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Endangered Species Monday | Brachylophus fasciatus.

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Endangered Species Monday | Brachylophus fasciatus

This Monday’s (ESP) Endangered Species Watch Post report I document on a rather “undocumented species” of iguana identified back in the 1800’s. (Photographer unknown)

Identified back the 1800’s, and listed as [endangered] the species was originally identified by French Dr Alexandre Brongniart (5 February 1770 – 7 October 1847) who was a French chemist, mineralogist, and zoologist, who collaborated with Georges Cuvier on a study of the geology of the region around Paris.

Dr Alexandre Brongniart was born in Paris, the son of the architect Alexandre-Théodore Brongniart and father of the botanist Adolphe-Théodore Brongniart. He was an instructor at the École de Mines (Mining School) in Paris and appointed in 1800 by Napoleon’s minister of the interior Lucien Bonaparte director of the revitalized porcelain manufactory at Sèvres, holding this role until death.

The young man took to the position a combination of his training as a scientist— especially as a mining engineer relevant to the chemistry of ceramics— his managerial talents and financial acumen and his cultivated understanding of neoclassical esthetic. He remained in charge of Sèvres, through regime changes, for 47 years.

Commonly known as the Fiji Banded Iguana, Lau Banded Iguana, South Pacific Banded Iguana, or Tongan Banded Iguana the species is unfortunately endangered and nearing extinction within the wild. A reptilian, and member of the iguana family the species has been placed within the order of (Squamata).

Within the past TWO DECADES the species has undergone a decline of some 50% throughout its range. Furthermore species declines are still ongoing with no apparent let up neither, (threats have been noted as significantly severe and widespread).

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. Basically unless conservation efforts are improved or continue then we will lose the species very quickly.

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Image: Fiji Banded Iguana (Credits: Robin Carter) 

Now to some humans this may not seem much to worry about. However let me ask you this. Have you experienced a rather large number of flies bothering you, mosquitoes, insects, and general bugs wreaking havoc with your everyday life? If the answer is “yes”, then maybe you need to be paying attention to my articles. Reptiles loves flies, and without reptiles there will be more flies.

Endemic to Fiji, the species has recently been introduced to Tonga. 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. That population size is concerning (especially when we take into consideration life span, gestation, and threats). 8,000 can soon turn into 1000 in under five years.

Although there is no official “population size estimates”, its believed from census reports (which I myself do question), within the past 35-40 years the species has undergone (as explained above) a decline of 50%. 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.

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. The sheer fact we only have on ELEVEN ISLANDS instead of FIFTY TWO Fiji Banded Iguanas, just goes to show we have serious problems here that need addressing before its to late.

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 (which could be a threat). 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 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%. 

“SO WHAT ARE THE THREATS?”

The current band at which the Fiji Banded Iguana sits in (in regards to known population levels) is 8,000 120,000 mature individuals. Now that doesn’t mean we have 8,000 or 120,000 mature individuals. The current band basically means what we have “assumed the population” based on very sketchy and rough census estimates. What we do know, is that from the last census conducted only 8,000 were eye balled (meaning that 8,000 were physically witnessed). Further census counts are underway.

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.

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.

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Image: Fiji Banded Iguana (Photographer unknown). 

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. 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.

The impact of aggressive ant irruptions on iguana reproduction and recruitment is not known, but is likely to suffer similarly to other lizards. Lau Banded Iguanas are sometimes locally kept as pets, and this was observed on three different islands during surveys in 2011 (as explained above).

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.

Listed as endangered, the current future is not as yet known. However what we do know is that the Fiji Banded Iguana does not inhabit the ground it once did. Threats are wide, and the species has undergone a large population decline.

Thank you for reading. 

Dr Jose C. Depre PhD. MEnvSc. BSc(Hons) Botany, PhD(NeuroSci) D.V.M.

Environmental, Botanical and Human Science.

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