Having attached a baby fox to a lead, I then tried to get it into my boat in the same way as I have with all other mobs: get in the boat, go out in the water a little bit before turning around and "running over" the mob. This always caused whatever mob it was to get in the boat.

In the case of this fox, however, this didn't work. Instead the fox just jumped around near the boat, but never got in.

In case this was some sort of behaviour for baby foxes that I was unaware of, I fed it berries until it grew up, but the adult fox behaved in the same way.