Introduction to Marine Mammals
MARINE MAMMAL CLASSIFICATION
The Southern California Bight (Point Conception to San Diego) has one of the most
diverse and largest populations of marine mammals in the world. Over 34 species of marine
mammals have been documented here, and over 150,000 animals representing up to 30 species
can be found in the Bight at one time.
At least 28 species of whales and dolphins have been sighted in the sanctuary and about 18
species are seen regularly and are considered "residents." Little is known about the areas of
concentration, life history or behavior of the resident populations. The sanctuary lies on the
migratory pathway of the California gray whale and other large baleen and toothed whales. Gray
whales with calves have been observed in the nearshore kelp beds of the sanctuary. The gigantic
blue whales have also been sighted in sanctuary waters in recent summers (since 1980's).
All marine mammals share the following characteristics:
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Hair/ fur/ vibrissae
Warm-blooded
Nurse young
Give birth to live young
Air breathing (have lungs)
Marine Mammal Adaptations
Marine mammals have adapted to the life at sea much like fishes, in some cases people
confuse marine mammals with fishes due to their similar shape and form. These shared
similarities/ adaptations are called convergent evolution.
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Streamlined bodies (no outer ear flaps or limbs)
Few hairs
Blubber
Classification:
Kingdom
Phylum
Class
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Order
Family
Genus
Species
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Introduction to Marine Mammals
Class Mammalia
Order Carnivora (bears, cats, dogs, otters, skunks…)
Family Mustelidae
• weasels, skunks, otters, badgers
local species: Sea Otter
Family Ursidae
• polar bear
Order Pinnipedia (“feather-footed”)
Family Phocidae
• true seals (harbor seals, elephant seals)
local species: harbor seal, elephant seal
Family Otariidae
• eared seals (sea lion, fur seals)
local species: California sea lion, Northern fur seal,
Guadalupe & Stellar sea lions
Family Odobenidae
• walrus
Order Cetacea (from the Latin “cetus” whale or sea monster)
Suborder Mysticeti (baleen “mustached whales”)
Family Balaenidae
• bowhead and right whale
Family Eschrichtiidae
• gray whale
Family Balaenopteridae
• blue, fin, humpback, & minke whales
Family Neobalaenidae
• pygmy right whale
Suborder Odontocete (toothed whales)
Family Physeteridae
• Sperm whales
Family Monodontidae
• Narwhale and beluga whales
Family Ziphiidae
• beaked whales
Family Delphinidae
• dolphins, orcas
Family Phocoenidae
• porpoises
Family Platanistidae
• river dolphins
Order Sirenia - Sea Cows, manatees
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MARINE MAMMALS: BASIC FACTS
Charles J. Rennie, III, M.D.
Research Associate, Marine Mammalogy
Santa Barbara Museum of Natural History
Why marine mammals? / Why the Santa Barbara Channel?
• Marine mammals have fascinated humans for millennia; the earliest known depiction of them
dates to the Neolithic period.
• Greek and Roman art provided frequent depictions of marine mammals. Both Aristotle (384322 B.C.E.) and Pliny the Elder (24-79 C.E.) wrote extensively about them.
• The North American whale fishery dates to at least the end of the fifteenth century, and
possibly to the mid-fourteenth century.
• Systematic observations of marine mammals began in the sixteenth century, although marine
mammal science as a discipline has existed only for the last 30-40 years.
• The Santa Barbara Channel is a semi-enclosed basin, bounded by the central California coast
on the north, Point Conception on the west, the Channel Islands on the South, and Point Dume
on the east. It averages 500 m in depth, and is adjacent to a major group of submarine
canyons. This area has a unique admixture of colder, northern water and warmer, southern
water and represents a boundary area for many marine species. Local upwellings are
common. This combines to create a rich area for marine mammals; some 39 species occur or
have occurred in the recent past here. The Santa Barbara Channel is one of the richest areas in
the world for marine mammals; it is also the only area in the continental United States where
one can reliably find both Balaenoptera musculus (Blue whales) and Megaptera noveangliae
(Humpback whales) in significant quantities.
What is a marine mammal?
• Marine mammals are mammals in perfectly good standing. They have hair (albeit
rudimentary follicles), four-chambered hearts, a diaphragm separating the thorax from the
abdominal cavity, bear live young, and nurse their young.
• There are seven broadly defined groups of marine mammals.
The order Carnivora includes five of those groups:
Family Otariidae (sea lions and fur seals)
Family Odobenidae (walruses)
Family Phocidae (seals)
Family Mustelidae (Enhydra lutris, the sea otter)
Family Ursidae (Ursus maritimus, the polar bear)
The order Cetacea includes whales, dolphins, and porpoises.
The order Sirenia includes the manatees and dugongs.
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Whales, Dolphins, and Porpoises
The order Cetacea is subdivided into the Mysticetes (from the Greek word for
moustache), or baleen whales, and the Odontocetes, or toothed whales, dolphins, and porpoises.
The words whale, dolphin, and porpoise are rather arbitrary. One (European) system of
grouping these animals by common names is to consider all of the mysticetes, the sperm whale,
and the pygmy sperm whale to be whales. All other odontocetes (except porpoises), even those
with whale in their common name, are actually dolphins. The porpoises are members of the
family Phocoenidae and are characterized by cusped teeth, blunt snouts, and triangular fins
(whereas dolphins have pegged teeth and frequently have “bottle-noses” and falcate (“fastback”) fins. All cetaceans are aquatic, have nostrils that have migrated to the top of the skull,
and have telescoped (elongated) facial bones.
Origins
The fossil record (and DNA evidence) suggests that Cetaceans are most closely related to
Artiodactyls (even-toed ungulates), with hippopotamuses as their closest living relative. The
Mesonychidae, small furry quadrupeds, are a possible ancestral group. The transition to water
probably entailed amphibious forms, perhaps like otters. These evolved into the Archaeocetes,
an extinct suborder of Cetacea that flourished from 49-34 million years ago. Both Odontocetes
and Mysticetes diverged approximately 34 million years ago. The three families of Mysticetes
are the Balaenidae (right whales), the Balaenopteridae (humpback whales, blue whales, and
similar species), and the Eschrichtidae (gray whales); they appear in the fossil record
approximately 20 million, 15 million, and 100,000 years ago respectively. Among the
Odontocetes, the ancestral record for Physiteridae (sperm whales) extends back 23 million years,
while those of Ziphiidae (beaked whales) and Delphinidae (dolphins) extend back 10 and 25
million years respectively.
Anatomy/Physiology
General: Mysticetes have baleen (see below); Odontocetes have teeth. In Mysticetes,
the skull is symmetrical with paired nasal openings; in Odontocetes, the skull is asymmetrical
with a solitary nasal opening. Mysticetes have fewer ribs that articulate with the vertebrae and
(unlike Odontocetes) only one pair of ribs articulate with the sternum. The Balaenidae are
stocky, with long baleen and no dorsal fin (their thick blubber, high oil yield, high-quality
baleen, slow speed, and habit of floating when dead gave them the common name of “right”
whales; they were the right whale to hunt.). The Eschrichtidae are fairly stout and have no dorsal
fin. The Balaenopteridae are more streamlined, have small dorsal fins, and have numerous throat
grooves (hence their grouping as “rorquals,” after the Norwegian word for furrow). Toothed
whales tend to be much more diverse in form; however, most are fairly streamlined and have
prominent dorsal fins (although some have no dorsal fin at all).
Hearing: Sound in water travels approximately four times as fast as it does on land and
sound reception poses unique problems. Cetacean hearing is complex. Neither Mysticetes nor
Odontocetes have an external ear. In Mysticetes, the ear canal is filled with a wax plug, which
may transmit sound; this plug is absent in Odontocetes. Whether either group transmits sounds
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through the ear canal remains controversial. In Odontocetes some sounds are received through
the lower jaw and transmitted directly to the inner ear. In both groups, the auditory bone
complex is isolated from the rest of the skull, which prevents sound conduction through bone
(bone conduction would hinder the animal’s ability to determine direction of sound source).
