Falklands Conservation

Rat Eradication in the Falkland Islands

Falklands Conservation have recently completed the first attempt to clear rats from a number of offshore islands in the Falklands.  This is a major conservation initiative which is expected to have a significant benefit to the indigenous wildife. The Falkland Islands comprise at least 778 islands of varying size most of which appear to have been affected to some degree by introduction of pest mammal species.

The dominant species of rat in the Falklands is the Norway rat, Rattus norvegicus.  

These rats have had a devastating effect on ground nesting birds.  It is probable that they have destroyed whole populations of Cobb’s Wren, a bird unique to these islands and now classed as ‘Vulnerable’ by Birdlife International.   Seabirds, particularly burrowing petrels, are also thought to have suffered severely from predation by introduced vermin.

The Tussacbird, formally abundant around all coasts, has become rare where rats are present.

It is almost certain that rats got to most islands in the Falklands by ‘human assisted’ means, either hitching a ride on boats (in the Falklands particularly the sealer or whaler boats of old), or from shipwrecks.  They may have even been cast adrift on whale carcasses pushed off the beaches after the whales were processed by the whalers only for them to wash up on the tides, with rats included, on nearby islands.

An expert team from New Zealand was contracted to undertake a pilot eradication programme on  four islands.   Eradication of rats from islands was developed as a conservation tool in New Zealand in the mid 1980s.  Since then the technique has been used successfully on more than 100 islands in New Zealand and an increasing number world wide.  Eradication means the removal of absolutely every last rat.

Two different techniques were used - one using bait stations set out in a grid system over the whole island, and the bait stations get refilled every day until the rats are all gone.

The bait station grid on Top Island

Setting up a bait station

The other method is hand-broadcasting which involves walking predetermined routes over the whole island, throwing our a measured amount of bait every few metres until the entire island is covered.  There is a small chance of accidental poisoning of other wildife through eating dead rats or the bait, but we have not detected any negative effects.  Fortunately most rats will die in their underground burrows making them inaccessible to scavengers.

All indications are that the pilot programme has been a success and rats have been cleared from Outer and Double Islands, off West Falkland (Falklands Conservation nature reserves) and from Top and Bottom Islands, which lie close to Stanley, in Port William.  A special open day to visit the experimental sites in Port William was laid on and proved very popular with nearly 80 visitors.  Experimental eradications were conducted on four further islands (Harpoon, Calf, Horse and Rat) with the idea of testing rat re-invasion ability.  This will provide information on understanding natural rodent dispersal abilities in the Falklands.

Removal of rats from offshore islands is a key conservation priority for Falklands Conservation. We aim to conduct further eradication programmes on four more of our island nature reserves (South West Horse, Cat, Inner North West Island and North East Islands) over the coming austral winter.  By removing rats the excellent tussac grass habitats here will once again be safe for nesting birds.

For full reports on the eradication project please click on the titles listed below:

• Final Report on Falklands Conservation Rat Eradication Project

• Criteria for Prioritising Rat Eradication from Islands in the Falklands

• Conservation Guidelines for Eradication of Rats from islands within the Falklands Group.

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