A surprise last night: this flash of full-grown adult otter disappearing upstream. I've seen otters before here, in Sept 2014 (previous otters) and twice over the years found their spraint, but I don't believe they use this tiny stream as anything other than a corridor. It's barely deep enough for an otter to paddle in, and only about two-otters-wide. Otters will take water voles but are too big to fit down the burrows in pursuit, so I'm hoping my little team will stay safe.
I've no idea whether this is related to the change in my voles' routines!