It shall be unlawful for any person to own or harbor or keep any dog six months of age or older within the city limits unless there shall be attached to such dog a collar upon which there shall be a current numbered metal tag. The collar need not be attached to the dog while such dog remains in the dwelling of the owner or other person having custody thereof, or in any enclosed yard adjacent thereto. Nothing herein contained, however, shall be construed to relieve the necessity of having a current tag for each dog. (Ord. 912, § 2, 1988.)