WHALES (Order Cetacea)

Whales, like humans, are mammals; they have lungs and must breathe air to survive, they are warm-blooded, they bear live young. Whales nurse their young with milk, and while you may not think of a whale having hair, all whales do have hair at some stage in their development.^[1] All members of the order Cetacea are believed to have evolved from hoofed mammals, such as cows, sheep, and camels, 45 million years ago. Comparisons of certain milk protein genes indicate that the closest, living, land relative to whales is the hippopotamus.^[2]

The order Cetacea contains more than eighty species; although, the precise number of species is debatable. Thirty-nine cetacean species have been recorded in the North American Pacific.^[3] This section will cover whales most commonly seen near Kodiak Island.

Cetacea is derived from the Greek word ketos, which means whale. All cetaceans have forelimbs that have been modified into flippers and no hind limbs. Their tails are horizontally flattened, and they breathe through a nostril, or blowhole, located on the top of the head.^[1] A blowhole has a nasal plug that remains closed except when forced open by muscular contractions to breathe. This plug is sealed when the whale dives.^[4] A whale has internal sensory and reproductive organs to reduce drag while swimming, and whales do not have external ears, but instead have a complex internal system of air sinuses and bones to detect sounds.^[2] The lungs of a cetacean are relatively small, highly elastic, and elongated. A whale's diaphragm is strong, allowing the animal to purge a large amount of air in a short time. Nearly 80 to 90% of the lung air is replaced with each respiration.^[4] During a deep dive, a cetacean will slow its heart rate and decrease blood flow to peripheral tissues.^[4]

Cetaceans living in the cold ocean waters of the North Pacific must somehow maintain a body temperature that is nearly the same as a human's body temperature. A whale uses a number of mechanisms to accomplish this feat. First of all, it has a thick layer of blubber that has few blood vessels, reducing the heat loss at the body surface. A whale has a counter-current heat exchanger, where veins at the periphery are surrounded by arteries. Heat lost by vessels flowing from the warmer core toward the cold periphery is at least partially absorbed by vessels flowing from the periphery to the core. A cetacean also has a fairly high metabolic rate to produce heat, and it has a low body surface to volume ratio which conserves heat. Finally, a whale has a slower respiration rate than a land mammal, so warm air is expelled less frequently.^[4]

Most cetaceans produce large calves, and the large body volume relative to surface area minimizes heat loss in the calf.^[3] Calves are born tail first, and as soon as the calf is out of the birth canal, the mother or another whale nudges it to the surface for its first few breaths.^[3] Cetacean mothers nurse their calves with a pair of teats that are concealed in slits along the body wall. The milk has a high fat content, and the calves grow at a rapid rate.^[4] Whale mothers tend and guard their calves closely, and a calf may ride the bow wave or the convection currents produced by its mother or another adult when whales are traveling. This is such an efficient means of travel that the calf barely has to move its flukes to keep up with the group.^[4]

The order Cetacea is divided into two suborders: The Mysticeti or baleen whales and the Odontoceti, or toothed whales.^[3]

The general body shape of most baleen whales is cylindrical and tapering at the ends. This shape is energy efficient for swimming and creates less drag.^[1] Their skin of a baleen whale is smooth and has no oil glands or pores. Many species of mysticetes have sparse hairs on the snout, jaws, and chin, but the lack of hair or fur on the body is an adaptation to reduce drag when swimming.^[1]

A baleen whale has a small, external ear opening on each side of its head that leads to an auditory canal. The middle and inner ear is similar to that of other mammalian species, but the ears are adapted for hearing under water. Scientists believe that baleen whales have good hearing.^[1]

Like other marine mammals, a whale’s eye is spherical in shape, and the lens is more like the lens of a fish than the lens of a land mammal. The retina contains mostly rod cells, which are sensitive to low-light conditions. There is a reflective layer called a tapetum lucidum that reflects light back through the retina, increasing visibility in low-light conditions.^[1] Very little known about tactile sensations or the sense of smell in baleen whales, but there are few olfactory nerves in adult whales, so it is believed that they have little or no sense of smell.^[1]

A whale holds its breath when under water, and when it surfaces, it opens its blowholes and blasts a loud exhalation. The whale then quickly inhales and closes its blowholes before diving. Most baleen whales surface and breathe several times before diving. The spout of water that is often the first visual clue of a whale s presence does not come from the whale' s lungs. As with other mammals, a whale' s lungs do not tolerate water. Instead, the water spout is produced from water that was on top of the blowhole when the whale exhaled. The water condenses as the respiratory gasses expand in the air.^[1] The size and shape of a whale' s " blow" vary from species to species.

Mysticetes are found in all oceans. They live in polar, tropical and temperate zones. There are three families in the suborder Mysticeti. These are Balaenopteridae, or the Rorqual Whales; Balaenidae, the Right Whales; and Eschrichtidae, the Gray Whale.^[1] In the family Balaenopteridae, I will cover the blue whale, the fin whale, the sei whale, the minke whale, and the humpback whale. In the family Eschrichtiidae, I will cover the gray whale.

Family Balaenopteridae: The Rorqual Whales

Blue whales are the largest animals to have ever lived on earth. An average adult is 85 ft.( 26 m) long and weighs 100 tons.^[7] The largest ever recorded in the Northern Hemisphere was a 92-ft. (28.1-m) long female and the largest recorded blue whale from the Southern Hemisphere measured 107 ft. (32.6 m) in length.^[5] Blue whales are mottled bluish-gray and streamlined with a broad, rounded head, long, slim flippers, and a very small dorsal fin that is located so far back toward the flukes that it is usually only seen when the whale is about to begin a dive. Blue whales have broad, triangular flukes that are only slightly notched.^[4] The baleen is solid black,^[4] and they have 270 to 395 3-ft. (1 m) long baleen plates on each side of the upper jaw.^[5] They have 60 to 88 throat grooves running from the tip of the lower jaw to the navel. ^[5] Their blow is column-shaped and very tall, sometimes reaching 39 ft. (12 meters).^[3] They normally blow once every one to two minutes and dive for three to ten minutes, but they may dive as long as twenty minutes.^[7]

From a distance, a small blue whale looks much like a large fin whale, but blue whales have a mottled coloration while fin whales have a dark-gray back and a white underside. Fin whales also have a more-pointed rostrum and pale chevrons behind the blowholes. Perhaps the easiest way to distinguish between the two species from a distance is that you can usually see the fairly large dorsal fin of a fin whale each time it surfaces while a blue whale only shows its dorsal fin when it arches its back to begin a dive.^[3]

Blue whales inhabit all the world s oceans and are usually found far off shore in deep water near the continental shelf.^[3] They are rarely seen in the bays around Kodiak Island, but in the summer, they can be found from the Gulf of Alaska to the Aleutians and the Bering Sea.^[5] In the winter, they migrate to warm temperate and tropical regions where they breed.^[3]

It is interesting that the largest animal on the planet dines on one of the smallest animals. Blue whales primarily eat euphausiids, small shrimp-like organisms that are commonly called krill. Blue whales fast most of the winter, but they eat approximately four tons of krill per day during the peak feeding time in the summer,^[5] and a single whale might consume eight tons per day.^[4]

Blue whales usually travel alone or in pairs. They are sexually mature at ten years, and a female gives birth to a single calf every two or three years. The gestation period is 12 months, and a calf stays with its mother for approximately eight months. Calves gain 200 lbs (91 kg) per day or 8 lbs (3.6 kg) per hour^[5] and are around 49 ft. (15 m) in length when they are weaned.^[4] Blue whales are so massive that they rarely if ever breach.^[3] They live up to 80 years.^[3]

