One possibility is St. Martin de Porres
, who led mice out of his friary rather than allow them to be poisoned by fellow friars upset that the mice were destroying needed linens. St. Martin told the mice that, if they moved to the friary's garden, he would bring them food every day (source
). He also nursed stray dogs and cats (source
). St. Martin de Porres is also a patron of social justice in general.