Echolocation/Sound Production: Echolocation has been demonstrated only in
Odontocetes. Unique fatty deposits in their heads (melon) and lower jaws facilitate both
echolocation and sound reception by focusing and transmitting sound beams. Sound production
in Odontocetes occurs by moving air through a complex system of nasal sacs, which branch off
from the nasal passages just below the blowhole. Low frequency clicks are used for general
scanning, broad frequency clicks for general information about objects, and progressively higher
frequency clicks for more detailed information about objects. Most species studied can
echolocate to distances of at least 800 m. Although some Mysticetes have been observed to emit
relatively narrow-band clicks, no unequivocal echolocation has been demonstrated. Mysticetes
lack the specialized fatty deposits of Odontocetes; any echolocation system they have would be
primitive at best. Among the Mysticetes, the humpback whales are noted for producing “songs”
of repetitive phrases. Within any population of humpback whales, the songs are identical. In all
populations, the songs change somewhat each year. Many of the larger Mysticetes produce loud,
low frequency (non-echolocating) sounds that are audible for thousands of miles.
Navigation: Although individual animals in some species may undertake annual
migrations of thousands of miles, little is known about navigation. “Spy-hopping” behavior has
been proposed as one method of orientation, but it is of no utility out of site of land, and the
quality of Cetacean eyesight in air is equivocal. There is some speculation that a sophisticated
sense of taste aids coastal migration by allowing animals to sample water flowing off land
masses. Recently, enthusiasm for a hypothesis involving a geomagnetic sense has increased
sharply. Geomagnetic senses have been demonstrated in other species, and magnetic crystals
have been demonstrated in tissues surrounding the brain in a number of Cetacean species.
Miscellaneous senses: Sense of smell is essentially absent (neuroanatomical evidence).
The sense of touch is highly developed; it is likely that the sense of taste is also.
Feeding: The two suborders differ widely. Odontocetes capture prey through
echolocation. Their teeth are “pegged” (no roots), except for Phocoenidae, and are used only to
grasp prey. There is no mastication. Mysticetes take large quantities of water into their mouths
and strain it through their baleen. The baleen is composed of parallel rows of keratin plates
(analogous to fingernails) with fringes that act to filter the water passed through them. Each
species has baleen of somewhat different length. Each of the three families feeds somewhat
differently, although there is a great deal of overlap. The Balaenidae tend to feed by skimming
through the water. The Balaenopteridae are “gulpers,” and the Eschrichtidae suction feed on the
bottom. Humpback whales have evolved a unique strategy called “bubblenet feeding.” The
whale, while at depth, blows a circle of bubbles around a school of fish. As the bubbles rise in
the water column, they are acoustically opaque; the fish will not swim through them. The whales
then rise within the circle, mouth open, and feed on the fish. Odontocetes have evolved a
diversity of feeding strategies, from the cooperative hunting of killer whales to the intentional
beaching of killer whales and some species of dolphins in a search for food. Cetacean stomachs
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are multi-chambered, as they are in many ruminants, and the intestines are not differentiated into
a “small” intestine and a “large” intestine as they are in humans. Large intestines are effective in
water conservation; cetaceans accomplish this through other means (see “Renal Functions”
below).
Respiration: Here the divergence between the two suborders is not as great as that
between the shallow divers and the deep divers. Sperm whales have been seen to dive to depths
of 3000 m on sonar; even at far lesser depths, there is enormous potential toxicity from air in the
lungs. Nitrogen at high pressures (great depth = great pressure) is toxic to mammals, and oxygen
in blood that is rapidly depressurized (e.g., ascent to the surface) forms bubbles much the way
champagne does when a bottle is rapidly opened. Cetaceans have solved this problem by not
using air when they are at depth. Deep divers have proportionately smaller lungs than other
mammals. All cetaceans have an extremely flexible thorax; at depth it collapses, forcing air out
of the lungs into the bronchi where no gas is exchanged. This air is then kept out of the lungs by
a series of functional valves created by smooth muscle sphincters extending from the mouth of
each alveolus up into the bronchial tree. Cetaceans have evolved a number of elegant
mechanisms for surviving dives without oxygen in their lungs. First, they store more oxygen in
their muscle than other mammals, and they have more oxygen-carrying red blood cells than other
mammals. Also, most of their organs function anaerobically during diving; that is, blood flow to
these organs ceases and they do without oxygen. Only the brain, the heart, the adrenals, and a
select group of muscles used in diving get blood. These mechanisms tend to be better developed
in deeper divers. Because diving represents a major metabolic stress, most cetaceans do not
make repeated dives to depth without lengthy surface intervals. During dives, cetaceans become
extremely bradycardic (slow heart rate). In shallow-diving species, the mechanisms described
above are often less well developed. Additionally, since shallow-diving species have less to
worry about from the toxic effect of oxygen and nitrogen at pressure, lung volumes are often
proportionately larger than in other mammals. All marine mammals exchange approximately
98% of the air in their lungs with each breath; humans exchange only 15%. Sperm whales may
dive for 2 hours and attain depths of 3000 m, rorquals for 40 minutes to a few hundred meters,
gray whales for 15-20 minutes at shallow depths, and dolphins for 2-15 minutes at depths of 50100 m.
Circulation/Heat Conservation: Cetaceans have large hearts, although their globular
configuration is less efficient than a cylindrical configuration. The circulatory system is marked
by a number of retia mirabilia (“wonderful nets” composed of arterioles and venules) in the
abdomen and thorax. These are poorly understood but may play a pressure-damping role or may
function to help prevent the bends. Better understood is a counter-current exchange system, in
which arteries traveling to the surface are surrounded by veins returning from the surface. The
arterial blood gives its heat to the venous blood returning to the central circulation, thus
conserving heat. The primary insulation of Cetaceans is through blubber. Although blubber is
commonly thought of as fat, a major component of it is a fibrous stroma of connective tissue.
Reproduction: Cetaceans have a bicornate (two-horn) uterus. Gestation is generally
approximately 12 months, and pregnancies are usually every two years or longer. More work
has been done on Mysticetes, which tend to migrate to tropical or subtropical breeding grounds,
than on Odontocetes. Genitalia are recessed in all species. Some species engage in “sperm
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competition,” in which massive quantities of sperm are infused during copulation; the functional
effect is to flush out the sperm of previous males. Right whales, which do exhibit sperm
competition, have testes that weigh 500 kg each.
Renal Function: Cetaceans have highly lobulated kidneys; this serves to increase
filtration ability. Cetaceans probably do not drink seawater (despite one highly flawed old study
that concluded otherwise), but instead derive their water from their prey and via metabolic
pathways.
Age: Techniques have been developed for determining age in Odontocetes (growth rings
in teeth) and in Mysticetes (growth rings in baleen). Age at sexual maturity and life spans are
data points that remain very tenuous for most species. Life spans range from 20-30 years to 7090 years.
Intelligence: A great deal has been written on this topic, and a great deal of effort has
been invested in developing indices for the comparative ranking of intelligence. Assessment of
the intelligence of marine mammals remains very difficult; they have evolved to function in a
world that is dramatically different from ours. There may be some correlation between
microgyri and microsulci (the micro-folds and grooves) in the brain and intelligence. My
personal experience in years of working with odontocetes is that they are about as intelligent as
an intelligent canine; many workers in the field share this view (anecdotal though it is).
Social Behavior: Wide differences exist among species here. Mysticetes tend to exhibit
less social structure than Odontocetes and less complex behavior. Among the Odontocetes, the
complex behavior and social structure of killer whales on the Northwest Coast of North America
have been under investigation for decades.
Sleep: Both observations in the wild and Russian experimental work indicate that
Cetaceans do sleep. This appears to occur with only one side of the brain at a time; in fact, one
eye is usually kept open. The awake side of the brain is then responsible for respiration (which
in cetaceans, unlike humans, requires a high level of consciousness) and the movement of the tail
flukes that keeps the animal near the surface.
Stranding: Two types of stranding occur: solitary strandings and mass strandings. The
latter may entail dozens or even hundreds of animals. In most solitary strandings the animals are
dead before they hit the beach; the live strandings are usually heavily diseased. Overt disease
and extremes of age account for virtually all solitary strandings. Mass strandings are another
matter. Theories of causation abound, but all have drawbacks and none can be definitively
proven. Middle ear or brain parasites held sway for a number of years, but incidental takes of
dolphins in the pelagic tuna fishery have demonstrated equal numbers of parasites in healthy
animals. Large herds of Odontocetes may be following a diseased leader onto the beach. This
theory has some currency. Once even a healthy animal is on the beach, the blubber that insulates
it so well in the water acts to trap a great deal of heat in a setting where there is already radiant
heat gain. Studies of some strandings have shown that anatomical and physiological changes
consistent with severe heat stroke appear rapidly, often within less than 30 minutes. This would
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help account for the low salvage rate even when apparently healthy animals are returned to the
water fairly quickly.
