Gray Whale How Can You Tell It's a Calf? By Biologist Wayne Perryman, SWFSC Image: Keith "Baja" Jones 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: Calves have very short heads relative to their body size. The distance from the rostrum to the blow hole is shorter in calves than in juveniles. Calves have a smaller blow than older whales. Calves and cows swim more tightly together than older whales do. A calf has a closer bond with its mother. Calves lack barnacles, or have far fewer barnacles than older whales do. Calves have a clumsy way of surfacing. We generally watch cow/calf pairs (and adult juvenile pairs) approach from about two miles away. Because we use 25X binoculars at the site, we can see and study them straight on for about 45 minutes as they approach. Facebook Pinterest Twitter © 1997 – 2019 Journey North. All rights reserved.