|Scientific Name:||Brachylophus vitiensis|
|Species Authority:||Gibbons, 1981|
|Taxonomic Notes:||Recent genetic data (Keogh et al. 2008) have shown that each subpopulation (island) of this species is genetically unique. This data, along with many morphological characters, clearly define this species, although the observed genetic inter-island variability might be consistent with subspecific differences after further assessment.|
|Red List Category & Criteria:||Critically Endangered A2abce ver 3.1|
|Assessor/s:||Harlow, P., Fisher, R. & Grant, T.|
|Reviewer/s:||Bowles, P. & Hilton-Taylor, C.|
|Contributor/s:||Tallowin, O., Allison, A. & Hamilton, A.|
With the exception of Yadua Taba, and possibly Macuata Island, Fiji Crested Iguana populations on all other islands are barely detectable and are expected to become functionally extinct within the next few years without immediate action. Iguanas have become extirpated from several islands where they were present in the 1980s (Harlow et al. 2007), a time period representing 2-3 generation lengths. Iguana habitat is continuing to be degraded due to goat grazing, presence of feral cat predators, intentional forest clearing and fires, and the spread of the invasive alien plant species. Although historic quantitative population data is not available for this lizard, it is estimated that the number of iguanas has declined by at least 80% over the last 40 years based on the size of their range islands and the area of former forest.
The Fiji Crested Iguana presently occurs on eight western dry forest islands in Fiji, including two islands in the Yasawa Group (Deviulau and Waya), four islands in the Mamanuca Group (Monuriki, Monu, Qalito, and Malolo Levu), one island off northern Viti Levu (Macuata), and Yadua Taba Island (off the west coast of Vanua Levu). Iguanas have not been seen in living memory on the human-inhabited island of Yadua where feral cats are common, only 120 metres from Yadua Taba. Several local extinctions have probably occurred recently in the Yasawas (for example Matacawa Levu and Naviti), as iguanas were reported there by Gibbons (1984) and local residents in 2000, but were not detected during field surveys since then.
Historically, Fiji Crested Iguanas were presumably widespread in the dry forest on the western portions of both Viti Levu and Vanua Levu. Prehistoric bones of this iguana were documented from cave sites in western Viti Levu (Worthy and Anderson 2009) as well as more recent evidence in layers approximately 100 years old among barn owl deposits.
The species probably occurred up to 500 metres above sea level historically, although most, if not all, now occur below 100 metres.
|Range Map:||Click here to open the map viewer and explore range.|
Historically, Fiji Crested Iguanas should have been widespread in the western dry forest portions of Viti Levu and Vanua Levu, but there have been no confirmed records from either of these islands recently.
Gibbons visited the Yasawa and Mamanuca island groups in 1982 and reported that Fiji Crested Iguanas occurred on at least eight islands, but were seldom seen except on Monuriki where sightings were still frequent (Gibbons 1984). In 2000, Crested Iguanas were located on only four of 17 islands surveyed in this area: three small uninhabited islands (Deviulau, Monu, and Monuriki) and one large, inhabited island (Waya). Because of the low numbers of iguanas detected (six total), abundance estimates could not be calculated (Harlow et al. 2007). Additional, more intensive surveying in 2003 on Monu and Monuriki detected more individual iguanas, although the number was still too few to calculate a population estimate (Harlow et al. 2007). Resident Fijians report that Crested Iguanas are still occasionally seen on two other inhabited islands where large dry forest patches remain (Matacawa Levu and Naviti). However, iguanas were not documented on any recent surveys and it is believed that if still present, they are not expected to survive long-term because of the presence of feral cats and the continuing rate of forest degradation resulting from goat grazing, intentional forest fires, and the spread of the invasive alien Vaivai Tree (Leucaena leucocephala).
