Whale, Dolphin and Seal Species Information

HUMPBACK WHALES (Megaptera novaeangliae)

Weight: approximately 30 tons as an adult whale.

Distinctive Characteristics: Flippers longer than any other whale, usually 1/3 the length of the body; a series of wart-like bumps called 'tubercules' (actually enlarged sensory hair follicles) on the upper and lower jaw; stocky body; low, knobby dorsal fin which is variable in shape; 25-50 pleats or grooves on the underside of the throat.

Diet: Usually small fish, with some krill (shrimp-like animals; their primary diet in the southern hemisphere). Humpback whales are very famous for their unique, spectacular, bubble cloud feeding behavior. Adults consume up to 3,000 pounds per day while on their feeding grounds. Humpbacks, like most baleen whales, are thought to feed only during the 6-9 months of the year they are on their feeding grounds (see below). They fast and live off their fat layer for the winter period while on their breeding grounds, since there is little food available at that time.

Distribution: Humpback whales are distributed world-wide, with three major distinct populations: the North Atlantic, North Pacific, and southern oceans. Genetic research has now indicated that these three populations do not interbreed, and have not in thousands of years. Each population shows similar migration patterns, from warm water winter breeding grounds in low latitudes (places like Hawaii, Australia, and the Caribbean) to colder water summer feeding grounds in higher latitudes (e.g., Alaska, Antarctica, and New England, respectively). Populations generally seem to be structured so that whales learn the migration route to a single feeding ground which they return to annually, while feeding 'herds' in the same ocean generally mix on their breeding grounds.

Life History: Humpback whales are born during the winter, at approximately 10-12 feet in length and 2,000 pounds in weight, after an 11 month gestation. They are typically weaned in the northern hemisphere during the following December or January, although we have two cases of weaning as early as October). During its first year of life the mother seems to lead her calf through a series of locations where it learns to find food. While the calf also learns how to feed on fish during its first year (both through observing the mother, other animals, and practicing), it nurses on a rich milk, gaining up to 60 pounds per day. The father plays no role in parental care. After leaving its mother, the now-juvenile whale generally stays in habitats of medium quality (with limited food supplies) for the next several years. Growth seems to occur in two major periods, one during the first year and one at 3-4 years of age. Females may have their first calf as early as five, and as late as ten years of age; six to eight is most common. Females typically have one calf every two to four years, although we have seen a few females calve in consecutive years. Males appear to be physically mature at close to the same age, they probably do not get to breed until much later in life. Expected life span is 40-50 years, perhaps (much) longer.

Social Organization: Humpback whales form generally fluid groups on their feeding grounds, which often seem to come together for cooperative feeding. In rare cases pairs of whales may stay together for weeks or months; in even fewer cases, these associations may last over years. Generally, though, the only stable associations are between mothers and calves; other groups split after brief periods of time (30 minutes to 24 hours). Migration probably also takes place in small groups, rather than in a larger aggregation. On the breeding grounds, males work hard to compete for females. In order to do this, males can use one of two strategies. Males sing the famous song of the humpback whale, which is believed to 'advertise' the fitness (size and power) of a male. More often, though, males join battles in 'rowdy' groups, where a number of males actually physically combat other males for proximity to a female, who is usually found at the center of the group. While mating has never been observed, it is believed that the female chooses one male to mate with in each year she mates, and the pair is together for only a brief period (several days or less).

Population Status: Humpback whales were killed extensively from the late 1800's through the first part of the 20th century. Although they were protected in the early 1960's recent revelations from the Soviet Union indicate massive illegal and unreported kills which went on up until 1970 in the southern oceans. Best estimates are that there are now some 8,000 humpbacks in the North Atlantic, perhaps 4,000 in the North Pacific, and some 3-4,000 in the southern oceans. Although these populations are now protected and recovering, they remain at 10%-20% of original estimates, still considered an endangered species. Currently, the largest threats to humpbacks are entanglements in fishing gear, collisions with ship traffic, and pollution of their coastal habitat from human settlements.