Whale Fisheries/Conservation
The North American (Basques in Canada) whale fishery was in full bloom by the end of
the fifteenth century, and may have begun as early as 1372. Shore-based whaling began in the
U.S. in 1640, with pelagic whaling following in 1712. In 1789 the first U.S. whaler rounded
Cape Horn. Whaling off Baja California occurred by 1809, although the gray whale calving
grounds were not discovered until significantly later. In 1848 the Arctic bowhead was
discovered. In 1856, Scammon discovered the gray whale calving grounds in Baja. Intense
whaling began in 1858, and the stocks were depleted by 1865. In 1854 the first shore-based
whaling station on the West Coast of the U.S went into operation in Monterey; by 1870, there
were 11 such stations. By 1900, Monterey and most of the others had closed, although the Del
Monte station in Richmond lasted until 1971. In 1868, pelagic whaling took a quantum leap
forward with the invention of the modern harpoon gun by Svend Foyn. Another quantum leap
occurred in 1924 with the introduction of the stern-loading factory ship. Pelagic whaling
flourished both before and after World War II. The highest one-year catch occurred in 1961,
after which whaling began a slow decline, due largely to stock depletion and the development of
substitutes for the whale products of commercial importance. In 1969 Greenpeace was founded,
and in 1972 the U.S. Congress passed the Marine Mammal Protection Act. Conservation efforts
essentially put a halt to commercial whaling at the end of the 1960s.
Unfortunately, a few nations have continued to hunt whales. In the mid-1960s, the
Russians quietly exterminated an entire stock of southern right whales. Persistent Russian,
Japanese, and Korean whaling have virtually exterminated the western Pacific stock of gray
whales. In the 1990s, Japan resumed “scientific whaling,” allegedly to gather data on stocks of
Minke whales for management purposes. However, DNA analysis done on whale meat
purchased at the Tokyo Fish Market has shown the presence of other species as well (including
fin and humpback whales).
Of note also is the persistent aboriginal whale fishery. The Inuit are allowed subsistence
hunting of gray whales (as well as bowhead), with a quota set at 124 animals. In 1995, they took
85. The right of the Makah to hunt whales was acknowledged in 1997, and the Nuu-Chuh-Nulth
nation is now seeking similar acknowledgement.
Whaling is not the only threat to Cetaceans. Recent research has demonstrated rising
levels of environmental toxins in some marine mammal populations; pollution is an ubiquitous
threat. A 20% decline in the resident population of Orcinus in the Pacific Northwest over the
past five years may be the result of toxins concentrated up the food chain. A recent proposal by
Mitsubishi to dramatically enlarge an existing saltworks in one of the gray whale calving lagoons
was narrowly turned back in one of the few recent victories for marine mammal habitat.
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Research/Public Display
Over the past two decades, research on marine mammals has exploded although, like all
human interactions with marine mammals in this country, it is subject to the provisions of the
Marine Mammal Protection Act. Telemetry devices and increased access to the underwater
realm have allowed us to monitor marine mammals in ways previously only dreamed of.
Molecular biology has given us new tools to explore not only the relationship of marine
mammals to each other, but also to the rest of the phylogenetic tree. Dogged effort has turned
photo-I.D. into a powerful tool: the work of John Calambokidis with blue whales in the Santa
Barbara Channel and along the central California coast is certainly evidence of that. Our own
efforts at the Santa Barbara Museum of Natural History have been directed toward the necropsies
of all strandings along our coast whenever possible. We also maintain a live-sighting database as
well as strong regional osteological and soft tissue collections.
Debate about the public display of marine mammals has accelerated in the last several
years. Recently the Vancouver Aquarium, an institution with enormous international respect,
decided after several decades of display to remove their killer whales from exhibit. Educational
benefits of keeping live marine mammals in collections will be increasing balanced against the
cruelty of maintaining pelagic animals in extremely confined quarters.
Some Comments on Blue Whales, Balaenoptera musculus.
General: General characteristics of Balaenopteridae include a streamlined shape
(Megaptera is the sole exception), small dorsal fins which vary widely among members of a
given species in shape (in general, the larger the species, the more posterior the dorsal fin), and
numerous throat grooves.
External Morphology: B. musculus is the largest organism ever to inhabit the earth. As
with all balaenopterids, females are larger than males. The largest individual ever measured (a
female) was 33.6 m (110 ft) in length. The heaviest weighed was 190 tons (if lost blood volume
were factored in, the weight would probably have been 200 tons). The mouth measures 6 m in
length and the flukes 4.5 m in width. Dorsal fins are small (0.4m) and posterior. > 300 baleen
plates (< 1 m in length) are in each upper jaw. The baleen and fringe bristles are black. 55-88
ventral pleats, of varying length, are found on the ventral surface. A single midline ridge extends
from the blowhole to the rostrum.
Blue whales are longer than 2 school buses laid end-to-end, and they are heavier than
1500 people. Their tongue weighs as much as an adult elephant, and their heart is larger than a
VW Beetle. When they spout, their blow is 3 stories high (9 m). Their flukes are as wide as a
soccer goal.
Subspecies: Three subspecies have been recognized: B. musculus intermedia (the
largest, inhabiting the Southern Hemisphere), B. musculus musculus (intermediate in size,
inhabiting the North Atlantic and North Pacific), and B. musculus brevicauda (the shortest,
inhabiting the tropical Southern Hemisphere in the Indian Ocean and Southeast Atlantic).
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Specimens from elsewhere are often assigned to intermedia, but their true subspecies is
unknown. B. m. brevicauda has a shorter tail than other subspecies, a proportionately longer
body, and is less than 24.4 m (80 ft) in length. Although controversy accompanied the first
description of brevicauda by the Japanese (many felt the separation into what was originally
claimed as a new species was simply a ploy to exceed International Whaling Commission limits
on blue whales), the subspecies is now widely accepted. The degree of hybridization among
subspecies is unknown. Theoretically, the temporal displacement of migrations between
Northern Hemisphere and Southern Hemisphere animals should prevent intermingling, but there
is some interchange of animals. There is evidence of some hybridization between B. musculus
and B. physalus.
Communication: Vocalizations are in the 15-20 Hz range with intensities of 180-190
decibels. There are two components to the vocalization, each lasting approximately 10 seconds.
The second component is at a lower frequency or ends in a downward mode. Vocalizations may
be repeated at one-minute intervals. Geographic variations or dialects may exist, but the
evidence is not substantial. Ultrasonic clicks have been recorded; echolocation (crude) has been
postulated but not substantiated. Communication in this species can potentially occur over entire
ocean basins, and it may be that widely spaced individuals are actually part of larger groups.
Respiration/Diving: Blue whales make 10-12 shallow dives, of 10-20 seconds duration,
in a row. 5-8 respirations are taken between dives. Deeper dives are of 10-30 minute duration.
This species is not a particularly deep diver; it usually feeds in the top 100 m of the water
column. The flukes are not regularly shown during diving, although the Makah refer to blue
whales as kwakwe axtli, or “noisy tail.” Blue whales generate peak respiratory flows of 624,000
liters per minute during exhalation/inhalation (human maximum is 800 liters per minute).
Feeding: Blue whales feed primarily on euphausids. In the North Pacific, the primary
prey species are Euphausia pacifica and Thysanoessa sp. They also take in small fish,
particularly sardines and capelin; this ingestion may be accidental. This species is considered a
“swallower” or “gulper” as opposed to the Balaenidae (right whales), which are considered
“skimmers.” Both side feeding and lunge feeding have been observed.
Blue whales migrate on a north-south axis. They feed seasonally (spring, summer, fall)
in high latitudes. The migrations correlate with euphausid abundance; timing may vary from
year-to-year. Peak feeding is in the evening and early morning, which correlates with euphausid
abundance in the water column. During their migration (and on their winter grounds) they may
either feed or fast. Intake for a full-sized adult is 3-4 million calories per day, which corresponds
to 4-5 tons of krill. The oral cavity of an adult blue whale can hold 2+ tons of water, while the
stomach can hold 1-2 tons of krill.
Reproduction: Blue whales mate in the fall and winter. Migratory phase differences
prevent substantial Northern and Southern Hemisphere interbreeding. Gestation is 10-11
months, and sexually mature females usually bear a single calf every 2-3 years. Calves are 23-26
feet and 3 tons at birth. Calves receive approximately 130 gallons of milk per day. The milk is
41-50% milk fat (human milk is 3-4% milk fat). Calf weight gain is 4 kg per hour, and length
gain is 4cm per day. Weaning occurs at 7 months, when calves average 16 m (53 ft) and 23 tons.
