|Scientific Name:||Brachylophus fasciatus (Brongniart, 1800)|
Iguana fasciata Brongniart, 1800
|Taxonomic Source(s):||Keogh, J.S., Edwards, D.L., Fisher, R.N. and Harlow, P.S. 2008. Molecular and morphological analysis of the critically endangered Fijian iguanas reveals cryptic diversity and a complex biogeographic history. Philosophical Transactions of the Royal Society Biological Sciences 363(1508): 3413-3426.|
Prior to analysis by Keogh et al. (2008), all the banded iguanas were lumped as this single species. The Lau Banded Iguana (Brachylophus fasciatus) is now recognized as distinct from the Fiji Banded Iguana (Brachylophus bulabula). Most previous references pertaining to iguanas in central Fiji are now attributed to B. bulabula. This taxonomic change includes references to the introduced population on Vanuatu, now described as B. bulabula (Bauer 1988, Keogh et al. 2008). The introduced population on Tonga remains as B. fasciatus.
Recent unpublished data finds some morphological and colour variability between islands in the Lau Group, but genetically these populations have less inter-island variability than within the other two species of Brachylophus. The systematics of the iguanas on the islands in the northern Lau Group (north of Tuvuca) is unknown, but for now they will be retained within this taxon.
|Red List Category & Criteria:||Endangered A2abce+4abce ver 3.1|
|Assessor(s):||Fisher, R., Grant, T. & Harlow, P.|
|Reviewer(s):||Bowles, P. & Hilton-Taylor, C.|
|Contributor(s):||Tallowin, O., Allison, A. & Hamilton, A.|
Lau Banded Iguanas have experienced significant declines of well over 50% in the last few decades and is currently not secure on any island where it occurs. During recent surveys of more than 50 islands where they should have been present, iguanas were detected on approximately 20% and several local extirpations were confirmed. On all but three islands, occurrence was extremely rare. There is a continuing loss and degradation of remaining habitat from deforestation, expansion of human development, and cat predation. Without conservation intervention, the degradation observed during the last 20 years is predicted to cause further declines over the next 20 years that approaches 80% and potentially will be found to be even higher with further population analysis.
The concept of this taxon has changed from what was previously assessed on the IUCN Red List. The previous concept of B. fasciatus has now been split into three separate species, hence the historic listings of B. fasciatus sensu lato are no longer included here.
The Lau Banded Iguana is native only to the islands in the Lau Group of eastern Fiji and it was introduced to Tonga. Because there is widespread sub-fossil evidence of B. fasciatus from the Lau Group but these fossils are absent from Tonga, it is believed that Lau Banded Iguanas were introduced from the Lau Group to Tonga in historic times, possibly as an alternative food source after Brachylophus gibbonsi was hunted to extinction soon after human colonization of the area, approximately 2,800 years ago (Pregill and Dye 1989, Pregill and Steadman 2004). Molecular data also supports this theory of introduction since the Tongan iguanas are nearly genetically identical to those from the Lau Group, while subpopulations of other Brachylophus species show sizeable genetic differentiation among them (Keogh et al. 2008).
Within the Lau Group, the iguana has been confirmed recently from only 11 islands ranging from Vanua Balavu in the north to Fulaga and Ogea in the south (R. Fisher pers. comm. 2011). Previously, iguanas had been known from Moce and Oneata, for example, and probably occurred on most islands throughout the Lau Group. The iguanas from Yacata and Vatu Vara, to the west of Vanua Balavu, were not designated as B. fasciatus by Keogh et al. (2008) due to lack of genetic samples and some morphological discrepancies observed in specimens collected in the 1920s. Preliminary analysis of iguanas from Taveuni and Qamea Islands to the north of Vanua Balavu indicate that these are most similar to B. fasciatus, but genetically different from all of the other animals sampled from the Lau Group (R. Fisher pers. comm. 2011).
Iguanas are probably found up to 200 metres above sea level, although most islands they occur on are lower than 100 metres.
|Range Map:||Click here to open the map viewer and explore range.|
Among all the islands surveyed for the presence of Lau Banded Iguana, only on the two Aiwa Islands were enough lizards found to estimate a population size, this was estimated to number less than 8,000 total (Harlow 2003). More recent surveys in July 2011 also determined that, where present, iguanas were very few in number except on the uninhabited 8.1 km² island of Vuaqava (R. Fisher unpublished data 2011). Although there is no historic population size data available, the Lau Banded Iguana is believed to have declined by at least 50% in the last 30-45 years based on their fossil distribution, an estimated abundance based on the size of their range islands, the area of former forest and known iguana abundance in intact forests, and the known impacts of humans and their associated goats, cats, and rats. Discussions with island residents indicate that on most islands the iguanas are now more rare than they had been in the recent past. Most islands in the region are now inhabited and iguanas were generally found in degraded forests or remnant forest patches, but not in proximity to villages or gardens. Surprisingly, among the uninhabited islands surveyed only one was found to have iguanas present, but this is likely due to the abundance of cats present on the iguana-free islands. It is known that local residents intentionally translocate kittens to these uninhabited islands for rat control.