FINBACK WHALES (Balaenoptera physalus)

Weight: approximately 40 tons as full grown adults

Distinctive Characteristics: An asymmetrical lower jaw which is white on the right side and the grey-black of the rest of the whale on the left (baleen also reflects this asymmetry); long thin body with a tall, erect, dorsal fin; 50-200 pleats on the lower jaw which expand during feeding.

Diet: A wide variety of small fish, with some krill (shrimp-like animals;their primary diet in the southern hemisphere). It is unknown whether this species fasts through the winter months.

Distribution: Finback whales are distributed world-wide, with three major distinct populations: the North Atlantic, North Pacific, and southern oceans. While there is certainly some structure to the stocks within each ocean, it remains to be determined what that structure is. Recent photo-identification work indicates that fin whales in the North Atlantic have been detected to move throughout the New England/Nova Scotia region but have never been resighted off of Newfoundland or the Gulf of St. Lawrence. Similarly, genetic work indicates that fin whales in the Mediterranean, on the other side of the North Atlantic, are a separate population. No wintering concentration area is known anywhere in the world; the speculation is that these animals go to deep waters and disperse. There is a possible year-round resident group in the Sea of Cortez in Mexico.

Life History: Fin whales are born during the winter at 15-18 feet and approximately 3,000 pounds after a 12 month gestation. Although no one knows where the calving grounds of fin whales are located, the approximate size of calves seen during spring and summer reflect an apparent winter birth season. The calf stays with its mother for 6-8 months, but can often wander up to several miles from the mother even well before weaning. Maturity is believed to take place at 6-8 years of age, and females produce a single calf every 2-5 years. There is some evidence that fin whales may have extremely long lives and may live up to 100 years, although confirmation of this depends on more accurate aging techniques.

Social Organization: Fin whales are primarily seen as solitary animals, although coordinated groups of up to 15 animals together have been observed. There appears to be considerable variation in grouping frequency by region; in the New England region groups are uncommon, while they appear to be observed much more regularly off the Newfoundland and Gulf of St. Lawrence coasts. There is some evidence that suggests the groups which are seen may have some stability, but this needs further study. Because of the loud, low frequency sounds made by fin whales, animals may remain in vocal contact over long distances, making it difficult to know when whales are or are not associated. Mating is thought to take place during the winter, although several observations of apparent mating activity have taken place during late summer off the Maine coast.

Population Status: Fin whales were killed extensively once 'modern' whalers had virtually extinguished blue whales. Between the 1930's and the 1960's over 500,000 fin whales were killed worldwide, mostly in the Antarctic. Although whaling for fin whales took place as recently as 1989, kills were highly limited after 1970. Now protected world-wide, fin whales are estimated to number 60,000 - 100,000 worldwide, and are listed on the Endangered Species list. Currently, the largest threats to fin whales is development and habitat destruction, entanglement, and the interest in several countries for resumed whaling on fin whales.

RIGHT WHALES (Eubalaena glacialis)

Weight: approximately 40-50 tons as full grown adults

Distinctive Characteristics: A stocky rotund body with no dorsal (back) fin; hardened patches of skin called 'callosities' on their head, often covered by colonies of cyamids ('whale lice'); a high, arching lower jaw and very long baleen plates with a fine fringe.

Diet: Exclusively plankton feeders, using a skim feeding technique (see photo). In the northern hemisphere copepods are the primary prey, while krill are the primary prey in the southern hemisphere.

