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Mysticetes, or baleen whales, share at least one thing in common: instead of functional teeth, all have baleen (sometimes referred to as “whalebone”) inside the mouth. Each plate of baleen consists of long flexible hairs bound together by connective tissue and embedded in the upper gum. Made of keratin, they are similar in appearance to human fingernails. Hundreds of plates, one alongside the other, line each side of the upper jaw, hanging downward. Where the whales’ tongue rubs against the baleen, the baleen is worked into a series of bristles. This inner fringe allows whales to filter large quantities of small prey from the water. Different species of baleen whales differ in the shape of the baleen and the fineness of the fringe. This reflects different feeding styles and food types: short baleen plates with a coarse fringe describes a fish-eating whale; long plates with a fine, silky fringe allow others to hunt smaller animals such as zooplankton.

At least three broad feeding styles can be found within the baleen whales: gulp feeders, skim feeders and bottom feeders.  Gulp feeders, like humpback, fin and minke whales, engulf a large mouthful of food and water, close the mouth part way and, with the tongue, force the water back out through the baleen. The food cannot pass through the baleen and is swallowed whole. Long, parallel grooves, or pleats, run the length of the throat, allowing the throat to distend - almost like the pouch of a pelican (baleen whales with these "rorqual grooves" are classified together as rorqual whales, such as fin and humpback whales). This feeding style works well with schools of small fish or large plankton.

Skim feeders, like right and sei whales, pass through patches of plankton-rich water with their mouths open. As food and water flow into the mouth, the water passes out through the baleen. Food items, trapped against the fringe of the baleen can be directed to the throat by the tongue. 

Gray whales, the only known bottom feeding baleen whales, plow rich sea bottoms, filtering invertebrates from mud and water. 

Besides the unique filtering system for feeding, most baleen whales share a number of broad characteristics in common. Most have wide ranges and extensive migrations. They lack any known capability for sonar or echolocation. They often have a mating system in which both males and females are promiscuous. Often, they exhibit a relatively short period of maternal care with no strong kinship bonds aside from a mother and her new calf. They have large bodies requiring massive quantities of small prey. 

Species descriptions:

blue whale | fin whale | sei whale | minke whale | humpback whale

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North Atlantic right whales, Eubalaena glacialis, are considered the rarest of the baleen whale species. Distinct populations of right whales were scattered across the oceans of the world until they were decimated by heavy and consistent whaling.

These are large whales, up to 17m. (56 feet) and may weigh up to 100 metric tons. Much of their body length is taken up by their massive head and long, curved mouth line that supports a massive rack of baleen. Each baleen plate is up to 3m (8 feet) long and very narrow. The fringe along the inside edge of the baleen is very fine, allowing right whales to filter very small but plentiful food items, especially copepods.

Large broad flukes help push the rotund body through dense patches of zooplankton, even with the extra drag the open mouth. Paddle-like flippers increase maneuverability for feeding and social behaviors. Not built for speed, right whales have no dorsal fin on the back. Over most of the body, the skin is smooth and black. Rough, light-colored areas can be found on the top of the head, around the blowholes, chin, jawline and above the eyes. Collectively known as callosities, these patches create the perfect home for cyamids or whale lice. Dense colonies of these invertebrates color these patches tan or white. Because the callosities do not change over the lifetime of the individual, the pattern can be used to identify individuals. 

Seasonal movements are still poorly understood but, generally, they move between rich summer feeding grounds and warm winter calving grounds. During summer and fall most of the population feeds on different banks in Southeast Canada such as the Bay of Fundy. "Courtship groups" are also seen at this time. During November and December right whales almost disappear with a few scattered reports coming from far flung areas such as Jeffreys Ledge off Northern Massachusetts and offshore of Cape May, New Jersey. By late winter and early spring, two distinct aggregations appear: calving females off southern Georgia/northern Florida and non-calving animals feeding (Mayo, 1998) off the Massachusetts coast (Cape Cod Bay, Great South Channel and Nantucket Sound).

