching the leaves of the trees among which it is found) with paler bands of a light bluish grey tint. My largest specimen is 19.7 inches in length of which the tail forms no less than 15.4 inches. I do not find its genus described in the Brit. Mus. Catalogue, but, judging from the characters there given it appears to be closely allied to Lophura + Physignathus especially the latter. An ugly brown gecko 10 inches long was occasionally brought on board by the natives, and small and active lizards of one or two species are abundant. A small banded Hydrophis—similar to one previously procured at Aneitium, was brought me the one day. Land snakes seem to be plentiful all that I saw are of one species including two varieties. It is usually of a greyish colour, steaked and mottled with black, and an individual of average size measures 3 ½ feet in length. It approaches the genus Engyrus.

Discussion and Conservation implications. Our lack of knowledge of diversity within Brachylophus  in the southwest Pacific has the potential of permitting the extirpation and extinctions of other divergent populations of iguanas ( Harlow et al. 2007). The Gau  iguana appears to be a single island endemic, as are several other iguana populations that most likely warrant species status (Fisher et al. unpub.). The nearest populations of Brachylophus  to B. gau  are Brachylophus cf. bulabula  on Nairai Island, approximately 15 km to the northeast ( Figure 12 View Figure ), and Brachylophus cf. bulabula  on Wakaya Island approximately 43 km to the northwest ( Fisher et al. 2013). Further analysis needs to be conducted to determine the relationships of these populations to B. gau  . As with other populations of iguanas in Fiji, this species is restricted to intact patches of forest and lives high in the canopy ( Figure 13 View Figure ). Currently much of the low to mid elevation forest on Gau  is highly degraded and no longer serves as iguana habitat, and iguanas are not known to cross these grassy or unsuitable plantation habitats to get to other forest patches ( Figure 12 View Figure ). Nothing is known of its reproduction but other species of Brachylophus  lay one clutch of a few eggs (4–6) per year or every two years. These are placed in a shallow hole in the soil under the forest canopy.

Revisiting conservation strategies for this group of enigmatic iguanas in Fiji is a priority, as there continues to be many threats in addition to forest loss and fragmentation, including invasive mammals such as mongoose, cats, and rats, and these iguanas continue to be harvested for the illegal wildlife trade. Local outreach and education will be an important tool in their long-term protection and the protection of their habitats into the future. Gau  Island had previously been identified as a site of conservation significance for Fiji due to its retention of an altitudinal range of moist forest in a large single block that supports Fiji’s only endemic seabird ( Olson et al. 2010). Although approximately 40% of Gau  contains forested habitats, many of these habitats occur as isolated patches at the lower elevations. Although alien invasive species are widespread on the island, cats in particular have the greatest impacts on iguanas ( Gibbons 1984; Priddel et al. 2009). Thorough surveys across the island are required to determine the actual range of the species, to identify critical hotspots of high abundance, and to identify cat control areas. Whether this species is found in the highest uplands of the island is also unknown, as we only surveyed coastal and at mid-elevation forests, with the highest record of an iguana being approximately 440 meters elevation.

As Gau  Island is the home of the only endemic sea bird in Fiji ( Watling 1986), it is presumed to have high levels of endemism in other groups as exemplified by our study here and studies on groups such as invertebrates and plants ( Keppel et al. 2010; Sarnat & Moreau 2011). In a comparison of 1 ha vegetation plots across the Pacific, Gau  had the highest level of recorded tree endemism (56.5%) across islands ( Keppel et al. 2010). So with Gau  Island there still is great opportunity to work with the local communities to conserve what is left of significant habitat patches that can serve for both the conservation of the endemic iguana and the rest of the endemic biodiversity on the island ( Remling & Veitayaki 2016).


University of the South Pacific














Brachylophus gau

Fisher, Robert N., Niukula, Jone, Watling, Dick & Harlow, Peter S. 2017


Brachylophus fasciatus

Gibbons 1984