Rats Threaten Native Species, Army Steps Up Attack
KAHANAHAIKI — Downtown Honolulu is just 30 miles away, but in remote Kahanahaiki, it feels like 3,000 miles.
Makua, home to explosives and military training exercises, looks serene from this gulch high up on the valley’s back wall. A canopy of a thousand shades of green, a chorus of bird chirps and wind gusts and a sweeping, unobstructed view of Oahu’s idyllic North Shore reinforce the notion that Kahanahaiki is largely unspoiled.
The most obvious exception is a chest-high metal fence shielding the 65-acre gulch and its sensitive ecosystem from feral pigs and goats. But look a little closer and you’ll see snap traps and bait boxes — measures to eradicate what is normally thought of as an urban menace: rats.
“People think rats are bad,” said Steve Mosher, Elepaio and Small Vertebrate Pest Program Manager for the U.S. Army‘s Natural Resources Program. “But in the forest they’re even more dangerous.”
Rodents prey on native birds and their eggs, sea turtle eggs and hatchlings, native tree snails and other invertebrates. They consume seeds, fruits and flowers and destroy plants by chewing on shoots, stems and trunks. Hawaii has 20,000 native species, half of which are found nowhere else on earth, and rats are among their worst threats.
Kahuli snails (Achatinella Mustelina) that are said to have once dripped from trees like bunches of grapes are long gone. Snail shells have been found destroyed in Kahanahaiki and elsewhere, their inhabitants’ deaths blamed on rats with a taste for escargot. Today, just a few hand-numbered snails remain in the gulch.
“Hawaii is such a test tube. There are treasures here that are nowhere else in the world and we can’t just let them go if we can do something about it,” U.S. Army Garrison-Hawaii spokesman Loran Doane said during a recent tour of Kahanahaiki. Among the steps being discussed is expanding rat eradication beyond Kahanahaiki: using helicopters to spread rat poison on isolated forests.
The Army, which owns Kahanahaiki, recently joined with the Hawaii Department of Land and Natural Resources, U.S. Fish and Wildlife Service and University of Hawaii Pacific Cooperative Studies Unit, all fellow members of the Partnership to Protect Hawaii’s Native Species, to launch to raise public awareness of the devastating impacts of rats. The website includes information about the impact of rodents on native species, cultural practices and human health.
Kahanahaiki — and some of the 51 species of native plants, seven types of snail and the endangered elepaio bird that the Army protects there — has seen benefits from a pilot project new to Hawaii. Implementing a technique employed in New Zealand, the Army has arranged 400 specially designed snap traps roughly 20 meters apart in a grid surrounding the most sensitive endangered species.
The traps are placed in wood enclosures about the size of a shoebox with metal grating covering both sides, save for a rat-sized hole that routes the rodents to their doom. The project is labor-intensive: A team of four staffers needs the better part of a day to drive to Kahanahaiki and hand-check the 400 traps once every two weeks. Boxes of rat poison are also used.
Anecdotally, endangered haha (Cyanea Superba) trees are thriving in Kahanahaiki, where the program is in effect, but not in the state-managed Pahole Natural Area Reserve next door, said Oahu Army Natural Resources Program Environmental Outreach Specialist Candace Russo. So there are positive signs.
But experts like Mosher say the fight to protect species from rats is a “never-ending battle” that won’t yield definitive results for years. There are millions upon millions of rodents on Oahu alone, ranging from the field mouse and five-inch Polynesian rat on the small end to the common black “roof” rat and the 10-inch brown Norway rat. So the Army is looking to add other tools to its toolbox.
The program is part of an effort to counterbalance the impact of weapons training exercises in Hawaii. The Endangered Species Act requires that landowners like the Army take steps to protect threatened plants and animals.
