Kill all them nasty rats; save the rare endangered mice

Rats (left) bad and must die. Sailing ships brought them to the island of Canna a century ago.

Wood mice (Apodemus sylvaticus) good and must be evacuated and saved.

The Herald (United Kingdom)
Wednesday 21 September 2005

Ratcatchers descend on island of Canna

by VICKY COLLINS
Environment Correspondent

ZOOLOGISTS are to begin evacuating a rare breed of mice from the Inner Hebrides this week before they launch a programme to eradicate rats on an island.

The £50,000 project will allow them to save about 300 wood mice, which are unique to Canna, which would otherwise be killed during efforts to wipe out rats.

The team from Edinburgh Zoo is working round the clock to trap the mice on Canna.

However, around 700 of the animals are still likely to be killed during the project to eradicate the rats, as the zoo admits it will be impossible to save them all.

The 300 mice that they hope to catch will be split into two groups, which will be taken to Edinburgh Zoo and to the Highland Wildlife Park.

They hope the mice will survive and breed, so that a colony can be returned to the island once the rats have gone.

Gavin Harrison, an Edinburgh zoologist working on the island, said they had already caught 12 mice in a few days.

He said: "I will be taking the first batch to Edinburgh with me on Friday.

"They are kept in individual cages because they are quite aggressive towards each other, and these cages will be packed into boxes and then shipped to the mainland.

"The boxes will be covered so it is dark and hopefully they will just fall asleep."

The team from Edinburgh Zoo set the traps this week and have since been checking them every four hours.

Mr Harrison said the project would be worthwhile if the wood mice could be saved and one day returned to Canna.

"We are not sure yet when we will be able to bring them back," he said. "If the rats are eradicated by next spring then it should be possible to return the original mice.

"If it takes longer then we will try to breed them in captivity, and it will be their descendants that return."

Work has already begun to poison the rats, which are threatening sea bird populations on the island.

It is thought there are around 10,000 rats on the island, which feed on the eggs and young of the seabirds nesting there.

In the 1980s there were around 1500 Manx shearwaters on the island, but now they have disappeared. Populations of razor bills, herring gulls and lesser black-backed gulls have fallen by more than 90% since 1995.

Bob Swan, project administrator for the National Trust for Scotland, which owns the island, said: "The rats were introduced hundreds of years ago, but until the 1990s the bird population was actually increasing slightly.

"When we used to get normal winters, the cold weather used to knock the rats back and provided a check on their numbers. With all the mild winters now, that isn't happening any more."

The National Trust for Scotland has hired a New Zealand firm, Wildlife Management International (WMI), to carry out the work, which is expected to cost more than £500,000, excluding the project to save the wood mice.

Biz Bell, WMI project manager, came to Canna from Wellington in New Zealand three weeks ago. She has previously directed similar eradications on Lundy Island and in the Pitcairns.

She and her team have already laid 1700 traps, and have killed 35 rats.

A further 2300 traps will be set across the island over the next few weeks, containing a total of 23 tons of diphacinone, a poison imported from America for the project.

"We have to get every single rat," Miss Bell said. "If we don't then we will have failed."

Once the project finishes on March 31 next year, the team is to carry out two years of monitoring to make sure there are no signs of any rats remaining on the island. "If there are any rats left we will set more traps to get them," said Miss Bell.

"This is important work. The rats are just not supposed to be here and they are affecting the ecosystem on Canna," she added.

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