Foraging and Feeding Flashcards
What are some ways in which marine mammalian diets can be observed?
- Direct observation
- Stomach contents
- Chemical composition of tissues: Fatty acid analysis and stable isotope analysis
What is a limitation of utilizing stomach contents to study marine mammal diet?
It only gives you information about prey items that were recently consumed
What are some limitations of direct observation of mammalian diets?
Biased towards…
- Near surface prey capture
- Large prey
- prolonged capture events
Only reliable with otters
What are some ways that scientists can obtain samples of the stomach contents of marine mammals?
- Lethal research (not done anymore)
- Strandings
- By-catches
- Lavage of live animals (washing out an organ)
What “hard parts” are utilized to identify prey types?
- Otoliths (ear bone in fish)
- Squid beaks
Species specific
What are some biochemical approaches to studying the diet of marine mammals?
- Fatty acid signature
- Stable isotope analysis
What are some benefits of utilizing biochemical approaches to study marine mammal diets?
Provide diet information over a broad time frame (several weeks to months)
How can fatty acid signatures be used to study diet in marine mammals
The fatty acid signature of a marine mammal is equivalent to the fatty acid signature of the prey that they eat
How can stable isotope analysis be used to study diet in marine mammals
- N2 levels increase as trophic levels increase (can identify the trophic level of prey items)
- C13 can be used to to identify if marine mammals are foraging in shore vs. offshore
Describe the feeding ecology of pinnipeds
Graspers: forage for single prey items
Describe the feeding ecology of sirenians
Grazers: feed on grass / plants
Describe the feeding ecology of otters
Graspers: forage for single prey items
Describe the feeding ecology of mysticetes
Strainers: forage for multiple prey items
Describe the feeding ecology of odontocetes
Graspers: forage for single prey items
Describe bubble net feeding in whales
- Cooperative feeding technique
- Whales dive below a school of fish while blowing bubbles to stun / trap the fish
- The whales then surge towards the surface with their mouths open and throats extended
Describe suction feeding in beaked whales
- Beaked whales have a gular region
- The gular region can be expanded to create a “vacuum” in the mouth
Describe otter foraging behavior
- Individual otters have different feeding behaviors
- The foraging behavior of otters remains the same throughout their lifetime
- Foraging behavior is inherited maternally
What are the different foraging behaviors of bottlenose dolphins
- Strand feeding
- Fish-whacking
- Kerplunking
- Crater feeding
- Begging
Describe strand feeding
Dolphins will herd fish into shallow water then half beach themselves in order to eat them
Describe fish-whacking
Dolphins will whack fish with their flukes in order to debilitate them
Describe kerplunking
Dolphins will slam their flukes again the water to scare fish out of their hiding spots so that they can be easily caught
Describe crater feeding
Dolphins dive head first into the sand in order to catch prey
Describe begging
- This behavior has been acquired through human interaction
- Dolphins will approach the edge of a boat and beg in order to get food from humans
What are the three phases of cooperative foraging
- Finding food
- Concentrating food
- Capturing food
What are the costs and benefits of cooperative foraging?
Cost: Sharing food
Benefit: Increased foraging success
Describe cooperative foraging in transient killer whales
- Transient killer whales hunt other marine mammals
- Found most often in groups of three where they were able to catch the most prey
- Smaller groups: harder to chase down individual prey items
- Larger groups: too loud
Communication is key in cooperative hunting, killer whales communicate using echo location as well as their prey items
Describe the foraging technique of Hawaiian Spinner Dolphins
- Take advantage of dial vertical migration
- Hunt for prey at night (prey = closer to the surface)
- Rest in coves during the day (prey deeper in water column)
- Cooperatively “bulldoze” (herd) prey in order to aggregate it
- Surround prey in circle formation
- Take turns going into fish aggregation to feed
