Marine Mammal Nutrition

Question 1

Describe the cause and clinical signs of thiamine deficiency.

Answer 1

Caused by feeding frozen fish (thiaminases), results in oxidation of vit B9, C, fat sol vit ADEK. CS - Depression, body tremors, CNS signs. (F8, Path book)

Question 2

What forms rapidly in fish tissues at warm temps and can trigger toxicity in cetaceans fed elevated levels in food fish?

Answer 2

Histamine (F8)

Question 3

Thermoregulation is a big energy expenditure of marine mammals.

What is the thermoneutral zone.

What mechanisms do marine mammals have to maintain thermoregulation?

Discuss how the following marine mammals adapt to temperature changes:

Pinnipeds

Cetaceans

Sea Otters

Manatees

Answer 3

Thermoregulation

• Thermoneutral zone (TNZ)- range of environmental temps where no additional metabolic energy production is necessary to maintain body temp.
  
  • Smaller species and younger animals have greater surface area to volume ratio
    
    • More likely to lose heat
  • Blubber (selective perfusion or vasoconstriction) can control heat loss
    
    • Can change composition, extent, altering size of thermal windows along body
  • Flippers and fins- controlled heat radiators
• Phocids
  
  • Harp seals have broad range TNZ- 0-30C
• Otariids
  
  • Rate of heat loss is partly determined by conductivity of the medium
    
    • Water is 26X that of air, so low water temps are more of concern
    • Concrete has an evn higher conductivity *heat loss can reach significant levels
• Cetaceans
  
  • Seasonally alter blubber layer
    
    • Depth and lipid content, even Fatty acid composition
  • Do not lose heat uniformly
    
    • Have THERMAL WINDOWS- high but variable blood flow and lower insulation
• Sea Otters
  
  • Thick fur
• Manatees
  
  • Primary mechanism for thermoregulation- appears to be peripheral vasocontricution
  • Response to cold weather is to relocate to thermal refugia (natural springs or warm water from power plants and coastal industries)

Question 4

What is the largest voluntary component of a marine mammal’s energy budget?

How does this related to body mass and distance?

Answer 4

Locomotion

• Energy required is a function of body mass, velocity, time spent traveling, distance, and mode of locomotion.
• Largest voluntary component of energy budget
• Cost of swimming (COT) is inversely related to body mass
• Locomotion cost (LC)- cost twice as much to move double the mass the same distance
• Optimal depths of swimming that may not be possible in captive environment
  
  • Hypometabolism when diving (harbor seals sleep for prolonged periods underwater)

Question 5

How do phocids and otarrids differ in their nutritional strategies while nursing? How long do they nurse for?

What is the nursing strategy of cetaceans? How long do mysticetes and odontocetes nurse for?

Describe the nutritional strategies of sea otters, manatees, and polar bears.

Answer 5

Gestation and Lactation

• Usually 1 offspring per season, except polar bears (2)
• Phocids
  
  • Milk composition varies across time/species
  • Phocids (capital breeders) do not consume food while lactating
    
    • High fat milk (50-60%) over short lactation period (4 wks)
      
      • Higher the fat content, shorter the lactation period
• Otariids
  
  • Longer lactation periods than phocids
    
    • 4 months (northern fur seals) to 2-3 years for Walrus and Galapagos fur seals
    • Periodically leave pups and go to sea for feeding
• Cetaceans
  
  • Continuous lactation strategy
  • Mysticetes (5-7 months), Odontocetes (1-3 years)
• Sea Otters
  
  • (23% fat)-More similar to marine mammal milk than mustelids
• Manatees- continuous nursing
• Polar Bears- fat content in milk from 38.5% when cubs emerge to 20% 1 year later.