From the article: "But the rats, which came ashore about 1900 from shipwrecks, are known to devour seabird eggs and young chicks."
1900 is rather less than 1000 years ago. And how is escaping from shipwrecks "self-introduced"? Did the rats build the ships themselves?
Are you really incapable of seeing the difference between an introduced non-native invasive species, and a native European species of bat which flies here naturally as part of its native range?
There are some really odd responses on this thread. The Black Rat is a highly damaging global pest species, especially on islands. It's not remotely 'rare' in terms of either its native range or its enormous global population. By the same logic, you could oppose the eradication of rats from any island on the grounds that the species would become locally extinct.
Answers in order, some of which come in the form of questions:
Yes, I think hitch-hiking is different from humans positively introducing pigs, stoats, foxes etc. Black Rats have been a naturalised part of the British fauna since at least Roman and probably Phoenician times.
First question: how long does an animal have to be present before it is considered part of the natural fauna? Under your definition the following animals and birds present for a thousand years or so would have to be considered as invasive and mostly damaging: Rabbit, Brown Hare, Fallow Deer, Pheasant. I haven't heard one suggestion that any of these should be eliminated from the British Isles, so I'm at a loss to understand how removing a small colony of an animal resident in the British Isles for a thousand years will help anything. In the meantime Pheasants have been shown to be serious predators of our native reptiles which are declining as a result, Fallow Deer cause road accidents and damage forestry interests.
Second question: what damage have these particular Black Rats been shown to do? I've been to the Shiants and the seabird colonies are immense whereas the rat colony is tiny. The rats are limited by year-round food supply and predation by BOP, gulls and skuas - unlike tropical islands where there is no real breeding season or Southern Ocean islands where there are no year-round predators. If there are declines going on (Puffins being a possible case in point) they must be due to factors such as climate change, because they are also going on in places where there are no rats of any kind.
Third question: are you really incapable of seeing the similarity between hitch-hikers that are simply making use of available human transport and animals expanding their range due to human induced climate change that are able because of their ability to fly, to jump the water barrier around our islands?
I'm perfectly prepared to see damaging invasive species eliminated. I don't think in this case that damage has been shown; the range is tiny and limited by the water barrier; other greater threats to biodiversity are being ignored due to the cuteness factor - imagine the outcry if it was announced that Fallow Deer were to be culled to extinction in Britain as a non-native invasive damaging species - or economic interests: six million Pheasants can't be wrong, even if they eat every last Adder in Britain.
The Black Rat has a place in British history which should guarantee it at least a limited future in Britain's fauna. Lets see the Brown Rat (here for a much shorter time but universal and universally abhorred) brought into relation with the power of the British state before we even start to worry about the relative importance of invasiveness versus cultural importance of our small population of Black Rats.
While we are on the subject of recent invasive species that the Government has not felt the need to tackle, lets mention Eastern Grey Squirrel (hugely damaging to Red Squirrel), American Mink (hugely damaging to Water Vole), Chinese Water-, Muntjac and Sika Deer (Muntjac being held to be damaging to forestry, Sika to the genetic integrity of native Red Deer). Where is the urgency being trumpeted to deal with any of these, all of which would appear to be more urgent matters than a small colony of Black Rats on one island of the many holding seabird colonies around Britain?
That's all that is being said. Hope it is a bit clearer for you now.
Cheers
John