1. Marine Mammal Energetics
MARE 390
Dr. Turner

2. Energetics
Employ a variety of methods to evaluate costs & benefits of specific life processes
Involves costs of acquiring resources
evolution of adaptations to aquatic existence - seawater
How resources are allocated
cost benefit interactions
energy-flow models

3. Energetics Allocate energy across three uses: - burned in metabolism
- allocated to growth
- used in reproduction

4. Metabolic Fuels Substrates used in metabolism
fat, protein, carbohydrate, combination
2X energy metabolized from lipid than amount from protein or carbohydrate
Lipids > proportion of metabolic fuel
Greater proportion of lipids in diet

5. Metabolic Rate Cellular mechanics similar to other verts
Typically other mechanisms when diving
Standardized units
Biological state of an organisms can affect metabolic rate

6. Basal Metabolic Rate (BMR)
Measure of the metabolic rate of mature (sex & phys), postabsorptive individuals at rest in a thermoneutral environment
BMR – used for comparison across groups

7. Most birds/mammals spend time in environments that fall within the TNZ
Lower lethal temp.
High and constant body temp
can be maintained at rest over a fluctuation
of temperatures of 5-10 C with little
Extra metabolic work—this is the TNZ.
Thermo neutral zone (TNZ)
Upper lethal temp.
Metabolic Rate
BMR
Lower critical temp.
Upper critical temp.
Ambient Temperature

8. BMR & Body Mass
Kleiber Curve – BMR to body mass to the 0.75 power (BMR = aM0.75)
Do marine mammals have higher metabolic rates??? – continues debate

9. Thermoregulation Live in cold, highly conductive media
Heat capacity of water 25X air
Several adaptations to reduce heat loss:
large body size – reduced SVR
increased insulation
conserving counter-current systems
Provide broad thermoneutral zones

10. Body Mass – SAV Ratios
Marine mammals span a body-mass range 4X from sea otters (5kg) to blue whales (10x104)
Surface area of a body ↑ proportionally to the square of its length
Volume (≈mass) ↑ proportional to its cube
Marine mammals capable of producing considerable heat with relatively little loss

11. Body Mass – SAV Ratios
SA/V Ratio ↑ ↓

12. Body Mass – SAV Ratios
Reduce heat loss by streamlining body form – reducing surface area
Surface area of pinnipeds, cetaceans, & sea otters are 23% < terrestrial mammals of similar body mass

13. Body Mass – SAV Ratios

14. Insulation Use dense fur or blubber
Fur: depends upon capacity to trap air
Blubber functions: thermoregulation, energy storage, buoyancy control, streamlining
Non-shivering thermogenesis – brown fat
large amounts in pups

15. Fur Fur – extreme sea otter (150,000 hairs/cm2)
In air: impedes thermoregulation
In water: works well in shallow water environment
Deep divers – air squeezed out (pressure)

16. Blubber
Insulative value a function of thickness, lipid content, & peripheral blood flow
Cetaceans – mostly lipid content
Very efficient in cetaceans & pinnipeds
less so in sirenians
manatees thinner than dugongs

17. Blubber Sirenians – 2 blubber layers
Functionally cuts insulatory capability in half
Skin
Skin
Blubber
Blubber
Muscle
Blubber
Muscle
Muscle
Cetacean
Manatee

18. Blubber
↓ Thermal Conductivity = ↑ Insulation

19. Peripheral Blood Circulation
Conserve heat in water (cold) – inhibits heat dissipation on land (warm)
Counter current heat exchangers – conserve heat by maintaining a heat differential between oppositely directed flows of blood

20. Counter Current Heat Exchangers
Heat is conserved before it is lost at the extremity
Parallel intermingling vessels (in contact)
= vascular bundles (rete)
39°C
37°C
35°C
33°C
31°C
29°C
27°C
38°C
36°C
34°C
32°C
30°C
28°C
Veins
Artery

21. Counter Current Heat Exchangers
Pinnipeds & cetaceans - Flippers & fins (flukes)
Use hindflippers & forsal fin to cool gonads
Sirenians – vascular bundles throughout body – expel heat in warm waters
Right & Gray whales – in mouths; when feeding in cold waters

22. Counter Current Heat Exchangers

23. Counter Current Heat Exchangers

24. Energetics of Locomotion
Up to 80% of daily activity budget
Frictional resistance of water has large effect – 800x more dense than air, 30x more viscous
Must overcome hydrodynamic drag

25. What a Drag
Frictional & Pressure Drag – associated with physical prcesses of water surrounding the body surface
Induced Drag – associated with water flow around the flippers, fins, & flukes
Wave Drag – moving at or near the surface

26. Body Streamlining
Drag reduced by streamlining body surface

27. Cost of Transport
Fitness ratio – measure of streamlining

28. Transport Adaptations
Wave Riding – large energetic savings
- bow or stern of ships & whales
Surfacing only to breathe
Porpoising – removes animal from high drag environment at surface while breathing; mammals < 10m
Crossover – velocity at which porpoising becomes more efficient (5m/s)
Movie
Movie

29. Osmoregulation
Hyposmotic – body fluids have a lower ionic content than surrounding water
losing water to hyperosmotic seawater
Larger kidneys than terrestrial mammals
Multi-lobed kidneys – reniculi
human & horses – single lobe
cetaceans – 450 to 3,000 reniculi

30. Osmoregulation

31. Osmoregulation
Cetaceans can concentrate urine to a greater extent than any other mammals
Allow them a net-gain to drinking seawater
In cetaceans: 1L seawater = 0.5L water gain
In humans: 1L seawater = 0.5L water loss

32. Strategic Energetics Approach
Model of how marine mammals respond to change