If you thought of deer, consider muntjac .This very small deer, about the size of a labrador dog, is now quite common in southern England.It prefers to live in woodland but can be quite happy with overgrown gardens and thickets.We have quite a number around . They turn up in gardens here quite often.This is a rural area, but comparatively densely populated, with sizeable villages quite close together, a few miles from Cambridge.
You are more likely to hear one than see one. They bark rather like a dog and do so at night as well as day. They seem quite happy to be active at dusk and just after dark..