Blue whales are listed for protection under the United States Endangered Species Act of 1983, and they have been protected by international agreement since 1965.^[5] It is estimated that nearly 350,000 blue whales were killed by commercial harvesters between the 1860s and 1960s. The worldwide population is now estimated at 12,000 individuals, and there are approximately 1200 to 1700 blue whales in the eastern North Pacific.^[5]

Fin whales are the second-largest species of whale. Adult fins range from 50 to 80 ft. (17-24 m) in length and may weigh up to 70 tons.^[5] The average adult male fin whale is 70 ft. (21 m) long and weighs 40 tons, and the average adult female is 73 ft. (22 m) long and weighs 45 tons (40823 kg).^[8] Fin whales are sleek and streamlined. A fin whale' s rostrum (upper jaw) is V-shaped and flat on top, and it has a distinct ridge on its back that extends from the dorsal fin to its tail fluke.^[8] Its dorsal fin is up to two feet (.61 m) tall and is curved with a steep backward angle and a blunt tip.^[8] The dorsal fin is located approximately one-third of the body length forward from the fluke notch.^[4] The flukes are broad and triangular with pointed tips and a central notch.^[8] A Fin whale has up to 475 two-foot (0.6 m) long gray and white baleen plates on each side of the mouth and between 55 and 100 ventral throat grooves that expand during feeding.^[8]

The fin whale is a light gray to brownish-black on the back and sides and has two lighter-colored chevrons that begin behind the blowholes and slant down the sides toward the fluke and then swirl up and end behind the eyes. The undersides of the body, flippers, and flukes are white.^[9] The left lower jaw of a fin whale is dark gray, but the right lower jaw is white, and this asymmetrical coloration extends to the baleen plates. Plates on the left side and the rear two-thirds of the right side are gray while those on the front of the right side are yellow.^[5] Scientists think that the asymmetrical jaw color may somehow aid fin whales in capturing prey.^[2]

Fin whales are one of the fastest-swimming big whales, and their speed has earned them the nickname, "greyhound of the seas." ^[10] Their normal swimming speed is 5 to 9 mph (8-14 km/h), but they travel at speeds as high as 18 mph (30 km/hr) when cruising or migrating, and they may swim as fast as 30 mph (48 km/h) in short bursts when they are alarmed.^[10] Fins rarely breach or show their tail flukes before a deep dive, but when diving deep, a fin whale arches its back and dorsal fin high above the surface.^[4] Fins usually dive for five to fifteen minutes to a maximum depth of 1000 ft. (300 m). After surfacing, their normal pattern is to blow 4 to 5 times at ten-to-twenty-second intervals before their next dive.^[8] A fin whale has a tall blow, 12 to 18 ft. (4-6 m) high, that can be seen from a long distance. The blow is shaped like a long, inverted cone.^[4] When swimming at the surface, fins expose their dorsal fin shortly after the blowholes appear.^[4]

Fin whales may be confused with blue whales and sei whales. Fins are darker than blue whales, and if examined closely, fins can be distinguished from blues and sei whales by the white right lower lip. From a distance, it is more difficult to distinguish a fin whale from a sei whale, but there are subtle differences. Fin whales usually feed deeper than sei whales, so they surface at a steeper angle, with the top of the head breaking the surface first. They then blow, arch the back, and roll forward, exposing the dorsal fin. Sei whales are primarily skimmer feeders and feed near the surface, so they surface at a shallow angle, exposing the head and the dorsal fin simultaneously, and even when making a deep dive, a sei usually does not arch its back as much as a fin whale does.^[4]

Fin and blue whales produce the loudest biological sounds in the ocean, and recent research on fin whales has revealed that only males produce these vocalizations.^[11] The sounds are simple and consist of low-frequency moans and grunts and high-frequency pulses.^[5] Scientists suspect that males emit these sounds to attract females from great distances.^[11

Fin whales are found worldwide in polar, temperate and subtropical waters, but they are not common in tropical areas.^[4] There are two named subspecies of fin whales. Balaenoptera physalus is found in the North Atlantic; Balaenoptera physalus quoyi resides in the Southern Ocean. Most experts consider the population of fin whales in the North Pacific to be a third, unnamed subspecies. These three subspecies rarely mix.^[12] For management purposes, fin whales in the U.S. have been divided into four stocks. These are 1.Hawaii, 2. California/Oregon/Washington, 3. Alaska (North Pacific), and 4. Western North Atlantic.^[12] In Alaska, fin whales are found as far north as the western Chukchi Sea, the Bering Sea, and the Gulf of Alaska. They are rarely seen in southeastern Alaska, but they were common in that area before commercial whaling.^[8]

The migratory movements of fin whales are complex and not well understood. They spend the spring and early summer in high-latitude feeding areas and then migrate to lower latitudes for the winter breeding season. Some fin whales do not migrate, though, and may spend the entire year in the high latitude range, especially if there is abundant food.^[8] Fin whales can be found year-round on the west side of Kodiak Island. They are often seen in groups of six to ten individuals, although they can be found in smaller groups, or even alone, and when food is plentiful in a certain area, groups of as many as 100 fin whales may be seen.^[8]

Fin whales feed mainly on krill (euphausiids) and small, schooling fish. A fin whale may circle a school of fish at high speed, rolling the fish into a compact ball, and then the whale turns on its right side to engulf the fish. It is thought that the asymmetrical jaw-color pattern somehow aids a fin whale in capturing prey in this manner.^[9] Fin whales feed primarily during the summer months when they can consume two tons (1814 kg) of food a day.^[9]

Sexual maturity for male fin whales is reached from six to ten years of age while females are sexually mature between the ages of seven and twelve. Both sexes attain physical maturity at approximately 25 years.^[12] Little is known about the mating behavior of fin whales, but unlike humpback and gray whales, they do not gather in specific areas to breed, and scientists believe that male fins use vocalizations to attract females, sometimes from great distances, for breeding purposes.^[11] In the northern hemisphere, the mating period is from December to February, and gestation lasts approximately 11 months. A female produces one calf that is 18 to 21 ft. (6-7 m) long and weighs up to 3600 lbs. (1600 kg). The calf is weaned at six to seven months of age, and this is followed by a six-month resting period, after which mating takes place.^[5] Fin whales grow rapidly during their first few years. They reach 95% of their maximum body size when they are nine to thirteen years old. Males grow faster than females, but they stop growing sooner.^[5]

A fin whale's normal lifespan is 80 to 90 years, and some researchers believe they may live to be 100 years old.^{[12, 8]} Current-day threats to fin whales include attacks by killer whales, collisions with vessels, entanglement in fishing gear and marine debris, habitat degradation, noise pollution, and reduced prey abundance due to over fishing. ^[12] According to reports, fin whales are hit by large ships more often than any other species of large whale,^[10] and sounds from commercial ships, military sonar, seismic surveys, and ocean acoustic research may reduce the distance over which receptive females can hear the vocalizations of males.^[11]

