Not quite wildlife, but I was on my way home after a bit of a slog last year, pretty banjaxed..
I took an old farm track on the last mile or two, and decided to try to use myself up completely on the final climb before home..
As I crested the hill, utterly blowing out my bum, I was confronted with the sight of a mahoosive white bull that had gotten out of a nearby field and into the lane.. He was pretty much blocking out the sun, such was his gigantic presence, and although he was facing away from me, nonchalantly munching blackberries, I wasted no time at all in turning tail and heading home the long way..
My heart rate was already at maximum before I saw the beast, but it somehow managed to spike considerably, and so with the maximum effort of making good my escape, I was certain that I was about to meet my end (probably as it exploded up through my chest and out of my mouth), especially once I realised that I had various flashing red lights on the back of the bike, all rationality replaced by boyhood fears and mythology
But I didn't die (as far as I am aware), and made it home safely, getting a KOM on some random road section on the way, the journey a terrifying blur..
I went back a couple of days later to peek over the gate to see if I could snap a photograph of this hellish gargantuan creature and was gifted with the opportunity to capture the Goliath on film for prosperity..