has a lot to do with environment and how nature treats the animal to be comfortable in its environment. takes much longer for water temperatures to consistently go below freezing point at the surface, whereas land animals such as canines, coons, etc. are alwasy exposed to the air temperatures.
beaver & rats swim in water that is never really all the way below freezing (only at surface) and dens are in ground or surrounded by a ton of vegetation, mud, and debris...or in other words very well insulated. beaver and rats prime up much later as a result. still has a lot to do with light duration vs. nighttime, but these animals are more directly impacted by their immediate environmental average temperatures.