Introduction

Humpback whales, Megaptera novaeangliae, may be the most unique of the rorqual whales (baleen whales with parallel throat grooves). Big and bulky, they are not built for speed like minke or fin whales. Instead, their massive bodies, up to 15 m (50 feet) and 40 metric tons (45 tons), are designed for tight turns and maneuverability.

One of the most obvious characteristics of humpbacks are their exceptionally long pectoral flippers, up to a third of their body length. Here, in the North Atlantic, the majority of humpbacks have flippers that are white on both sides that appear greenish when viewed through plankton-rich, high-latitude waters. By contrast, the flippers of North Pacific humpback whales tend to be black on the top. These long appendages are what allow humpback whales a surprising array of complex movements and behaviors. At the same time, long flippers may increase the surface area where body heat can be lost to the surrounding water, a helpful asset to a well insulated mammal during migrations to warm water breeding grounds. Just before a dive, humpbacks often raise their flukes, perhaps as an extra push on the way down. Across the underside of these flukes there is a variable pigmentation pattern of black and white. The whales are born with this pattern and it stays pretty much the same throughout their life (scarring through competition, play or encounters with predators certainly leave their marks).

Much of what is known of humpbacks comes from the fact that, as whales go, individuals are relatively easy to identify. The unique shape of the dorsal fin along with the pattern on the underside of the flukes can be used for positive identifications. Researchers need only watch and photograph. Once a whale is seen and photographed for the first time, it is catalogued and named. Later identifications of this same individual at different times and places begin to create a story of that individual and of humpback populations as a whole. Humpbacks are often considered the best studied of the baleen whales. Despite this, humpbacks are far from well-understood.

Throughout their summer range, humpbacks feed on a wide range of animals, depending upon what is locally available at a given time. On Stellwagen Bank, the abundance of humpbacks may be tied to the abundance of their favored food item sand lance. In years of low sand lance productivity humpbacks may bypass the Bank for more productive areas further north or offshore (in turn, this may create opportunities for other whales). Stellwagen Bank, a small area of the Gulf of Maine, is only one of several summer feeding areas scattered across the North Atlantic, including the Canadian Maritimes, and across to Norway, Iceland and Greenland (see map). Whales make use of these seasonally-rich, high latitude habitats to put on blubber in preparation for long migrations to the warm breeding grounds to the south. Southern habitats, like the Caribbean, rarely offer whales much in the way of food.

The primary preoccupation of most humpbacks in the winter time is reproduction. The stores of fat, packed on at the rich feeding grounds in the North, can be used for wintertime activities (Mattila, 1994): pregnant females give birth to, nurse and bond with their calves, non-pregnant females breed; males compete, through physical battles and perform whale song (long, complex vocalizations created only by male humpback whales, usually on the breeding grounds). Whale song is still poorly understood: how these behaviors are learned and what kind of information they communicate is still unknown.

Long term studies of humpbacks in the North Atlantic have been a cornerstone of our work at the Center for two decades and represents one of the longest running and largest data collections of a wild baleen whale population. Our research has followed the increase of this still endangered species. Hit hard by commercial whaling, protections through the International Whaling Commission and more locally, the Marine Mammal Protection and Endangered Species Acts have allowed for some recovery (Smith et al., 1999).