Foraging and Feeding Flashcards

1
Q

What are some ways in which marine mammalian diets can be observed?

A
  • Direct observation
  • Stomach contents
  • Chemical composition of tissues: Fatty acid analysis and stable isotope analysis
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2
Q

What is a limitation of utilizing stomach contents to study marine mammal diet?

A

It only gives you information about prey items that were recently consumed

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3
Q

What are some limitations of direct observation of mammalian diets?

A

Biased towards…
- Near surface prey capture
- Large prey
- prolonged capture events
Only reliable with otters

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4
Q

What are some ways that scientists can obtain samples of the stomach contents of marine mammals?

A
  • Lethal research (not done anymore)
  • Strandings
  • By-catches
  • Lavage of live animals (washing out an organ)
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5
Q

What “hard parts” are utilized to identify prey types?

A
  • Otoliths (ear bone in fish)
  • Squid beaks
    Species specific
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6
Q

What are some biochemical approaches to studying the diet of marine mammals?

A
  • Fatty acid signature
  • Stable isotope analysis
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7
Q

What are some benefits of utilizing biochemical approaches to study marine mammal diets?

A

Provide diet information over a broad time frame (several weeks to months)

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8
Q

How can fatty acid signatures be used to study diet in marine mammals

A

The fatty acid signature of a marine mammal is equivalent to the fatty acid signature of the prey that they eat

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9
Q

How can stable isotope analysis be used to study diet in marine mammals

A
  • 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
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10
Q

Describe the feeding ecology of pinnipeds

A

Graspers: forage for single prey items

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11
Q

Describe the feeding ecology of sirenians

A

Grazers: feed on grass / plants

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12
Q

Describe the feeding ecology of otters

A

Graspers: forage for single prey items

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13
Q

Describe the feeding ecology of mysticetes

A

Strainers: forage for multiple prey items

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14
Q

Describe the feeding ecology of odontocetes

A

Graspers: forage for single prey items

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15
Q

Describe bubble net feeding in whales

A
  • 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
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16
Q

Describe suction feeding in beaked whales

A
  • Beaked whales have a gular region
  • The gular region can be expanded to create a “vacuum” in the mouth
17
Q

Describe otter foraging behavior

A
  • Individual otters have different feeding behaviors
  • The foraging behavior of otters remains the same throughout their lifetime
  • Foraging behavior is inherited maternally
18
Q

What are the different foraging behaviors of bottlenose dolphins

A
  • Strand feeding
  • Fish-whacking
  • Kerplunking
  • Crater feeding
  • Begging
19
Q

Describe strand feeding

A

Dolphins will herd fish into shallow water then half beach themselves in order to eat them

20
Q

Describe fish-whacking

A

Dolphins will whack fish with their flukes in order to debilitate them

21
Q

Describe kerplunking

A

Dolphins will slam their flukes again the water to scare fish out of their hiding spots so that they can be easily caught

22
Q

Describe crater feeding

A

Dolphins dive head first into the sand in order to catch prey

23
Q

Describe begging

A
  • 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
24
Q

What are the three phases of cooperative foraging

A
  1. Finding food
  2. Concentrating food
  3. Capturing food
25
Q

What are the costs and benefits of cooperative foraging?

A

Cost: Sharing food
Benefit: Increased foraging success

26
Q

Describe cooperative foraging in transient killer whales

A
  • 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
27
Q

Describe the foraging technique of Hawaiian Spinner Dolphins

A
  • 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