The term ‘’Marine Mammals’’ refers to all mammals that derive all or most of their food from the Marine
Environment and in some cases from freshwater environment.
WHAT ARE THE MARINE MAMMALS ?
These are warm-blooded aquatic vertebrates belonging to the class Mammalia , breath air through lungs,
locomotion by fins and flippers, Viviparous(internal nourishment and development of a fetus) and produce
milk(mammary glands) to nurse their young ones.
They represent a variety of ecological roles, including herbivores(manatees), filter feeder(baleen whales), and top
predators(killer whales). Marine mammals are coming from land-dwelling ancestor.
All species are protected under the Marine Mammal Protection Act(MMPA) 1972, some are protected under ESA
and CITES(Convention on International Trade in Endangered Species of Wild Flora and Fauna).
Name IUCN STATUS
Blue Whale, Bowhead Whale, Gray Whale, False killer Whale, Hector’s Dolphin,
Humpback Whale, Killer Whale, North Atlantic right Whale, Sperm Whale, Vaquita
Bearded seal, Northern Fur seal, Spotted seal, Steller sea lion Threatened
Dugongs, West Indian manatee, Amazonian manatee Endangered, Threatened
Polar Bear, Marine Otter, Southern sea otter Threatened , Endangered
• Body covered with hair, reduced in some.
• Integument with sweat, scent, sebaceous and mammary glands(Cetaceans and sirenians lack both sweat and sebaceous
• Mouth with teeth(baleen whales lack teeth in adult stage).
• Movable eyelids and fleshy external ears(Cetaceans and many pinnipeds lack the fleshy external ear).
• Forelimbs in most, adapted for many forms of locomotion: In cetaceans, modified into paddle-like flippers and the hindlimbs
are totally absent, In pinnipeds the limbs modified for swimming and steering, Sirenians forelimbs are modified into flippers
and their hindlimbs are reduced to nothing more than a vestigial pelvis.
• Four-chambered heart.
• Respiration system with lungs and larynx; presence of muscular diaphragm.
• Brain highly developed.
• Endothermic and homeothermic.
• Viviparous( Internal fertilization); eggs developed in a uterus with placental attachment with fetal membranes (amnion,
• Young nourished by milk from mammary glands.
• The hypodermis or blubber layer is a loose connective tissue beneath the skin composed of fat cells interlayered with
bundles of collagen of marine mammals(except polar bear and sea otter). This thick layer of fat provides insulation
from cold ocean temperature, also it can store energy.
• Cylindrical body shape with small appendages reduce the surface are to volume ratio of the body, reduces heat loss.
• Fur in marine mammals functions by trapping dry air next to the skin and keeping water away from the skin surface,
thus maintain the temperature.
• They have a Countercurrent heat exchange mechanism, involves an intertwined network of veins and arteries
where heat from the arteries is transferred to the veins as they pass each other before getting to extremities , thus
reducing heat loss.
BREATHING AND DIVING ADAPTION :
• To withstand with the pressure, They can exhale up to 90% of the of the air before a dive, as they have very muscular and
efficient lungs. Thus, removing the air from their body, they have very little problems with changing pressure.
• They have a higher percentage of red blood cells (Human= 36%, Seals=50%), making their blood very thick and viscous but
more adept at O2 storage. They also have a high conc. Of hemoglobin in their blood and myoglobin in their muscle, both can
store large amount of O2 so it can hold their breath during dive.
• They have a high tolerance to CO2 and lactic acid, their muscle can work anaerobically while they hold their breath.
• The diving response help them to conserve energy and use O2 efficiently during a dive.
COMMUNICATION: They can communicate with or without sound.
• Acoustic communication: 1.Pinnipeds, polar bears and sea otters produce sound in air and in water by vibration of the vocal
folds in the larynx, into the throat and out through the mouth. Their arial vocalization includes barks, cries, grunts, howls, roars
and squeaks and underwater includes bell-like sound, warbles and whistles.
2. Odontocetes produce sounds(whistles, burst pulses) by a complex system of air sacs and specialized soft tissues that vibrate
as air moves through the passages . In the melon(lipid-filled sac) a narrow/broad beam of sound is produced.
3. Mysticetes use only larynx for sound production, sound is produced by a thick, U-shaped ridge of tissue(=vocal folds), when air
vibrate and produce sound.
4. They can also produce sounds by slapping fluke (in cetaceans) or slapping pectoral flippers.
• Non-acoustic communication: 1. Muzzle-to-muzzle contact is also common among pinnipeds when they greet one another. 2.
Dolphins and whales may rub or caress one another with their flippers and other appendages.
Echolocation involves an active process of emitting in the form of short broad-spectrum burst-pulses (clicks) and gaining
information on the surrounding environment (nearby objects, obstructions) by analysis of the returning echoes. The only marine
mammals known to have evolved echolocation are the odontocetes. It enables to locate prey, navigation and hide from predator.
