Marine mammals Characteristics of marine mammals: Warm-blooded Breathe air Have hair (or fur) Bear live young Females have mammary glands that produce milk for their young

Marine mammals: Order Carnivora All members of order Carnivora have prominent canine teeth Includes: Sea otters Polar bears Pinnipeds (flipper-footed) Walrus Seals Sea lions/fur seals California sea lions Figure 14-17c

Differences between seals and sea lions/fur seals Seals: Lack ear flaps Have small front flippers Have claws Cannot rotate hind flippers beneath themselves Figure 14-18

Whales, dolphins and porpoises are cetaceans (Class Mammalia, Order Cetacea) Of all the marine mammals, cetaceans (and sirenians) have made the most complete transition to aquatic life Spend their entire lives in the water The bodies of cetaceans are streamlined and look remarkably fish-like; an example of convergent evolution

Convergent Evolution: Streamlining Convergent evolution is the process by which unrelated species evolve similar physical characteristics because they have similar lifestyles

Whales, Dolphins, and Porpoises Cetaceans have a pair of front flippers, but the rear pair of limbs has virtually disappeared Remain in adults as small, useless bones – Most cetaceans have a dorsal fin, like fishes – Their muscular tail ends in a pair of fin- like, horizontal flukes

Whales, Dolphins, and Porpoises Blubber provides cetaceans with insulation Cetacean nostrils are on top of the head, forming a single, or double opening called the blowhole

There are ~90 species of cetaceans All are marine, except for 5 species of freshwater dolphins Cetaceans are divided into two groups: Toothed whales – includes dolphins & porpoises Baleen whales; toothless, filter-feeding whales Photos property of the Riverhead Foundation

Marine mammals: Order Cetacea Cetacean characteristics: Blowholes on top of skull Skull telescoped (streamlined shape) Very few hairs Includes: Whales, dolphins, and porpoises

Marine mammals: Order Cetacea Figure 14-20

Two suborders of order Cetacea Suborder Odontoceti (toothed whales) Echolocate (send sound through water) Includes killer whale, sperm whale, dolphins, porpoises, and many others Suborder Mysticeti (baleen whales) Have rows of baleen plates instead of teeth Includes blue whale, finback whale, humpback whale, gray whale, and many others

Types of baleen whales Baleen whales include three families: Gray whale (a bottom-feeder with short baleen) Rorqual whales (medium-sized baleen) Balaenopterids (blue whales, finback whales, and other large whales ) Megapterids (humpback whales) Right whales (surface skimmers with long baleen)

Mysticeti: The baleen whales Mysticeti whales have baleen instead of teeth Baleen plates: Hang as parallel rows from the upper jaw Are made of keratin Are used as a strainer to capture zooplankton Allows baleen whales to eat krill and small fish by the ton

Baleen Figure 14-25

Baleen Whales

Baleen whales are characterized not only by their baleen, but by the double opening of their blowholes (double blowhole) Baleen whales can be further divided into the rorquals; rorquals feed by gulping up schools of fish and swarms of krill The lower portion of the throat expands during feeding, along distinctive grooves

BALEEN

The majority of cetaceans are toothed whales Toothed whales use their teeth only to catch and hold prey, not to chew it Toothed whales have a single blowhole (one opening) on the top of their head Though they are all whales, most of the small toothed whales are called dolphins or porpoises

The Toothed Whale Whales The toothed “whales” include the sperm whale, beluga, pilot whales, beaked whales, and orca, each divided into their own families

Differences between dolphins and porpoises Dolphins have: An elongated snout (rostrum) A sickle-shaped (falcate) dorsal fin Teeth that end in points Figure Killer whale jawbone

Generation of Odontoceti echolocation clicks Figure 14-23

Echolocation

Odontoceti echolocation Sound is bounced off objects to determine: Size Shape Distance Internal structure Figure 14-24

Marine mammals: Order Sirenia Sirenian characteristics: Large body size Sparse hair all over body Vegetarians Toenails (on manatees only) Includes: Manatees Dugongs

An example of migration: Gray whales Gray whales undertake the longest annual migration of any mammal: Spend wintertime in birthing and breeding lagoons in Mexico Spend summertime feeding in highly productive Arctic waters Figure 14-27