On Saturday we went for a short walk along the Forth and Clyde Canal. Although little snow was lying, the canal was frozen for most of its length.
We saw footprints in the snowy surface of the ice on the canal, leading a to a patch of water where it appeared that the animal had fallen in and swum for quite a distance before emerging and continuing over the ice. They were probably the tracks of an otter.
During the course of the morning we noticed increasing numbers of circular patches where the ice was melting. Each one was centered on a submerged plant, usually a waterlily leaf. Somehow these must have been causing just enough heat to melt the ice.