Although iguana sightings were described as “frequent” on Monuriki in the 1980s, transect surveys in 1998 detected only 13 animals (Harlow and Biciloa 2001), two in 2000, and eight in 2003 (Harlow et al. 2007). In 2010 and 2011, 20 iguanas from Monuriki were captured for captive breeding at Kula Eco Park, Viti Levu, with the intention of future reintroduction (P. Harlow pers. comm. 2012). The small number of iguanas remaining on Monuriki were too difficult to capture (J. Niukula pers. comm. 2011). In 2012, both goats and Pacific Rats (Rattus exulans) were removed from Monuriki, so it is hoped that captive-bred iguanas can be returned to the island as soon as forest regeneration begins.
In 2011, Fiji Crested Iguanas were captured at tourist resorts on Malolo Levu and Qalito Islands in the Mamanucas. Follow-up surveys on both islands failed to detect further iguanas, indicating these are critically small populations. Qalito was discussed by Gibbons (1984) as containing good habitat, but lacked iguanas due to the presence of cats. The Qalito iguana found in 2011 had been clearly attacked and injured by a cat. Malolo Levu contains very little native forest, but the resort has recently implemented a cat control programme and a couple of hatchling iguanas have since been observed on the resort grounds.
Populations of Fiji Crested Iguana have declined dramatically on all islands with the exception of Yadua Taba and Macuata, where iguanas are increasing in number as a direct result of conservation efforts. Forest burning ceased on Yadua Taba in 1980, goats were removed in 2004, and an invasive plant management programme was developed and some invasive plants were removed (Taylor et al. 2005). A 2002 vegetation survey of Yadua Taba and comparison with aerial photographs from the 1980s suggest that 10–20% of the dry forest had regenerated in the last two decades (Olson et al. 2002). In response, the iguana population on this small island (72 hectares) has grown from an estimated 6,000 (Harlow and Biciloa 2001) animals to more than 10,000 in 2007 (Morrison et al. 2007), and approximately 12,000 currently (Morrison et al. 2009).
A population of 80 Fiji Crested Iguanas was estimated for Macuata, a 40 hectare uninhabited island off the northern coast of Fiji’s largest island, Viti Levu by Olson and Keppel (2004). More recently, the population is estimated at approximately 690 iguanas (P. Harlow unpublished data 2011). In 1988, only one iguana was located on this goat-ravaged island when very little forest habitat remained (D. Watling pers. comm.). In 1994, goats were removed and forest regeneration has been rapid, with 60–70% of the island now covered in recently regenerated forest that includes six of the important iguana food tree species. The iguana population is expected to continue to grow on Macuata as the forest recovers.
|Habitat and Ecology:||
Fiji Crested Iguanas are an arboreal, herbivorous lizard restricted to coastal dry forest habitat. They eat leaves, buds, fruit, and flowers from a range of forest plants (Morrison et al. 2007). Vegetation surveys suggest that where found, the abundance of Crested Iguana reflects the relative abundance of food trees present, with 63% of forest trees on Yadua Taba being edible species, compared to only 2% on Monuriki. Although both islands are uninhabited and have no introduced predators, Monuriki has been subjected to over three decades of intensive goat grazing and regular dry season burning. The single most important food tree, Cevua (Vavaea amicorum), was recorded in nine out of ten vegetation quadrats on Yadua Taba but in none on Monuriki. This fire-sensitive species accounts for 40% of trees in the beach forest on Yadua Taba (Harlow and Biciloa 2001).
On Yadua Taba, iguanas lay a single clutch of 2-4 eggs in a carefully excavated burrow on the forest floor in the mid-wet season (February-April) every second year (Morrison et al. 2009). Their eggs are known to have one of the longest incubation times of any lizard, taking approximately nine months to hatch (Gibbons and Watkins 1982).
The Fiji Crested Iguana is the largest of the living South Pacific iguanas, obtaining a maximum snout-to-vent length of 25 cm. Unlike the two species of banded iguanas, they have large spines on the back. Additionally, they lack the colour dimorphism of the banded species, in that both males and females have dorsal stripes.
Fiji Crested Iguanas are dependent on healthy beach and dry forests that are regarded as Fiji’s most critically endangered habitat (Morrison et al. 2009) and is under ongoing threat on most islands. Very few islands currently contain significant patches of healthy dry forest. Remnant populations of iguanas are threatened by the continuing degradation of remaining native forests resulting from clearing, burning, conversion to plantations and grassland, goat grazing, invasive alien plants, and village expansion and tourism development.
