Comment by ceejayoz

https://en.wikipedia.org/wiki/Castoroides

> Stable isotopes suggest that Castoroides probably predominantly consumed submerged aquatic plants, rather than the woody diet of living beavers. There is no evidence that giant beavers constructed dams or lodges. The shape of the incisors of Castoroides would have made it much less effective in cutting down trees than living beavers. It was likely heavily dependent on wetland environments for both food and protection from predators.