Killer Mice: Part 37
- Just when we'd all agreed that rodent traps have to be managed
very carefully so as not to kill the birds as well, David Duthie
of UNEP in Geneva brings word that you can just dump the poison
from low-flying aeroplanes. David is a real scientist who's
quite well-known in the fields of biodiversity and biosafety.
If he says it, it's probably true.
Bob Conrich, simple islander
Anguilla, British West Indies
It is a long time since I first trumpeted the New Zealand Biosecurity policy (see posting on New Zealand Under Siege).
Below is a nice update on some real practical progress being made on the most intractable of the invasives problem -
I did not make a posting last weekend on the breaking story, mentioned below, of the "giant" mice eating albatross chicks
ten times their size, but those wishing to read more, and watch some not very pleasant video, can go to:
NZ tackles its island pest problem
By Kim Griggs
in New Zealand
When the pest eradication team from New Zealand's Department of Conservation (DOC) arrived on the sub-Antarctic Campbell
Island, they hunted for an iconic New Zealand [flightless] insect, the weta.
"They had been reported there in the past. One guy spent a year there and saw one," explains Lindsay Wilson, a member of
the DOC team.
"We went searching for them. We didn't see any."
But after poisoning the introduced Norway rat population, the weta, along with many other island fauna, rebounded.
"When we went down there on the follow-up visit, the first bush we looked under, there were half a dozen of these weta,"
New Zealand has developed undoubted expertise in the business of eradicating invasive pest species from islands.
It is a major problem. The recent Millennium Ecosystem Assessment showed that invasive species were responsible for the
greatest loss of biodiversity on islands; and second only to habitat loss globally as a major cause of extinctions.
And this week, the UK announced it would be seeking New Zealand's advice on dealing with the mice that were attacking
albatross colonies on one of its South Atlantic territories.
New Zealand first managed to eradicate rats from a group of small offshore islands in the early 1960s.
Now it is tacking more and bigger islands thanks to two modern technologies: second-generation anti-coagulant bait and the
GPS systems that allow bait to be applied with precision from helicopters.
"Prior to that, rodent eradications were typically on small islands and they were done as ground-based," says Alan
Saunders, a former long-serving DOC staffer and now University of Auckland conservation ecologist.
These days pilots follow a grid pattern to ensure an island is swathed in bait, with printouts of the paths flown enabling
the conservation team to check for any gaps.
The 11,300-hectare (27,900 acre) Campbell Island, the biggest of the more than 100 islands New Zealand has cleared of
pests, is one of the most challenging eradications that DOC has so far attempted.
It is surrounded by 200m-high (660ft) cliffs, is battered by wind and rain almost all year round, and has an average
temperature of just 6 degrees Celsius (43 degrees F).
The island also had the world's highest density of Norway rats.
But it took the team three weeks one winter - a flying hazard, the albatrosses are fewer there then - to apply all the
bait and now, a few years on, the island is once again a haven for fauna such as weta, the New Zealand pipit, the Campbell
Island snipe and one of the world's rarest ducks, the Campbell Island teal.
"The DOC have yet to fail in an aerial eradication operation for rodents," says Saunders.
The New Zealand conservationists have also eradicated mice from 12 offshore islands, one as large as 710 hectares (1,750
Mice don't range as far as rats so the bait needs to cover "every little nook and cranny," says Wilson.
So fine-tuned is the DOC technique that "virtual" islands are now springing up on the country's main islands.
In the middle of New Zealand's North Island, a community group is half way through ringing 3,400 hectares (8400 acres) at
the top of a local mountain, Maungatautari, with a 47km (29 miles) predator-proof fence.
When the fence is completed, the mammalian pests within will be poisoned.
Already four North Island brown kiwi have been reintroduced into a small pest-free enclosure on the mountain, the first
kiwi there in living memory.
Says Saunders: "The bottom line is that you just make sure that every rat has access to bait and if you do, then they'll
all be dead."