In the spring and summer of 2015, 43 dead whales were spotted in the western Gulf of Alaska, with the majority clustered around Kodiak Island. The dead whales included fin whales, humpbacks, and, at least, one gray whale. None of the whale carcasses that could be accessed were in good enough shape to provide a clue to the cause or causes of the deaths, but the National Oceanic and Atmospheric Administration (NOAA) was so concerned that they classified the deaths an "unusual mortality event" (UME). A UME is defined as a significant die-off of a marine mammal population that demands an immediate response, and such a designation triggers a focused, expert investigation into the cause. Marine mammal specialists speculate that the whales ate something toxic, but they do not understand why only whales were found dead. Why weren' t other consumers of the same prey that whales eat also affected? Ocean water temperatures were higher than normal, and toxic algae blooms were more prevalent in the summer of 2015, so toxic algae are at the top of the list of the suspected causes for the whale deaths, but starvation and other factors have not been ruled out.^[13]

The sei (pronounced "say" ) whale is the third largest whale. Its name comes from the word seje, which is the Norwegian name for Pollock since these whales appeared off the coast of Norway each year at the same time as schools of Pollock came to feed on plankton.^[14] Sei whales are sleek and streamlined. They may reach a length of 65 ft. (20 m), but a length of 45 to 55 ft (13.7 to 16.8 m) and a weight of 14 to 17 tons is more typical.^[14] Sei whales have a dark bluish-gray body with white on the ventral surface. The flukes and flippers are dark on both the dorsal and ventral surfaces.^[5] Unlike fin whales, sei whales have a uniformly dark-gray lower lip. The snout is pointed, and there is a single prominent rostral ridge running from the blowholes to the tip of the snout.^[4] Sei whales have 32 to 60 ventral grooves that end well before the navel. The dorsal fin is tall and curved and is located one-third of the body length forward from the fluke notch. The dorsal fin is slightly farther forward than a fin whale's.^[4] The pectoral fins are fairly short and have pointed tips.^[14] Sei whales have 300 to 410 baleen plates on each side of the upper jaw. Each plate is up to 2.7 ft. (0.8 m) long.^[15] The baleen of the sei whale is uniformly ash black with fine, silky white fringes.^[4] The fine baleen allows sei whales to feed on small copepods.^[14]

Sei whales are one of the fastest swimming baleen whales.^[7] They normally feed near the surface, and they typically stay submerged for five to ten minutes.^[15] They usually blow two to six times between dives. When they surface, they break the water with the tip of the rostrum, and the back remains visible for a longer period of time than it does for other large whales.^[7] The blowholes and the dorsal fin become visible at nearly the same time and remain visible for a while.^[4] When submerging, the dorsal fin slowly sinks straight down into the water, instead of rolling forward like on a fin whale. Sei whales rarely arch their backs like fin whales when diving.^[7] Since sei whales feed near the surface, they often leave a series of tracks or "fluke prints" on the surface. These are simply smooth circles of water caused by the movement of their flukes just below the surface.^[14] The blow of a sei whale resembles an inverted cone and is very similar to a fin whale' s, except that it is lower and less dense.^[4]

Sei whales may be confused with fin whales or minke whales in the northern part of their range. In the southern part of their range, they may easily be confused with Bryde's whales. Sei whales are much larger than minke whales, so that helps distinguish those two species, but differentiating between sei and fin whales can be difficult. If seen up close, the right lower lip color is definitive. Fin whales have a white right lower lip while the lower lip of a sei whale is uniformly dark gray. If seen from a distance, subtle differences in the appearance of the dorsal fin and surfacing and diving behavior may help to distinguish one species from the other. A sei whale's dorsal fin is taller and more curved than that of a fin whale's, and a fin whale arches its back before diving while a sei whale usually just sinks below the surface. Sei whales and Bryde's whales are very similar in appearance and size, and the biggest difference between them is that a Bryde's whale has three ridges on the top of the head, while a sei whale only has one.^[4]

Sei whales are found worldwide, and they migrate between high-latitude feeding grounds in the summer to low-latitude breeding grounds in the winter.^[15] In the eastern North Pacific, Sei whales are found from California to the Gulf of Alaska in the summer and from central California to the equator in the winter.^[15] They do not venture as far toward the poles as fin whales in the summer, and they seem to favor more tropical waters than fins in the winter.^[4] Sei whales may be found singly or in groups of two to five whales. Thousands of sei whales have been observed together in areas where food is abundant.^[15]

Sei whales are primarily skimmers, but they may also feed by gulping, the feeding technique employed by both blue and fin whales. When skimming, a sei stays near the surface and swims with its mouth open, its fine baleen allowing it to retain small copepods. When skimming, sei whales feed most heavily at dawn when their prey is near the surface, and their feeding diminishes during the day as the zooplankton sink deeper in the water column.^[5] Sei whales also feed on krill and eat small fish, particularly in the north Pacific.^[14] It is estimated that a sei eats approximately one ton per day during the summer feeding period.^[15]

Both male and female sei whales reach sexual maturity at about ten years, but the average age of sexual maturity declined two to three years in areas where their populations were nearly depleted due to whaling.^[5] Females average 50 ft. (13.1 m) in length, and males are approximately 40 ft. (12.2 m) long when they reach sexual maturity,^[14] but they may not reach their full size until they are 25 years old.^[15] Little is known about the breeding behavior of sei whales, but they breed primarily in the winter months. The gestation period lasts 11 to 12 months,^[15] and newborn calves are 14 to 15 ft. (4.3 to 4.6 m) long and weigh approximately 2000 lbs. (909 kg).^[14] Calves are weaned at seven months, after traveling to the feeding grounds with their mothers.^[5] Female sei whales give birth to one calf every two to three years.^[15]

Sei whales have a lifespan of approximately 60 years.^[15] Causes of death include disease, infestation by parasites and predation by killer whales. It is estimated that 58,000 to 62,000 sei whales lived in the North Pacific before commercial whaling, but that population was reduced to 7,260 to 12,620 by 1974. The reported worldwide commercial harvest between 1947 and 1987 was 61,500 sei whales.^[15] The current worldwide population is estimated at 54,000, or one-fifth the pre-whaling population.^[14] There are no current population estimates for the North Pacific, but the population appears to be recovering. Sei whales are listed as "endangered" under the Endangered Species Act of 1973 and as "depleted/strategic" under the Marine Mammal Protection Act of 1972.^[15] In June 2015, 337 sei whales were found beached in a region of southern Patagonia in Chile. This is one of the largest whale strandings ever recorded, but while these whales were found beached, researchers think they died at sea and washed up on the beach. Scientists are uncertain why the whales died, but they suspect they may have ingested toxic algae.^[16]

The story is that the minke (pronounced mink-ey) whale was named after a Norwegian whale spotter named Meincke, who mistakenly identified a minke whale, the smallest of the rorquals, as a blue whale, the largest of all whales. Until the late 1990s, all minke whales were grouped into one species, but the Antarctic minke whale is now categorized as a second species (Balaenoptera bonaerenis), while Balaenoptera acutorostrata is the common minke whale. The common minke whale is further subdivided into three subspecies: the North Atlantic minke whale (B. a. acutorostrata), the North Pacific minke whale (B. a. scammoni), and an unnamed Southern Hemisphere dwarf minke whale. The dwarf minke is genetically closer to the North Atlantic minke than it is to the North Pacific subspecies.^[5]

Minke whales have the same general body shape as blue, fin, and sei whales. Male adult minke whales average 26 ft. (8 m) in length with a maximum length of 31 ft. (9.4 m). Adult females average 27 ft. (8.2 m), reaching a maximum of 33 ft. (10.2 m). Both males and females weigh approximately 10 tons.^[17] The rostrum of a minke is narrow and pointed and is proportionally shorter than in other rorquals. A single ridge runs from the tip of the rostrum to the blowhole.^[17] The dorsal fin is tall and curved and is located two-thirds of the way back on the body. The flippers are slender and pointed at the tips, and the flukes are broad, pointed at the tips and notched at the center.^[17] The body is black to dark gray on the back and white on the ventral surface. Some minkes have a light-colored chevron on the back behind the head. The common minke whale has a distinctive white band on each flipper, and the extent and orientation of the band vary between individuals.^[4] This band is absent on the flippers of the Antarctic species.^[17] The common minke whale has 280 to 300 yellowish-white baleen plates on each side of the upper jaw. The plates are no more than 11 inches in length. It has 50 to 70 ventral throat grooves, ending just before the navel.^[4]