The two largest islands in the Lau Group would have once supported very large numbers of Lau Banded Iguanas. Lakeba is the largest (55.9 km²) although the majority of the island has now been deforested and planted with Caribbean Pine (Pinus caribea) which is unsuitable for iguanas. According to Franklin et al. (2008), Lakeba has less than 9% of native forest remaining. At least one small subpopulation of iguana might remain, as one captive individual was seen in a village in 2011 that had been captured from one of the remaining forest patches. This is the first time an iguana was documented on Lakeba since the 1940s. The inhabited island of Vanua Balavu is the next largest island (53.2 km²) and has also experienced severe deforestation, although it was one of only two islands where B. fasciatus was detected during surveys of Northern Lau in 2007 (M. Tuiwawa pers. comm.). All other islands in the Lau Group are much smaller and vary in the amount of forest remaining, from those that completely lack native forests to uninhabited islands such as Aiwa and Vuaqava where native forests are largely intact.
The Lau Banded Iguana was not found in recent surveys on the inhabited Yasayasa Islands of Moala, Totoya, and Matuku (R. Fisher pers. comm. 2011) where they were reported to occur by Gibbons and Watkins (1982). Interviews with local residents indicate iguanas are likely to have been extirpated from these islands. Field surveys in July 2011 of the southern Lau Group and Yasayasa Islands included 25 islands, and night surveys were conducted on 15. Lau Banded Iguanas were confirmed on only six of these islands; in some cases only a few individuals were detected. Historically, iguanas were probably abundant throughout most of these islands. In 2007, islands in the northern Lau Group were surveyed and iguanas were found on only two of the 15 islands visited (M. Tuiwawa, pers. comm.). Although night surveys were not conducted on every island, presence or absence of iguanas was confirmed by interviews with residents during these visits that are highly knowledgeable of local fauna and flora. In 2008, 12 islands in the central Lau Group were surveyed and iguanas were found only on the two Aiwa Islands as was previously known (M. Tuiwawa pers. comm., Harlow 2003). An additional uninhabited island (16.2 hectare Olorua, Kabara) was reported to have iguanas by the residents of Komo, but unfortunately this island was inaccessible during the survey. Iguanas were not detected on Lakeba in 2008 and it is believed they are extremely rare.
In summary, a total of 52 islands in the Lau Group and Yasayasa Islands were visited between 2007 and 2011 and iguanas were detected or reported from only 11 islands, with an additional report from one island that was not visited. Iguanas were abundant on only three islands, the two neighbouring Aiwa Islands and Vuaqava, all of which are uninhabited. Goats have recently populated all three of these islands and Vuaqava has a seemingly large cat population. Most of these 53 islands should have had resident iguana populations. For example, two islands with historic populations, Moce and Oneata, were described by the Whitney Expedition (Burt and Burt 1932) and have since been extirpated. Given these results, it appears that iguanas could be remaining on about 20% of the islands in the region and are abundant on only 5%.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
The Lau Banded Iguana occurs in a range of habitat types on differing island formations. In the north, islands are volcanic in origin and contain wet forest, whereas in the south the islands are raised limestone and contain dry forest, often with very little open soil. The lack of soil and dry nature of the limestone islands potentially restricts where nesting can occur, but since Harlow (2003) reported finding many eggshells on Aiwa during their surveys, it may not be a limiting factor for iguana reproduction.
Iguanas are primarily found in remnant stands of native forests on the islands they occupy, but are sometimes found in marginal habitats of non-native plants, native hibiscus, and degraded forest around villages and also along ocean margins, but always where trees are at least six metres in height. The highest densities of this iguana were found on Aiwa and Vuaqava, both of which are lacking understory due to overgrazing by goats. As was seen on Yadua Taba for Fiji Crested Iguanas (Brachylophus vitiensis), the removal of goats has a big impact on restoration of dry forest habitat and can allow the iguana population to expand greatly.
As with most iguanas, this species is herbivorous, although a comprehensive study of its diet in the wild has never been studied as it is so rare. They are assumed to prefer the same food plants as the better studied Brachylophus vitiensis, as many or most of these same plants occur on the islands occupied by B. fasciatus. All the Brachylophus iguanas are very difficult to observe during the day and occupy the highest levels of the tree canopy on the islands.
A combination of data for the genus and specific to B. fasciatus indicate that wild Lau Banded Iguanas are not reproductive until age four and the mean generation length is likely to be 10-15 years. They lay an average of five eggs per clutch. This lizard is the smallest South Pacific iguana species with a maximum snout-to-vent length of 18 cm. This species is differentiated from the other two Brachylophus iguanas both genetically and by several morphological characters including body size, the diminutive size and higher number of dorsal crest spines, the low number of femoral pores, nostril colour and shape, and overall colour pattern.
