Lecture 5- Foraging (what to eat)- Decisions, decisions, decisions. Flashcards
What are animals always doing?
Give an example of a decision animals need to make.
Are there a lot of decisions related to food?
Making decisions.
When to search for food.
Yes- all the optimal foraging decisions (card 3).
Does the life of an animal revolve around eating?
Explain.
What do animals have to decide?
No.
No point in being well nourished if you do not leave any descendants.
When to stop feeding and do something else.
What are all the optimal foraging decisions?
What can animals adopt to all these questions?
1) When to search?
2) Where to search?
3) How to search?
4) When to give up and search somewhere else?
5) What to eat? What prey to capture?
6) Whether to be selective or not?
7) When to stop feeding (and do something else)?
Different solutions- each solution comes with benefits and costs.
What are the benefits?
What are the costs associated with?
What are the costs?
What is there between costs and benefits?
Get energy from food (calories), water and nutrients (macro and micro).
Getting/processing food.
Time, danger (e.g. predators) and toxins (poison).
Trade-offs.
Foraging efficiency and natural selection:
What has evolution done?
What has it shaped?
Can they do everything perfectly?
Shaped animals to make optimal decisions- are efficient foragers.
Their nervous system- to make optimal decisions- in terms of things like where to look for food etc.
No- are trade offs.
What to eat + what prey to capture:
What can some animals be when it comes to things to eat?
In some species, what can you look at to see what they have been eating?
Choosy.
Poo.
Continuation from what to eat + what prey to capture:
What would barn owls be considered?
What do they eat?
Why would they be considered specialists?
What are they being?
Specialists.
Small rodents.
Many types of rodents in their environment- but mostly eat meadow voles and shrews- are rare- shows they are being choosy.
Effective predators- mice could be aggressive- do not want to see something that could bite back.
Optimal choice of food type:
Give examples of things prey can vary in.
What else do they vary in?
What does this factor into?
Give an example.
Size, agility, nutritional value, toxicity etc.
Handling time.
Costs and benefits of different feeding strategies.
- Peanuts = easy to eat- just put it into your mouth.
- Walnuts- take time- crunch shell first- take it out- then eat.
- Both have different handling times.
Continuation from optimal choice of food type:
What is profitability?
What is the cost?
Benefit in comparison to cost of eating.
Energy + time taken when capturing, handling and digesting food- some things require too much effort to eat that it don’t give you much benefits.
Continuation from optimal choice of food type:
What do researchers assume?
What animal is this the case in?
That animals can distinguish between prey types that differ in profitability + select the most profitable type (optimal strategy).
Barn owls- are choosy with food- assume this is for a good reason- optimal strategy.
What can you take to a question?
Take- optimality approach- to question of what to eat- basically going through all its steps + answering the question.
GO THROUGH SLIDE 15 AND ONWARDS FOR AN EXAMPLE.
Optimal foraging:
What are most animals trying to do?
To see whether they are doing this, what do we need to quantify?
How do you work this out?
What is the rate at which they ingest food?
Maximize amount of energy gained per unit of time spent feeding.
How rapidly they are ingesting energy.
Energy ingested ÷ time it took to ingest it.
Calories ÷ time (s).
Continuation from optimal foraging (more formal):
What is optimality?
What is currency?
What is the constraint?
What is the assumption?
Maximizing energy gained per unit time (e/t).
Currency = energy (e).
Constraint = time (t)- can think of time as a constraint.
Maximizing profit (net benefit) during foraging maximizes fitness.
How can you represent the rate at which it ingests food?
What would the gradient of the line be?
What kind of strategy is better?
With a line.
How fast it ingest food per minute- is e/t- steeper = ingests food more rapidly.
One which makes a steeper line, not a shallow line.
Does it always need to be calories?
Give an example of when this is needed.
No- can be fat, protein, weight etc.
E.g. crow- ate a muscle- cannot measure calories as it has been eaten- need to estimate caloric value from weight or size.