Like most other rorquals, minke whales are fast swimmers and may reach speeds of 18 to 24 mph (29 kph to 38.6 kph). Minkes are curious and may approach boats and sometimes even ride in the bow wake of a ship.^[17] Most of the time, though, minkes are hard to spot in the ocean. They are relatively small, have an inconspicuous blow, and spend little time at the surface. They have a dive pattern of five to eight blows, followed by dives up to 20 minutes. When surfacing, a minke often exposes its dorsal fin at the same time as its blow, much like a sei whale does. Minkes arch their backs high like a fin whale before diving, but they rarely show their tail flukes.^[7] Minkes are usually solitary but are sometimes seen in pairs or small groups. They regularly breach, particularly in rough seas and have occasionally been seen spy hopping.^[3] At close range, minke whales can be distinguished from other rorquals by their smaller size, acutely pointed head, relatively tall, curved dorsal fin, and white flipper bands. From a distance, a minke whale may be confused with a small sei whale. A minke surfaces much like a sei whale, exposing its dorsal fin at the same time as its blow, but a minke usually dives by humping its tail stock like a fin whale.^[4]

Minke whales may be found in all oceans, but they are rarely found in the tropics and seem to prefer icy waters at the edge of the ice pack in polar regions, where food is concentrated. They segregate by sex and age more than do other baleen whales. Females remain close to shore while males remain farther offshore. Some minkes undertake long migrations while others migrate only a short distance, and some do not migrate at all.^[17]

Minke whales feed primarily on krill in the southern hemisphere and on krill and small schooling fish in the northern hemisphere. They also occasionally eat copepods.^[4] Scientists believe that minke populations increased when they began to eat the food that was previously eaten by the large whale species that were depleted by commercial whaling.^[17]

Minke whales reach sexual maturity at seven to eight years. Breeding peaks in the summer, and the gestation period is ten to eleven months.^[17] Calves are weaned after six to seven months.^[5] Females give birth every one to two years. The pregnancy rates in some populations remain at 90%, which means that females in these populations give birth every year.^[5] Calves are ten ft. (3 m) long and weigh 1000 lbs. (450 kg) at birth.^[17] Minke whales have a lifespan of 50 years, and they are often preyed upon by killer whales.^[17]

Because of their relatively small size, minke whales originally were of little interest to commercial whalers, but by the early 1970s, when the larger whale species had been depleted, whalers became more interested in harvesting minkes. Both Norway and Japan still hunt minke whales, and they are also a significant bycatch in set nets in Japan and Korea.^[5] Approximately 9000 minkes exist in the North Pacific,^[7] and the present worldwide population is estimated at over one million animals.^[17] Most minke whale stocks are in good shape, but researchers worry about the effects of continued whaling.^[5]

The humpback whale is the best known of the large rorquals. It is famous for its playful acrobatic behavior and its curiosity. Like all rorquals, humpbacks have a dorsal fin and numerous ventral grooves running from the tip of the lower jaw to the belly area, but humpbacks differ in many ways from the other species in the family Balaenopteridae, and because of these differences, humpbacks are listed in a separate genus from the other rorquals.

The body of a humpback is more robust and not as streamlined as that of other rorquals.^[18] The top of the head and the lower jaw have a series of rounded, fleshy knobs, each containing, at least, one stiff hair,^[18] and the median head ridge that is characteristic of balaenopterids is less distinct in humpbacks.^[4] Humpbacks have extremely long pectoral flippers with large knobs on the leading edge. These flippers may be 25 to 30 percent of the total length of the body.^[19] They have a very narrow tail stalk or peduncle, and the tail has ridges on the trailing edge.^[19] Unlike most other rorquals, humpbacks are slow swimmers and travel at an average speed of 3.7 to 7.5 mph (6-12 km/hr).^[4] Despite their slow swimming speed, humpbacks are the most acrobatic of the rorquals. With their long flippers and flexible tail, they can easily leap out of the water or slap the surface with their tail or fins.

Adult female humpbacks average 49 ft. (15 m) in length and weigh approximately 35 tons, and males are slightly smaller.^[19] Humpbacks are mostly black in color but have some white on the throat, belly, flippers, and flukes. The shape of this white color pattern on the dorsal fin and ventral surface of the fluke are unique to each individual and can be used as identification, much like a human s fingerprints can be used for identification. Once researchers realized that color patterns were unique for each whale, it changed the course of humpback research, leading to photo-identification research, where individuals are identified, cataloged, and monitored. This research has provided information about migration, sexual maturity, behavior patterns, and population sizes.^[18]

Humpbacks have 14 to 35 ventral grooves that extend to the navel. They have 270 to 400 baleen plates on each side of the upper jaw that are about 30 in (76 cm) long. The baleen is usually all black.^[4] The dorsal fin often has a step or a hump, and this is the derivation of the common name, " humpback" .^[4] The flukes are up to 18 ft (5.5 m) wide and are serrated on the trailing edge and pointed at the tips.^[18]

^{(Photo by Tony Ross)}

Humpbacks are found in all the world s oceans. In the Pacific, humpbacks can be seen year-round in Alaska, but most humpbacks winter in temperate or tropical waters near Mexico, Hawaii, and in the western Pacific near Japan. Humpbacks migrate 3,000 miles (4,800 km) each way between summer feeding and winter breeding grounds. They return to Alaska in the spring and concentrate in several areas, including Southeast Alaska, Prince William Sound, Kodiak, the Barren Islands, the mouth of Cook Inlet, and along the Aleutian Islands.^[19]

Female humpbacks reach sexual maturity at five years and males at seven years.^[19] They have a polygynous mating system, and males compete aggressively to mate with estrous females. These competitions can last for hours and may involve tail slashing, ramming, and head-butting. It is thought that groups of males form coalitions during these competitions.^[5] Males also sing long, complex songs during the mating season. It is assumed that the purpose of these songs is to attract females, but it has also been suggested that the songs may be used between males to establish identity or dominance, or perhaps their purpose is to both attract females and establish dominance between males. The songs are long and complex and are only sung by males. A song usually lasts for ten to twenty minutes and may be repeated for hours at a time. All male humpbacks in a population sing the same song, but males in separate populations sing different songs. The songs change slightly over time, but the whales somehow coordinate these changes.^[5]

Humpbacks have a gestation period of 11.5 months, and most calves are born mid-winter. At birth, calves average 10 to 15 ft (3-5 m) in length and weigh 1.5 tons. They nurse for six to ten months, and females give birth about every two years.^[5]

The reasons for some of these behaviors seem obvious. A whale probably spy hops to get a better look at something above the water surface, such as an approaching boat or channels through pack ice, and it undoubtedly flukes to gain momentum for a dive, but many of the other behaviors are not so easily explained. Breaching or slapping the water surface with its tail, flipper, or head may be a sign of aggression, a form of communication, an expression of excitement, or something more practical such as a means to stun prey or remove parasites.^[3] These behaviors are probably used for a variety of reasons, including play. When I see a huge whale leap out of the water, I think it looks fun.

