Chapter 12: Marine Mammals

1. Chapter 12: Marine Mammals

2. Introduction • Insulating body covering of hair • Maintain a constant warm body temperature (homeothermic) • Mothers produce milk with mammary glands • Placental animals • Retain young inside their body until ready to be born • Provide parental care • High metabolic rate

3. Sea Otters • Found along coast of California and Alaska • Skin covered by thick fur with underlying air layer • Protects from cold • Short, erect ears • 5-fingered forelimbs • Well-defined hind limbs with finlike feet

4. Hunted by sharks and killer whales • Stay close to shore • Consume 25% of their body weight in food per day • Ex: sea urchins, mollusks, crustaceans, and fish • Diurnal • Playful and vocal • Population of 130,000

5. Pinnipeds • Name means “featherfooted” • Come ashore to give birth, molt, mate, and sleep • Found in all oceans • Most prefer colder water • Feed on fish, penguins, and some seals • Hunted by sharks, killer whales, and humans • 30 million today

6. Characteristics: • Body is spindle-shaped • Several thick layers of subcutaneous fat • Round head carried on a distinct neck • Can move independently of body • Large brains with well-developed senses • 2 sets of limbs modified into flippers

7. Swimming and diving: • Fast swimmers (25-30 km/hr) • Can remain underwater for 45 minutes • Decrease metabolism to conserve oxygen • Some can dive deep

8. Reproduction: • Leave water and go to breeding beaches • Bulls (males) arrive first to establish territories • Some are polygynous  1 male with up to 15 females • Most mate annually • Gestation between 9-12 months • 1-2 pups born • The shorter the lactation period (nursing) the faster a pup develops insulation

9. 3 families of Pinnipeds: 1. Eared Seals (Otariidae) • Visible but small external ears • Forelimbs main propulsive force for swimming • Look like flying underwater • Hind limbs remain motionless during swimming • Used for steering

10. Examples of Eared Seals: Sea Lions • Course coat of hair • Naturally playful • Highly social  congregate in groups

11. Examples of Eared Seals: Fur Seals • Thick, dense underfur beneath stiff, outer guard hairs • Smaller than sea lions • 9 species with 1.5 million population

12. 2. Phocids or True Seals (Phocidae) • Lack external ears • More streamlined for swimming underwater • Propel themselves with a sculling movement of hind flippers • Forelimbs closer to the head and smaller than hind limbs

13. Less adapted to life on land • Drag bodies or slide/roll • Male mates with single female for entire breeding season • Ex: crabeater seal, harbor seal, harp seal, leopard seal, and elephant seal

14. 3. Walruses (Odobenidae) • Lack external ears • Streamlined for swimming underwater • Rely on forelimbs to move bulky body • Distinct neck • Hind limbs used for walking on land • 3-5 m in length

15. Can weigh up to 1364 kg (3000 lbs) • Canine teeth of upper jaw developed into tusks in males • Used for fighting with other males • Can help lift body onto ice like a pick ax • Appear at 5 years old

16. 1 large male with a harem of females • 11 month gestation with 1-2 calves • Stay with mom until 4-5 years old • Found in the Arctic

17. Sirens • Confined to coastal areas and estuaries of tropical seas • Similar to whales • Streamlined, hairless bodies • Forelimbs that form flippers • Vestigial pelvis with no hind limbs • Tail flukes

18. Completely aquatic • Gentle animals who are trusting in captivity but shy and elusive in India

19. 2 families: 1. Dugongs (Dugongidae) • Found in Indian Ocean • Strictly marine • Feed on shallow-water grasses • Larger head and shorter flippers than a manatee • Notched tail • 1 species (Dugong dugon) • Endangered

20. 2. Manatees (Trichechidae) • Found in Atlantic Ocean and Caribbean Sea • Can also be in inland rivers and lakes • Rounded tail • 3 species: • Northern manatee • Brazilian manatee (freshwater species) • African manatee • All hunted

21. Mate and give birth underwater Male remains with mate 11 month gestation  1 calf Strict vegetarians (eat 60 lb/day) Stellar’s Sea Cow Extinct 27 years after discovery

22. Cetaceans • General characteristics: • Body resembles fish (streamlined) • Probably evolved from ancient land-dwelling carnivorous mammals • Flippers with bone structure of a 5-fingered hand that only move up and down

23. Nostrils form a blowhole • Allows them to surface and breathe • Thick layer of blubber under the skin • Provides insulation • Energy reserve • Source of water when fat is metabolized

24. No neck  head is continuous with body and cannot be moved separately • No external ears • Small opening on side of head • Plugged with wax to prevent water from damaging eardrum • Body has no hair except a few on the head • Skin lacks sweat glands • Tails consist of flat flukes

25. Adaptations for diving: • Large lungs that collapse easily when diving  contain little air • Metabolism and heart rate decrease • Blood moves to vital organs • Blood contains huge amounts of hemoglobin • Absorb and transport more oxygen • Muscles can tolerate more lactic acid with no ill effects

26. Behavior: • Intelligent and inquisitive • Spy hopping  stick head straight up out of water to survey surroundings • Breaching  completely or almost completely leaves the water • Can go as high as 45 feet • Horizontal position as it falls back to the water • Slapping  lift huge tails above water and slap them to make splash and noise • Aggressive behavior

27. Reproduction and development: • Travel in groups called pods (adults and young) • Bear 1 offspring at a time • Fed rich milk to grow fast

28. Types of whales: 1. Baleen whales (Mysticeti) • Lack teeth (plates of baleen) • Filter food from water • Largest whales • Feed on plankton, krill, or fish

29. 2. Right whales • Lack dorsal fin • Absence of grooves on throat and chest • Rare • Slow and easily hunted

30. 3. Rorquals • Have dorsal fin and ventral grooves • Slender and streamlined

31. Examples of Rorquals: Blue whale • Largest of whales (24-30m) • Over 100 tons

32. Examples of Rorquals: Fin whale • 2nd largest whale (19-22m) • 45-75 tons • Large dorsal fin that slopes backward • Dark gray to brownish black • White ventral surface

33. Examples of Rorquals: Humpback whales • Low hump on back • Large bumps (bosses) on its snout • Long pectoral fins • Slow-moving and heavyset • Still endangered • Coastal species

34. Examples of Rorquals: Gray whales • Eastern Pacific only living population (15,000) • Female aggressively defend young • Carry barnacles on skin

35. 4. Toothed whales (Odontoceti) • Teeth simplified • Feed on larger prey

36. Examples of toothed whales: Sperm whale • Massive blunt snout • No real dorsal fin • Series of humps • Aggressive • Polygynous • Still rare and endangered • Oily, wax-like substance in animal’s head

37. Examples of toothed whales: White whales • Beluga whale • Narwhal • Males develop tusks

38. Examples of toothed whales:Porpoises • Stocky body • Rounded head with no beak • 100-200 identical teeth fused to jaw

39. Examples of toothed whales: Dolphins • Most numerous group • Definite beak separated from snout by a groove • Ex: bottlenose dolphins • Used for scientific studies of intelligence • Playful • Very intelligent • Socialize with other species

40. Examples of toothed whales: Killer whale (orca) • Largest of dolphins • Only cetacean that feeds on homeothermic animals • High dorsal fin • Broad, rounded flippers

41. Echolocation • Allows animal to distinguish and home in on objects from distances of several hundred meters • Dolphins use series of clicking sounds • Acts like sonar