Resource acquisition by societies part 1

Question 1

what do animals need to balance when deciding when and where to forage for food?

Answer 1

1. time
2. reward
3. risk

Question 2

what does optimal foraging seek to explain?

Answer 2

it seeks to explain the diversity of approaches to foraging based on the costs and benefits of alternative strategies available to an organism

Question 3

define Central place foraging

Answer 3

a mode of foraging where the forager must return to a central location to process, consume, store and/or share food resource

Question 4

what benefit/cost do greater foraging distances provide?

Answer 4

• benefit of more food and a greater variety of food types
• cost of time, energy expenditure, and risk

Question 5

What kind of decisions do foragers have to balance?

Answer 5

• How long to look?
• How hard to work?
• Once food is located, how much should be retrieved?
• How quickly should it be retrieved?

Question 6

Central-place foraging is the foraging mode for what kinds of organisms

Answer 6

any shelter-building social organism, and many others with a well-defined core area

Question 7

Having a shelter and central-place foraging may allow what?

Answer 7

it may allow new food types

Question 8

Having a shelter and central-place foraging may allow new food types - Many group members may what?

Answer 8

further facilitate access to new food types

Question 9

Having a shelter and central-place foraging may allow new food types - tradeoffs of having many group members

Answer 9

a subset of all society members must feed the whole society

Question 10

Having a shelter and central-place foraging may allow new food types - what is the cost for the tradeoff

Answer 10

• cost is that individual foragers must forage longer and further from the central location than a solitary organism would
• time, distance, and risk costs are amplified

Question 11

Central-place social foraging - Example

Answer 11

leaf-cutting ants

Question 12

central-place foraging - leaf-cutting ants

Answer 12

A leaf-cutting ant forager may travel several hundred meters to a foraging site

Question 13

central-place foraging - costs

Answer 13

• Time and energy spent foraging
• Increased forager mortality rates

Question 14

central-place foraging - which social traits offset the costs?

Answer 14

• Division of labor
• Foraging specialization tied to increase in age and/or a decline in fecundity

Question 15

what do individual strategies in social foraging do

Answer 15

Balances the costs and benefits of foraging at the level of individuals

Question 16

individual strategies

Answer 16

• Search behavior.
• Orientation mechanisms.
• Load size.
• Morphological adaptations.

Question 17

search behavior - define Correlated random walk

Answer 17

Each subsequent step is in a random direction, but with a degree of correlation to the previous direction of movement.

Question 18

correlated random walk - Optimal turning angle (tortuosity) depends on what?

Answer 18

the probable distribution of food sources and the number of cooperative searchers

Question 19

correlated random walk - Encounters with other group members or lack of food favors what?

Answer 19

favors straighter search paths and greater distances

Question 20

correlated random walk - how do single foragers perform optimally

Answer 20

they use a tortuous search path to maximize area coverage around the “central place”.

Question 21

search behavior - example

Answer 21

silver desert ants

Question 22

search behavior: silver desert ants - What pattern of tortuosity and social coverage do they engage in?

Answer 22

• They move in different directions to cover more ground
• They all typically maintain a straight movement (less tortuous path/shallower angle)

Question 23

search behavior: silver desert ants - What might we predict about foraging distance and food availability from their tortuosity

Answer 23

• Widely scattered food
• Food is not near the nest

Question 24

Once food resources are acquired, how does the individual return to the central place?…What are the possible mechanisms of orientation back to the “central place”?

Answer 24

• individual orientation
• can involve a combination of 4 things

Question 25

Individual orientation can involve a combination of what?

Answer 25

- Visual cues. - Acoustic communication between group members. - Chemical orientations. - Biomechanical detection of distance.

Question 26

individual orientation - visual cues example

Answer 26

honeybees

Question 27

individual orientation: visual cues - how do honeybees estimate distance

Answer 27

“Strobing” of images past the bee is used to estimate distance

Question 28

individual orientation: visual cues - honeybee experiment

Answer 28

the bee flies through a tunnel where the visual pattern can be manipulated.

Question 29

individual orientation: visual cues - what does manipulation do to the honeybees

Answer 29

Manipulation of pattern to reduce frequency of image cues reduces distance estimates by bees.

Question 30

individual orientation: visual cues - result of honeybee experiment

Answer 30

A visual “odometer” from environmental visual cues is used in bee orientation and distance calculation.

Question 31

individual orientation - what is the most reliable and simple mechanism?

Answer 31

retracing path along persistent path route

Question 32

individual orientation: retracing path - Path persistence can include what

Answer 32

- Remembered path, typically via landmark orientation. - Physical and/or chemical signature from outbound journey

Question 33

individual orientation: retracing path - What’s the main cost of retracing outbound path?

Answer 33

The retraced path may be longer than it actually is

Question 34

individual orientation - what does path integration involve?

Answer 34

it involves the use of outbound journey information to calculate a straight(er) return route of known direction and distance.

Question 35

individual orientation - path integration example

Answer 35

silver desert ant

Question 36

load size - what do social mammals tend to do?

Answer 36

tend not to retrieve and instead rapidly consume and defend in place

Question 37

load size: social mammals - if retrieval does happen, what should selection favor?

Answer 37

selection should favor maximum load size that does not hinder the overall efficiency of foraging strategy

Question 38

load size - define "load matching"

Answer 38

loads are matched to body size but are still small enough to not hinder retrieval speed.

Question 39

load size - when is "load matching" common

Answer 39

in social animals that retrieve resource loads

Question 40

Contrasting examples load transport with load-matching

Answer 40

army ants vs leaf-cutting ants

Question 41

contrasting examples load transport with load-matching - army ants

Answer 41

- Faster than leaf-cutting ants - Collaborative behavior - Carrying prey below body

Question 42

contrasting examples load transport with load-matching: army ants - what are the benefits and costs of carrying prey below body

Answer 42

- benefit: can carry heavier items - cost: must fit below the legs

Question 43

contrasting examples load transport with load-matching - leaf-cutting ants

Answer 43

- A lot slower than army ants - More individualistic with load carrying - Carry prey above head

Question 44

contrasting examples load transport with load-matching: leaf-cutting ants - what are the benefits and costs of carrying prey above the head

Answer 44

- benefit: can carry bigger pieces - cost: move a lot slower

Question 45

Morphological adaptations for foraging - in social mammals

Answer 45

primary tools are teeth and claws.

Question 46

morphological adaptations for foraging - in social insects

Answer 46

primary tools are the mandibles and sting (or other chemical weapons)

Question 47

Morphological adaptations for foraging are heavily dictated by what?

Answer 47

- heavily dictated by the evolutionary history of the group - but are often enhanced in the context of social life.

Question 48

Morphological adaptations for social foraging - example

Answer 48

- porter caste in army ants - social dogs vs social cats

Question 49

morphological adaptations for social foraging - porter caste in army ants

Answer 49

- has specialized mandibles, big heads, and long legs - evolves in species that carry awkward prey - but must “fit” in the developmental space between workers and soldiers, so morphological traits are constrained by evolutionary history.

Question 50

morphological adaptations for social foraging - social dogs

Answer 50

Run prey to exhaustion and use teeth for take-down

Question 51

morphological adaptations for social foraging - social cats

Answer 51

High-speed prey capture with teeth and rotatable, clawed paws.