Until about half a century ago, the North Atlantic population was believed to be extinct. Since the discovery of a relic population, research and conservation efforts have worked to learn more about right whales and their habitat requirements with an eye to recovery. The right whale population in the North Atlantic currently includes between 300 and 350 individuals. Although protected from hunting, the right whale population still carries heavy losses from entanglements and ship strikes. How the population might be affected by habitat degradation is still being studied through long term research efforts here, at CCS, by collaborating research labs and government agencies along the eastern seaboard. 

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Blue whales, Balaenoptera musculus, are rarely seen on Stellwagen Bank. As the largest animal on earth (up to 33m or a hundred feet), much of the Bank is simply too shallow for them - they would hit their chin during a dive! A more realistic average size might be something like 80 - 85 feet; yet, even with this extra clearance, most blue whales would find Stellwagen uninhabitable for any length of time. Quite simply, there is little here for a blue whale to eat. Krill, the favored food of blue whales, cannot be found on the Bank in quantities suitable for a population of 80 or 90 ton animals. 

Despite the fact that Stellwagen is not ideal blue whale habitat, they have been spotted a few times. Small, periodic explosions of krill on Stellwagen may support a stray blue as it moves on to richer feeding grounds further offshore or to the North, such as the Gulf of St. Lawrence, in Canada. Add to this their extreme rarity due to historic over hunting, the sight of a blue whale here is exceptionally rare. 

Their large size, relatively tiny dorsal fin and mottled gray-blue skin make them relatively easy to identify from the more common, local whales such as the closely related fin whales. 

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Fin whales, Balaenoptera physalus, are second only to the blue in size. At over 60 feet (18 m) and over fifty tons, large fin whales are a spectacular sight on Stellwagen. Built for speed, their body is long and sleek. The tail stock is flattened vertically to a thin keel to reduce drag as the wide flukes are pumped up and down for swimming. A tall dorsal fin probably helps to keep the whale from rolling during high speed swimming, with sprints up to 12 (20 km) an hour. 

The overall color tends to be dark brown or warm gray above and cream or white beneath. Fin whales are unusual in that the coloration of the head tends to be asymmetrical: the right hand side of the lower lip, and much of the baleen, is usually stark white as opposed to gray or brown on the left side. This "blaze" and other light patches, or chevrons, about the head and back (along with the shape of the dorsal fin) can be used to identify individual fin whales over time. 

Relatively little is known about the movements and behavior of fin whales: they travel quickly and individuals are difficult to identify in the field, making research a real challenge. Photo-identification of fin whales (Agler, 1993) has begun to clarify their natural history. In some years, Stellwagen provides good feeding for large numbers of fin whales in spring, summer and fall. This includes females and their young calves. Many of these whales visit Stellwagen year after year. Just where most fin whales spend the winter, and where (or if) breeding grounds may be, is still a mystery. 

Feeding on small schooling fish like sand lance, herring or mackerel, fin whales rely on speed. After locating a patch of bait, fin whales may spend some time circling the school, possibly concentrating the fish. During the final sprint, they may roll on their side, mouth agape, engulfing as many fish as possible. Massive amounts of oily fish will translate into layers of fat to be used as food storage for the lean times of winter and as milk for growing calves.

Fin whales are a cosmopolitan species, found usually in subpolar and temperate seas across the globe. Protected by their speed during the early stages of whaling, abundant fin whale stocks were decimated by the technology of modern whaling: exploding harpoons and engine driven catcher boats. Today they are listed as endangered by the U.S. Endangered Species Act and are afforded protection by the Marine Mammal Protection Act.

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Sei whales, Balaenoptera borealis, are another little-known whale species that is found only sporadically on the Bank. Their long, streamlined shape is reminiscent of the closely related fin and minke whales; a body design built for efficient speed. At sea they are easily confused with the larger fin whales but, they tend to be a dark, cool gray, the dorsal fin tends to be smaller and more falcate (sickle-shaped), and they are symmetrically colored about the head. They also tend to be smaller than fin whales, rarely pushing 15 m (50 feet). 

