At Penrhyn Glas, a dozen shapes were bobbing in the green water of Porth y Gwichiaid, the “winkle cove”. We peered at them. The shapes seemed to peer back. Given the spread of visual acuity in our small group, there was some confusion about what we were seeing. It wouldn’t be the first time one of us had mistaken a fisherman’s buoy for a creature’s head. For myself, while everything at the end of my nose is a blur, objects at a distance have uncanny clarity. The distinguished profile, the colouring, the shape of the nostrils could only be a grey seal.
We edged closer to the shoreline and as we did so, the seals lifted themselves further out of the water, also fascinated. Every so often, one would turn and slip under the water and then re-emerge at a slight distance to resume viewing. I knew what I could see, but what about the seals? Their ancestors were mustelids, like otters or weasels, which, as Darwin theorised, made the natural transition from freshwater to salt. As it spent more time at sea, the proto-seal’s eye evolved to new conditions. Otters have some perception of colour, having two cone receptors in their eyes, but seals lost one along the way. They can differentiate colours from subtle contrasts in brightness, but otherwise their world is monochrome.