Humpbacks live approximately forty to fifty years.^[19} Their bodies and flippers are usually infested with barnacles and whale lice.^[18] Humpbacks are sometimes preyed upon by killer whales and large sharks, but as with most whales, humans are the greatest threat to humpbacks. They were given worldwide protection from commercial whaling in 1966.^[18] They were listed as endangered under the Endangered Species Conservation Act of 1970 and as depleted under the Marine Mammal Protection Act of 1972.^[19] The greatest threats to humpbacks today include pollution, boat strikes, and entanglement in marine debris or commercial fishing gear.^[19} Humpbacks, with their acrobatic behavior, curiosity, long pectoral flippers, and flexible tail, are extremely susceptible to entanglement in anchor and crab pot lines and fishing nets. I have seen two humpbacks entangled in crab pot lines, and a scar analysis study done on humpbacks in Southeast Alaska determined that 78% of the population in that area have scars indicating the whale had recently been entangled.^[20] The whale can sometimes, but not always, disentangle itself.

The gray whale is one of the most ancient species of mammals, estimated to have been on earth for approximately 30 million years.^[21] It is one of the most-researched and best-understood species of whales. Gray whales are baleen whales, but they are not rorquals in the family Balaenopteridae. Instead, they are the only species in the family Eschrichtiidae. Unlike rorquals, gray whales do not have a dorsal fin, and instead of the numerous throat pleats found in rorquals, gray whales have only two to seven, short longitudinal creases on the throat.^[5] Gray whales are also stockier than most rorquals, and they have the shortest, coarsest baleen and the fewest number of baleen plates of any mysticete. Gray whales have about 20 baleen bristles per inch (7-8 per cm) compared to 100 per inch (42-50 per cm) in Sei whales.^[21] They are also slower swimmers than most rorquals, averaging 3 to 5 mph (5-8 km/hr) when migrating.^[21] Finally, their unique style of suction, bottom feeding sets them apart from any other baleen whale.^[5]

Gray whales are medium-sized whales. At birth, they measure 15 to 16 ft. (4.6-4.9 m) in length and weigh 1,100 to 1,500 lbs ((500-680 kg). They grow until they are 40 years old, when adult males average 45 to 46 ft (13.7-14 m) in length, and females are slightly larger. The average adult weight for both sexes is 30 to 40 tons.^[5] As their name suggests, gray whales are slate gray in color with gray and white patches on their skin. They are covered by scars, blotches, clusters of barnacles, and orange whale lice. A gray whale may be infested with over 400 pounds of barnacles and whale lice.^[22] A gray whale has a stocky but streamlined body, and while it has no dorsal fin, it does have a prominent dorsal hump about two-thirds of the way down the back, followed by six to twelve knobs extending to the tail stock.^[21] The head of a gray whale is narrow and triangular in shape when viewed from above, and is moderately arched downward when viewed from the side.^[5] Gray whales have 130 to 180 baleen plates on each side of the upper jaw, and their baleen is cream to pale yellow in color. The baleen ranges in length from two to sixteen inches (5-40 cm).^[5] Their throat grooves are approximately five ft. (1.5 m) in length, the pectoral flippers are paddle-shaped and pointed at the points, and the tail fluke is very broad and deeply notched.^[5] Gray whales have a bulging tailstock cyst that is unique to the species. The cyst is located on the ventral surface of the caudal peduncle, and its purpose is unknown.^[5]

At one time there were three stocks of gray whales: a North Atlantic stock, an eastern North Pacific stock, and a western North Pacific stock. It is believed that the North Atlantic stock became extinct in the 17^th century. Gray whales were nearly hunted to extinction in the Pacific in the 1850' s after the discovery of their calving lagoons and then again in the early 1900's after the introduction of floating factory ships which processed whales on board. In 1937, gray whales were given partial protection, and they received full protection in 1947 by the International Whaling Commission. Since then, the eastern North Pacific stock has made an incredible recovery. The population is now estimated at 26,000 animals, which is probably close to its original size. The western North Pacific stock has not fared as well, though, and it is considered critically endangered with approximately only 100 animals. This stock is listed as endangered under the Endangered Species Conservation Act of 1970.^[21]

Gray whales are the most coastal of all baleen whales and usually stay within a few miles of shore. They are the only baleen whales that are primarily bottom feeders. When feeding, a gray whale scrapes the side of its head along the ocean floor and scoops up sediment with its mouth, capturing small invertebrates in its baleen while expelling the sediment through the baleen fringes. On their feeding grounds, gray whales are often seen surfacing with clouds of mud streaming from the sides of their mouths. Benthic gammarid amphipods are the favorite food of gray whales.^[4] When gray whales bottom feed, they disturb the substrate, leaving large, oblong, bowl-shaped pits measuring three ft. by six ft. (1 x 2 m), and amphipods seem to thrive in these disturbed communities. Amphipod concentrations of 12,000 to 20,000 per square yard (meter) have been measured in the southern Chukchi and northern Bering Seas where gray whales feed.^[21] Feeding dives to the bottom may last three to fifteen minutes.^[21] Gray whales feed almost exclusively during the summer on their northern feeding grounds, and they may feed continuously for 24 hours a day during this period. They have been impacted by ocean warming in recent years. Increasing seawater temperatures in the Bering Sea have reduced winter ice cover in the region, which has led to a reduction in productivity. Primary productivity in the northern Bering Sea declined 70% from 1988 to 2004, and the previously ice-dominated, shallow ecosystem that favored large communities of benthic amphipods has been replaced by an ecosystem dominated by pelagic fish. Gray whales have responded by migrating further north to the Chukchi Sea, but it is not certain what will happen if amphipod communities disappear from this region.^[5] By the time gray whales return north after a winter of fasting, they have lost 16-30% of their body weight, and they must feed all summer to regain that weight. Lactating females must gain 25-30% more weight than other gray whales.^[5]

Gray whales have the longest migration of any mammal. Most of the population spend May through November feeding in the northern Bering, the Chukchi, and the western Beaufort Seas. They then migrate to their winter breeding and birthing lagoons neeear Baja California and mainland Mexico. This migration spans 55p of latitude and is 5,000 to 7,000 miles (8,050-11,275 km) each way.^[5,21] Since they are slow swimmers, this migration takes a long time. The northward migration to the feeding grounds takes place in two phases. Newly pregnant females begin their migration in late January through March to maximize their time on the feeding grounds. They are followed by adult females and males and then juveniles. The second phase of the migration consists of mothers and calves, who begin their migration from April to May. They remain in the breeding area longer to allow the calves to grow and strengthen.^[5] Gray whales stay close to the coast while migrating, and they can easily be observed from shore. They enter the Bering Sea through Unimak Pass, mostly in April and May. They then move along the coast of Bristol Bay, past Nunivak Island, to St. Lawrence Island, where they arrive in May and June. The whales then disperse and spend the summer feeding in the northern Bering, the Chukchi, and the western Beaufort Seas.^[21] On their northern migration, they pass by Kodiak Island in April and May, where they can be viewed from bluffs along the outside perimeter of the island. The gray whales' migration is considered a rite of spring on Kodiak and is celebrated with a 10-day Kodiak Whale Fest with many activities, including guided trips to good whale-watching spots.^[23]