By all accounts, inshore sightings of sei whales tend to be sporadic and, likely, are related to abundance of their prey. Records from northern whaling stations reported that most sei whales had copepods in their stomachs as well as krill and small, schooling fish. This varied diet is reflected in their feeding styles: they can be found travelling slowly, just below the surface, mouth open, skimming for zooplankton (likely copepods) or, lunging through patches of fish or krill with the rorqual pleats extended, as they gulp feed. 

Sei whales may be a good indicator of cyclical changes on Stellwagen Bank. For example, during the summer of 1986 (Schilling, 1992), whale-watchers were surprised by the fact that very few humpback whales were present on the Bank. The population of sand lance, the small fish that makes up a bulk of the humpback's diet here, seemed to be exceptionally low. Copepods, the main source of food for sand lance, exploded in their absence, creating a temporary hot spot for feeding sei and right whales Perhaps coincidentally, one of the few sightings of a blue whale, another planktivorous species, came from this year as well. 

Like fin whales, sei whales were not heavily hunted until the advent of modern whaling. As high speed vessels evolved, the sei whale population crashed. They are listed as endangered on the U.S. Endangered Species List and are poorly understood. 

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Minke whales, Balaenoptera acutorostrata, are the smallest baleen whale species on Stellwagen Bank. At about 8 m (25 feet long), they have a sleek body design built for speed. Like many marine animals they are counter shaded: dark on top (dorsally) for camouflage when viewed from above, and light below (ventrally) to blend in with the light at the surface when viewed from below. The dorsal surface tends to be a dark, cool gray, sometimes with swaths of pale gray or white on the flanks and back, while the ventral surface is stark white with areas of pink. In the North Atlantic, most minkes have a bright white band on each, short flipper. Their head is long and pointed; the dorsal fin is tall and sickle-shaped. 

Minke whales are relatively small, they usually travel alone or in very loose groups, they don't generally create a spout when at the surface and often change direction quickly. All of these characteristics make them a challenging whale to observe. Consequently, relatively little is known about minke whales: calving rates, where the different sub-populations go for different seasons, their habitat requirements, etc. One of the few systematic studies of minke whales in this area, was carried out by Margaret Murphy, here at CCS (see 1995 Murphy). The number of minkes that use Stellwagen Bank changes from year to year and calves are rarely observed here. May through September seems to be a peak time for minkes in this area. Like the sei whales mentioned above, identifying individuals can be a big challenge due to their speed and the subtle differences between individuals. 

On the Bank, minke whales can be found in areas where other whales, like fin and humpback, are feeding. Studies of minkes in other areas indicate that their diet may be more diverse than other local baleen whales, taking advantage of whatever is abundant in a given area or given time: copepods, krill, capelin, herring, sand lance and squid. Interestingly, the smaller minke may feed on larger food items than the larger whales do, taking fish as large as cod and pollock. Minke whales may be very flexible in their feeding strategies: chasing down small groups of large, fast swimming fish or lunging through dense patches of bait fish or zooplankton. Despite these observations, just how minke whales use Stellwagen Bank is still poorly understood. Minkes are rarely observed feeding at the surface on the Bank. 

Minke whales are a cosmopolitan species with populations scattered throughout the oceans of the world. In the North Atlantic, at least three different stocks are recognized. Minke whales on Stellwagen Bank are part of the Canadian East Coast stock including all of the Gulf of Maine. These populations seem to be separate and genetic variability between populations may represent different species. Certainly, they are the most numerous baleen whale species at present. Their small size and unobtrusive behavior made them unattractive to many whaling operations until other larger whale species became commercially extinct or rare. Today minkes are still hunted by a few nations including Norway and Japan. 

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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, see the sei whale above). 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)

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