Because Fiji Crested Iguanas are small in size, they are particularly vulnerable to predation by feral cats (Felis catus) in all age classes (Gibbons 1984) and perhaps invasive alien Black Rats (Rattus rattus). For example, Deviulau Island (23 hectares) has a high proportion of iguana food tree species (69%), yet the presence of cats is likely responsible for the low number of iguanas remaining.
The presumed extirpation of Fiji Crested Iguanas from Viti Levu and Vanua Levu was likely associated with Small Asian Mongoose (Herpestes javanicus) predation as well as conversion of the majority of the land that historically contained dry forest into sugarcane plantations and urbanization.
The impact of the recent introduction and spread of the invasive alien Common Green Iguana (Iguana iguana) in Fiji are not yet known for this species but have been shown to have significant detrimental effects everywhere they have been introduced (Thomas et al. 2011). Eradication for this invasive now appears unlikely, and it is possible the Green Iguana will continue to spread to other well-forested islands despite eradication efforts. Green Iguanas are vastly more fecund and aggressive than native iguanas and may have significant effects on remnant small island populations. At minimum, this introduction has caused considerable confusion in the local education programmes aimed at protection of native iguanas versus eradication of the Green Iguanas.
Although they were found in prehistoric middens (Worthy and Anderson 2009) and Gibbons (1984) cited reports of consumption of Brachylophus species in the 1800s, Fiji Crested Iguanas are no longer hunted or eaten.
Currently, Crested Iguanas are found captive at various resorts in the Yasawas, the legality of which is unknown, and whose origins are from the resort’s island or Monuriki. It is known that at one time Crested Iguanas were regularly captured on Monuriki and sold to various resorts and individuals. Iguanas are also illegally held captive as pets on Viti Levu, and escapees have been discovered in various locations and transferred to the captive programme at Kula Eco Park. One animal recently brought in from the town of Lautoka was genetically determined to originate from Waya Island. This informal and illegal trade is likely to have impacted some of the critically small populations.
In 2004, a Species Recovery Plan Workshop was held in Suva, Fiji, and outlined a number of action steps needed to reverse the decline of Fiji Crested Iguanas. The entire island of Yadua Taba is protected as a national park administered by the National Trust of Fiji Islands and known as the Crested Iguana Sanctuary. Recent natural habitat regeneration, after goat removal in 2004, has greatly increased the number of iguanas and demonstrates the real potential for restoring populations of iguanas on other islands. Monuriki Island is currently undergoing regeneration as goats and Pacific Rats have been recently removed. Additionally, captive breeding and eventual release of Monuriki iguanas should jump-start recovery on that island. However, together with Macuata, these three islands comprise less than 160 hectares and habitat protection and restoration of other islands will be needed in the iguana’s range to ensure the long-term viability of this lizard.
Because of the success of recovery efforts on Yadua Taba, this iguana has benefited from the celebrity status it receives from the National Trust and is used as a symbol for Fiji biodiversity conservation. Now that this site is more stable, attention needs to focus on the remaining at-risk subpopulations.
Further surveys need to be completed in small forest patches on some of the larger islands in the Yasawa Group to determine if any additional isolated subpopulations still persist. This includes islands where only one or two individuals were detected during field surveys in 2000. Genetic confirmation is needed for the iguanas recently found on Malolo and Qalito, as well as determining their abundance. Additional research and conservation needs include life history and ecology studies, threat mediation, reintroduction strategies, and further clarification on the taxonomy of the Brachylophus iguanas.
Although Fiji Crested Iguanas have not been observed on Viti Levu and Vanua Levu for many decades, surveys should be conducted in the relict patches of dry forest remaining to confirm their absence.
Like all of the Brachylophus iguanas, Fiji Crested Iguanas are protected from international trade by Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
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|Citation:||Harlow, P., Fisher, R. & Grant, T. 2012. Brachylophus vitiensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 05 December 2013.|
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