Distribution: Right whales are distributed world-wide, with three major distinct populations: the North Atlantic, North Pacific, and southern oceans. There are two species of right whales: northern right whales, which are found in the North Atlantic and North Pacific ocean, and the southern right whale, which is only found in the southern hemisphere. Like humpback whales, there appears to be a seasonal migration for at least a portion of the population from cold water summer feeding grounds to warmer water winter breeding grounds. However, there may also be a substantial portion of the population which does not migrate as extensively, and may spend the full year in colder waters. In the North Atlantic, whales summer in the Bay of Fundy and Nova Scotian shelf; pregnant females and juveniles then move to coastal Georgia and Florida for calving. Some right whales spend the late winter and early spring feeding in Cape Cod Bay and the Great South Channel on George's Bank. Distribution in the North Pacific is largely unknown, and sightings are uncommon. In the southern hemisphere, whales probably feed below the Antarctic convergence, and move to coastal breeding grounds off Australia, South Africa, and South America.

Life History: Right whales are born during the winter at 10-15 feet and approximately 3,000 pounds after a 12-14 month gestation. Calves stay with their mother for up to a year, although the calf of a mother killed by a ship collision when only 8 months old did survive and was sighted in subsequent years. Right whales have been observed to give birth as early as five years of age, but seven to ten appears to be more common. Calves are born once every 3-4 years, and the mother is entirely responsible for caring for the offspring. Right whales can live extremely long lives; one whale photographed back in 1935 with a calf was re-photographed as recently as 1995, making her the oldest non-human mammal ever confirmed.

Social Organization: Right whales are usually solitary feeders, although dense plankton swarms in a limited areas may attract a number of whales to the same location. Cooperative feeding, as often seen in fish feeding whales such as humpbacks and fin whales, is uncommon. Right whales do aggregate into apparent mating groups, where numerous males compete for access to an adult female. Up to 35 males have been seen in a single group! It is thought that multiple males may mate with a single female, and much of the actual competition for fathering offspring is internalized in the female, through sperm competition. These 'surface active groups' are observed year-round, even though the calving season is highly seasonal. No one knows whether these groups have some other social function besides reproduction.

Population Status: Right whales got their name because to early whalers they were the 'right' whale to kill: they were slow swimmers, lived close to shore, floated when dead, and gave a good oil yield when their thick fat layer was melted down. Right whales were hunted as early as the 11th century, and were probably endangered by the mid-1800's. They were protected world-wide in 1937, although there have been both 'research' kills and illegal takes long after that date. Currently, there are approximately 4,000 southern right whales. Some 300 right whales remain in the North Atlantic (with the population growing at an average of only 2.5% per year, as opposed to a 7-8% annual growth of southern right whale populations), and an undetermined small number (probably less than 100) live in the North Pacific. Collisions with ships are the largest single cause of human mortality, but entanglements in fixed fishing gear have at least scarred almost 60% of the whales in the North Atlantic. Preliminary evidence also suggest that North Atlantic right whale populations have dropped to the point where they have lost some genetic diversity, and inbreeding may also be a problem in their recovery.

MINKE WHALE (Balaenoptera acutorostrata)

Weight: approximately 5-8 tons as full grown adults

Distinctive Characteristics: A sleek, small dolphin-like baleen whale; in the northern hemisphere there is a white strip across each flipper; dorsal fin is tall, sickle shaped, and near the middle of the back.

Diet: Generally fish feeders in the northern hemisphere, krill feeders in the southern hemisphere. Because of their relatively small size, and lowered energetic needs, their diet is a wider variety of fish than the larger fin and humpback whales. At times, they may even take single larger fish rather than large quantities of smaller fish.

Distribution: Minke whales are distributed world-wide, with three major distinct populations: the North Atlantic, North Pacific, and southern oceans. However, genetic work now indicates that the two hemispheres may contain different species of minke whales, as opposed to distinct populations of a single species. During summer minke whales are found from temperate waters all the way up to the ice pack. Their winter movements are poorly known; some may stay in temperate waters year-round, and there is recent acoustic evidence that some minke whales in the North Atlantic may move into tropical waters in the Caribbean during winter. Within their range, they are widely distributed, and are found over a more widespread area than their larger relatives.

