PORTLAND, Maine - It would seem difficult to miss a 15,000-pound (6,804-kilogram) baby, but for months scientists who study rare whales did just that, and now they couldn't be happier.

Researchers in Canada captured images of an unidentified baby North Atlantic right whale, one of the rarest sea mammals in the world, off Anticosti Island in Quebec in September.

Scientists with the New England Aquarium in Boston said this week that after analyzing photos and data about right whales, they have determined it was a calf likely born months ago that went unseen during winter surveys for the giant animals.