Foraging

Question 1

What is foraging?

Answer 1

The process of obtaining food

Question 2

What are the 4 stages involved in foraging in predators?
Clue - SACH

Answer 2

1. Search
2. Assessment
3. Capture
4. Handling

Question 3

What is patch cycle foraging?
Give an example.

Answer 3

• Foraging on aggregations/clusters of prey/food
• E.g. birds feeding on berries

Question 4

What are the 3 steps involved in patch cycle foraging?
Clue - SAE

Answer 4

1. Search
2. Assessment
3. Exploitation

Question 5

What is central place foraging?
Give an example.

Answer 5

• Movement between foraging site & fixed place to which the animal returns with food
• E.g. bird nest

Question 6

What are the 4 steps involved in central place foraging?
Clue - SLRU

Answer 6

1. Search
2. Loading
3. Return
4. Unloading

Question 7

What are foraging bout cycles?

Answer 7

• Foraging that occurs in discrete periods interspersed with periods of other activities

Question 8

What are the 4 steps involved in foraging bout cycles?
Clue - SEPO

Answer 8

1. Search
2. Eat
3. Processing of food - digestion/assimilation
4. Other activities - may overlap with digestion/assimilation

Question 9

What does the optimal foraging theory state?

Answer 9

Animals can maximise their fitness by foraging in ways that increase the net rate of energy gain and decrease energy costs.

Question 10

What are 4 benefits of optimal foraging?

Answer 10

1. Less time foraging, I.e. less chance of predation
2. More energy for other activities/processes
3. Fitter (better immune system, ability to escape predators etc)
4. Derive benefit from fewer resources when in short supply

Question 11

What does diet width describe?

Answer 11

• The range of foods consumed by an animal

Question 12

What are generalists?

Answer 12

• Animals that consume a large proportion of available prey/food it comes across
• E.g. Red fox

Question 13

Give 1 advantage & 1 disadvantage of generalists.

Answer 13

Advantage:
- Spend little time searching for food

Disadvantage:
- May eat items of low nutritional value so energy intake is often low

Question 14

What are specialists?

Answer 14

• Selective animals
• Spend more time searching for specific food

Question 15

Give 1 advantage and 1 disadvantage of specialists.

Answer 15

Advantage:
- Energy intake is often high

Disadvantage:
- Spend more time searching

Question 16

What 3 predictions arise from optimal foraging theory?

Answer 16

1. If handling times are short & search times are long = predator should be a generalist
2. If handling times are long & search times are short = predator should be a specialist
3. If environment is unproductive or unpredictable = predator should be a generalist

Question 17

What is optimality modelling?

Answer 17

• A tool for analysing foraging strategies or decisions’ of animals in terms of costs:benefits

Question 18

What does the slope of the line on optimality models show?

Answer 18

• Rate of energy intake
• If slope is greater = more profitable
• If slope is shallower = less profitable

Question 19

As search time for profitable prey increases, what happens to net intake & slope of line?

Answer 19

Decreases

Question 20

Give an example of a generalist.

Answer 20

• Shore crabs
• Larger mussels take too long to open & smaller ones have too little meat to be worthwhile
• Usually eat a range of sizes around optimum

Question 21

What is the marginal value theorem?

Answer 21

• Developed by Charnov (1973).
• Describes the foraging behaviour of animals in patches.
• Must decide when to leave a patch to start searching for a fresh one.

Question 22

What is a model?

Answer 22

A numerical or graphical representation of a hypothesis designed to predict a relationship

Question 23

Give an example of optimality modelling.

Answer 23

• Prey choice model
• Predator faced with 2 sizes of prey
• 1 is more profitable than the other
• Prey 1 is large with energy (E1) + handling time h1
• Prey 2 is small with energy (E2) + handling time h2

Question 24

Describe a herbivore diet (3 points)

Answer 24

• Low protein
• Large quantities of indigestible material
• Low nutrients

Question 25

What type of stomach do ruminants have?

Answer 25

Multi-chambered stomachs

Question 26

What are foregut fermenters?

Answer 26

- Animals that digest food in foregut - Multi-chambered stomachs

Question 27

What is rumination?

Answer 27

The process of regurgitating food to breakdown plant matter further & stimulate digestion

Question 28

What are hindgut fermenters?

Answer 28

- Animals that digest food in hindgut (colon) - Single-chambered stomachs

Question 29

Where is the main site for bacterial digestion in most large herbivores (e.g. a horse)?

Answer 29

Colon

Question 30

Where is the main site for bacterial digestion in smaller hindgut fermenters (e.g. a rabbit)?

Answer 30

Caecum

Question 31

What is coprophagy?

Answer 31

Where an animal reingests its own excreted faeces

Question 32

What is a disadvantage of being a hindgut fermenter rather than a foregut fermenter?

Answer 32

- By the time food reaches caecum & colon, it has passed small intestine so less absorption of products of digestion is possible - Large numbers of dead microbes also cannot be digested, as they can in ruminants, where they pass from the rumen into the small intestine with the remainder of the partly digested food.

Question 33

Do small herbivores have a high or low mass-specific metabolic rate?

Answer 33

High

Question 34

What does the Jarman-Bell principle suggest?

Answer 34

Large-bodied mammalian herbivores can subsist on lower quality diets because of their lower metabolic requirement/gut capacity ratio

Question 35

Why do ruminants keep large fibre particles in the rumen until reduced to about 1mm?

Answer 35

To allow for more extensive microbial digestion but delays passage of food through gut

Question 36

Why are hindgut fermenters able to obtain more energy from an abundant food compared to ruminants?

Answer 36

- They have higher passage rates of food through gut - Allows them to eat more, outweighing reduction in digestion efficiency

Question 37

If tall & shorter vegetation have similar digestibility, which is preferred?

Answer 37

Taller vegetation

Question 38

If taller vegetation has lower digestibility compared to shorter vegetation, which is preferred?

Answer 38

Shorter vegetation

Question 39

Give 3 mechanical/structural defences of plants.

Answer 39

1. Thorns, spines & trichomes (fine hairs that may contain irritants) 2. Resin or waxy coatings 3. Armour (e.g. nuts)

Question 40

What are post-ingestion defences?

Answer 40

- Digestion inhibitors & make plant cell walls indigestible to animals - The more ingested, the less nutrition the herbivore can gain from eating the plant

Question 41

Give 3 potential benefits to an animal that optimally forages?

Answer 41

1. Predation risk decreases 2. More energy for other activities 3. ‘Fitter’

Question 42

Where is the main site for bacterial digestion in cows?

Answer 42

Rumen

Question 43

Give an example of a species that has a physical adaptation to optimally forage.

Answer 43

- Egrets (heron) - Yellow feet on black legs - Used to hunt small fish as the feet either attract of disturb prey - Makes them easier to catch - By wading through water, egred can assess the density of prey.