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Vertebrate > Lecture 18 > Flashcards

Lecture 18 Flashcards

1
Q

What are some factors that affect foraging behaviour?

A

. Prey species
. Prey movements and location (benthic vs pelagic)
. Bathymetry
. Time of year
. Sex of animal
. Time of day (because prey changes it’s behaviour with time of day- usually depends on light levels)
. Physical state of the animal (fatter animals tend to be more buoyant)
(See chapter 8- marine mammal biology hoelzel)

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2
Q

When do prey usually come to the lesser depths?

A

Night (depends on light levels, so for predators it is better to forage at night)

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3
Q

Why is it usually better for predators to dive at night?

A

Usually prey come closer to the surface at night due to light levels and so predators would have lesser amounts to dive and therefore will have longer when they get there, so have more time to forage

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4
Q

Why can’t some animals dive at night?

A

Because they need light to see and be able to forage- a constraint

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5
Q

What are constraints on diving behaviour?

A

. Light levels
. Predators (may not come to the surface very frequently because they don’t want to come in contact with predators)
. Diving ability (swimming efficiently, how quickly they can get to depth/ swim- linked to how much diving costs them)

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6
Q

What do Pinnipeds usually feed on ? Give examples of specialists

A

. Feed primarily on fish or squid
. Birds and other Pinnipeds
. Crabeater seals and Antarctic fur seals feed on krill/ are krill specialists

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7
Q

What do seabirds feed on?

A

. Fish or squid
. Plankton
. Crustaceans
. Molluscs

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8
Q

What do dugong and manatee feed on?

A

Herbivores

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9
Q

What do polar bears feed on?

A

. Pinnipeds

. Increasing number of birds (due to changes in landscape)

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10
Q

What do sea otter feed on?

A

. Echinoderms, bivalves, Crustacea

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11
Q

What do Cetacea fees on?

A

. Krill and invertebrates
. Fish or squid
. Other marine vertebrates

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12
Q

How far do sea otters dive?

A

Not far only 10 metres

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13
Q

When you see a flat bit in a dive when recording the dive of an animal, what kind of feeder is it?

A

A benthic feeder/ benthic dwelling prey items

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14
Q

Why do seals tend to have pointed teeth?

A

To hold onto slippery prey (convergent evolution with other fish eaters species such as crocodiles)

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15
Q

What are crabeater seals specialists of eating?

A

Krill

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16
Q

What kind of teeth do Cetacean have? What are they predominantly feeders of?

A

Single pointed teeth ‘coned shaped’. Squid or fish feeders

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17
Q

What teeth adaption do krill specialists have?

A

Have holes between the teeth so that when they take a bite water can come out from the side (push water out leaving krill in the mouth)

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18
Q

What do we attach to animals such as seals to record/ studying them?

A

Time-depth recorders

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19
Q

Why to time-depth recorders have a radio transmitted?

A

So that when animal comes ashore they can be alerted

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20
Q

What did early time-depth recorders record?

A

The depth the animal was diving, the number of dives the animal took

21
Q

What was the first time- depth recorder like and how do they differ now?

A

Was bulking and was attached by a harness however, this would affect the diving ability of the animal by adding drag.
Now they are much smaller and are glued on

22
Q

What added things to newer time-depth recorders record?

A

Swim speed
Angle of incline
Not just radiotransmitter but also a satellite transmitter (so we don’t just know what they are doing but where they are doing it)
Etc.

23
Q

How are time-depth recorders on puffins differ to those on seals? How much do they weigh?

A

They are much smaller

Weigh about 5g

24
Q

How do epipelagic feeders dive?

A

. Feed in the water column
. Close to shore
. Not very deep diving

25
Q

How can we tell that Epipelagic feeders are feeding within the water column?

A

Because their dive profile is U or V shaped

26
Q

What does a U or V shaped dive profile suggest?

A

That they are diving within the water column

27
Q

What is the dive profile of Benthic feeders (e.g. sea otters) shape?

A

Goes down, hits the bottom, stays on the bottom/ is flat (does go up and down but that is because the surface is not completely flat), no wiggles. So is a square- shaped dive profile

28
Q

What is the mesopelagic dive profiles shape? (Deep divers)

A

Go down, often have wiggles associated with them while they are at depth, tends to be a U-shape rather than a flat like Benthic feeders

29
Q

What does a soft-square or U-shaped dive shape tell us about the animal?

