Characteristics of Marine Mammals All organisms in class Mammalia share these characteristics: They have hair on some part of the body. Oil glands lubricate and condition hair and skin Hair, horns, claws, nails, hooves grow from skin They nourish their young with milk provided by mammary glands. Mammals are homeothermic (warm-blooded) with a constant internal temperature. The majority give birth to live young.

Hair Many have thick fur Whales and dolphins have little hair Porcupines and hedgehogs have modified hairs (quills and spines) Cats, mice and otters have sensory hairs (whiskers)

Teeth Incisors – front teeth that bite and cut Canines – grip and tear Premolars and molars – shred, grind, crush Herbivores = animals that eat only plants Carnivores = animals that eat only meat Omnivores = animals that eat both plants and meat

Nervous system Brain, spinal cord, and nerves Relatively large brain Able to learn and remember Echolocation Depend little on sense of smell and keen vision Emits sound waves and listens for echoes when waves bounce of object Produced by low-frequency clicks vocalization

Reproduction Reproduce sexually Most give birth to living young Parents are protective because young are helpless Penis is internal to aid in streamlining Contains a bone to maintain rigidity Can be as long as 10 ft (over 3 m) Males create breeding territories Harem Bachelor groups

Digestive system Carnivores have short digestive systems Meat is more easily digested than plants Circulatory system Four-chambered hearts Network of blood vessels Well-developed lungs

Mammal classification (based on how young develop) 1. Monotremes Lay eggs and female incubates them When young hatch, they lick milk from female’s skin Ex: Duckbilled platypus

2. Marsupials Pouched mammals Kangaroo gives birth to tiny baby kangaroo (size of a honeybee) Baby kangaroo crawls into pouch and attaches to nipple After a few months, the joey (young kangaroo) crawls out of pouch Ex: Opossums, Koalas, Tasmanian devils

3. Placental mammals Embryo develops inside uterus Time in uterus is called gestation period Placenta Saclike organ developed by growing embryo Attaches to the uterus Absorbs oxygen and food from mother’s blood Umbilical cord attaches embryo to placenta Mother’s blood never mixes with the blood of the embryo

The marine environment poses several challenges to mammalian physiology: 1. Compared to living in air, life in water demands high oxygen consumption. Marine mammals meet this challenge by breathing air. 2. There is a need to dive holding their breath for long periods. They use myoglobin, a protein, to bind reversibly with oxygen to make it available for use in metabolism. They use the mammalian diving reflex – is when diving pulse rate slows and blood flow diverts from the muscles to the heart and brain.

Characteristics of Marine Mammals (continued) 3. The water pressure and a need to equalize. Marine mammals’ lungs and sinuses are very flexible, allowing compression without pain or injury. Some dolphins and whales have lungs that engorge with blood thus offsetting the compressed space. 4. The challenge of easy movement through the dense medium of water. The use of streamlining and hydrodynamics helps with this. 5. The challenge of the senses. They need to hear, see, and smell underwater. Dolphins and whales use echolocation (natural sonar) to determine distance, size, density, and shape. Seals and sea lions have sensitive hearing and excellent underwater eyesight. They see poorly above water, but have a keen sense of smell.

Special Attributes of Seals and Sea Lions The seals and sea lions belong in order Pinnipedia. Seals: don’t have ear flaps, rear flippers point backward and cannot rotate forward, out of water seals crawl on their stomachs. Sea Lions: have ear flaps, hind flippers rotate, can sit upright and run. Walrus: don’t have ear flaps, hind flippers rotate, can sit upright.

Special Attributes of Dolphins, Whales and Porpoises Whales, porpoises, and dolphins come from different families organized under the order Cetacea. Cetaceans are divided into two suborders: Suborder Mysticeti: a group of filter feeders made up of baleen whales. Suborder Odontoceti: a group of toothed whales made up of sperm whales, dolphins and porpoises. They are predators. Family Delphinidae: are the dolphins and orcas, one of the most varied and successful groups among the toothed whales. Most cetacea use echolocation and communicate by sound.

Special Attributes of Dugongs and Manatees Dugongs and manatees (sometimes called sea cows) belong to order Sirenia, which has four species. All four are the only herbivorous marine mammals. Manatees are known for migrating to and from fresh- and saltwater environments.

Marine Mammals and Human Interaction Human activities have endangered marine mammals and continue to do so. Whaling brought whales to the verge of extinction. Banned or greatly limited by international convention today, some species seem on the rise, others do not seem to be recovering. People have hunted seals for their fur and manatees for meat. Dolphins have been killed as bycatch in tuna fishing. Pollution and overfishing raise new threats. Because of their high metabolisms and energy demands, marine mammals require highly productive environments to survive.