Aerial Baiting on Galápagos Islands to Eradicate Non-Native Rats
Helicopters equipped with bait spreader baskets were visible in the skies above the equatorial region of the Galapagos Islands in January as skilled pilots broadcast tons of bait specially formulated by Bell Laboratories to eradicate rats threatening the seabird and other wildlife populations on these delicate island ecosystems.
In early January, Phase I of the Galápagos Restoration Project, the first large-scale project in South America conducted on oceanic islands, began when the Galápagos National Park Service, aided by its partners, launched what is described as a "full-scale assault" on non-native rats.
Over two weekends, Jan.7-8 and 14-15, helicopter pilot John Oaks of Central South Island Helicopters from New Zealand broadcast 10 tons (9,195 kg) of bait on the small islands of Rábida, Bartolomé, Sombrero Chino, and Plaza Norte, and five islets - the two Beagle islets and three of the Bainbridge Rocks - covering 1,740 acres (704 hectares).
Flying at 40 to 50 knots, the pilot dispersed two applications of bait, with each treatment taking two days. The entire helicopter operation, which was managed by Fraser Sutherland of HeliGal, took 37 hours of flight time, in addition to the work of ground crews loading bait pellets into the helicopter's bait bucket which holds 600 lb. (272 kg) of bait.
Karl Campbell, a senior program director with Island Conservation in Santa Cruz, Calif., one of the project partners, was at the site during the baiting. "For a first operation in a country, the aerial baiting went extremely well," he reported. "The few minor operational issues we encountered were quickly resolved and did not impact the timeline or efficacy of the operation."
Equatorial heat on the Galápagos Islands was a factor during the aerial baiting which, in recent years, has become a more common way of dispersing bait on large islands and locations with challenging topography.
Located some 600 miles (965 km) off the coast of Ecuador, the islands had summer temperatures of 85° F (30° C) at mid-day, making personal protective equipment, especially masks, very hot to wear. "With the heat, the island also generated winds during the middle of the day, making it hard for the pilot during this time as he was having to attempt to fly straight lines with gusty cross winds that were topography driven," Campbell pointed out.
Galápagos Restoration Project to Permanently Remove Non-Native Rats
Over the past 40 years, small-scale rodent control efforts on the Galápagos Islands have targeted rodent populations in specific regions. However, January's aerial baiting was the first step in what could be a 20- to 25-year process to permanently rid the islands of non-native rats and mice, and to put in place an on-going management system.
The Galápagos Islands, named a World Heritage Site in 1979, is the only tropical archipelago with over 95 percent its biodiversity intact. Yet non-native rodents are so pervasive and pose such a threat to the islands' rich natural flora and fauna that international experts on rodent removal joined forces to permanently eradicate them.
Run by the Galápagos National Park Service, the Galápagos Restoration Project is supported by the Charles Darwin Foundation which is dedicated to the conservation of ecosystems of the Galápagos Islands, Island Conservation, the University of Minnesota Raptor Center, the Durrell Wildlife Conservation Trust and Bell Laboratories.
Rats, which first came to the islands aboard ships in the late 17th century, have seriously endangered some 50 bird species, including the Galápagos petrel, a seabird that breeds in excavated tunnels on high islands only in the Galápagos.
The smaller islands baited in January are home to 12 unique Galápagos species threatened with extinction, including Galápagos penguins (yes, penguins near the equator) and the plant, Scalesia stewartii, viewed as the plant equivalent of Darwin's finches.
Many native plants, iguanas and even the giant Galápagos tortoises are at risk from rats. On the larger Pinzón Island, rats prey on tortoise eggs and hatchlings. It is only through intervention, namely collecting/incubating eggs and growing out hatchlings until they are large enough to return to their original islands, that tortoises still survive.
Protecting Native Galápagos Species
At the same time as they eradicate invasive rodents, researchers also face the challenge of protecting the islands' native species. As a precaution before the January baiting, scientists from the Raptor Center of the University of Minnesota removed 20 Galapagos hawks from the two largest islands and held them in a specially built facility on a nearby island until the risk of them feeding on poisoned rats was over.
Released on February 17 and 18 to the islands where they were captured, all 20 hawks were in excellent health and even gained an average of 100 grams each while in captivity. Prior to release, each was fitted with a telemetry transmitter that lets researchers track and monitor their activities for at least a year.
Monitoring for Next Two Years
Now the critical task of monitoring for rodent activity begins.
"Monitoring has been conducted for conservation targets and possible non-target species by the Galápagos National Park and the Charles Darwin Foundation," Campbell reported. "Dead rodents have been found post bait applications. Chew tabs will be placed out later on the islands to monitor for activity.
"Successful eradication of non-native invasive rodents is typically only able to be confirmed after approximately two years - a time period within which rodents, if present, can breed to high densities and cover large areas, allowing them to be detected," he explained.
Like Darwin's theory of evolution which grew out of his observations on the Galápagos Islands in the 1830s, this project, too, will evolve as researchers learn from their trials on these smaller islands and, later, adapt methods to eradicate rats on larger islands, such as Pinzón, where giant tortoises may one day again breed and flourish in the wild.
For additional information, visit:
www.islandconservation.org www.darwinfoundation.org http://galapagospark.org www.theraptorcenter.org
© Photos courtesy of Island Conservation