Gray whales become sexually mature between the ages of six to twelve years and at an average length of 38.4 ft. (11.7 m) for females and 36.4 ft. (11.1 m) for males.^[5] They have a promiscuous mating system, meaning that both sexes may mate with several partners during the breeding seasons. Since multiple inseminations likely occur, sperm competition is a factor in reproduction in gray whales.^[5] Most mating occurs during the middle of the southward migration, but courtship and mating also continue throughout January and February when the whales reach their winter assembly areas. Males may mate annually, but females usually mate, at the most, once every two years. Females usually conceive after their first ovulation, but if they do not conceive, they may undergo a second ovulation in about forty days.^[5] Copulation is belly to belly, and the gestation period varies between 11 to 13 months. Cows bear one calf usually every two years.^[5] Calves are born between December and early March, and they nurse for seven to eight months.^[21] The bond between the cow and calf is very close, and a cow will fight to the death to defend her baby. This aggressive, maternal instinct earned gray whales the name  Devilfish by Yankee whalers.^[4]

Gray whales usually live in small groups of about three whales, but groups of sixteen have been observed, and when feeding, hundreds of whales may be seen in the same area.^[21] They are not known to form long-lasting social bonds, and the close relationship between a mother and its calf ends once the calf is weaned.^[5]

Gray whales have a heart-shaped blow. Their normal dive pattern is to blow four to six times between dives of three to five minutes. Like humpbacks, gray whales usually raise their tail flukes in the air before a long dive.^[7] They also frequently engage in breaching, lobtailing and spy hopping and sometimes lie on their sides and wave a flipper in the air. They travel near shore and seem to enjoy surfing on waves.^[3] Underwater hearing seems to be their most important sense, and they emit a variety of mostly low-frequency sounds to communicate. Manmade noise pollution in the ocean from air guns for seismic exploration, military and civilian sonar systems, offshore drilling, construction, industrial activities, supertankers, and icebreakers may interfere with this communication and even damage a whale s hearing.^[5] Gray whales can see fairly well in both air and water, but since they feed on the bottom in a turbid environment, hearing is probably more important than seeing. They also have a tiny, functional olfactory system, a well-developed sense of touch, and taste buds at the base of the tongue.^[5]

It is estimated that gray whales live 40 to 80 years.^[5] Killer whales and humans are the only major predators of gray whales. There are many reports of killer whales feeding on the tongues of gray whales, and living gray whales often have healed scars from killer whales on their flukes and flippers.^[4,20] From 1999 to 2002, gray whale numbers in the eastern North Pacific population mysteriously plunged from an estimated 26,635 whales in 1998 to 17,414 whales in 2002. The die-off stopped in 2002, but scientists still do not know what caused it. It has been blamed on everything from the flu, to cyanide-based fluorescent dye used to mark illegal narcotic drops in the ocean, to toxic algae blooms, to nuclear waste, to old military toxic waste on the ocean floor, to noise pollution, to the whale population exceeding its food supply. Since gray whales, unlike other whale species, are bottom feeders, they are more susceptible to ingesting high concentrations of pollutants. Also, since they spend most of their time in shallow coastal waters, they are more likely to encounter run-off pollution from land. As mentioned earlier, the food supply of gray whales has been negatively impacted by global warming and higher ocean temperatures.

On May 28^th, 2000, a 37-foot male gray whale washed ashore on Pasagshak Beach near Kodiak. The residents in the area obtained permission from the National Marine Fisheries Service to bury the whale, allow it to decompose, dig it up four years later, clean the bones, and reassemble the skeleton. This massive community effort, headed by high school biology teacher Stacy Studebaker, was a complete success, and the whale skeleton now hangs in the Kodiak National Wildlife Refuge Visitor's Center.^[24]

(Photo by Bob Munsey)

Toothed whales comprise the suborder Odontoceti in the order Cetacea. As the name implies, species in this suborder have teeth instead of baleen, and they also differ from species in the suborder Mysticeti (the baleen whales) in several other ways. The bones in the skull of odontocetes are telescoped, and odontocetes have a specialized, elaborate echolocation system. Toothed whales have only one blowhole while baleen whales have two, and most toothed whales show some degree of dorsal asymmetry in their skull and facial tissue, while baleen whales have symmetrical skulls and soft facial tissue. Most species of odontocetes are smaller than baleen whales and display some degree of sexual dimorphism. Unlike mysticetes, most odontocetes do not have long-distance seasonal migrations, and since they are not dependent upon seasonal plankton biomass production, they can feed year-round and do not need to fast for long periods of time. Odontocetes chase, capture, and consume single, relatively large prey items instead of swallowing swarms of zooplankton and schools of small fish as mysticetes do, and because of this, odontocetes tend to have greater body flexibility than do mysticetes.^[5]

The suborder Odontoceti includes ten diverse families and 71 species. There are three commonly-seen species of odontocetes in the waters around Kodiak Island, and all three species are in the superfamily Delphinoidea. The killer whale is a true dolphin in the family Delphinidae, and harbor and Dall s porpoises are both in the family Phocoenidae.^[5]

Most odontocetes are darker in color on their dorsal surface than on their ventral surface. This countershading aids as camouflage from predators and prey. When viewed from below, their lighter ventral surface blends with light entering the ocean, and when viewed from above, they appear dark like the deeper ocean water or the substrate.^[5] Unlike land mammals, the teeth of odontocetes are all uniformly shaped. Most dolphins have peg-shaped teeth while porpoises have spade-shaped teeth.^[5] All odontocetes are believed to use echolocation to gain a sort of electronic image of their environment, and to do this, the produce pulse-like clicks in the ultrasonic range, well above the range a human can hear.^[5] Odontocetes have large brains and complex social lives. Their brain to body ratio is similar to that of gorillas or chimpanzees.^[5]

Other than man and perhaps the Norwegian rat, the killer whale is the most widely distributed mammal on the planet, inhabiting all oceans from the tropics to the polar ice pack. Killer whales are most often found in temperate, coastal waters.^[5] There is mounting evidence that killer whales should be subdivided into several subspecies and perhaps even into several different species, and this makes a cohesive description of killer whales as one species a difficult task. Extensive research in the Pacific Northwest, British Columbia, and Alaska on genetics, sound production, and movements of individuals and pods has pinpointed three distinct forms of killer whales, and there appears to be no breeding between the forms. The three forms, named residents, transients, and offshores, are highly distinct in both mitochondrial and nuclear DNA composition.^[5] Throughout this section, I will refer to behaviors and attributes that apply to each of these types. Killer whales in other parts of the world probably also form distinct populations, but more research is needed to be certain.

Killer whales exhibit sexual dimorphism, which means that males look different from females. In the North Pacific, adult males grow to a length of 27 ft. (8.2 m), while females attain an average length of 23 ft. (7 m). An adult male may weigh 13,300 lbs. (6,000 kg), while females weigh only half that much.^[25] In addition to size, males have much larger appendages than females, including pectoral flippers, tail flukes, and a larger dorsal fin, which may reach six ft. (2m) tall in males but does not exceed three ft. (1 m) in females.^[5] Both sexes are predominantly black on the dorsal surface and white on the ventral surface. They have an elliptically-shaped, white eye patch above and behind each eye on the lateral sides and large white patches that extend from the ventral area onto the flanks. A grayish-white saddle patch is often present behind the dorsal fin. This saddle patch varies between individuals, and it, along with the shape and size of the dorsal fin and distinctive scars, nicks and marks on the dorsal fin, can aid researchers in identifying individuals.^[26] The head of a killer whale is conical in shape, and the pectoral flippers are broad and paddle-shaped. The female' s dorsal fin is falcate while the male' s is triangular. The flukes have a slightly concave trailing edge and a distinct median notch. The mouth contains ten to twelve large, conical teeth in each row (approximately 48 teeth total) that curve toward the throat.^[4] A killer whale' s teeth can grow up to 4 inches (10 cm) long,^[27] and upper and lower teeth lock together when the jaws are closed.^[5]

