L9 - Foraging Ecology and Physiology of Pinnipeds & Seabirds Flashcards
What are the 4 problems pinnipeds face when they go foraging?
- navigation
- distribution of prey - vertically, horizontally
- Environmental factors - tide
- physiological limitations
Why is oceanography important?
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
Why are coastal upwellings important?
they bring cold, nutrient rich water to the surface. Deep ocean currents are like a conveyer belt
What are oceanic fronts?
Temperature and salinity discontinuity
What are oceanic eddies?
- 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
How does El Nino effect primary productivity?
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
How does El Nino effect Californian Sea Lions?
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
What are the 4 aspects of a dive?
- Dive
- Surface - time spent between dives
- Dive cycle - dive + surface
- Dive bout - a group of dives in a foraging trip
What are the 3 sections of a dive?
decent
foraging time
ascent
Give 7 factors that effect foraging behaviour
- Prey species
- bathymetry - shallow or deep
- time of year - breeding?
- sex of the animal - large males/small females
- time of day - light or dark
- physical state of the animal
- dentition - e.g. crabeater seals
What are the benefits and losses of hunting at night?
- 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
Who developed the method that we use to monitor how deep animals dive?
Jerry Coyman
What are the 3 types of divers?
- Mesopelagic - out in the open ocean
- Benthic - animals or plants on the sea floor
- Epipelagic - within the water column
Give an example of divers that dive in a soft square shape and a hard square shape
soft: baleen whale
hard: benthic divers
What are the shapes a dive can be?
- 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
Describe how penguins dive
Have to dive in the day as they’re visual divers - usually dive to a depth where they can just about see
Describe how the Australian sea lion dives
- 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
What happens to the lungs when animals dive?
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
What are the 3 places O2 is stored in diving animals?
- blood
- myoglobin
- spleen
Give 3 ways in which diving animals lower their metabolism
- larger body size
- swim efficiently - streamlining
- hypo metabolism - vasoconstriction,, increased tolerance to hypoxia, bradycardia
How does the spleen store O2?
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
What are the 2 things used to calculate the aerobic dive limit?
- usable O2 stores
- 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
If anaerobic respiration has been used and O2 stores are depleted, the animal must somehow get rid of lactate. How does it do this?
Either:
- oxidise lactate at the surface - increasing recovery time
- recycle lactate back into glucose at the surface - increasing recovery time
OR not wasting time
- oxidise lactate during subsequent dives - reduce dive duration
- recycle lactate during subsequent dives - reducing dive duration
