Iguanas of the South Pacific 83
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Iguanas of the John Gibbons Two species of iguana inhabit the islands brown spines, narrow white bands bordered by of the Fiji goup: one, the crested iguana, black, and is generally much larger and higher at was discovered as recently as 1979 and the shoulder than the banded iguana. Sexual dimorphism is lacking, and both sexes exhibit the other, the banded iguana, once extreme colour labity, from light green when common enough to be an important sleeping or in shade to greyish-black when source of food for humans, is now listed aroused during aggressive or sexual encounters. in the IUCN Red Data Book. The author, The banded iguana has a feeble crest of spines, in his three-year study, discovered that the longest not exceeding 0-3 cm, broad bluish- both species still exist in relatively dense white bands and a smaller, more slender body than the crested iguana. Sexual dimorphism is populations on a few, small uninhabited marked, most females either having a reduced islands, although they have disappeared banding pattern, or none at all and a small, pale from those that are developed. He dis- dewlap. Colour change, though marked, is never cusses the threats to their survival and the as great as in the crested iguana, the maximum conservation efforts being made. darkening possible being a chocolate brown. More detailed information on species differences, including ethological as well as morphological The iguanine genus Brachylophus of Fiji and data are given elsewhere (Gibbons, 1981; Tonga is of considerable biogeographical interest Gibbons and Watkins, 1982). in being the only true iguana (sub-family Iguaninae) found outside the Americas. Brachy- lophus is also of great interest on account of its Information on the biology of the banded iguana, strikingly beautiful appearance, and its rarity in especially on its distribution, abundance and museum and zoological collections. At present habits in the wild is extremely limited. Most pub- two species are recognised; the banded iguana lications on the animal have been written by over- Brachylophus fasciatus (Brongniart, 1800) and seas scientists on short visits to Fiji or Tonga (e.g. the crested iguana, B. vitiensis (Gibbons, 1981). Bustard, 1970; Cogger 1974) or by local natural- The former is widely distributed throughout Fiji ists with little opportunity for full-time study (e.g. Group and, probably, Tonga also. In addition, a Cahill, 1970). All are in agreement that the wild population is known to exist on Efate Island banded iguana is now uncommon or rare on in Vanuatu, but this probably represents a recent most islands. Indeed, the species is listed as introduction (Gibbons, 1981). The latter is endangered in the IUCN Amphibia and Reptilia restricted to a few very dry rainshadow islands in Red Data Book (Honegger, 1975). There is the north-west of the Fiji Group including reliable evidence (Williams, c. 1843-45; Yaduataba and the Yasawas (Figure 1). Tischner, 1965) that the banded iguana was quite common, at least on Viti Levu, until late in the The two species are readily distinguished. The nineteenth century. A major reason cited for this crested iguana has a well-developed crest of soft, decline has been the introduction of the Indian 82 OiyxVoll8No2 Downloaded from https://www.cambridge.org/core. IP address: 43.130.79.121, on 04 Oct 2021 at 20:47:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300018755 South Pacific Top left: Crested iguana; in this species males and females have similar colour patterns (John Gibbons). Top right: Male banded iguana; note the broad bands and feeble crest (John Gibbons). Below: Female banded iguana; note the lack of bands (John Gibbons). mongoose Herpestes auropunctatus to Fiji in servation of the crested iguana population on 1883 (Gorman, 1975), and Bustard (1970) has Yaduataba Island, which represents the only field stated that Brachvlophus is 'rare throughout study on Brachylophus yet undertaken. almost all its range'. The present paper presents a re-assessment of Distribution and abundance the above conclusions based on a three-year Contrary to Bustard (1970), Brachylophus is not study of iguanas throughout the Fiji Group. A rare throughout almost all its range. The popu- detailed account is given on the ecology and con- lation of B. vitiensis on Yaduataba is extremely Iguanas of the South Pacific 83 Downloaded from https://www.cambridge.org/core. IP address: 43.130.79.121, on 04 Oct 2021 at 20:47:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300018755 77" ] a" 179 i 0 79' kobia A B. vitiensis B. ascialus , 100 Itm 0 16 * • Dracnylopnus '6 "*: species uncertain - II? l.aui ala . % Yasawa Yaduata •^ 'TAX KIXI atacawalevu ^Dj Vanuabalavu ^JJWaya laiala ,,A •P oro tu \araOMago '5- ~ JVIonuriki jf- _ ; a <*. ',\ VALAl'1 ,. • 0 ^ ^ ^Alaioun ,riki"p Cum • ./, ^ H^ Levuy VITI LEVU \ *M ' •J.