From stomach-content analyses, biologists have determined that salmon, and specifically, fatty salmon such as chinook and coho salmon seem to be the preferred prey of residents when salmon are available. At other times, they feed on squid and other fish. Transients, on the other hand, feed on harbor seals, Dall' s porpoise, Stellar sea lions, California sea lions, sea otters, minke whales, and other marine mammals. Transients have not been observed to eat any species of fish, and no fish remains have been found in the stomachs of stranded transients.^[5] It is interesting to note that while marine mammals actively try to avoid transient killer whales, their mortal enemies, they seem to ignore fish-eating residents. The third ecotype offshores, are believed mainly to eat fish, including sharks.^{[25] (Photo by Bob Munsey)}

Residents and transients must employ different foraging skills and tactics. Residents are very vocal and produce a variety of clicks, whistles, and pulsed calls for echolocation and communication. Studies on killer whales in British Columbia found that vocal exchanges among foraging residents are dominated by repetitive calls from a repertoire averaging 12 call types per pod.^[5] The call repertoire of each pod has distinct segments, and the repertoire is shared by all members of the pod. Some portions of a pod' s repertoire may be shared with other pods, and the amount of similarity between the repertoires of two pods is an indication of how closely the pods are related. Biologists suspect that a killer whale from one pod will avoid breeding with a whale from a pod which has a call repertoire similar to his own pod' s.^[5] Mammal-eating transients in the northeastern Pacific make very little sound when they are foraging to avoid alerting their prey. Echolocation has been found to be used 27 times less often by foraging transients than by residents. Transients are often very vocal after a successful kill, however.^[5] Killer whales have good hearing and excellent vision below and above water. Their skin is sensitive to touch, but not much is known about their sense of taste or smell.^[26]

Killer whales exist throughout the marine waters of Alaska, but they are most commonly found from Southeast Alaska through the Aleutian Islands and northward to the Chukchi and Beaufort seas.^[25] Killer whales usually travel in groups containing a few to more than twenty individuals. These groups have complex social structures, and this structure is better understood in resident groups in the northeastern Pacific than it is in transient and offshore groups in the same area or than it is in populations in other parts of the world. Resident societies in Coastal British Columbia, Washington, and Alaska can be divided into a number of groupings based on maternal genealogy, acoustical relationships, and social associations.^[5] The most basic unit of resident whales is the matriline, a stable group of individuals linked by maternal descent. This unit would likely consist of a mother, her sons, her daughters, and the offspring of her daughters. Since females live 80 to 90 years, a matriline may contain four generations of related whales. The bonds between members of a matriline are very strong, and members seldom stray away from the group for more than a few hours.^[5] The pod is the next level of organization, and the pod consists of related matrilines that likely shared a common maternal ancestor in the recent past. Pods are less stable than matrilines, and matrilines within a pod may travel apart from each other for periods of weeks or months. The clan is the next higher level of social structure, and all pods within a clan have similar vocal dialects, suggesting some degree of relatedness. The top level of this social structure is the community, which is made up of pods that associate with but are not necessarily related to each other. Pods from one community rarely travel with pods from another community. Three communities of residents have been described in the northeastern Pacific.^[5]

^{(Photo by Bob Munsey)}

Transients appear to have a looser social structure than residents. Their basic social structure is also a matriline, but unlike the matrilines of residents, members of transient matrilines often disperse for long periods of time or even permanently, and as a result, transient matrilines tend to be smaller than those of residents, and some transients, usually males, travel alone. Furthermore, the associations between matrilines are dynamic, and they do not form consistent groupings equivalent to resident pods.^[5] Three stocks or communities of transient killer whales have been recognized in Alaskan waters. One stock occurs from Prince William Sound west through the Kenai Fjords. The second stock can be found from the Gulf of Alaska to the Aleutian Islands and the Bering Sea, and the third stock occurs between Southeast Alaska and California.^[25]

^{(Photo by Bob Munsey)}

Killer whales can swim at speeds over 28 mph (44 km/hr).^[3] Not much is known about their diving behavior, but a typical dive lasts for three to five minutes. ^[25] In addition to vocalizations, killer whales socialize by employing a wide range of aerial acrobatics and other behaviors, including spy hops, breaches, flipper slaps, tail lobs, and head stands.^[5] They are very curious and will often swim up to a boat, dive beneath it, breach beside it, and even float on their backs near it.

The average lifespan for male killer whales is estimated to be approximately 30 years with a maximum lifespan of 50 years. Females are believed to live an average of 50 years with a maximum lifespan of 80 to 90 years. There are no worldwide population counts for killer whales, but most Alaska stocks are considered stable.^[26]

^{(Photo by Bob Munsey)}

Two species of porpoises are commonly seen in the harbors and bays near Kodiak Island: The harbor porpoise and Dall' s porpoise. I am often asked if the terms dolphin and porpoise can be used interchangeably, and the answer is no! Porpoises and dolphins are as distinct as cats and dogs, and they belong to different taxonomic families. Porpoises are smaller than dolphins, and they are stocky and lack the characteristic " beak" of a dolphin.^[5] Porpoises have spade-shaped teeth while dolphins have conical teeth.^[5] Porpoises grow faster and reach sexual maturity at a younger age than most dolphin species. Most porpoise species are less social than dolphins, and porpoises usually occur alone or in small, fluid groups.^[5]

The harbor porpoise is one of the smallest oceanic cetaceans, and it is the smallest cetacean found in Alaska.^[7] Harbor porpoises are found throughout the coastal waters of the North Pacific, the North Atlantic, and the Black Sea. These three populations are reproductively isolated from each other, resulting in three separate subspecies. Phocoena phocoena inhabits the North Atlantic Ocean; Phocoena phocoena relicta resides in the Black Sea, and Phocoena phocoena vomerina is found in the North Pacific. There probably is an additional subspecies in the western North Pacific. The subspecies differs from each other both morphologically and genetically.^[5] In Alaska, harbor porpoises are found from Point Barrow along the entire coastline to the Aleutian Islands and down through Southeast Alaska. They are usually found near shore in depths under 300 ft. (91.4 m) and are often seen in fjords, bays, harbors, estuaries, and even large rivers.^[28] The Alaska population has been divided into three stocks. The Bering Sea stock is estimated to have 66,076 animals, the Gulf of Alaska stock has approximately 41,854 porpoises, and the Southeast Alaska stock is the smallest with an estimated 17,076 animals.^[28]

The body of a harbor porpoise is small but stocky and rotund through the mid-section, tapering to a slender tail stock. An average harbor porpoise measures five ft. (1.5 m) in length and weighs 130 lbs. (60 kg). Females are slightly larger than males.^[28] A harbor porpoise's snout is blunt and rounded, and its small mouth tilts upward. It has 22 to 28 spade-shaped teeth on each side of the upper jaw and 22 to 26 on each side of the lower jaw. It has small, oval flippers that are rounded at the tips, and its dorsal fin has a broad base, is low in height and triangular in shape. The dorsal fin is located just behind the center of the body, ^[28] and often has several tubercles or small, hard bumps on the leading edge. The purpose of these bumps is not known.^[5] The flukes are small and curved with a noticeable median notch.^[29] The body of a harbor porpoise is dark gray or dark brown on the back, fading to a lighter gray on the sides. The throat and belly are white, but there may be a streak of gray on the throat and a dark chin patch. The flippers are dark in color, and a dark stripe extends from the flipper to the eye.^[28] Harbor porpoises have extremely thick blubber compared to their body size, and this in addition to their rotund body shape, aids in thermoregulation and helps them conserve heat in cold water.^[5]

