I'm doing an island challenge, started in winter. The island is medium, maybe around 15-20 land tiles. And "winter" of course starts in dead month, when the ice is still perilous. Throughout Dead and Winter three ungulates (two reindeer and an elk) have spawned on the island, and all three, seemingly within a day or two thereafter, wandered out onto thin ice and died. This was, of course, great for my character (free fur and meat, no chasing/trapping required). And of course I'm no expert on real life reindeer/elk; maybe lots of them do die in this manner. But just on general evolutionary principles it does seem like an extraordinary casualty rate; I would expect animals that evolved by the ice and the ocean to not fall in quite so readily. Maybe they should have a little more aversion to thin ice that can't support them programmed in? Other in-game animals also wander out on the sheet ice of course, but none are so heavy and so they usually don't break through.