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The mother may lose 50 tons (one-third her body weight) while nursing. Northern Hemisphere
females are 21-23 m at sexual maturity and 25m at physical maturity. Northern Hemisphere
males are 20-21 m at sexual maturity and 24m at physical maturity. Sexual maturity occurs at
5-7 years; this has been lowered considerably by the population pressure exerted by hunting
during the twentieth century.
Miscellaneous: The maximum estimated life span for blue whales is 30-90 years
(difficult to estimate). Individuals are usually solitary or found in groups of 2-3. Swimming
speed is 2-6.5 km/hr for feeding animals, 5-33 km/hr for cruising or migrating animals, and
20-48 km/hr for chased animals. Maximum speeds cannot be maintained for sustained periods
of time.
Population: The pre-exploitation population of blue whales was approximately 350,000
animals. With the invention of the modern harpoon gun in the latter part of the 19th century and
fast catcher vessels in the early 20th century, this species became the favored target of hunters
(because of large size and high oil yield). Approximately 350,000 were taken in the 20th century,
with 30,000 taken in 1930-31 alone. Approximately 9000 remain today, some 2000 of which
summer off the coast of California.
Disease/Mortality: Little is known about diseases in blue whales. They appear to be
less parasitized than other species, which may be due to a diet low on the food chain. This may
also account for the relatively low level of pollutants found in their tissues (although much more
work is needed). The ventral surface of blue whales often becomes covered with diatoms,
particularly in the Antarctic; this has given rise to the name “sulphurbottom.” Blue whales may
also act as host to remoras. Shipping accidents and Orcinus attacks are causes of mortality.
Research: Blue whales are the focus of intensive photoidentification work. The use of
satellite tagging and “kritter kams” is also giving new insights into their world. Krill research is
yielding additional insight into their life history. Much of this work is in progress in the Santa
Barbara Channel.
Some Comments on Gray Whales, Eschrichtius robustus
General: Gray whales are not evident in the fossil record until 100,000 years ago
(although many consider them to be a primitive balaenopterid of some antiquity). A North
Atlantic population existed but became extinct in 1750. A Western Pacific population exists but
has been nearly eliminated by Russian, Korean, and Japanese hunting.
External Morphology: As with all Mysticetes, females are larger than males. Physical
maturity is attained at approximately 20 years; the average male is 13.0 m (maximum 14.6 m)
and the average female 14.1 m (maximum 15.0 m). Weight is approximately 20-35 tons. The
skull is slightly more arched than balaenopterids. There is no dorsal fin, but there is a series of
6-12 ridges along the posterior third of the dorsum. Coloration is gray with white mottling,
scarring, and a heavy ectoparasite burden that may reach several hundred pounds. 2-4 ventral
grooves are present.
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Respiration/Diving: Shallow dives of 3-5 minutes are usually separated by 5-6 blows.
Deeper dives may last up to 25 minutes and are usually accompanied by a display of flukes.
Maximum depth is thought to be 120 m, although gray whales rarely go deeper than 100 m.
Feeding: Alone among the Mysticetes, gray whales are bottom feeders, which they
accomplish by suction. Most individuals feed with the right side down. Gray whales were
formerly thought not to feed during their migration or calving period; multiple observations have
now proven this to be false.
Reproduction/Migration: Gray whales undertake an extraordinary migration of some
8000 miles, one of the longest migrations of any mammal. From the end of May through
September, they feed on the shallow continental shelf of the Bering and Chukchi Seas.
Beginning in October, they migrate to the calving lagoons of Baja California: Laguna Guerrero
Negro, Laguna Ojo de Liebre, Laguna San Ignacio, and Estero Soledad. Pregnant females
migrate first, followed by recently ovulated females, immature females, adult males, and
immature males. Only about a week is spent in the calving lagoon itself, although the return
north is not immediate. On the northward migration, pregnant females migrate first, followed by
non-pregnant females, adult males, and immature males. Cow/calf pairs migrate last; their peak
numbers pass Pt. Piedras Blancas on 1 May (on average).
Calves are 4-5 m and 500-680 kg at birth. Milk intake is 40-50 gallsons/day. Weight
gain is 90 kg/day. Calves are weaned at 6-9 (average 7) months. Gestation is 13 months females
usually breed every other year.
Miscellaneous: Swimming speed is 7-9 km/hr; speeds of 16 km/hr may be attained
when individuals are chased. Gray whales may show aggression, particularly when calves are
threatened; during the era of commercial whaling they were known as “devilfish.”
Population: The current population of gray whales is approximately 22,000-25,000,
which is probably higher than pre-contact levels. A history of aboriginal whaling in the Pacific
Northwest and Alaska extends back several thousand years (it continues today). See comments
under Whale Fisheries/Conservation.
Disease/Mortality: Gray whales are among the most heavily parasitized of cetaceans.
They are particularly noted for both barnacles and “whale lice” (actually Crustaceans) as
ectoparasites, with parasite burdens often reaching several hundred pounds. Observations of
predation by Orcinus are not uncommon.
Some Comments on Humpback Whales, Megaptera novaeangiae
General/External Morphology:
The scientific name means “big-winged New
Englander,” which refers to the large pectoral fins and the first scientific description of the
species in New England in 1781. The species common name refers either to the back flexion
while diving or the hump-like dorsal fin. Humpbacks are stockier than other balaenopterids.
They lack a dorsal ridge and have a slender tail stock. The head constitutes almost 30% of body
CHAPTER 7
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12
length and contains numerous dermal tubercles, which are actually hair follicles that contain
well-innervated vibrissae (whiskers). The baleen plates are blackish-brown/gray, 85-104 cm in
length, and number 270-400 in each upper jaw. The dorsal fin is 0.3 m and is highly variable in
appearance. 12-36 pleats are present on the ventral surface, the least of any species of
Balaenopterid. Basic coloration is black, with white patches on the chin, throat, abdomen,
pectorals, and flukes. Some authors have remarked on the greater presence of white in Northern
Hemisphere animals. The pectorals are the longest of any marine mammal and may reach onthird total body length. The rather slender flukes are unique in shape and coloration in each
animal and are the basis for extensive research based on photoidentification
Females are slightly larger than males; the largest measured is 19 m (62 ft), with a
corresponding weight of probably 40-50 tons. Average length is 12-13 m. Average calf length
is 4.2 m (14 ft).
Communication: Songs are 2 or more notes repeated in a pattern. Units of sound are
phrases; repeated phrases are themes. Singing occurs on the humpback whale wintering
grounds. The “singers” appear to be sexually mature, isolated males. Although little is known
about song function, it probably occurs in a breeding context. Humpback whale songs have 2-9
themes. The themes are sung in a specific order and last from a few minutes to one-half hour.
The song is then repeated, which may continue for hours-days. All animals from the same
population sing identical songs, although there may be subtle differences among subpopulations
and individuals. There are major differences between different populations. The songs change
annually, with each individual in the population somehow learning the differences. All
individuals in a population learn the differences. Over a period of 5 years, the song will change
almost entirely. Most frequencies are 40-5000 Hz. Other humpback vocalizations include
clicks, chirps, moans, cries, and squeaks, which have often been bundled together as “social
sounds.” Occasional song-type sounds are heard in northern feeding grounds. Although
occasional higher-frequency clicks (2-14 kHz) are heard, there is no evidence for echolocation.
Low frequency vocalizations in this and other Mysticetes may be important in orientation,
navigation, and locating large prey aggregations.
Respiration/Diving: Humpback whales undertake short dives of 2-4 minutes with
surface intervals of 1 minute. In this dive pattern, the blows are irregular and the flukes are not
shown. Longer dives are of 8-15 minute duration (30 minute maximum), with surface times of 4
minutes, regular blows, and flukes shown during dives. The longest dives occur on the shallow
wintering grounds. During these dives, the animals may frequently be observed resting on or
near the bottom.
