Telling calves from yearlings is really tough. Calves average about 7.1 m in length, while yearlings average about 8.5 m in length. That's not much difference! It takes experience and a really good look to get it right. We are lucky at Piedras Blancas because the cow/calf pairs swim directly towards us. The water is very calm. They often surface several times within 50-200 meters of us. This all helps us get a good look!
Basically, calves differ from juveniles in these ways: