Originally posted by Emelio Lizardo:

Importantly this seems to indicate the possibility that (land) critters are subject to the same water stamina limitations as the player. I've wondered about that and now there is a data point. Maybe a DEV can comment.

Not a DEV, but I'll comment anyways. This is not true. The only mobs affected by stamina in any way are Lox that you tame, and then only while riding them.