One of the noisy pikas from the scramble up the Tower of Babel (the one near Moraine Lake in the Canadian Rockies, not the one from Babylon). One of the pikas we saw on the way up was carrying a small leafy tree branch, and as it ran across the scree it looked exactly as if it was pretending to be a bush so we wouldn’t notice it. It would have worked perfectly if it wasn’t for the fact pikas are incapable of the sort of slow sneaking movements you need to use to pull off “No honestly, I’m a bush” trick.