WHISKERS: Pinnipeds and fissipeds have well developed facial whiskers , during deep-diving it gives adapted vision and also
help to locate prey by detecting hydrodynamic trails generated by the prey.
• Cetacea comes from the Greek “ketos”(Latin cetos) meaning sea monster or any large marine creature
• The Greek philosopher Aristotle was the first to study these animals through direct observation by performing
dissections on them.
• Size ranges from 1.2m to 33.5m in length.(Blue Whales is the largest sp)
• They are characterized by having a fusiform, streamlined (“torpedo-shape”) body, with paddle-like flippers
(modified forelimbs) used for steering, balancing, and stopping. (not for moving forward)
• Propulsion by up and down movement of tail ends with a paired flattened horizontal flukes.
• Most species also have a dorsal fin, which serves as a stabilizer.
• The flukes and dorsal fin are mostly composed of dense connective tissue but no bone.
• They have a smooth, rubbery skin, the lack of glands and hairs, instead they have developed a thick layer of fat
called blubber under the skin that insulates them from the cold and provides buoyancy,
• “telescoped skull” i.e., both the upper and lower jaw extending well beyond the entrance of the nasal passages
• The position of nostrils has shifted to the top of the head creating a blowhole that allows them to more effectively
come to the surface for air.
• 85 extant species and entirely aquatic group comprising Whales, dolphins and porpoises.
• Derived from Greek odontos, a tooth; ketos (Gr) = a
sea monster, whale.
• Most diverse group, comprising 72 species(including
sperm whales, killer whales, dolphins, porpoises, and
• usually small to medium in size.
• The most distinguishing features of odontocetes are
the presence of teeth in one or both jaws.
• Presence of one blowholes.
• They have a more or less developed melon, i.e., a
region of adipose tissue on top of the skull with
connective tissue within it, used in their acoustic
• Besides communication, they also use sounds for
echolocation, food search, and for navigational
• Mostly marine, but some families travel into rivers or
live their entire lives there(some Dolphins).
• As they are capable of grabbing larger, individual
prey like fish, squid: even sea birds and mammals.
(Toothed Whales) (Baleen Whales)
• Derived from Greek word “mustakos “( =
moustache);“ketus“(= sea monster, whale).(referring
to the baleen plates attached to the upper jaw)
• Group having largest animal on the planet(Antarctic
blue whales,98feet in length).
• Presence of two blowholes.
• Characterized by having a series of vertical baleen
plates(flexible substance made of keratin/ whalebones
) instead of teeth , hang in the mouth from the upper
jaw to sieve planktonic creatures from water(filter-
• Diet include zooplankton such as shrimp-like krill
other crustaceans, fishes such as mackerel and herring,
• Exhibit various feeding techniques, including “skim
feeding” in the right whales, “gulp feeding", "bubble
netting” in Humpback whales, “bottom feeding” in
• The order Carnivora is comprised of 11 families and about 275 species and includes sea otters, polar bears, sea
lions, walruses, seals,
• They have well-developed claws and a pair of specialized cheek blade-like teeth for cutting/tearing hard foods.
• Teeth are the carnassial(blade-like teeth) that in pinnipeds are modified as premolars.
• Mostly semiaquatic, often hauling out on land(except sea otter).
• They have powerful jaws for stabbing and holding prey and incisors for biting off pieces.
• Pinnipedia comes from the Latin ‘pinna’ (=feather, wing, fin) and ‘pedis’(=foot), referring to the paddle-like fore-
and hind limbs, use for locomotion on and in the water.
• They have adapted to an amphibious marine existence, they forage at sea but most come ashore or onto ice at
some time of the year for matting, giving birth or molting purpose.
• They have four webbed flippers used to propel their spindle-shaped bodies.
• Sensory organs are adapted to function in both air and water.
• Large eyes and well-developed whiskers allow feeding in dimly lit water.
• They have retained canine teeth but molars are modified for consuming whole prey.
• They have a thick layer of fur(primarily insulated by blubber).
• Externally the ears are small or entirely absent but they have excellent hearing capability especially underwater.
• Size ranges from 1.1-6.5 m .
• Habitat ranging from ice to tropics, coastal to pelagic water and may live a migratory or sedentary existence.
• Opportunistic feeders and consume prey whole or in chunks.
• 34 species comprising seals, sea lions and the walrus.
Seals Sea lion Walrus
• No external ear flaps, instead have
• Limbs have claws and smaller
• Rear fins cannot bend down from
the body so they are not able to
walk on land.
• Unique ear canal and well
protected to efficiently withstand
• Active hunters , feed on fish,
squid, octopus ,penguins
• Lack external ear flaps.
• Limbs modified to form fins
for locomotion in water and
on land effectively.
• Have adipose layer of
fat(15mm thick) , helps
• Presence of long canine
• Rounded head, wide
muzzle with thick vibrissae
• Sociable animal
• Presence of external ear flaps.
