1. Marine Mammal Locomotion
MARE 390
Dr. Turner

2. Locomotion Swimming by marine mammals is derived from:
Paired flipper movements – pinnipeds & sea otters
Vertical movement of caudal flukes – cetaceans & sirenians

3. Pinniped Mechanics
Terrestrial & aquatic locomotion achieved differently
Aquatic - three distinct patterns:
1. Pectoral Oscillation – forelimb swimming used by otariids; flapping
2. Pelvic Oscillation – hindlimb swimming in phocids; alternating
3. Pelvic Oscillation (variant) – hindlimb swimming in odobenids; forelimbs also

4. Pectoral Oscillation
Aquatic – flapping forelimbs, no hindlmbs
Movie

5. Pectoral Oscillation
Otariidae

6. Pectoral Oscillation
Otariidae

7. Pectoral Oscillation Movie
Terrestrial – posture (hind facing forward) allows for weight on all four limbs
Movie

8. Pectoral Oscillation
Otariidae

9. Pelvic Oscillation Movie
Aquatic – alternating hindlimbs, forelimbs for steering
Movie

10. Pelvic Oscillation Movie
Aquatic – alternating hindlimbs, forelimbs for steering
Movie

11. Pelvic Oscillation
Phocidae

12. Pelvic Oscillation (Variant)
Aquatic – hindlimbs used in alternating force; forelimbs either as rudders or paddles

13. Pelvic Oscillation (Variant)
Odobenidae

14. Pelvic Oscillation (Variant)
Terrestrial – hindlimbs can be rotated forward (like otariids)
Belly supports more of body than limbs

15. Pelvic Oscillation (Variant)
Odobenidae

16. Cetacean Locomotion
Vertebral column – cervical, thoracic (rib attachments), lumbar regions (chevron bones)

17. Cervical Vertebrae All cetaceans have 7 cervical (neck) vertebrae
Different from other mammals – flat, fused
Sperm whale – 6 fused
Most others – 2+ fused
Adaptation to high-speed swimming

18. SCTS Subdermal Connective Tissue Sheath
Collagenous sheath that restrains thoracic & lumbar vertebrae and gives rigidity to thorax & ↑ surface area for muscle connections of the back & tail

19. Zygopophyses
Anterior & posterior facing articular processes on vertebrae
Work to link vertebrate together
stiffens vertebral column
Ligaments align
vertebrae

20. Flippers & Locomotion In cetaceans – forelimb proportions altered
Pectoral fin is forearm & hand – elbow not external
Also seen in marine reptiles, ichthyosaurs, mosasuars

21. Pelvic Girdle & Locomotion
Pelvic column reduced to innominate bones
Portions of femus, tibia, or foot
No direct connection to vertebral column

22. Tail Fluke Locomotion Following basic components:
1. Cutaneous layer – like rest of body
2. Blubber layer – far thinner than rest
3. Ligamentous layer from caudal keels
4. Extremely dense fibrous material within ligamentous envelope

23. Tail Fluke Shape
The shape of the flukes differs among cetaceans in response to varying hydrodynamic parameters
Trailing edges of most are slightly convex
Other straight (Sperm whales)
Curved (Humpbacks)
Falcate (sickle-shaped; rorquals)
Biconvex (narwhals)

24. Dorsal Fin Shape Predominant in most cetaceans
Supported by tough fibrous tissue – similar to flukes
Provide additional surface for balance & maneuverability, thermoregulation, & conspecific recognition

25. Mechanics of Locomotion
Modern cetaceans are caudal oscillators; swim by vertical movements of the flukes by alternate actions of epaxial & hypaxial muscles
Similar to billfishes & tunas except plane
Movie

26. Cetacean Locomotion
Delphinidae

27. Cetacean Locomotion
Balaenopteridae

28. Cetacean Locomotion
Physeteridae

29. Cetacean Locomotion
Phocoenidae

30. Cetacean Locomotion
Monodontidae

31. Cetacean Locomotion
Iniidae

32. Evolution of Cetacean Locomotion
Evolved from an initial quadruped, pelvic phase, caudal undulation phase, & caudal oscillation

33. Evolution of Sirenian Locomotion
Caudal oscillation
Poor swimmers compared to cetaceans
Unable to reach sustained high speeds
Movie
Movie

34. Evolution of Sirenian Locomotion
Terrestrial quadrupeds – alternate thrusts of limbs
Aquatic quadrupeds – dorsal ventral spinal undulation & thrusts of hind limbs
Completely aquatic animals swimming with tail alone

35. Sirenian Locomotion
Trichechidae

36. Sirenian Locomotion
Dugongidae

37. Evolution of Mustelid Locomotion
Hind limb much larger than forelimbs
- terrestrial locomotion slow
Walking & bounding
Movie

38. Mustelid Locomotion

39. Evolution of Mustelid Locomotion
Aquatic locomotion achieved by pelvic paddling (surface) & pelvic undulation (submerged)
Movie

40. Mustelid Locomotion

41. Evolution of Ursid Locomotion
Polar bears have few adaptations to the aquatic environment
Movie

42. Ursid Locomotion

43. Evolution of Ursid Locomotion
Swim with crawling motion – only use forelimbs; hindlimbs trail behind
Movie

44. Ursid Locomotion