inquiline

n.
An animal that characteristically lives commensally in the nest, burrow, or dwelling place of an animal of another species.

adj.
Being or living as an inquiline.

[Latin inquilīnus, lodger, tenant : in-, in; see in-² + colere, to inhabit.]

inquilinism in'qui·lin·ism (-lə-nĭz'əm) or in'qui·lin'i·ty (-lĭn'ĭ-tē) n.
inquilinous in'qui·lin'ous (-lī'nəs) adj.