By James Lynn
BBC News, Newcastle
For decades, the grey squirrel has been demonised in the UK for its impact on the native red.
There are about three million grey squirrels in the UK
Since being introduced in the 19th Century, the North American species has dominated habitats and food supplies.
So imminent is the threat, that one scientist described attempts to save red squirrels on the mainland as "a waste of money".
But recently, a conservation group launched an onslaught on greys in Northumberland, killing 12,000 - or one third of the county's population, in just over a year.
The Red Squirrel Protection Partnership (RSPP) claim their methods prove the foreign species can be cheaply and quickly brought under control.
First introduced in 1876 to Henbury, Cheshire
It is illegal to release into the wild a captive grey
Spreads pox virus that kills reds
No concrete figure for population
But is the culling of grey squirrels really the answer?
Ross Minett, campaigns director at Advocates for Animals, says the approach is "morally wrong".
"A century or so ago reds were the ones being called 'tree rats', and hundreds of thousands of them were killed in Scotland. It's a problem of man's making.
"Humans have completely and utterly changed the environment, and greys just happen to be more adaptable.
"If we go down this route, we are going to be killing and killing squirrels for a long time, but no amount of poisoning or trapping is going to get rid of them.
"It's our responsibility to find an ethical and practical long-term solution."
Conifer forest is ideal for red squirrels, but less suitable for greys
The RSPP's "pest control" methods are part-funded by the Department for Environment, Food and Rural Affairs (Defra), though government ministers have ruled out a out a mass cull of greys.
Instead, they are targeted only in areas where red squirrels are being squeezed out.
Birth control is also being considered, but researchers must first find a way of administering contraceptive drugs without affecting other animals, especially red squirrels.
Others, however, believe there is a more natural solution.
The Forestry Commission is concentrating its efforts on conserving habitats.
In particular, conifer forests are seen as prime locations, according to one spokesman.
"Because the red is smaller and more delicate they can reach into pine cones and get out the seeds, unlike the grey squirrel.
"Reds are in their element among Scotch Pine, Norway Spruce and the like.
Red squirrels typically die within days of contracting squirrel pox
"What we're doing at the moment is encouraging conifers around red squirrel populations and creating distinct boundaries from broad-leaved forests, which are favoured by the grey.
"It's not a magic bullet, but for the most part it keeps the two species separate."
However, one major barrier stands in the way of co-existence - SQPV or squirrel pox.
Carried harmlessly by grey squirrels, the disease is fatal to reds, and makes an imminent end to culling unlikely.
There is no vaccine for SPQV, though research is ongoing.
Without one, a single grey can pose a threat, meaning neither contraception nor isolation can completely protect the red.
Tellingly, it remains illegal in the UK to release a grey squirrel once it has been trapped.
Cull them no reds left here, The grey is just a tree rat, vermin !!!
Louis Fernandez, Cardiff
I don't agree with the grey squirrel culling - I have a family of grey squirrels living in the trees behind my house and they are regular visitors to my garden and I find them fascinating little creatures. Whilst it's a shame that the red squirrel population is in decline I feel there is room for all creatures in this world and it's up to us to find a better way of controlling its grey counterpart.
Bridget, Kettering, Northants, England
I agree with the culling programme and would like to see it taken further, so that red squirrels could be re introduced to other parts of the country. Perhaps reds from europe could be brought over to help our population recover.
Dawn Rutherford, Telford, Shropshire
It was a human error to introduce grey squirrels into mainland Britain and if we take no action we can expect the extinction of the red squirrel and several song bird species, most notably the spotted flycatcher. I do not think it is acceptable to allow extinctions like this to happen because the 'fluffy bunny brigade' cannot stomach reality.
Steven Penn, Chertsey, England
Seems to me some people's only solution is to kill, kill, kill. Haven't we a more moral way? Cant we just live alongside our wildlife and tolerate nature. I could weep at the way some species are demonised.
Jennie Cook, Minehead, Somerset