Life History: Very little is known of the life history of minke whales. Females are thought to give birth to one calf at a time once every 1-2 years. Mother-calf pairs are rarely observed, although in the past several years we have started to see what we think are independent calves (based on their size) with a probable mother staying in the general vicinity, but not with the youngster, with some frequency during September and October on Stellwagen Bank. Life span is unknown at this point.

Social Organization: Minke whales are almost always seen by themselves, although they appear to aggregate (in concentrations which can number up fifty at a time) in productive food areas. While true side-by-side associations are unusual, these whales may work in small bands where individuals stay in each other's general vicinity. This appeared to be the case when two distinctive minke whales were seen on Stellwagen Bank throughout the summer of 1994; on days when one was seen, the other was also observed. However, this may have also been a coincidence of two whales following the same environmental cues. In the San Juan islands, where minke whales were studied for several years in the 1980's, individuals were found to be extremely site-specific and have feeding strategies which were specialized within the locality. How applicable these findings are to more open-ocean areas remains to be determined.

Population Status: Minke whales are the most abundant whale in the world today, numbering well over 1,000,000 world wide. The highest population density is in the southern hemisphere, where up to 750,000 whales spend the summer feeding. Large populations also exist in the North Atlantic and North Pacific oceans. Minke whales are still commercially hunted by Norway, which kills up to 500 per year, and Japan (under a provision where research is done on the carcass, but the meat can still be sold on the open market), who takes up to 800 Antarctic Minke whales per year. The meat of these whales is considered a delicacy in Japan, where it sells for several hundred dollars per pound. Current threats to minke whales include expansion of the current hunt (which is being promoted by Japan, Norway, and Iceland), entanglements in fishing gear (since minke whales are not as strong as the larger species, they are more likely to become entangled and die), and degradation of their habitat from pollution.

SEI WHALE (Balaenoptera borealis); pronounced 'say'

Weight: approximately 40-50 tons as full grown adults

Distinctive Characteristics: A very sleek whale with a tall dorsal fin that is curved and pointed on top. Their baleen has an unusually fine inner fringe. Unlike many other whales which will blow several times in rapid succession and then dive for a longer period, sei whales often will stay at the surface and blow once every 90-120 seconds.

Diet: Sei whales have been known to eat a wide variety of prey, including many fish species and squid. However, their primary diet seems to be plankton, especially copepods. As such, they are often found in the same area as other copepod feeding whales, including right whales. Unlike other rorqual whales (those with pleats and a dorsal fin), sei whales will sometimes feed by skimming along, mouths opened, as they feed on plankton.

Distribution: Sei whales are widely distributed, from the tropics up to the ice pack. However, they are somewhat more common in colder waters. Their annual movements are poorly known and understood. In many parts of their range, they are known for episodic influxes into areas where they were previously rare, but where plankton is abundant.

Life History: Sei whales are born at approximately 15 feet, and 1,500 pounds. It is presumed that they are born in warm waters, although specific breeding grounds remain unknown. It is thought that females give birth once every 2-3 years, after a gestation of about a year, and the calve stay with the mother for 6-10 months.

Social Organization: Sei whales are usually seen in small groups, from single animals to groups of four. However, in areas of dense prey, they may aggregate with many such groups in a very limited area. It is thought that they, like most whales, do not form long term a bond between males and females, but little is known of their breeding behavior.

Population Status: Over 200,000 sei whales were killed in the 20th century, primarily in the southern hemisphere. While they are classified as endangered today, exact numbers or population estimates are difficult to generate. In general, they are thought to be fairly abundant throughout the northern hemisphere, and depleted in the southern hemisphere. The only sei whales being killed today are those killed by Japan, who started a small hunt as part of their "research" program in the North Pacific Ocean in 2002.

