Marine Mammals

Marine Mammals What does it mean to be a marine mammal? What are some other Marine Mammals? Fur Give Birth to Live young Mother produce milk to feed their young Live in the ocean

Pinnipeds, Cetaceans, Manatees/Dugongs, Sea Otters, Polar Bears Each group is adapted to life in the water. All mammals but have evolved separately. Cetaceans share a common ancestor with cows. Manatees and Dugong are closely related to elephants. Polar bears are considered marine mammals because they can swim great distances, live on floating ice packs and live closely tied to the sea. Photograph from Save The Manatee Club Photograph by Dan Guravich from Polar Bears Alive Photograph by Warren and Leora Worthington

Order Sirenia Manatees, Dugongs, Sea Cows Herbivorous diet consisting of aquatic plants Steller sea cow hunted to extinction Mermaid myths believed to be attributed manatee sightings Threatened to habitat destruction, boat collisions and other anthropogenic threats Closest living relatives elephants and rock hyraxes. Graphics from Save the Manatee Club website: Rock hyraxes live in Africa. Photo from

Order Carnivora Sea Otters (Enhydra lutris) Distributed throughout the northern Pacific rim from Japan to Baja California Use air trapped in fur instead of blubber to maintain body temperature Use tools Threats include oil spills, pollution and fishery interactions Photo by R. Mattison.

Order Carnivora Family Ursidae Polar Bears Spend significant portion of life in/on water, life closely tied to ocean Scientific Name – Ursus maritimus Latin for Sea Bear Distribution – Circum polar Diet consists primarily of ringed and bearded seals. But feed on many other animals, vegetation, carcasses and garbage. Conservation concerns include bear hunting, oil exploration and POPs. Graphics obtained from Sea World website:

Introduction to Pinnipeds Order Carnivora Sub Order Pinnipedia Sea lions, fur seals, walruses and seals 33 species Evolved 25 million years ago from bear-like ancestor Two endangered species in USA: Steller Sea Lions and Hawaiian Monk Seals Photographs from the Seal Conservation Society web site. Walrus Steller Sea Lion Hawaiian Monk Seal

25 Million years Ago Sea lions & Fur seals True seals Walrus Modern Bears

© 2006 Thomson-Brooks Cole Swimming and Diving Fast swimmers and expert divers Adaptations for diving –exhale before diving to decrease buoyancy –metabolism slows by 20% and heart rate decreases while under water –blood redistributed to direct oxygen to vital organs such as the brain and heart

© 2006 Thomson-Brooks Cole Reproduction in Pinnipeds Most congregate on well-established breeding beaches to mate/give birth Some species are polygynous—bulls establish harems of 15 or more females Males arrive to establish territories; females arrive, give birth to pups, then mate again

© 2006 Thomson-Brooks Cole Reproduction in Pinnipeds Gestation = 9-12 months Lactation period (length of time pups nurse) depends on species and habitat –coldest habitats = shortest lactation –nursing stresses the mother and she loses weight –some breed on pack ice, and must wean pups before it breaks up and becomes dangerous to the pups

Family Otariidae Sea lions and fur seals Range: Worldwide except the Atlantic Ocean Known as the eared seals because they have external ear flap. Can rotate their hind flippers enabling them to walk on all fours. Northern fur seals will stay out at sea for up to eight months. Photographs from the Seal Conservation Society web site. Northern fur seal pups Steller Sea Lion

Family Odobenidae Walrus Two sub species primarily located in the eastern and high Arctic. Also seen in Hudson Bay. Historically their range extended as far south as Cape Cod but the southern populations were overexploited for oil and ivory Easily recognized by their tusks Share characteristics of both Otariids and Phocids. Photographs from the Seal Conservation Society web site.

Family Phocidae True or Earless Seals 18 species alive today 19th species Caribbean Monk Seal extinct Have no visible external ear Move on land by using fore flippers for traction and move caterpillar-like Very diverse group with most species located at both poles Northern Elephant Seal Ribbon Seal Leopard Seal Photographs from the Seal Conservation Society web site.

Order Cetacea Whales, Dolphins and Porpoises Two types: Mysticete- baleen whales Odontocetes - toothed whales Completely aquatic mammals that must surface to breathe air. Mysticetes include right, humpback and gray whales. Odontocetes include sperm whales, killer whales, beaked whales, dolphins and porpoises. Blue whales are the largest animals on the earth. They can reach lengths of 90 feet and 125 tons. Drawings from American Cetacean Society web site

© 2006 Thomson-Brooks Cole General Characteristics of Cetaceans Thought to have evolved from terrestrial carnivores (now extinct) Bodies closely resemble those of fishes and are very streamlined –blowhole—nostril at the top of the head –uniformly thick layer of subcutaneous blubber –streamlining of body results in lack of neck, inability to move head separately –internal ears with wax plugs

© 2006 Thomson-Brooks Cole

Baleen Whales Enormous plates of baleen –each plate has an elongated triangular shape and is anchored at its base to the gum of the upper jaw –composed of keratin—a tough protein—in fibers fused except at the inner edge, where they form a fringe –hundreds of plates form a tight mesh –used to capture plankton, especially krill, and fish