\a,r;,, —18°<^ (r I* 5TW C5 . ia° «Gau A SIVA ^Lakeba g Yanuca* ^ Betja ^^'^.Onea'ta •\Valulelc >ala (^Kabara ".' )9° olova ^KADAVl gjMa.uku 17 7° 178' 1 9' 1 o' i Figure 1. Map of the Fiji Islands showing the distribution of the banded iguana Brachylophus fasciatus and the crested iguana B. vitiensis. even after a detailed search in the 'right' habitat, dense, well in excess of 300 animals occupying an since the animals are extremely well camou- area of 0-7 sq km. There are strong indications that a small number of uninhabited islands, in- flaged. cluding Vatu Vara and Aiwa in the Lau Group One of the major problems in working out dis- contain relatively dense populations of B. tribution oiBrachylophus has been the complete fasciatus. On many islands, including Koro, lack of museum records of specimens from the Nairai, Kadavu, Ovalau and Yacata, the banded wet, forested interiors of the two main islands. iguana is encountered on a fairly regular basis by Indeed, until recently, the available hard evi- Fijians. Several specimens have been sent to dence indicated that Brachylophus was almost Suva from each of these islands during the past exclusively a coastal species (see Gibbons and three years. This species seems less common on Watkins, 1982). This was puzzling because there many other islands, but populations still occur is much historical evidence that iguanas were throughout most of the coastal area of southern once a widespread food item in the interior of Viti Viti Levu. Occasional sightings of the banded Levu. The Reverend Thomas Williams (c. 1843- iguana have been made within metropolitan 45) gives the following account: Suva in the last decade. This is not to say that the '... a chief from Dan Vungalei who with his father-in-law were average person might expect to see an iguana, served with food consisting in part of cooked guanas—there 84 OryxVoll8No2 Downloaded from https://www.cambridge.org/core. IP address: 43.130.79.121, on 04 Oct 2021 at 20:47:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300018755 was one for each of them—unhappily the chief in passing on intermediate between typical B. fasciatus and B. the guana intended for his father-in-law broke off part of the vitiensis (see Gibbons, 1981). tail and ate it. For this the angry father-in-law watched (for) an opportunity and slew him telling him before he did what was For both species, the present-day distribution is his motive'. very patchy. For example, iguanas are unknown Theodor Kleinschmidt's 1877-78 account of Viti on -many of the more developed, populated Levu (Tischner, 1965) also includes reference to islands in the Mamanuca Group, and they are the banded iguana. On page 380, he states, in seldom seen on other islands except for Monuriki. translation: The patterns of distribution of the two species 'Lizards, tree-geckos and Chrescartes (= Brachylophus) indicate that vitiensis is restricted to dry islands fasciatus axe eaten. From the C. fasciatus the natives collect the leathery eggs. These eggs are cooked and the empty shells with low winter rainfall (May-October), while are blown up and placed on a stick for decoration inside a fasciatus occupies a whole range of habitats from house. ..." dry beach forest to wet rain forest experiencing This puzzle was further complicated by reports more than 500 cm annual rainfall. Significantly, (Boulenger, 1887) of an agamid lizard Gono- Malolo Levu is considerably wetter than icephalus godeffroyi, which superficially re- Monuriki, Yaduataba or the Yasawas, and unlike sembles Brachylophus, on Viti Levu. Even these other islands supports a population of the though some herpetologists doubted the exist- introduced cane toad Bufo marinus. ence of a natural population of this species in Fiji (Pernetta and Watling, 1978), lingering un- Causes of decline certainty remained as to the identity of Williams's Nineteenth-century accounts of the banded 'guanas'. The problem was finally solved when a iguana in Viti Levu noted earlier leave no doubt specimen of Brachylophus fasciatus collected at that the species was very common in former Monasavu (altitude c. 1000 m) in the wet rain times. Now eggs are extremely difficult to find forest interior of Viti Levu was brought to Suva in even for relatively dense Brachylophus popu- 1981. lations. What were the causes of this decline? For The crested iguana B. vitiensis remained un- many declining or disappearing species, habitat known to science until its discovery in 1979 on destruction and/or killing by man are the primary Yaduataba. For nearly two years thereafter no causes.