Harbor porpoises primarily eat fish, but they may also feed on squid, octopus, and crustaceans. In Alaska, they feed on fish such as cod, herring, and pollock, and it has been estimated that they eat approximately 10% of their body weight each day.^[28] They normally feed individually, but groups have been observed herding schools of fish to the surface.^[5]

Harbor porpoises reach sexual maturity at three to four years, and females usually give birth every two years.^[28] Mating and calving seasons for harbor porpoises vary from region to region, but in Alaska, breeding takes place in the summer.^[7] Mating generally takes place a month and a half after the calving season.^[5] After a gestation period of approximately 11 months, a female gives birth to a single calf, and calves are nursed for eight to twelve months.^[28] At birth, calves weigh 14 to 22 lbs (6.4 -10 kg) and are 27 to 35 inches (70-90 cm) long.^[29] Harbor porpoises have an average lifespan of eight to ten years, but they have been known to live as long as twenty years.^[28]

Harbor porpoises surface in a slow roll and rarely "porpoise" out of the water. They are shy and seldom approach vessels, and they never play in the bow wake like Dall' s porpoises do. They are often seen alone or in small groups of less than ten individuals. They dive for an average of four minutes, and while they usually don' t dive deep, research has shown that they can dive to 721.8 ft. (220 m).^[5]

Large sharks, dolphins, and killer whales all prey on harbor porpoises. In Greenland, harbor porpoises are hunted for food and oil, and they are susceptible to entanglement in marine debris and commercial fishing gear in all portions of their range.^[28] Since they live near the shore, they are also highly susceptible to manmade pollution.^[5] Harbor porpoise populations in Alaska are considered healthy.^[28]

Dall's porpoise was named after American naturalist W.H. Dall, who collected the first specimen of this species, now on display at the U.S. National Museum.^[30] A Dall's porpoise is easily identified by its striking black and white coloration that resembles the markings of a killer whale and by the characteristic rooster-tail splash it often makes when surfacing.

Dall's porpoises are found in the cold waters of the North Pacific Ocean from Japan to southern California and north to Alaska and the Bering Sea.^[31] While they do make some seasonal inshore-offshore and north-south movements, they are present in the eastern North Pacific all year.^[5,30] This is a cold-water species that avoids the tropics and subtropics. Dall's porpoises are an offshore species, but they can also be found in deep nearshore and inshore waters.^[5] They prefer deep water and use underwater canyons and deep channels to approach the coast.^[31] Although the number of Dall's porpoises worldwide is not known, it is estimated that there 104,000 along the Pacific coast of Japan, 554,000 in the Okhotsk Sea, 83,000 in Alaska, and 100,000 along the U.S. west coast.^[5]

A Dall's porpoise averages six ft (1.8 m) in length and weighs approximately 270 lbs. (160 kg).^[29] It has a stocky, muscular body. It is particularly robust through the mid-section, and the male is much thicker than the female. It has a very small, round head that slopes steeply to a short, poorly defined beak.^[30] The eye of a Dall's porpoise has a black or dark blue iris and a deep, iridescent blue-green pupil.^[30] It has a small mouth with very small teeth shaped like grains of rice. The teeth are the smallest of any cetacean species, and they often do not rise above the surface of the gums.^[5] Each tooth is separated by rigid growths called "gum teeth," and it is speculated that since the teeth are so small, these growths aid in grasping slippery food such as squid.^[30] The lower jaw extends slightly past the upper jaw.^[30] A Dall's porpoise has a dorsal hump as well as a ventral hump, both located slightly forward of the flukes. The ventral hump is more pronounced in males, but its purpose is not known.^[30] The color pattern of Dall's porpoises varies between individuals, but most are black on the upper sections of the body, with large oval-shaped white sides and white bellies. A band of white usually borders the flukes and the dorsal fin.^[30]

A Dall's porpoises usually forage at night, and they feed on a number of species of small fish and cephalopods. They are known to feed at great depths, but it has not been determined how deep they can dive.^[5] In Alaska, they eat squid and small schooling fishes such as capelin, lantern fish, and herring.^[31] A Dall's porpoise consumes approximately 28 to 30 lbs. (12.7-13.6 kg) of food each day.^[30]

Male Dall's porpoises reach sexual maturity between five and eight years of age while females are mature between the ages of three and six.^[31] Little is known about their mating habits, but it is believed they have a polygynous mating system, where one male mates with several females.^[5] After a gestation period of 12 months, a female gives birth to a single calf, usually during mid-summer.^[31] Calves average 3.5 ft. (1m) at birth and weigh 55 lbs. (25 kg).^[30] Lactation lasts two to four months, and a female normally has a calf every three years.^[31] Dall's and harbor porpoises sometimes interbreed, and hybrids between these species are often observed near Vancouver Island, British Columbia. The ability of these two species to interbreed suggests they are closely related.^[5] The average lifespan of a Dall's porpoise is 16 to 17 years, but they may live 20 years.^[31,7]

Dall's porpoises usually travel in small groups with a maximum of 10 to 20 individuals, but at times, they form much larger groups.^[31] They are considered to be the fastest of the small cetaceans, reaching speeds of 35 mph ( 56.3 km/hr), which is a tie with killer whales for the fastest marine mammals.^[31] You can often see Dall's porpoises from a distance slicing through the water, creating a V-shaped splash called a rooster-tail. This splash creates a hollow cone that allows the porpoise to breathe under the surface of the water.^[31] Dall's porpoises rarely engage in acrobatic behavior such as breaching or leaping out of the water, but they will charge a rapidly moving boat to ride the bow or stern waves. Once in the bow wave, they may remain in there for half an hour or more, darting in and out of the wake and making steep-angled turns. They sometimes even "snout ride" on the bow waves pushed forward by the heads of large whales.^[5] When moving slowly, they roll at the surface, much like a harbor porpoise.

Dall's porpoises may be preyed upon by killer whales and sharks, but because of their speed, agility, and fairly large body size, they probably often can escape predators. They are negatively impacted by pollution and habitat alteration, but the biggest impacts are intentional and unintentional fishery kills. There is still a fishery for Dall's porpoises in Japan, and many other Dall s porpoises are caught accidentally in driftnets and gillnets.^[5] It is estimated that about 30 porpoises per year are killed as a result of being caught in fishing nets in Alaska.^[31] It is unclear why Dall's porpoises get caught in salmon nets, since they do not feed on salmon, but many of the deep-sea species they do feed on come to the surface at night when these porpoises feed, making it more likely the porpoises will run into nets. It has also been suggested that their sonar may not detect the type of netting used in Japanese driftnet fisheries. It is interesting that the majority of the Dall's porpoises caught in nets are females, and most are pregnant or are nursing mothers.^[30]

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28. Harbor Porpoise (Phocoena phocoena). Alaska Department of Fish and Game. Available at: http://www.adfg.alaska.gov/index.cfm?adfg=harborporpoise.main .

29. Harbor Porpoise Phocoena phocoena. American Cetacean Society. Available at: http://acsonline.org/fact-sheets/harbor-porpoise/ .

30. Dall's Porpoise Phocoenoides dalli. American Cetacean Society. Available at: http://acsonline.org/fact-sheets/dalls-porpoise/ .