Feeding: Prey species vary among regions. Antarctic humpbacks feed almost entirely
on euphausids, while North Pacific humpbacks feed on euphausids, mackerel, sand lance,
capelin, and herring (and even an occasional gull). As with other Balaenopterids, this species is
a “gulper” rather than a “skimmer.” Humpbacks demonstrate a wide variety of feeding
techniques. They may create a ring of foam by circling prey while striking the water with their
flukes, thus herding the prey by creating an acoustically opaque wall of bubbles. They may
undertake bubble net feeding by (either alone or in groups) releasing bubbles from their
blowhole while circling prey, then lunging up through the bubblenet cylinder. They may also
CHAPTER 7
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13
employ bubble cloud feeding, in which one animal releases a large exhalation of bubbles, with
the same result as above. Cooperative feeding may entail aggregations of up to 20 animals.
North Pacific animals utilize more bubble net than bubble cloud feeding.
Reproduction: Calves are born in well-defined tropical wintering grounds. Gestation is
11-11.5 months, and the calves are 4-5 m at birth. More than 43 kg milk is consumed daily.
Weaning occurs at 5 months, when calves are 7.5-9 m. Sexual maturity is attained at 4-5 years
(comments made for blue whales are applicable here also). Calving intervals average 2-3 years.
As with most species of Cetacea, little is known regarding copulation. Females in estrous swim
with sexually mature male “escorts.” Intense competition occurs for females, with occasional
injuries to males. Competitors of the escorts may form cooperative groups of up to 20
individuals.
Miscellaneous: Maximum age for humpback whales is estimated to be 40-50 years.
Common swimming speeds are 3.8-14.3 km/hr, although wounded animals may swim as rapidly
as 27 km/hr. Social behaviors are spectacular in this species and include breaching, lobtailing,
tail slapping, and flippering. The functions for these behaviors are largely unknown but muchspeculated upon. Proposed reasons for breaching include excitation, aggression, communication
of alarm, and dislodging of parasites. This species may show agonistic behavior toward boats
during breeding season.
Population/Migration:
The pre-exploitation population of humpbacks was
approximately 150,000. Over 250,000 were killed in the Antarctic in the first two-thirds of the
twentieth century. Between 1910 and 1916, 60,000 were harvested. The aggregation of
humpbacks in tropical calving grounds and their inshore winter feeding grounds made this
species an easy target for whalers. Current population estimates are extremely difficult to come
by, but the total world population is probably somewhere around 12,000 animals. The species
appears to be extremely resilient, and the size of most populations is increasing. Current
estimates for annual population increase in the North Pacific is 6-8%. In 1998, 911 humpbacks
were estimated to summer off the California, Oregon, and Washington coast.
Humpbacks undertake well-defined north-south migrations. During spring, summer, and
fall they feed in cold, high latitude waters. In the winter they migrate to shallow, tropical waters
to calve (but not feed). Winter populations were traditionally thought to winter off Mexico,
Hawaii, and Japan. Recently, a previously unknown wintering ground in Costa Rica was
discovered (there was some initial thought that this wintering ground might include a mixing of
Northern and Southern Hemisphere individuals, but further research has not borne this out). The
Hawaiian wintering ground is relatively new; anthropological research has shown that it has only
been used for the past 200 years. The exchange rate with the Mexican population has led to
speculation that it derives from the Mexican population, with the shift in breeding grounds
perhaps induced by early commercial whaling.
Most of the population that winters in Costa Rica feeds off California in summer. Recent
DNA and photoidentification work has shown that humpback whales have extraordinary site
fidelity to their feeding grounds. The population that summers off central California may be
CHAPTER 7
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14
seen as far north as central Washington, but it rarely mixes with the population off British
Columbia. Whether this holds for other species of balaenopterids remains to be determined.
There is little (but some) mingling of Northern and Southern Hemisphere populations of
humpbacks, as the migrations are 6 months out of phase.
Disease/Mortality: Little is known about diseases in humpbacks. They are the most
heavily parasitized of the Balaenopteridae (both endo- and ecto-parasites). Significant levels of
DDT and chlorinated hydrocarbons have been found in tissues. There is also some evidence for
fatalities from brevitoxin, the agent in paralytic shellfish poisoning.
Pinnipeds
Pinnipeds (from the Latin for “feather-footed”) include the Family Otariidae (sea lions
and fur seals), the Family Phocidae (the “true” seals), and the Family Odobenidae (the walrus).
Historically, the families have usually been considered diphyletic—that is, descended from two
different terrestrial ancestors. Otariids and Odobenids were considered descended from ursid
(bear-like) ancestors and Phocids from mustelid (weasel-like) ancestors. Recent re-evaluation of
morphologic evidence, as well as molecular evidence, now points toward a monophyletic origin
with ursids as ancestors.
Origins
Pinnipeds first appear in the fossil record some 27 million years ago. Otariidae and
Phocidae diverged shortly thereafter.
Anatomy/Physiology
General: Otariids have an external ear; phocids do not. Otariids can turn their hind
flippers forward and use them to walk; phocids do not.
Hearing: Pinniped ears show acoustical isolation similar to that of cetaceans.
Additionally, phocids show modification of the middle ear bones (otariids do not).
Echolocation/Sound Production: Pinnipeds lack the nasal sinuses and well-developed
cranial fatty deposits of cetaceans. They emit a wide variety of vocalizations that probably serve
a multitude of purposes. Some phocids may echolocate (the evidence is somewhat equivocal),
but any echolocation is primitive at best.
Navigation: Little is known, but species undertake long migrations between feeding and
breeding grounds. Elephant seals have been tracked all the way from San Miguel Island to
Hawaii.
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Miscellaneous senses: Eyes in pinnipeds are relatively large and can accommodate to
allow them to see fairly well out of water. The oral vibrissae (whiskers) are well innervated.
They greatly augment tactile sense and augment the reception of some sounds. Although
pinnipeds have blubber, heat conservation is also aided by the presence of fur. All pinnipeds
have both an outer layer of guard hairs and an inner layer of underfur hairs.
Feeding: Pinnipeds have evolved a wide variety of feeding strategies. Those whose
distribution overlap have also evolved niches which partition resources.
Respiration: Much of the description of the cetacean respiratory system applies here
also. Some species (Weddell seal) can dive to depths of 1500 m and stay submerged for over an
hour. Cetaceans dive on full inspiration; pinnipeds tend to dive on full expiration.
Circulation/Heat Conservation: Much of the comments regarding cetaceans apply here
also. Pinnipeds have a large venous sinus posterior to the liver (cetaceans do not).
Reproduction: Reproduction in pinnipeds is complex and may be either monogamous
or polygynous. Monogamy occurs when the species does not aggregate into large breeding
groups. When breeding aggregations occur, males may either defend territories (resource
defense polygyny) or establish dominance hierarchies (female defense polygyny). California sea
lions are an example of the former; elephant seals are an example of the latter.
Renal Function: Pinniped kidneys are generally not as highly lobulated as those of
cetaceans.
Age: Maximum age is generally significantly lower for pinnipeds than it is for cetaceans.
The energy expenditure in defending territories is a significant life stress in males.
Intelligence: A great deal of work has been done on pinniped intelligence. In general,
my comments on cetaceans apply here also.
Pinniped Fisheries/Conservation
Native American take of local pinnipeds was significant; it may well have grossly
depleted the local elephant seal population prior to 1200 years ago. Commercial sealing depleted
most stocks in the Southern California Bight (SCB) in the nineteenth century and rendered
California sea lions, Guadalupe fur seals, and elephant seals almost extinct; these species passed
through a significant genetic bottleneck on the road to recovery. Although all species are
protected under the Marine Mammal Protection Act, ecosystem perturbations such as El Niño
and epizootic diseases pose very real population threats.
Some Comments on California Sea Lions, Zalophus californianus
CHAPTER 7
CHANNEL ISLANDS NATURALIST CORPS TRAINING MANUAL
16
The Northern Pacific population of this species is almost 160,000. Almost 90,000 are in
the Southern California Bight (SCB), with a breeding population on San Miguel Island of
approximately 80,000 animals.
Significant sexual dimorphism exists. Mature males average 2.25m and 325 kg, females
average 1.8m and 110 kg.
California sea lions breed from the Channel Islands to Mexico. After breeding, males
undertake a northward migration; females are less migratory. Breeding season is June-July.
This species was rare in SCB prior to 1930. It is now growing at the rate of 12% per year
but has suffered significant losses due to El Niño events.
Some Comments on Stellar Sea Lions, Eumetopias jubata
The population of this pinniped has crashed in the North Pacific over the past two
decades. It was formerly the most abundant pinniped in the SCB, with a substantial rookery on
San Miguel Island. The last pup was born on San Miguel in 1982, and the last confirmed
sighting of an adult was in 1984. Ecosystem disruption by fishing appears to be a major factor in
the decline of this species both locally and in its current range.
