Last year, I was running Dungeons & Dragons Encounters in a local gaming store. Encounters is a series of adventures provided by the publisher with the intention of attracting new players/consumers to their product. There was one point during this particular story, Beyond the Crystal Cave, in which the players had the opportunity to use giant otters as mounts. I made the clay miniatures but they didn't get done in time for the game. Over a year later, I finally got around to painting them. Some are more otter-like than others. One looked more like a tiger cub so I painted it as such.
The otters are designed to allow a D&D mini to be placed on top. This is illustrated with my Kenku assassin. It would probably work better with the standard plastic figures.