2. For: breed for later release, educate public, research into health and behaviour, preserve species extinct in the wild.

Against: stress to animals, enclosures too small, not able to show usual behaviour, individual animals may be isolated from other members of species, members of endangered species removed from the wild.

3. Introduce disease, escape and increase in numbers, predators of native species, damage to vegetation and habitats.

4. Spraying would kill other plant species.

Trimming would not remove roots, which can grow a new plant.

5. Natural predator attacks the pest animal. Predator must hunt only specific prey and must be unable to survive in the wider environment.

6. Large numbers of predators will devastate local small mammals. There will be knock-on effects on other species in the food web.

7. Microchips under the skin that can be read when animals are recaptured, radio transmitter collars, fur caught on sticky tape, droppings, calls, scrapes and scent marks.

8. Grey squirrel introduced. It competes successfully for food, is more aggressive and has introduced the parapox virus, which has a more serious effect on red squirrels.