This species is much larger than the California Sea Lion. Males average 2.9 m and
1000 kg.
Some Comments on Guadalupe Fur Seals, Arctocephalus townsendii
The historical range of this species was from the Farallones to the Islas Revillagigedos,
with a major rookery on San Miguel Island. They were hunted intensively in the nineteenth
century and were considered extinct by 1900. Carl Hubbs discovered a small breeding colony on
Guadalupe Island in 1954. The species breeds primarily on Guadalupe Island and is increasing
by 10% per year. Occasional visitors are seen on San Miguel and San Nicholas Islands. The
first adult female was seen on San Miguel Island in 1997; it gave birth in June of that year and
reared the pup to weaning age.
Some Comments on Northern Fur Seals, Callorhinus ursinus
San Miguel Island was colonized by this pinniped in the 1960s, 5500 km south of its only
other breeding areas. Population size has increased at slightly more than 10% per year, but El
Niño events (primarily 1983 and 1997) have caused dramatic population declines in recent years.
1997 population size on San Miguel Island was approximately 12,000 animals. Total North
Pacific population is more than 1 million animals.
CHAPTER 7
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This species weans its young at 120 days, which is much earlier than most other North
Pacific otariids.
Some Comments on Harbor Seals, Phoca vitulina
The North Pacific population of this species is 312,000. The SCB contains 5000, 75% of
which occur around the northern Channel Islands. This is the only west-coast pinniped that
occurs in the Atlantic also. It is usually found within 10 km of land.
The population in the North Pacific is stable and is increasing at the rate of 10% per year.
Some Comments on Northern Elephant Seals, Mirounga angustirostris
This is the largest of the extant pinnipeds. Males average 4.5 m and 2500 kg; females
average 3 m and 900 kg.
Breeding Season occurs from December to mid-March. Females and juveniles molt from
mid-March through May. Males molt in July and August. Juveniles haul out from September
through November.
Elephant seals were hunted intensively in the nineteenth century and by the end of the
century were presumed extinct. The 1890 population has been estimated at 20-100 individuals
limited to Guadalupe Island. By 1968, it bred also at the western tip of San Miguel Island.
Today, it breeds all the way around San Miguel Island, on Santa Rosa Island, and on the
mainland at San Simeon. Current population is approximately 140,000. The largest breeding
population, approximately 50,000 animals, occurs on San Miguel Island.
Elephant seals have been intensively studied. They are noted for deep diving.
Sea Otters, Enhydra lutris
This species is a member of the mustelid family. Its former range was from Alaska to
Mexico, and it occurred on both sides of the Pacific Rim. Pre-hunting populations were
approximately 150,000-300,000 animals. Hunting began in 1741, and by 1900 there were
probably only 1000-2000 animals left.
The Russian and Alaskan populations have experienced a significant recovery and until
recently numbered 100,000-150,000 animals. The California population numbers approximately
1900; it is descended from a colony of approximately 30 animals known since 1915.
The Russian and Alaskan populations are now experiencing dramatic declines. With the
decline of some pinniped populations (especially Stellar sea lions), killer whales have increased
predation on otters.
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This species has been extremely controversial from a resource management standpoint.
The California population is extremely tenuous and passed through a genetic bottleneck.
Otters were transplanted to San Nicholas Island (part of their former range) in attempt to increase
dispersal of the species, but the transplant was a disaster.
Sea otters have no blubber. They depend on an extremely dense layer of underfur (it
functions by trapping air) and a high basal metabolic rate for insulation.
Sea otters are the only marine mammals to use tools.
References
Berta, Annalisa and J L Sumich. Marine Mammals: Evolutionary Biology. New York:
Academic Press, 1999. This is a great, current, highly technical general treatise on marine
mammals.
Mark Carwardine, ed. Whales, Dolphins, and Porpoises (2nd ed.). New York: Facts on File,
1999. I am not always enthusiastic about natural history volumes from this publisher, but
this is probably the best one-volume summary of Cetacean biology for the informed
layperson. Highly recommended despite its “coffee-table” size.
Calambokidis, John, and G Steiger. Blue Whales. Grantown-on-Spey (Scotland): Colin Baxter
Photography, 1997. See comments for Clapham below.
Clapham, Phil. Humpback Whales. Stillwater, MN: Voyageur, 1996. This is one in the
Worldlife Library series. Typical of the series, the coverage is broad but superficial and the
pictures are great. The series is aimed at the informed layperson.
Dierauf, Leslie, and F M D Gulland. The CRC Handbook of Marine Mammal Medicine. New
York: CRC Press, 2001. This is probably the most up-to date reference in the bibliography.
The quality of some of the chapters is a bit uneven, but the volume is indispensable. It
includes a chapter on electronic databases.
Heyning, John. Masters of the Ocean Realm: Whales, Dolphins, and Porpoises. Seattle:
University of Washington Press, 1995. This is a brief, but masterful, overview of marine
mammal biology. The author is a marine mammal anatomist, authority on the Ziphiidae
(beaked whales), and the Associate Director of the Los Angeles County Museum of Natural
History.
Jones, Mary Lou, S Swartz, and S Leatherwood. The Grey Whale. New York: Academic Press,
1984. This volume is now somewhat outdated, but is remains the best single volume treatise
on the grey whale.
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19
Leatherwood, Stephen, R R Reeves, W E Perrin, et al. Whales, Dolphins, and Porpoises of the
Eastern North Pacific and Adjacent Arctic Waters. NOAA Technical Report NMFS Circular
444, 1982. Since reprinted by Dover and widely available, this is an excellent reference. It
is filled with data on distribution and identifying characteristics, and the black-and-white
photos are very good.
Leatherwood, Stephen and R R Reeves. The Sierra Club Handbook of Whales and Dolphins.
San Francisco: Sierra Club Books, 1983. This is an outgrowth of the reference above and a
companion volume covering the Atlantic. It offers excellent color drawings (supplemented
by good black-and-white pictures) and a terse, well-informed text. It is aimed at the
informed layperson and is global in scope. It is an excellent choice for carrying into the field
anywhere in the world.
Leatherwood, Stephen and R R Reeves, eds. The Bottlenose Dolphin. New York: Academic
Press, 1990. This is a thorough, well-written treatise on the biology of this species.
Le Boeuf, Burney J and R M Laws, eds. Elephant Seals: Population Ecology, Behavior, and
Physiology. Berkeley: University of California Press, 1994. This is another single-species
volume, well written, and edited by the dean of elephant seal biology.
Orr, Robert T and R C Helm. Marine Mammals of California. Berkeley: University of
California Press, 1989 (revised). This is a volume in the California Natural History Guides
series. It features line drawings and concise text and covers both cetaceans and pinnipeds.
Reeves, Randall R, B S Stewart, and S Leatherwood. The Sierra Club Book of Seals and
Sirenians. San Francisco: Sierra Club Books, 1992. This is a companion volume to the
Leatherwood volume above. The comments offered above apply here also.
Reynolds, John and S A Rommel, eds. Biology of Marine Mammals. Washington, D.C.:
Smithsonian Institution Press, 1999. This is another good, technical, current text on the
biology of marine mammals.
Reynolds, John, R S Wells, and S D Eide. The Bottlenose Dolphin: Biology and Conservation.
Gainesville: University Press of Florida, 2000.
Rice, Dale. Marine Mammals of the World: Systematics and Distribution. Special Publication
no. 4, The Society for Marine Mammalogy, 1998. This is a list of all known species and
subspecies of marine mammals and their distribution.
Riedman, Marianne. The Pinnipeds. Berkeley: University of California Press, 1990. Overview
of pinniped biology with emphasis on behavior.
Ridgway, Sam H and R Harrison. Handbook of Marine Mammals, vol. 1-vol. 6. New York:
Academic Press, 1985-1999. These volumes provide excellent summary accounts of all
species of cetaceans and pinnipeds.
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Slijper, E J. Whales. New York: Basic Books, 1962 (republished by Cornell in 1979). The date
of publication might lead one to consider this volume long outdated, but it remains the single
most indispensable text on cetacean biology. What was often only speculation in Professor
Slijper’s day has usually been proven true. Many of us still use slides made from the
drawings in this text to illustrate papers presented at technical meetings.
Tonnessen, J N and A O Johnsen. The History of Modern Whaling. Berkeley: University of
California Press, 1982.
