There’s a little concrete check dam in Albuquerque’s riverside woods at the bottom of a pond built by humans as wildlife habitat. Among the wildlife that has taken up residence is a family of beavers, who have built a palatial home on the island in the middle of the pond. But they seem dissatisfied with the workmanship of the dam, and have been making their own helpful additions (the stick in the center has characteristic beaver chew marks on the upper end):

Bosque beavers, dissatisfied with human dam construction, making their own slight modifications: