Lecture 15: Marine Mammals

• Marine mammals are warm-blooded, have hair or fur, breathe air, nurse their young with milk, and give birth to live offspring.
• Diving physiology of marine mammals: do not breathe a continuous supply of air and can collapse their alveoli during dives.
• Dive response for oxygen storage: high volume of blood, high carrying capacity of blood, high oxygen carrying capacity of muscles and brain tissue, release of red blood cells saturated with oxygen from the spleen.
• Dive response for oxygen demand: exhibit dive bradycardia (lowering of the heart rate), vasoconstriction of protracted dives (switch of blood flow to vital organs only), lower metabolic rate.
• Reduced ventilatory response to carbon dioxide: no strong urge to breathe.
• High lactic acid tolerance: anaerobic respiration due to lack of oxygen brought to muscles.
• The three orders of marine mammals: Carnivora, Sirenia, Cetartiodactyla.
• Two parts of Carnivora: Marine Fissipedia and Pinnipedia
• Marine Fissipedia: sea otters and polar bears
• Pinnipedia: seals, sea lions, and walruses
• Pinniped reproduction: often born on ice, breed on ice sheets, time of lactation depends on species and habitats
• Pinniped reproduction: breeding beaches, sexual dimorphism, polygyny
• Carnivora Otariids: eared seals (sea lions and fur seals); small ears, swim with forelimbs, walk on land, long neck
• Carnivora Phocids: true seals; no external ears, scull hind flippers, slither on land, short neck
• Sea lions have a coat of short coarse hairs.
• Fur seals have thick woolly underfur with stiff guard hairs.
• Walruses have no external ears, swim with forelimbs, have a long neck, and walk on land.
• Walruses have sensory vibrissae that is useful for detecting organisms within substrates. Either through chemical responses or tactile responses.
• Order Sirenia: Manatees and Dugongs
• Manatees are found in marine and freshwater environments. They have a small head with long flippers and a rounded tail.
• Dugongs are only found in marine environments. They have a large head, short flippers, a notched tail, and a downward angled face.
• Stellar's Sea Cow is part of the order Sirenia. Discovered in 1740s and went extinct in 1768. Found within the Arctic Waters.
• Order Catartiodactyla: Whales and Dolphins
• Two types of Cetartiodactyla: Mysticeti and Odontoceti
• Mysticeti do not have teeth; use of baleen plates.
• Odontoceti have teeth.
• Whales and dolphins have heat conservation through countercurrent blood flow in cetacean flippers and tail flukes. A large artery is surrounded by smaller veins; the artery expands and collapses for heat dissipation.
• Whales and dolphin reproduction: mate and give birth in water, form pods, typically only one offspring per cycle, have very fat rich milk for young to grow quickly.
• Mysticeti: Baleen whales (right whales, rorquals, gray whale)
• Odontoceti: Toothed whales (sperm whales, dolphins, killer whales, porpoises, white whales).
• Types of whale and dolphin surfacing: spy hopping (bobbing), breaching (coming out of the water), and tail slapping as an aggressive behavior.
• Mysticeti Baleen whales have 150-400 baleen plates in the upper jaw.
• Types of feeding for mysticeti: skimming (right and bowhead whales), gulping (blue whales, fin whales, humpback whales), bubblenetting (humpback whales), suction feeding (grey whales).
• Odonticeti use echolocation for low (genera) and high frequency (precise) emission.
• Echolocation process: air movement though the nasal sacs, concentration in the melon, reflection absorbed by fats in the lower jaw and brought to the inner ear for the creation of a mental image.
• Anthropogenic noise can interfere with echolocation systems by creating a sensitivity decrease that no longer allows the detection of certain frequencies.
• Odontoceti sperm whales contain the spermaceti organ which is a high grade wax used to focus sound waves. Also contain the ambergris which is a waxy material used to protect the digestive tract.
• Odontoceti dolphins and porpoises have differences in the rostrum (snout), dorsal fin, teeth, and distribution.

  Dolphins have longer rostrum, more prominent dorsal fin, sharper teeth
• Odontoceti killer whale is the largest of dolphins. Prey on fish, seals, sea lions, baby walruses, penguins, and other cetaceans.

  Residents and transients (stay in one area or move about)
• Odonoticti white whales are composed of the Beluga whale and the Narwhal.