Euthanizing shall be done by the most humane means possible by a rehabilitator or the rehabilitator's veterinary consultant, and in a manner prescribed by the veterinary consultant. These procedures shall conform to the standards set by the American Veterinary Medicine Association or the National Wildlife Rehabilitation Association. An animal listed as a threatened or endangered species may be euthanized after the rehabilitator has obtained the approval of the Wildlife and Heritage Service if: It is necessary to relieve immediate pain; or The Department determines that recovery is highly unlikely.