A

These are mid-water forages so these are pursuit predators, these chase after there prey in the water

30
Q

What does a hard-square dive shape say about the animal/ their prey?

A

They are feeding on the sea floor, their prey tends to be very localised and tends to be relatively slow moving (if moving at all)

31
Q

What does skewed (right or left) dive shape tell you about the animal?

A

Lots of ways of interpreting them. Depends on buoyancy. E.g. easy to sink if the animal is negatively buoyant but it takes longer to get back to the surface because they have to work against the distance to get up but also the negative buoyancy, so it is harder (so skewed to the right?). If they are positively buoyant then they have to fight against that buoyancy to get down and then when they are down they have to work against that buoyancy the whole time. But also some spend a lot of time at depth and may come back up to the surface slowly when they are doing things like digestion

32
Q

What kind of buoyancy makes it easy to get done to depth?

A

If the animal is negatively buoyant

33
Q

What would be an issue if an animal did a series of lineal dives (using the same angle in which they dive)? Give an example. How is this resolved?

A

Would travel a long way
If it was a female whale with a carf that doesn’t dive then she would have travelled a long way (could end up 3/4 km’s away from their carf
Dives change direction (cork skew shape) and are not linear so they will end up coming back to relatively the same place (also this way they can go back to the same place if they know that they is a resource there)

34
Q

What angles are sperm whales recorded to dive at?

A

55 degrees

35
Q

When may a dive be linear?

A

If they are searching for new prey

36
Q

How have most fur seals been recorded diving? When are these mostly recorded to have been done?

A

In oscillations.

Most recorded at ‘0 hours’- at night

37
Q

Why are crabeater seals recorded to forage at night?

A

Because that is when the krill come closer to the surface and therefore they don’t have to dive as deep

38
Q

Give examples of animals that dive to deep depths/ feed mostly during the day. What is this directly linked to?

A

King penguins, Adelie penguins. Directly linked to light levels- they are vision forages (means they have to dive deeper because they have to forage during the day)

39
Q

What are vision forages?

A

Forages that need light to catch prey

40
Q

Give an example of a species that’s diving pattern is not related to light

A

Australian sea lion (prey is on the sea floor so will always be at exactly the same location)

41
Q

What is the percentage of time elephant seals spend under water? How is this?

A

85% because they don’t take any breaks, only comes to the surface to exchange oxygen for carbon dioxide. This is possible because they do their normal bodily functions e.g. tissue repair, digestion under the water. They have foraging dives, processing dives and travelling dives

42
Q

What do diving animals usually do when they are at the surface? Why is this?

A

. Tissue repair
. Digestion
Because these activities/ normal bodily functions cost oxygen and these animals want to optimise the amount of oxygen they have to increase their time at depth

43
Q

Explain the difference between the foraging dive, processing dives and travelling dive of an elephant seal

A

They take place in a limited area in foraging dives.
The animal moves between foraging patches (not as deep)
The animal doesn’t move between sites in processing dives but are doing shorter dives, not as deep as foraging dives and are a different shape

44
Q

What are the pressure effects when diving?

A

. Hydrostatic pressure- pressure at depth due to weight of water column
. Boyle’s law- how pressure changes as a function of depth
. Lung collapse (have no support)
. Deeper= more pressure and any air space you have is going to collapse or be put under pressure or reduced in size

45
Q

How do diving species deal with the pressure increase with depth with would cause air space to collapse, be put under pressure or reduced in size?

A

The upper part of their lung has cartilage associated with them that extends all the way to the alveolar which means they are much more structured and rigid then other animals (e.g. dogs) so they don’t collapse. So the bits that don’t have support are going to collapse first. The alveolar sacs will totally collapse but not the rest of the lung

46
Q

Where does gas exchange take place?

A

The Alveolus

47
Q

What is the issue when parts of marine mammals lungs collapse? How is this resolved?

A

They are very difficult to inflate because they are stuck together.
Get through this by reducing the surface tension (having what is called a suffacted?). The bronchioles can go in them and re-inflate them

48
Q

What is the issue when the alveolar sac’s collapse? So how does this change how an marine mammal prepares for a dive?

A

There is no gas transfer, so any oxygen is not available for these animals
They dive out as much as possible and empty their lungs because it would give them a greater buoyancy

Vertebrate (20 decks)

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