• Unlike seals , their long limbs
can flex to move on land
• Fur coat is short, less coarse
and sticks to the skin
• Long fins covered with the skin
• Inhibit both water and land
• They are “split-footed” members of the order Carnivora and are more closely related to terrestrial carnivores, as
they lack many of the physiologic adaptation to marine life seen in pinnipeds and cetaceans.
• They comprises a unique group as they depend on the sea for survival or as a hunting ground, though they spend
most of their time on land.
• Mainly sea otters and polar bears are the marine fissipeds.
• They spend most of their time on land and only part of time in the water.
•Compared to other bears, polar bears have elongated bodies and long
• Strong swimmers(can swim for several hours at a time over long
• Elongated muzzel with a “Roman-nosed” (slightly arched) snout
• Thick layer of fat up to 11cm keeps them warm while swimming,
• Temperature is maintained through a series of fur(lower fuzzy hair
and outer guard hair), a tough hide and an insulating fat layer,
• Incisors to shear off pieces of blubber and flesh. Canine teeth grasp
prey and tear tough hides. Jagged premolars and molars tear and chew.
• Black footpads on the bottom of each paw are covered by small, soft
papillae which help them to grip on the ice and keep them from
• Thick, curved, sharp claws to catch and hold prey,
• Short and compact tail and ears to prevent heat loss,
• Black eye and nose to absorb heat.
• Fur is oily and water repellent. which make them water-resistance.
• Apex predator.
• Smallest, most recently evolved, and least “marine” marine
• Lack of a blubber layer and absolute dependence on fur for
• They have external ears
• Long whiskers help them to detect vibrations in murky water
• Sensitive forepaws with retractable claws which help them to
locate and capture prey underwater
• Webbed and flipper-like hind feet to propel them through the
• Long, flattened tail used as a rudder and for propulsion.
• Two layers of fur, underlying short brown dense fur and a top
layer of long, waterproof guard hairs for keeping them warm
• Flattened and rounded molar teeth with no cutting cusps
• Eat 25% of their bw./day, Diet consists of sea urchin, crabs,
mussels and clams.
• Party animal(intelligent, rambunctious & gregarious)
• The Greek name SIRENIA is derived from the sirens of Greek mythology.
• Like cetaceans, sirenians spend their entire lives in water, group of animal.
• They are herbivores group of animals and confined to shallow coastal waters.
• Their forelimbs are modified to form flippers, their hindlimbs are reduced to a vestigial pelvis, and their tail is enlarged and
flattened horizontally to form a fluke or paddle.
• Streamlined body and nearly hairless.
• Eyes lack obvious eyelids, but are closed by a sphincter-like mechanism.
• 2 nostrils are located on top of their snouts(muzzle) and closed by valves.
• Lips are large and mobile, and they are covered with stiff bristles.
• Skull is unique with large premaxillae that are deflected downward.
• Ears have no pinnae.
• They are social, occurring in large aggregations and interacting frequently with one another.
• Mostly are endangered species(Steller’s sea cow extinct 1768).
• living sirenians consist of one species of dugongs (family Dugongidae) and three species of manatees (family Trichechidae)
• The sole sirenian species found in the Indo-pacific.
• Adults range in length from 2.4 to 4 meters and weigh 230 to 908 kg.
• Streamlined body(like cetaceans),divisible into head, trunk and tail.
• Thick, tough, smooth skin sprinkled with short hair.
• Valve like nostrils found on top of snout.
• The upper lip has a broad, horseshoe-shaped extension(muzzle), which overlaps the sides of the moth
• Muzzle carrying a large number of bristles, hair and pores.
• Forelimbs are modified as flippers( 35-45 cm long), containing no nails for propulsion and steering.
• The tail fluke( lobes of tail) is horizontal and crescent-shaped and with a V-shaped notch: used for locomotion.
• Incisors present in the form of tasks(in males).
• Primarily herbivorous, bottom-feeding browsers.
• Dorsal fin is absent.
• IUCN RED LIST status : Vulnerable.
• They have a fluked tail , made up of two separate
lobes joined together in the middle.
• The snout is broad, short and trunk-like, faces
downwards for feeding off the ocean floor(strictly
• Strictly marine.
• They have only one mate and live as a couple for
• They have two incisors/tusks.
• They have horizontal, paddle-shaped tail with only one
lobe moving up and down during swimming.
• They have a divided upper lip and a shorter snout, so
they can feed at any level in the water column
• May live in the sea or in estuarine or riverine waters.
• They are devout polygamists, a male can have several
• Do not have tusks, instead they have molar teeth, no
distinction between molars and pre-molar and replace
molars throughout life “marching molars”.
• Aldemaro Romero, The Biology of Marine Mammals,2009
• Kumaran Sathasivam, Marine Mammals of India,2004,Universities Press(India)Private Limited
• Ratheesh Kumar R et al , Taxonomy of Marine Mammals,2022