© 2006 Thomson-Brooks Cole Baleen Whales Whale feeds by swimming open-mouthed through the water, then straining out water through baleen –bubble net—a ring of bubbles blown by a humpback whale to trap krill near the surface for collection Baleen is protected by the underlip when the whale is not feeding

© 2006 Thomson-Brooks Cole

Toothed Whales Sperm whales (Physeter macrocephalus) –3 rd blunt snout –have a series of humps on the rear third of the body, no real dorsal fin –aggressive attackers of squid and fish –polygynous – males accompanied by several females –named for spermaceti—an oily, wax-like substance in the animal’s head

© 2006 Thomson-Brooks Cole

Sperm whales (continued) –ambergris—a digestive product; a secretion thought to function in protecting the enormous digestive system from undigested squid beaks and cuttlefish cuttlebone –spermaceti was sought as a high-grade wax; ambergris, as a base for perfumes

© 2006 Thomson-Brooks Cole Toothed Whales Porpoises (family Phocaenidae) –porpoises have a rounded head with no beak (dolphins have a beak) –harbor porpoises are small cetaceans known for great intelligence, and have a wide distribution in the North Atlantic –Dall’s porpoise is perhaps the first animal to be protected by law – Europeans once considered it a rare delicacy

© 2006 Thomson-Brooks Cole Toothed Whales Dolphins (family Delphinidae) –collectively referred to as delphinids –common dolphin has a definite beak separated from the snout by a groove; known for encircling and following ships –bottlenose dolphins are used in research on cetacean intelligence, and as performing animals at aquariums –orca (killer whale) is the largest dolphin; only cetacean that eats homeothermic prey (e.g. seals, sea lions, penguins)

Toothed Whales Dolphins (continued) –pilot whales have a globular head, projecting forehead, and muzzle that forms a small beak known for beaching themselves in large numbers

© 2006 Thomson-Brooks Cole Echolocation Ears are modified to receive a wide range of underwater vibrations Echolocation allows cetaceans to distinguish and hone in on objects Dolphins emit clicking sounds –orientation clicks—low-frequency clicks that give the animal a general idea of its surroundings –discrimination clicks—high-frequency clicks that give the animal a precise picture of a particular object

© 2006 Thomson-Brooks Cole Echolocation No vocal cords; sounds are produced by a ring of muscles in the larynx, which allows control of air flow Sounds are directed by being focused in the melon –melon—an oval mass of fatty, waxy material located between the blowhole and the end of the head Clicking sounds bounce off objects; echoes picked up by sensitive areas on the lower jaw

© 2006 Thomson-Brooks Cole

Echolocation Echoes provide 4 types of information: –direction from which echo is coming –change in frequency –amplitude –time elapsed before the sound returns This reveals object’s range, bearing, size, shape, texture and density Traveling dolphins move their heads side to side and up and down, scanning for objects

© 2006 Thomson-Brooks Cole General Characteristics of Cetaceans Bodies closely resemble those of fishes and are very streamlined (continued) –essentially hairless, except for a few hairs on the head –lack of sweat glands conserves water –forelimbs modified into stabilizing flippers –tail composed of flat flukes composed of dense connective tissue is the main organ of propulsion –countercurrent circulatory system with cold blood directed to un-insulated flippers conserves heat

© 2006 Thomson-Brooks Cole

Adaptations for Diving Prior to dive, a whale inhales an enormous breath, oxygen is rapidly transferred to blood, and the whale exhales to reduce buoyancy Proportionately large lungs with many alveoli—small air sacs –increases internal lung surface area exposed to blood vessels –allows for more efficient diffusion of gases into and out of blood

© 2006 Thomson-Brooks Cole Adaptations for Diving Lungs and rib cage structured to collapse easily upon descent –contain little air during a dive –animal avoids problems of compression and decompression while diving/surfacing During a dive: –metabolism and heart rate decrease –blood is preferentially shunted to vital organs and tissues (e.g. brain, spinal cord)

© 2006 Thomson-Brooks Cole Adaptations for Diving Medulla oblongata is less sensitive to CO 2 levels in blood –can hold breath without urge to breathe Large amounts of hemoglobin and myoglobin –hemoglobin—molecule in red blood cells responsible for carrying oxygen –myoglobin—molecule in muscle tissue that is a reservoir of oxygen for muscle activity

© 2006 Thomson-Brooks Cole Adaptations for Diving Muscles less sensitive to lactic acid –lactic acid—a waste produced during vigorous or extended muscle activity in the presence of insufficient oxygen Exhalation of mucus from blowhole upon surfacing helps eliminate nitrogen from inhaled air, preventing the bends –the bends—condition in which nitrogen gas dissolved in blood comes out of solution and forms gas bubbles

© 2006 Thomson-Brooks Cole Adaptations for Diving Water is prevented from entering respiratory passages –larynx opens into the nasal chambers instead of the back of the throat –cetaceans can open their mouths under water without food or water entering respiratory passages

© 2006 Thomson-Brooks Cole