Although prevalent, grey squirrels are not native to Scotland
"Extreme measures" must be taken on occasions to destroy non-native species to better protect Scotland's wildlife, a conservation expert has said.
Dr Kirsty Park, of the University of Stirling, said sometimes decisions to cull a plant or animal were not being taken quickly enough.
She said such action was also necessary to avoid "homogenising the world's species".
Non-native species include grey squirrels and American signal crayfish.
Hedgehogs introduced to the Western Isles about 25 years ago was another example raised by Dr Park.
The mammals, which were blamed for eating the eggs of ground nesting birds, are being trapped and relocated to the mainland following a public outcry over plans to cull them.
Dr Park, a lecturer in conservation ecology, has been delivering talks on the issue in Stornoway and Inverness.
She said: "I came into conservation from the animal rights route, so I know where people are coming from when they react negatively to the prospect of an animal cull.
"They tend to talk about introduction of a species as being 'not the animal's fault', which is absolutely true.
"If blame is to be apportioned, it's ours for having introduced an invasive species in the first place. However, this isn't about who is to blame, it's about what we do to rectify a situation which adversely affects our indigenous wildlife."
Dr Park said there had been a misunderstanding over the need to tackle hedgehogs on the Hebrides.
She said: "One newspaper referred to the 'Massacre of the TiggyWinkles' and using this child's story book reference would inevitably create an emotive response in many readers."
In March it was announced that nearly 400 squares miles of Scottish forest could be set aside as safe havens for red squirrels.
Eighteen "strongholds" providing ideal conditions for the red variety were planned.
Greys venturing into the safe havens would be trapped.
Last year, American signal crayfish, which can eat young fish and destroy their habitat, were found in increasing numbers at Loch Ken in Dumfries and Galloway.