Seals and walruses are two possibilities.
bull
A bull seal and a cow seal have seal pups.
A Cygnet is young swan .
Animal skins. Mainly bull and deer.
A young bull, or any male of the ox kind., An ox, steer, or stag., To bully.
mammals
to ensure continuity of their kind
A pit bull
The young of any animal of the Horse family (Equidae); a colt; a filly., To bring forth (a colt); -- said of a mare or a she ass., To bring forth young, as an animal of the horse kind.
The type of animal that the Zodiac sign Taurus repersents, is the Bull. It has been portrayed for eons of time. It is a very strong symbol of history as we know it.
bull fish
A bird. Birds feed their young food they find. I believe that any animal that is not a mammal does not have nipples.