ICS, IDC take action to control invasive yellow crazy ants on Farquhar island |30 January 2024
In a collaborative effort between the Island Conservation Society and Islands Development Company, urgent measures are being implemented to control and eradicate the invasive yellow crazy ants on Farquhar island.
The discovery of this species in a zone spanning four to five hectares has raised concerns about potential ecological threats.
Desroches, another island under the Islands Development Company’s (IDC) management, is also grappling with the presence of these voracious predators.
Speaking to Seychelles NATION, Gregory Berke, director of conservation and science at the Island Conservation Society (ICS), highlighted the danger posed by yellow crazy ants. He explained that these ants are predators that defend themselves by spraying formic acid, which can harm invertebrates like crabs and hermit crabs, causing blindness and disorientation.
The species' invasive nature and ease of transport make them challenging to control. Determining their arrival method is challenging, but control efforts are underway to contain the infestation.
"We have done several attempts with IDC, and we are looking at bait, which is the most effective method to control them," said Mr Berke.
He disclosed that ICS has observed the ants on Desroches for a while. Regarding Farquhar, it appears to be a more recent introduction. As such, Farquhar is the top priority due to its perceived new infestation, making it more manageable.
As per Mr Berke, eradication efforts might vary for different islands based on their unique environments. The effectiveness of bait depends on the ants' feeding habits and available food sources, with invertebrate communities being particularly vulnerable. Fortunately, the outer islands' invertebrate communities are not as rich and complex as those on Mahe and Praslin, and the ICS is yet to observe any adverse effects.
ICS is exploring the use of AntOfffipronil, similar to the pesticide employed by the Seychelles Islands Foundation (SIF) in the Vallée de Mai.
Although the non-governmental organisation currently lacks pesticide importation approval, the organisation is working with local suppliers to acquire the bait. Additionally, it is working towards securing import approval.
While aiming for long-term eradication projects, ICS's immediate focus is on controlling the ants' distribution to prevent harm to other species, such as shearwater colonies on Desroches Island.
However, deploying bait during the rainy season presents challenges.
The ICS team plans to deploy the granular baits and utilise gridding deployment around affected areas.
Continuous mapping and monitoring efforts on the islands aim to assess the extent of ant spread. Although eradicating the ants is difficult, containment measures are essential, Mr Berke highlighted.
IDC chief executive Glenny Savy emphasised the unexpected nature of the situation in a press conference last week.
"In principle, yellow crazy ants do not exist on the outer islands. We are doing all possible to stop it from spreading and to eliminate it,” Mr Savy stated.
He noted that the IDC faces pressure from hotel operators to introduce certain plants to the outer islands, for beautification purposes. Despite efforts through fumigation, some species continue to survive in specific plants, leading to unintended consequences. IDC has implemented a system that involves thorough plant inspections before their introduction to the islands.
Mr Savy acknowledged past mistakes, such as transporting red soil from Mahe to improve gardens, which inadvertently introduced snail eggs to islands like Desroches and Coetivy.
He stressed the importance of preventing such errors, to preserve the delicate ecological balance of these pristine island habitats, and protect them from the potentially devastating impact of yellow crazy ants and other invasive species.
Laura Pillay