Marine Vertebrate Foraging Ecology Flashcards
what are the 2 scales of foraging ecology ?
Ranging behaviour - where they go to forage as seen from above, their range
Foraging itself - what they do when they go down
What are the problems associated with foraging in the sea?
- navigation in a featureless environment
- spatial distribution of prey
- environmental factors eg. Tide
- prey are not normally visible from the surface
- physiological limitations
What is primary productivity a helpful tool for?
Predicting where populations of marine vertebrates will be
What determines the location of food?
Sunlight
Nutrients
What affects major surface currents
Gyres
Wind patterns
What are the oceanographic features?
Coastal upwelling
Bathymetry
Fronts
Eddies
Where do upwelling occur and why?
The coast
Wind and tides
What are fronts and eddies?
Patterns in water movements on smaller scales (still over 100’s of km)
Caused by flow of water over topographical features
Affect food distribution
What do all these different oceanic movements mean?
That the ocean isn’t so featureless, as there are predictable aggregations of foods near water movements that increase primary productivity
Where is productivity highest?
Higher latitudes and cooler waters
Give an example of the effects ocean movements can have
El Niño and La Niña
Last year La Niña happened, gave us harsh winter, on other side of world
What is the difference between El Niño and La Niña
El Niño causes warm water tongue in equatorial Pacific
La Niña causes cold water tongue in equatorial Pacific
What happened to California sea lions in 2004/5
They had to move out to forage much further at sea because of El Niño
What is the TOPP scheme
Top Predators being tagged in the Pacific and finding out where they move and aggregations
Including fish seals sharks tuna birds turtles
What is a dive cycle
Time of dive
+
Time at surface between dives (recovery and preparation)
What is a dive bout?
A group of dives
What affects foraging behaviour?
Prey species Prey movements + location Bathymetry Time of year Sex of animal Time of day Physical state of animal
What can constrain diving behaviour?
Light levels
Predators
Diving ability
What do pinnipeds eat?
- primarily fish or squid
- some crustacean specialists
- some eat other pinnipeds and birds
What do Cetacea eat?
- krill & invertebrates
- fish or squid
- other marine vertebrates
What do seabirds eat?
- fish or squid
- plankton
- crustaceans
- molluscs
What do Dugong and manatee eat?
They are herbivores
What do polar bears eat?
- pinnipeds
- an increasing number of birds
What do sea otters eat?
- Echinoderms
- bivalves
- Crustacea
What morphological feature can help indicate what food marine vertebrates eat?
Dentition
Eg. Crab eater seal has specialised teeth for sieving krill from water
What pinniped teeth types are there?
Peircing - fish catching
Cage like - sieving
How do they measure foraging activity?
Time death recorder - measures pressure at set time intervals
What is epipelagic diving?
Foraging in the upper layer of the ocean also known as the epipelagic zone or water column
What’s benthic diving?
Foraging down to the sea floor ‘square diving’ eg. Sea otters
What is mesopelagic diving?
Diving deep into the sea off of the continental shelf
When does most fur seal diving take place?
Night time
Which marine vertebrate spends the most time at depthV
Elephant seal, 85% of time submerged
Because elephant seals spend so little time at the surface with oxygen, what do they do about digestion etc
They do processing dives where they use the oxygen to process instead of foraging
What does pressure do to marine vertebrates in water?
Can change nervous system function, chemical reactions
But most importantly on lungs, air spaces get compressed and lungs begin to collapse
How do marine vertebrates avoid permanent lung collapse?
Produce a detergent that reduces the surface tension, allowing the collapsed lung to separate
Also have rings of cartilaginous support all the way down to the alveoli (but not the alveoli)
Why do a lot of marine vertebrates breathe out before diving?
- Because the alveoli collapse shortly after beginning the dive, so no gas exchange will be taking place from the last gulp of air
- Reduces buoyancy so easier to dive
How do marine vertebrates store/preserve oxygen for dives if they don’t take the last breath
- lungs, will be available for first 10’s of metres (very small component of oxygen stores)
- muscle, attached to myoglobin
- blood,
- reduce oxygen usage, restricting blood flow to vital organs and muscles
Does higher percentage blood volume mean longer dive duration
Yes
How is the stellate plexus different in diving animals?
It is bigger and has better blood supply because it is acting as a store of oxygenated red blood cells, acting as a scuba tank
What does the caval sphincter do?
It controls the release of the store of oxygenated blood during the dive
What happens to the spleen during a dive?
It contracts forcing the oxygenated blood into the blood stream giving extra oxygen
How can marine divers reduce metabolic rate?
- increase body size, bigger you are, more efficiently you metabolise
- swim efficiently, streamlining
- vasoconstriction
- increase tolerance to hypoxia
- bradycardia
Dive response was measured in diving animals by ‘force diving’ them, why do this not reliable
Forced dive: - no control over duration - maximum response (fear) Natural dive - animals control duration, effort, oxygen use - graded response
What is the ADL?
Aerobic dive limit
The maximum duration an animal can sustain aerobic metabolism, after this point an animal would have to rely exclusively on anaerobic metabolism
What is ADL calculated from?
- the useable oxygen stores
- the metabolic rate of the animal during submersion
What is the problem with the ADL?
It suggests a sudden switch from aerobic to anaerobic respiration when ALL oxygen is run out
But this would be death, as there always has to be SOME oxygen for the brain to function, cannot Work anaerobically
Where would the ADL actually be?
When anaerobic respiration really starts to increase in use, possibly in inactive tissues, and eventually the active ones
Why does lactic acid levels shoot up after the dive ends?
Because during the dive the blood supply to the muscles that are respiring anaerobically is shut off, so it builds up in the muscle, then when it flushes everything with blood once back at surface, the lactic acid enters the blood
What is the surge in lactic acid after a dive called?
The lactic acid flush out
What 4 ways can the animal deal with the lactic acid flush out?
Oxidise lactate: - at surface -> increase recovery time - during dive -> reduce dive duration Recycle lactate back to glucose - at surface -> increase recovery time - during dive -> reduce dive duration
Why are weddel seals and emperor penguins commonly used to investigate diving?
Because they dive from ice holes, so can make them use your hole because so far away from others, so they are free diving but able to measure them
What was the first every ADL measured for an animal?
20 minutes for a weddell seal
What 3 animals have had ADL measured?
Emperor penguin
Baikal seal
Weddell seal
Which way of diving (dive for 60 mins recover for 100 OR dive for 20 recover for 2 mins) is more efficient?
Shorter dives, much more efficient to maintain their body within the aerobic capacity