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Marine Mammal Migration in the Santa Barbara Channel
Mammal
Blue Whales
Bottlenose Dolphins
California Sea Lions
Common Dolphins
Dall's Porpoises
Gray Whales
Harbor Seals
Humpback Whales
Minke Whales
Northern Elephant Seals
Northern Right Whale
Dolphins
Orcas (Killer Whales)
Pacific White Sided Dolphins
Risso's Dolphins
Sperm Whales
Jan
Feb
Mar
Apr
**
**
**
**
**
**
*
*
**
*
**
**
**
**
**
**
*
*
**
*
**
**
**
**
**
**
*
*
**
*
**
**
**
**
**
**
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
May
*
**
**
**
**
*
**
**
*
Jun
**
**
**
**
**
**
**
**
*
July
**
**
**
**
**
**
**
**
**
Aug
**
**
**
**
**
**
**
**
**
*
*
*
*
*
*
**
*
*
**
*
** Frequently seen in the channel
**
*
**
*
Sep
**
**
**
**
**
Oct
*
**
**
**
**
**
*
**
*
*
**
*
*
*
*
**
*
*
*
**
*
*
Nov
Dec
**
**
**
**
**
**
**
**
**
*
*
*
*
**
*
*
**
*
*
*
*
*
*
*
*Occasionally seen in the channel
(Based on information provided by Condor Whale Watching)
CHANNEL ISLANDS NATURALIST CORPS TRAINING MANUAL
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22
MARINE MAMMALS OCCURRING IN THE WATERS OF
CALIFORNIA
Charles J. Rennie, III
Channel Islands National Park
ORDER CETACEA
Suborder Mysticeti (Baleen whales)
Family Balaenidae (Right whales)*
Eubalaena glacialis (Northern right whale)
Family Balaenopteridae (Rorquals)
Balaenoptera acutorostrata (Minke whale)
Balaenoptera borealis (Sei whale)
Balaenoptera brydei (Bryde’s whale)**
Balaenoptera musculus (Blue whale)
Balaenoptera physalus (Fin whale)
Megaptera novaeangliae (Humpback whale)
Family Eschrichtidae
Eschrichtius robustus (Gray whale)
Suborder Odontoceti (Toothed whales)
Family Physeteridae
Kogia breviceps (Pygmy sperm whale)
Kogia simus (Dwarf sperm whale)
Physeter macrocephalus (Sperm whale)
Family Ziphiidae
Berardius bairdii (Baird’s beaked whale)
Mesoplodon carlhubbsi (Hubbs’ beaked whale)
Mesoplodon densirostris (Blainville’s beaked whale)
Mesoplodon ginkgodens (Ginkgo-toothed beaked whale)***
Mesoplodon perrini (Perrin’s beaked whale)
Mesoplodon stejnegeri (Stejneger’s beaked whale)
Ziphius cavirostris (Cuvier’s beaked whale)
CHANNEL ISLANDS NATURALIST CORPS TRAINING MANUAL
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23
Family Delphinidae
Delphinus delphis (Short-beaked common dolphin)
Delphinus capensis (Long-beaked common dolphin)
Globicephala macrorhynchus (Short-finned pilot whale)
Grampus griseus (Risso’s dolphin)
Lagenorhynchus obliquidens (Pacific white-sided dolphin)
Lissodelphis borealis (Northern right whale dolphin)
Orcinus orca (Killer whale)
Pseudorca crassidens (False killer whale)
Stenella attenuata (Pantropical spotted dolphin)
Stenella coeruleoalba (Striped dolphin)
Steno bredanensis (Rough-toothed dolphin)
Tursiops truncatus (Bottlenose dolphin)
Family Phocoenidae (Porpoises)
Phocoena phocoena (Harbor porpoise)
Phocoenoides dalli (Dall’s porpoise)
ORDER CARNIVORA
Family Mustelidae
Enhydra lutris (Sea otter)
Suborder Pinnipedia
Family Otariidae (Fur seals and sea lions)
Arctocephalus townsendi (Guadalupe fur seal)
Callorhinus ursinus (Northern fur seal)
Eumetopias jubatus (Steller sea lion)****
Zalophus californianus (California sea lion)
Family Phocidae (True seals)
Mirounga angustirostris (Northern elephant seal)
Phoca vitulina (Harbor seal)
This list is accurate as of December 2007. However, as DNA-based research proliferates
and field work increases, some of these taxonomies will undergo significant revision.
The status of Bryde’s whales is a case in point. Two species were recently delineated
from the previously accepted one, and it’s likely that more species will be split off (the
local species has been changed from Balaenoptera edeni to Balaenoptera brydei).
*Known from very limited sightings.
**Species recently revised.
***Known from skeletal material only in this range.
****The last reliable sighting of this species in the Santa Barbara Channel was in 1984.
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Evolution of Marine Mammals
45 – 50 million years ago a hoofed animal resembling pigs and cows, called mesonychids,
began feeding along the shores of ancient seas, as the number of animals increased some were
forced to deeper water to feed. This in turn created pressure on these animals to dive for food
and plants in deeper water, which led to the development of the archaeocete (40 million years
ago). The archaeocete’s blowholes started to move further back on its head, and the front legs
developed into flippers, and the tail developed a paddle-like structure. Baleen whales emerged in
fossil records some 20 –25 million years during the Oligocene period. A modern day example of
the process of adaptation to aquatic life can be found on the Tokelau islands in the South Pacific
where pigs feed on the coral reefs at low tide. Genetically, todays closest relative to whales are
cows, pigs, and horses. Diving for food filled a new niche in evolutionary development, and has
allowed for the development of the largest animal on earth. A total of 79 species of cetaceans
now roam the world’s oceans. Pinnipeds evolved from a “bear-like”, carnivorous ancestor ~30
million years ago Oligocene/ Miocene. Sea otters more recent ~ 5-7 million years ago
Miocene/Pliocene. However, it is still unclear whether or not the seals, sea lions and walruses
evolved from a common ancestor such as the cetaceans (monophyletic vs. diphyletic).
Facts on the evolution of whales:
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Returned to the sea 30-70 million years ago
Hairless, streamlined bodies
Modified arms created flippers
loss of all external evidence of hind legs
No Sebaceous glands (produce oil and lubricants for hair and skin of terrestrial
mammals)
No sweat glands
No scent glands
No ear flaps
Nipples of females retract into slits on either side when not in use
Nostrils (blowholes) situated on top of head
Pair of blowholes in baleen whales
Single blowhole in toothed whales
Upper and lower jaw elongated
Thick layer of body fat, to protect from loss of body heat. Up to 1/3 of body mass can be
fat
Respiratory and circulatory systems specialized to withstand long periods underwater
The number of red blood corpuscles per millimeter is twice that of terrestrial mammals
Pulse rate during a dive can drop to 1/8 of what it may be at the surface
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Whale, Dolphin, and Porpoise Terms
ADAPTATION
Physical and behavioral changes that occur slowly over time that help an
organism live more easily in its environment
AMBERGRIS
Wax like substance found in the intestines of Sperm whales, used in
perfumes.
BALEEN
Rows of triangular plates that hang from the upper jaws of Mysticetes.
The plates of baleen are composed of a material which is very similar to
fingernails. The baleen is used to filter the planktonic prey and fish from
the water.
BLOWHOLE
The nasal opening of a whale, which is located on the top of the head.
Baleen whales have two external nasal openings while toothed whales
have only one.
CALF
A new born or young whale that is still dependent on its mother for
protection and of nourishment.
CETACEAN
Marine mammals of the order Cetacea which includes the great whales,
dolphins and porpoises. Generally, all members of this order are
considered whales.
COW
A mature female whale.
DOLPHIN
A toothed whale having sharp, conical teeth, and a beak.
DORSAL FIN
A triangular structure found along the back of many whales, thought to
help stabilize the whale during swimming, diving and regulation of body
temperature.
ECHOLOCATION The process employed by toothed whales to locate distant objects by use
of sound waves that are reflected back to the whale from the object.
EVOLUTION
A process of continuous growth and change over millions of years.
FLIPPER
A famous dolphin from the television program of the same name and the
distinctive structures found on either side of the whale’s body. These are
for steering, turning, and controlling the whale's vertical position in the
water.
KRILL
The common name for euphausiid shrimp, upon which are small
crustaceans that many species of baleen whales feed.
CHAPTER 7
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Whale, Dolphin, and Porpoise Terms
MELON
A wax-like organ, located in the front of the skull of toothed whales, used
for echolocation.
