I have a mooring bouy at my home. For quite a few years it has been used only infrequently, but this year and last, I have moored Retreat there for as much as several weeks. That increased use has led me to seek a solution for the Otters that come to visit.
They show up singly and in families of up to 5. They leap onto the swim grid easily. I know I will never stop that.
I hang my dinghy from stern davits. The dinghy bow hangs up as high as the top rail. The stern hangs at the height of the cap rail. The otters leave evidence of their visits in the dinghy, but so far, not on the boat.
I have tried blocking the steps on the transom by hanging up to 4 fenders over those steps. When I hung only a single large fender over the steps I could tell the otters had simply moved it out of their way. With 4 fenders, I have seen no evidence that they have moved the fenders.
This evening, I watched a family group of 5 otters swimming towards the boat. I watched through binoculars, from my dining room, about 400 ft away.
The boat was swinging, so I had a view of the transom, dinghy, parts of the aft deck, and of course, 5 otters. They first leaped onto the swim grid. I didn't see any movement of the 4 fenders, but then I did see an otter on the aft deck of the boat. As I watched, it slipped through the hawse hole on the far corner of the aft deck, the hole on the port side of the boat, and disappeared. On that side, I have my swim ladder, inverted, that I sometimes use to climb aboard from the swim grid. I don't think there is any other possibility for the otters than to climb that 1" SS ladder to the height of the Hawse hole on the port end of the transom and slip aboard.
My shelter neighbour at my Coal Harbour moorage has plastic dinosaurs on his boat and on the dock, which he claims keeps the otters away. I now have plastic dinosaurs on my dinghy for that purpose, but those in Houstoun Passage don't seem at all deterred.
I will be lowering my swim ladder on my next visit to my boat, likely tomorrow, but ask this TF group for other otter-deterrent ideas.
Curiously what they leave behind is not simply excrement, though there is lots of that, but when they have come into my dinghy for lunch, they leave the face of the fish they have otherwise completely consumed. Some blood and guts too, but they are quite clean eaters, except for always leaving the face.