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||10-15|
|Use and Trade:||Lau Banded Iguanas are sometimes locally kept as pets, and this was observed on three different islands during surveys in 2011. Historically, these iguanas would have been a local food source, similar to the larger extinct species (Lapitaiguana and B. gibbonsi) in the region, but there are no recent records of human consumption. The black market trade in Brachylophus does not include this species and is unlikely to be a threat in the future as its remaining localities are very remote.|
Black Rats (Rattus rattus) and feral cats (Felis catus) are the main mammalian predators threatening the persistence of iguanas and are capable of causing local extinctions in a relatively short time period. Fortunately, mongoose has not been introduced to the Lau Group yet, and maintaining it free of them is an important biosecurity issue. On a few islands, free-roaming domestic pigs (Sus scrofa) were observed to cause major disturbance in small forest patches, turning large areas to bare mud that is no longer suitable for iguana nesting. Free-ranging domestic goats (Capra aegagrus) are an important concern on many of the smaller islands as they also browse the plants most important to iguanas, and effectively remove these plants from the habitat. Also, intentionally-set fires are used to round up the goats, further enhancing the transition to grassland and inhibiting native forest regeneration.
Even in the absence of goat herding, forest burning is widespread and is increasingly one of the biggest threats to iguana habitat and their persistence. Continued deforestation on the small islands where Lau Banded Iguanas remain is predicted to cause additional local extinctions over the next 40 years. In particular, on the large islands of Lakeba and Vanua Balavu where iguanas should have been numerous, there has been significant forest loss through deforestation, burning, and fragmentation (R. Fisher pers. obs. and Google Earth).
Additional threats to the native forests include further development of urban and village areas, plantation agriculture, and logging. In particular, harvesting Vesi Tree (Intsia bijuga) for use in traditional carving on several islands (for example, Kabara) has significantly reduced the native forest. Forest conversion to Caribbean Pine plantations is also significant, especially on Lakeba. Proposed development of tourism resorts, on the smaller islands in particular, has significant impacts on these habitats, possibly leading to losses of entire iguana populations as has been observed elsewhere in Fiji. Finally, proposed new cruise ship routes to the remote Lau islands will require construction of new infrastructure and is likely to be a source of invasive species from Viti Levu unless strict biosecurity measures are enforced.
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 Banded Iguanas versus eradication of the Green Iguanas, since juveniles of the latter appear superficially similar. The northern Lau Islands are very close to Qamea where the Green Iguana was first introduced and are at high risk of invasion.
Irruptions of invasive alien Yellow Crazy Ants (Anoplolepis gracilipes) are known to occur on many of the southern Lau islands. Even though these ants were introduced to Fiji over 100 years ago, it is not understood what causes populations to periodically irrupt in huge numbers on some islands. When Crazy Ants irrupt, the entire ground surface, shrubs, and trees are entirely covered with ants and it has been observed that native skink and gecko abundance drops greatly during this time (R. Fisher unpublished data). The impact of aggressive ant irruptions on iguana reproduction and recruitment is not known, but is likely to suffer similarly to other lizards (Holway et al. 2002).
Lau Banded Iguanas are sometimes locally kept as pets, and this was observed on three different islands during surveys in 2011. Historically, these iguanas would have been a local food source, similar to the larger extinct species (Lapitaiguana and B. gibbonsi) in the region, but there are no recent records of human consumption. The black market trade in Brachylophus does not include this species and is unlikely to be a threat in the future as its remaining localities are very remote.
There are no national conservation measures in place for the Lau Banded Iguana and they are not found in any protected areas. All of the Brachylophus iguanas are protected from international trade by Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Further surveys are needed in the small forest patches on some of the larger islands in the Lau Group to determine if any additional isolated populations still persist. The smaller islands with recently confirmed iguana populations need to be resurveyed quantitatively to develop population estimates and map the remaining habitat on each island. Island assessments for feral cats and Black Rats in the region are needed also, as these appear to be the most important predator for Brachylophus iguanas. Further research on the role of invasive ants in possible iguana declines is also needed.
Genetic confirmation is needed for iguanas that were recently sampled and appear to be B. fasciatus, particularly from the newly surveyed areas of southern Lau and Vanua Balavu. The iguanas of Yacata and Vatu Vara, which were identified in Keogh et al. (2008) as possibly belonging to this species, need to be assessed systematically, as do the other islands in the northern Lau Group lacking recent survey information.
Education programmes for the local community need to continue to stress the importance of the role of iguanas in the ecosystem, its value for protection, and the differences between native and invasive Green Iguanas. Within the conservation community, education and awareness are needed to better inform people about the differences between this species and the recently separated Fiji Banded Iguana, Brachylophus bulabula, as much of the literature regarding banded iguanas in Fiji still refers to B. fasciatus in name, regardless of which species the information actually pertains to.
A Conservation Action Plan is badly needed for this species as no specific conservation actions have been designed or implemented to ensure its survival. The confusion with Brachylophus bulabula, and the assumption that they occur on many islands, significantly under-represents the threats to this species. Based on the rate of habitat degradation over the last 20 years, the number of Lau Banded Iguanas and the persistence of their remaining subpopulations will have declined by at least 70% by the end of the next 20 years without intervention. With more data on past and current trends, it is likely this predicted loss would be much higher.
|Citation:||Fisher, R., Grant, T. & Harlow, P. 2012. Brachylophus fasciatus. The IUCN Red List of Threatened Species 2012: e.T19243030A2791124.Downloaded on 18 August 2018.|
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