Progress made against invasive alien species in Seychelles’ world heritage sites |03 August 2013

Seychelles Islands Foundation’s (SIF) invasive alien species four-year project funded by the European Union (EU) reached its mid-point earlier in 2013. The project has already achieved several invasive species milestones which have been internationally recognised.  

The EU project is addressing non-native species threats to the two Seychelles world heritage sites of Aldabra atoll and the Vallée de Mai. Such species have been unintentionally or knowingly brought into Seychelles since human colonisation for various reasons, and some now threaten the natural treasures of the islands, especially animals and plants that are only found in Seychelles.
These invaders pose one of the main threats to the unique and internationally renowned world heritage sites. With generous funding from the EU, the SIF has embarked on the project to eliminate or control the invasive alien species that threaten the animals and plants of the two sites.  

Feral goats eliminated from Aldabra    

Since the project started in 2011, the SIF has secured several successes in invasive alien species work, the most celebrated so far being the elimination of feral goats from Aldabra.  
After being present on Aldabra for over 130 years, goats had damaged the native vegetation and had they been left to thrive, would have threatened the survival of the giant tortoises.
In August 2012 the last goat was successfully eliminated by the SIF, which was a crucial step in safeguarding the native wildlife of Aldabra and this is an internationally acclaimed achievement.

Introduced bird eradication success on Aldabra

Work is also ongoing on Assumption, the closest island to Aldabra. Large populations of two bird species – Madagascar fodies and red-whiskered bulbuls – on Assumption introduced in the 1970s, pose a threat to Aldabra’s endemic birds.  

To reduce this threat, an eradication programme, partnered by the Islands Development Company and Island Conservation Society, was initiated in 2011. Populations of both species were larger than estimated which makes the progress to date, of over 75% of Assumption’s invasive birds eradicated, even more impressive.

In the meantime, in early 2012, both introduced bird species were discovered in a remote part of Aldabra at Takamaka in eastern Grand Terre. This is the closest part of Aldabra to Assumption so the founder birds had probably flown or been blown over in the last few years. The Madagascar fody population was sufficiently large and well established to suggest that their arrival pre-dated eradication activities on Assumption and their discovery had simply taken a while in this rarely visited part of Aldabra.

With the help of a Unesco Emergency Funding Grant, which is only awarded to world heritage sites whose outstanding universal values are considered to be under imminent and serious risk, eradication preparations at Takamaka were able to start almost immediately. The sheer size of Aldabra, the treacherous terrain, and the difficulty of access made this an extremely challenging project.

Logistics had to first be organised, and a new field camp with a functioning water harvesting system was built to enable a permanent staff presence in this remote and very arid area.

In mid-July 2013, after more than a year of efforts and five months of permanent presence, the SIF staff team of Terence Mahoune and Jeremy Raguain successfully eradicated the red-whiskered bulbul from Aldabra.

The achievement means that, within Seychelles, this introduced species is once again restricted to Assumption, where, thanks to the eradication efforts there, its numbers are much reduced and there is a good chance of total eradication from the country, which would be a first in the history of invasive bird management. The teams on both islands will continue attempts to eradicate the Madagascar fody from Aldabra and both species from Assumption in the coming months.

Not forgetting Praslin

Closer to home, invasive species activities are also underway on Mahé and Praslin. To protect the ancient palm forest of the Vallée de Mai, in 2012 an extensive plant survey of the area was completed. This enabled researchers to identify the location of invasive plant species, such as cinnamon. Data collected will be used to make management decisions about the removal of these plants.  
Some invasive alien species are so small that it is hard to imagine the damage they could cause; yellow crazy ants are one such species.  These long-legged ants may be small but have had devastating effects on islands worldwide. They can easily overpower and threaten insects and animals such as snails, slugs and reptiles that are found only in Seychelles. Research so far has shown that although these ants are present in the Vallée de Mai, they are not spreading which should make it easier to control them.

Controlling Kato Ver to protect Kato Nwanr

Praslin is also home to the iconic Seychelles black parrot (kato nwanr), one of the 12 endemic bird species of Seychelles. The black parrot is only found on Praslin and is one of the rarest birds in Seychelles. The parrot’s small population size and limited range make it very vulnerable to external pressures, the most serious of which is the presence of the introduced ring-necked parakeet, or Kato Ver, on Mahé.  

The ring-necked parakeet is the world’s most successful parrot, with a huge native range across southern Asia and northern Africa, and an introduced range of more than 35 countries on five continents. An unmistakeable green parrot with a long tail and high-pitched squawk the parakeet has caused many problems. In Mauritius, it transmitted a new virus to endemic Echo Parakeets which resulted in the death of many birds. In Australia, the species is considered a major agricultural pest, causing substantial financial losses to farmers.

The parakeet was accidentally introduced in Seychelles in 1996, when two captive birds escaped. These birds quickly bred and the current population is around 300 birds. Although currently established only on Mahé there is a real danger that the parakeets could populate other islands in Seychelles (single birds are already known from Praslin). The establishment of parakeets on Praslin would pose a serious threat to the black parrots, as they would compete for food and nesting sites, and potentially transmit novel diseases. An effort to control this destructive parakeet and protect the black parrot has therefore been launched by the SIF and the environment department.

There has never been a successful large-scale eradication of the ring-necked parakeet, although the species is locally controlled in many countries. The environment department and the SIF believe it is possible in Seychelles but project success on an island the size of Mahé depends on public contribution and support. (See inset box for how you can help)

Ultimately, what this project has shown so far is that with the collaboration of international and national agencies, such as the European Union, Unesco, the Seychelles government, local non-governmental organisations and companies, and local people, it is both possible and achievable to maintain the natural splendour of these magical islands, and safeguard the beauty and biodiversity of Aldabra and the Vallée de Mai for the future.