L9 - Foraging Ecology and Physiology of Pinnipeds & Seabirds

Question 1

What are the 4 problems pinnipeds face when they go foraging?

Answer 1

1. navigation
2. distribution of prey - vertically, horizontally
3. Environmental factors - tide
4. physiological limitations

Question 2

Why is oceanography important?

Answer 2

It determines the location of food:

• primary production site - sunlight dependent on season ,depth and stratification, and nutrient content
• where food gets aggregated and concentrated - prey isn’t homologous

Question 3

Why are coastal upwellings important?

Answer 3

they bring cold, nutrient rich water to the surface. Deep ocean currents are like a conveyer belt

Question 4

What are oceanic fronts?

Answer 4

Temperature and salinity discontinuity

Question 5

What are oceanic eddies?

Answer 5

• They result from circular patterns
• they can concentrate warm and cold jets into a swirl, creating a concentration of nutrients
• biologically significant - studies show birds such as kittiwakes flock on top of them

Question 6

How does El Nino effect primary productivity?

Answer 6

Normally:
- current from Antarctica bringing cool nutrient rich water that upwell and spill into the Pacific Ocean creating a very productive area

El Nino:

• change the movements of air and the underlying water
• no upwelling occurs, creating a lack of nutrients at the surface and a huge drop in productivity

Question 7

How does El Nino effect Californian Sea Lions?

Answer 7

Normally - 2003-4
- 23 males tagged, and were observed foraging close to the coast

El Nino - 2004-5

• some coastal foraging for much larger deeper forages away from the coast
• cool temperatures only out at sea, so only food there
• costing sea lions lots of energy

Question 8

What are the 4 aspects of a dive?

Answer 8

1. Dive
2. Surface - time spent between dives
3. Dive cycle - dive + surface
4. Dive bout - a group of dives in a foraging trip

Question 9

What are the 3 sections of a dive?

Answer 9

decent
foraging time
ascent

Question 10

Give 7 factors that effect foraging behaviour

Answer 10

1. Prey species
2. bathymetry - shallow or deep
3. time of year - breeding?
4. sex of the animal - large males/small females
5. time of day - light or dark
6. physical state of the animal
7. dentition - e.g. crabeater seals

Question 11

What are the benefits and losses of hunting at night?

Answer 11

• they will only dive to where the prey is likely to be
• prey more likely to at the surface at night-time
• therefore hunting is most efficient at night time
• constraints - predators, visual constraints, diving ability

Question 12

Who developed the method that we use to monitor how deep animals dive?

Answer 12

Jerry Coyman

Question 13

What are the 3 types of divers?

Answer 13

1. Mesopelagic - out in the open ocean
2. Benthic - animals or plants on the sea floor
3. Epipelagic - within the water column

Question 14

Give an example of divers that dive in a soft square shape and a hard square shape

Answer 14

soft: baleen whale
hard: benthic divers

Question 15

What are the shapes a dive can be?

Answer 15

• soft square
• hard square
• V
• skewed right
• skewed left

These different functions may be due to dives used for other functions, also the animals buoyancy

Question 16

Describe how penguins dive

Answer 16

Have to dive in the day as they’re visual divers - usually dive to a depth where they can just about see

Question 17

Describe how the Australian sea lion dives

Answer 17

• completely not a visual predator
• benthic diver on the sea floor
• not effected by the time of day as their prey is always on the sea floor

Question 18

What happens to the lungs when animals dive?

Answer 18

Hydrostatic pressure increases

Lung collapses

• any air space or pressure unless protected will be compressed
• whole ribcage is compressed
• all the way down to the alveolar sacs there are cartilaginous rings, as if not it is very hard to reopen

Question 19

What are the 3 places O2 is stored in diving animals?

Answer 19

1. blood
2. myoglobin
3. spleen

Question 20

Give 3 ways in which diving animals lower their metabolism

Answer 20

1. larger body size
2. swim efficiently - streamlining
3. hypo metabolism - vasoconstriction,, increased tolerance to hypoxia, bradycardia

Question 21

How does the spleen store O2?

Answer 21

The spleen is diving animals is used to store O2:

• it stores oxygenated blood cells
• so that when the animal needs O2, it contracts the spleen into the hepatic sinus releasing O2 into the body

Question 22

What are the 2 things used to calculate the aerobic dive limit?

Answer 22

1. usable O2 stores
2. metabolic rate of the animal during submersion

ADL switch is likely to be gradual switch rather than a sudden switch to anaerobic metabolism. It cant be sodden as some organs require O2

Question 23

If anaerobic respiration has been used and O2 stores are depleted, the animal must somehow get rid of lactate. How does it do this?

Answer 23

Either:

1. oxidise lactate at the surface - increasing recovery time
2. recycle lactate back into glucose at the surface - increasing recovery time

OR not wasting time

3. oxidise lactate during subsequent dives - reduce dive duration
4. recycle lactate during subsequent dives - reducing dive duration