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| Shipwreck remains on Niihau beach, with Lehua in background. |
The `iwa or great frigatebird swept low over a cluster of
trucks, stacks of equipment and a Jet Ranger helicopter on the northern end of
Ni`ihau.
As I followed its black-winged form with binoculars, the
angular bird made several passes and then returned to its roost on Lehua
Island, a gray-brown tuff cone island, just a thousand yards across the
Kumukahi Channel from Ni`ihau.
Teams of wildlife professionals worked both Ni`ihau and
Lehua in late August and early last month,
using a helicopter guided by computer mapping programs to deliver rat
bait across the rugged islet. I was present for one of the sessions.
A month after the final application, indications are that
rats no longer populate Lehua, although a final determination of rat presence will be made a year from now, which any survivors--if they exist--will have had a chance to reproduce and make their presence known.
For now, survey teams are finding no footprints at
burrows or other indications of rat activity, according to Sheri Mann, head of
the Kaua`i office of the state Division of Forestry and Wildlife. They will
keep monitoring for the next year, to confirm that preliminary finding.
The Lehua Island rat eradication project should improve
habitat for frigatebirds and dozens of other bird and plant species on the
little island—just as wildlife has thrived after similar eradications at other
offshore Hawaiian islands, like Mokoli`i Island off O`ahu and Mokapu off north Molokai.
After eradication of black rats on Mokoli`i, successful
shearwater nesting became common, coastal naupaka sprouted, and seashore
rat-predated species like pipipi and `a`ama crab became abundant.
At Palmyra Atoll to the south of Hawai`i, after rat removal long-absent
seabird species established successful nests, shoreline fiddler crabs thrived,
and native tree seeds sprouted where they once were eaten.
Lehua has now been given three applications a pale blue
pellets of rat bait containing diphacinone—less than a pound of the
anticoagulant in several thousand pounds of food grade cereals like wheat and
oats and other rat-friendly food items. The new bait was developed by Bell
Laboratories in Madison, Wisconsin.
“We’ve had really high acceptance rates of this new, more
palatable bait,” said Gregg Howald, North America regional director for Island
Conservation, the non-profit that conducts invasive species eradication efforts
on islands around the world, in association with partners and landowners.
The Lehua operation’s partners include the state Division of
Forestry and Wildlife and its parent agency the State Department of Land and
Natural Resources, U.S. Fish and Wildlife Service, U.S. Department of
Agriculture’s National Wildlife Research Center in Hilo, Niihau Ranch, U.S.
Coast Guard, National Tropical Botanical Garden and several other associated
organizations and agencies.
The $1 million Lehua project has funding from several
sources, including the Department of Land and Natural Resources, National Fish
and Wildlife Foundation and Island Conservation. The results will be monitored
for several years.
Several hundred small islands from the equator to the arctic
have now been cleared of rats and other invasives. Why islands? Because although
their land area is small, they are important crucibles of biological
diversity--home to many endangered species, and once home to many species now
extinct.
Through my binoculars, I could see the white, brown and
black forms of petrels, great frigatebirds, boobies, noddies and other bird
species, wheeling on the thermals above Lehua’s sloping spine.
One species, the tiny band-rumped storm petrel, is now
entirely missing—arguably because its small size and noisy habits on the nest
make it particularly vulnerable to rats, said Nick Holmes, Island
Conservation’s Director of Science.
Perhaps on a rat-free Lehua, it will be able to re-establish
itself.
Meanwhile, planning in Hawai`i is already underway for a
much bigger challenge—clearing the island of Kaho`olawe of species like mice that
are inhibiting the island’s revegetation. The Kaho`olawe Island Reserve
Commission is in discussion with Island Conservation and others about the best
ways to accomplish that goal.
© 2017 Jan W. TenBruggencate
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