MYSTICETE
A sub-order of whales that possess baleen instead of teeth. These whales
strain their food from the water with their baleen. The Mysticete include
the largest animals on earth, such as the Blue and the Finback whale.
ODONTOCETE
A sub-order of whales which have teeth of uniform shape and function.
Dolphins, porpoises, and the Sperm whale are all Odontocete. These
whales eat primarily fish and squid.
PORPOISE
A toothed whale having rounded teeth and no beak.
SPOUT
The expired air of a whale that forms "steam," (a cloud of condensed
water vapor) often called the “blow."
A series of pleats found along the underside of most Mysticetes.
VENTRAL GROOVES
These grooves are related to the feeding behavior of the whales which
requires them to expand and accommodate large volumes of water.
VERTEBRAE
CHAPTER 7
The bones that make up the backbone of vertebrate animals.
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Porpoises vs Dolphins
Characteristics
Porpoises
Dolphins
Family
Phocoenidae
Delphinidae
Length
Seldom exceed 7 feet
Many can exceed 10 feet
Shape
More robust, chubby
Lean sleek body
Triangular
Sickle-shaped
Lack a rostrum or a beak.
Very prominent rostrum (often)
Spade-shaped
Cone-shaped
Life span
Rarely to 20 years
Up to 50 years
Behavior
Shy (usually)
Ride bow waves
Harbor porpoise
Dall's porpoise
Common dolphin
Bottlenose dolphin
Pacific white-sided dolphin
Risso's dolphin
Killer whale (Orca)
Pilot whale
Dorsal fin
"Nose"
Teeth
Examples
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CHAPTER 7
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Page 1
Marine Mammal Identification Keys, © Peter Howorth
Key to Identifying Seals, Sea Lions and Sea Otters in the Ocean
Seals:
No external earlobes; heads smooth
Dive by descending vertically until snout disappears
Very short, stubby tails
Swim with hind flippers
Pacific harbor seal Phoca vitulina richardsi
Northern elephant seal Mirounga angustirostris
Round head profile
Round head profile
Ear holes
Smooth head; no visible ear holes
Long whiskers
Long black whiskers
Short fore flippers with claws
Short fore flippers with claws
Short hind flippers with claws
Short hind flippers without claws
Mottled coat: silver, tan, brown, and/or black
Uniform tan or brown
Coastal
Coastal and pelagic
Sometimes rafts in kelp with hind flippers out of water
Males and females:
Male:
Female:
Very little difference in size, shape, length, or weight
Massive head
Large, wide skull
Both up to about 300 pounds and 6 feet
Pronounced snout
Up to 2000 pounds
Up to 5000 pounds
Notes: The main differences between the two species are the massive size, thicker head, and uniform color of the northern elephant
seal.
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Page 2
Marine Mammal Identification Keys, © Peter Howorth
Key to Identifying Seals, Sea Lions and Sea Otters in the Ocean
Sea lions, fur seals and sea otters:
External earlobes
Dive by swimming forward, then submerging headfirst
Sea lions:
Yellowish tan, brown or black coat
Very short, stubby tails
Swim with fore flippers
Coastal out to about 200 miles; sometimes raft in kelp or float on surface with front and/or hind flippers out of water
California sea lion Zalophus californianus c.
Steller sea lion Eumetopias jubatus
Concave head profile, long head
Concave head profile, boxlike, thicker head features
Short, stubby ears
Short, stubby ears
Tan to black whiskers about length of snout
Tan to black whiskers about length of snout
Long fore flippers edged with black
Long fore flippers edged with black
Short hind flippers
Short hind flippers
Male:
Female:
Male:
Female:
Prominent crest on head
Long, streamlined head
Massive shoulders & head
Large, wide skull
Crest white or light tan
Yellowish tan to brown
Thicker fur around shoulders Yellow or tan fur
Very dark brown or black
175-350 pounds
Yellow or tan fur
5-6 feet long
1600-2000 pounds
body
350-500 pounds
600-1200 pounds
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Page 3
Marine Mammal Identification Keys, © Peter Howorth
6-8 feet long
Notes: The main differences between the two species are the massive size, thicker, boxier head, and yellow to tan color of the
Steller sea lion.
Key to Identifying Seals, Sea Lions and Sea Otters in the Ocean
Sea lions, fur seals and sea otters:
External earlobes
Dive by swimming forward, then submerging headfirst
Fur Seals:
Reddish brown, brown or black coat
Very short, stubby tails
Swim with fore flippers
Pelagic; sometimes raft in kelp or float on surface with front and/or hind flippers out of water
Often roll and rub themselves with flippers
Northern fur seal Callorhinus ursinus
Guadalupe fur seal Arctocephalus townsendi
Convex head profile
Concave head profile
Short, stubby snout
Long, collie-like snout
Very long, down-turned ears
Medium length ears
Very long, often white whiskers
Long tan whiskers
White patches on cheeks and breast
Generally similar to California sea lion
Large, round eyes
Hind flippers short
Hind flippers long and flexible; equal to 1/3 body length
Male:
Female:
Male:
Female:
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Page 4
Marine Mammal Identification Keys, © Peter Howorth
Thick neck and shoulders
125-175 pounds
Thick neck and shoulders
125-175 pounds
Up to 450 pounds
5 feet
450 pounds
5 feet
6 feet
6 feet
Notes: The main differences between the two species are the short, stubby snouts and very long whiskers and hind flippers of the
northern fur seal, which contrast with the collie-like snout of the Guadalupe.
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Page 5
Marine Mammal Identification Keys, © Peter Howorth
Key to Identifying Seals, Sea Lions and Sea Otters in the Ocean
Sea lions, fur seals and sea otters:
External earlobes
Dive by swimming forward, then submerging headfirst
Southern sea otters
Enhydra lutris nereis
Brown or black coat; white heads in older animals
Long, bushy tails
Swim with hind flippers
Stay very close to coast; sometimes raft in kelp or float on surface with front and/or hind flippers out of water
Often roll and rub themselves with flippers
Often place prey on bellies
Whiskers end in horizontal line beneath snouts
Male:
Female:
Up to 80 pounds
Up to 50 pounds or so
Up to 5 feet
Up to about 4 feet
Notes: The main difference between sea otters and pinnipeds is the small size of the otter. Also, sea otters only stay down from a
few seconds to a few minutes at most; pinnipeds can remain submerged much longer. Finally, sea otters generally remain very
close to shore in water 120 feet in depth or less.
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Page 6
Marine Mammal Identification Keys, © Peter Howorth
Key to Identifying Large Whales off California
Species
Blow
Dorsal
Flukes
Habitat
Key features
Blue
Tall and straight Very small (up to 1 foot),
very far back, appears after
blow
Huge, straight when seen from rear Near escarpments; open Glows turquoise, mottled
sea; subtemperate in CA blue-gray, wide, flat head
Fin
Similar to above, Larger (18 to 24”); appears with
smaller
blow or immediately afterward
Virtually never seen
Near escarpments &
open ocean;
subtemperate &
temperate in CA
Sei
Medium, bushy
Large (24” or more), 1/3
forward of flukes
Virtually never seen
Tropical to subtemperate; Dorsal large, third
rare off CA
of length forward from
flukes, gray with oval white
patches
Bryde’s
Short, bushy
Medium (18-24”)
appears to sink when diving
Virtually never seen
Tropical to temperate;
extremely rare off CA
Three ridges on snout
Minke
Short, bushy
Small (12-18”)
Virtually never seen
Fairly common near
escarpments and plains
Smallest rorqual whale
(35’); white stripe on each
flipper, sharp, pointed
snout
Humpback
Tall and straight, Misshapen, bumpy
sometimes bushy
Large, down-turned at tips
Common near
escarpments
Down-turned tips of flukes,
long flippers, warty snout
Gray
Heart-shaped
None, but bumpy ridges
Straight when diving
Coastal
Mottled gray color, heartshaped blow
North Pacific
right
short, bushy
None
Large
Extremely rare off CA
No dorsal, high arch to
lower jaw
Sperm
Short, bushy,
forward and to
left
None, but bumpy
Hang straight up for long time
Offshore canyons
and seamounts
Boxy head shape; blow
forward and to left
Baird’s beaked
Short, bushy
Triangular; 1/3 forward of flukes
Sometimes shown
Continental borderline;
rare
Bulbous head; dolphinlike
snout
Lower right jaw white, rest
gray or black, sometimes
gray or white chevron
behind head.
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