1 / 33

Marine Mammals—Cetaceans and Sirenians

Marine Mammals—Cetaceans and Sirenians. Lecture 9. Marine Mammals—Cetacean origins . Share a common ancestor with the modern hippopotamus. Pakicetus > 50 mya —whale-like skull Mainly terrestrial, foraged in freshwater. Ambulocetus < 50 mya —vertebrae suggest undulation swimming.

dick
Télécharger la présentation

Marine Mammals—Cetaceans and Sirenians

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Marine Mammals—Cetaceans and Sirenians Lecture 9

  2. Marine Mammals—Cetacean origins • Share a common ancestor with the modern hippopotamus Pakicetus > 50 mya—whale-like skull Mainly terrestrial, foraged in freshwater Ambulocetus < 50 mya—vertebrae suggest undulation swimming Coastal species—still bred on land

  3. Marine Mammals—Cetacean origins Protocetids—a diverse group 45-35 mya Larger global distribution—open water Large nasal openings—higher on head; eyes lower Dorudontids < 40 mya— over 15 feet long Dorsal nasal openings; tail fluke Toes still evident; vestigial hind-legs

  4. Order Cetacea • Two major groups of cetaceans • Mysticeti—baleen whales • 15 species • Odontoceti—toothed whales (and dolphins) • 75 species—5 freshwater • Possess all mammal characteristics— • ____________ evolution  more fish like

  5. Cetacean Characteristics • Well developed tail—undulations dorsoventral • Why dorsoventral? • Vestigial hind limbs • Hair eliminated—streamlining

  6. Cetacean Characteristics • Nostrils  top of head—blowhole • No pharynx • Most odontoceteshave lost smell • Blubber—insulation, buoyancy, energy storage • Up to 1 foot thick • Capillaries constrictable

  7. Blubber • Historically, whales hunted for blubber • Food, lamp oil, soap, margarine, cosmetics, candles • Harpoon tip (1880) in bowhead whale

  8. Echolocation • Natural SONAR system • Odontocetes • Sounds (clicks, whistles) produced—phonic lips

  9. Echolocation • Odontocetes vary frequency and duration of clicks • Can produce > 1000 per second • Frequency often too high for humans • Higher frequency  short range & small prey • Differences in echo timing  density differences • Solid structures • Fish buried in sand http://swfsc.noaa.gov/textblock.aspx?Division=PRD&ParentMenuId=148&id=5776 Melon acts as a lens—direction and width of sonic signals can be modified

  10. Echolocation—Sperm Whales https://www.youtube.com/watch?v=W_PuO7gzfqI

  11. Minke Whale Cetacean Hearing • Inner ear outside skull • External ear canal vestigial • Acoustic fats—channel sound toward inner ear • Amplified Dolphin

  12. Mysticete sound production • Lack phonic lips and melon • No echolocation • Boat collisions • Sound produced with larynx • Supported by cartilage and muscles • Tissue folds vibrate—resonation chamber • Air recycled • Variable among species http://whalewatch.com/research/sounds.php

  13. Humpback vocalizations Whalesong—males on breeding grounds repeat 5-20 minute-long “song” • Projects > 20 miles • Song is population-specific • Evolves over time Bubble-net feeding

  14. Mysticete Feeding Baleen—fibrous-keratin plates hang from upper jaw • Inner surface bristled • Evolved 25 to 30 mya • Embryonic mysticetes have teeth precursors • Tongue removes strained prey • Largest animals in history

  15. Mysticete Feeding—Family Balaenidae Right Whale

  16. Mysticete Feeding Gray whale Rorqual Whales Pleats

  17. Odontocete hunting • Coordinated group hunting common • Population & individual-specific hunting tactics • Learned behavior & innovation • Foraging specialists— • Reduces competition • Pacific & Antarctic Killer whales • Dolphins in Florida Bay • Common odontocete hunting tactics • Chasing, herding, echolocating buried prey, stealing from fisherman

  18. Odontocete hunting Strand feeding

  19. Odontocete hunting Mud-ring feeding prey-specific strategy

  20. Osmoregulation • Poorly understood compared to other vertebrates • Water gained from prey • Well developed kidneys • Seawater is not ingested • Unless fasting • Concentrated urine eliminates salt • Respiration loss minimized  efficient O2 extraction • Metabolic water—

  21. Cetacean diving Oxygen storage ability • Some species have large lungs • Large tidal volume—highest among vertebrates • Large airways  • High blood volume • concentration of RBCs • RBCs with hemoglobin • Muscles myoglobin • Narwhal ½ O2 in muscles Up to 40’

  22. Cetacean diving • Breath holding at surface— • Heart rate slows when diving • Blood flow to extremities and guts restricted • Lungs collapsible, air  nonrespiratory areas • Rib cage flexible Artery • Counter-current heat exchange in tongue Veins

  23. Migration More common among mysticetes • Breeding/calving areas in tropical latitudes • Feeding in temperate or polar regions

  24. Reproduction • Poorly documented in most species • Internal fertilization • Internal—protrusible penis • 10 feet long in blue whale • Males aggressive with eachother • Courtship displays common • Fat-rich milk • Blue whale calf  up to 200 lbs. per day

  25. Reproduction—vulnerable life-history • Age at maturity variable—average 10 years • Males later for some species • One calf • Gestation 10 - 12 months • Timed with migration for mysticetes • Breed every other year at most • Some species females  5 year interval • 1+ years of infant care • Life-span variable • 40 to 130+ years

  26. The Mighty Manatees • Order Sirenia(dugongs & manatees) shares common ancestry with elephants • 1rst appear 50 mya • Peak diversity ~20 mya • Only herbivorous fully aquatic mammals in history • Two genera • 3 sp. manatee • 1 sp. dugong

  27. Manatee Characteristics Dorsal placed nostrils Nails on flippers Vestigial hind limbs

  28. Manatee Characteristics Small brains Manipulative lips https://www.youtube.com/watch?v=6c6yYq1wjOU Tactile sensory whiskers

  29. Manatee Characteristics • Osmoregulation • Need to drink freshwater • Freshwater springs • Effective kidneys • Diving physiology • Large dorsal lungs • Short dive duration • < 20 min

  30. Manatee Characteristics—feeding • High food intake—5-7% of body wt. per day • Aquatic plants—non algae • May consume animals—tunicates, entangled fish • ~60’ of intestines • Gut microbes • Tooth replacement throughout life • Slow metabolism Marching molars

  31. Florida Manatee • The largest Sirenian • > 3000 lbs, 12 feet • Restricted to Florida during winter • Freshwater springs • Migrate as far north as Virginia in summer • Possess layers of blubber • Less developed than cetaceans

  32. Manatee Threats • Slow population growth • 1 calf per female every 2-3 years • Hunted for meat • Presently very rare in Florida • Habitat loss/deterioration • Fishing gear interactions • Boat strikes—25% of FL mortality • Florida Manatee ~5000 individuals • Endangered

More Related