ATLANTIC WHITE-SIDED DOLPHIN (Lagenorhynchus acutus)

Weight: approximately 300-600 pounds

Distinctive Characteristics: A white and yellow stripe on both flanks which is highly visible at sea; a single blowhole (characteristic of all the toothed whales); a tall erect dorsal fin mid-way on the back

Diet: A combination of squid and fish, often herring and its relatives. Atlantic white-sided dolphins, like all dolphins, feed on single prey items, so they are less likely to feed on the large numbers of small fish that the whales usually feed on.

Distribution: Atlantic white-sided dolphins are found only in the North Atlantic, generally from waters just south of New England north to Norway. A close relative, the Pacific white-sided dolphin, is found in similar latitudes in the North Pacific ocean. Atlantic white-sided dolphins are members of the genus Lagenorhynchus, which are typically adapted to colder water; one species (the hourglass dolphin) is only found in the Antarctic! Recent genetic work indicates that this genus is only distantly related to the other genuses within the dolphin family, and may be split into its own taxonomic family in the near future. Atlantic white-sided dolphins appear to be very nomadic and rarely stay in one spot for long, but do not show any set seasonal migrations.

Life History: Atlantic white-sided dolphins are born in the summer, usually anywhere from late June to late July. It is believed that they stay with their mother for up to a year. Interval between calves is not known, but we know of one case where a distinctively marked dolphin was seen with what appeared to be young-of-the year calves in two straight years. Dispersal may be sex-related (see below). Unlike the baleen whales, males are slightly larger than females. Dolphins are thought to mature at 6-10 years of age, and can live for at least 25 years and possibly more.

Social Organization: Atlantic white-sided dolphins are sighted in groups as small as 10-15 animals, and as large as several thousand together. Groups of 100 or more are generally called 'superpods,' and are believed to be temporary associations which may form for foraging, cooperative feeding, or just travel. Smaller groups may be more stable; in many dolphin species, these groups are comprised of related females and their young, while males move from group to group. Although little is known about the social organization of this species, it appears groups are either primarily female-young groups or 'bachelor' male groups without any females present. We have typically seen group size increase through our field season, and most superpod sightings occur in August through October.

Population Status: Although there is no good estimate of the number of Atlantic white-sided dolphins, there is no question they are an abundant species. While they are not commercially hunted, several animals may be killed each year by native groups in northern climates. Today the primary threats to Atlantic white-sided dolphins are from pollutants (all dolphin species seem to build up unusually high pesticide loads), and entanglement in fixed fishing gear, which is often fatal to the dolphin.

HARBOR SEALS (Phoca vitulina)

Weight: Up to 350 pounds (larger for males than females)

Distinctive characteristics: Fur is tan to silver in color, with dark mottling on the back; head is "dog-like," with a broad snout.

Diet: Harbor seals feed primarily on fish, but can supplement their diet with octopus, squid, or shrimp. They can stay at sea for weeks while feeding and foraging.

Distribution: There are five subspecies in the world; in our area, the subspecies is P.v. concolor, which ranges from northeastern Canada, Greenland, and Iceland south along the U.S. coast to New Jersey. They are the most common seal in New England and can be seen here year-round.

Life History: Harbor seals give birth in the spring and early summer, and females nurse their pups for three to four weeks. Mating occurs soon after pups are weaned. They are relatively solitary while they are in the water, but they can come on land in "haul-out" sites, which can have up to several hundred seals. While they are on land, seals spend the majority of time resting, stretching their flippers, often towards the sun, and scanning for potential threats. There are several winter haul-out sites on Cape Ann (see seal survey information). Harbor seals are one of the least vocal seal species, but they do sometimes growl or grunt when threatened.

Conservation/Status: There are currently thought to be approximately 99,000 harbor seals in the Western North Atlantic, and there may be as many as 500,000 in the world. They are protected in the United States by the Marine Mammal Protection Act. However, Canada, Norway, and the United Kingdom now have legal kills of harbor seals, supposedly to protect local fishing industries.