Just to answer your question: it's in its genetic material. It really is fascinating; it can even make evolutionary sense to think of the dam as an extension of

Just to answer your question: it's in its genetic material. It really is fascinating; it can even make evolutionary sense to think of the dam as an extension of the beaver's physical body, in as much a beaver's dams are "built by" its genes just like the cells of its body are. Google "extended phenotype" if you'd like more detail.