When I was doing my site visits in the Peak District I had a female adder slither right in front of my feet while taking pictures at Barbrook V. Managed to get some pics of it then looked it up at home - that's how I know it was a female.
Then at another site (Ladder Hill I think) I had a stoat pop out of a dry stone wall and carefully check me out for a while. Cute lil bugger. Got pics of it too.