BIO150Y: Optimal Foraging Exercise


Background to Optimal Foraging


Hummingbirds are tiny birds (some weigh a mere 3.5 grams) but they have a frantic lifestyle which requires huge amounts of energy each day. In flight they beat their wings up to 80 times per second. They burn fats and sugars so fast that if a hummingbird does not feed for 90 minutes it can lose up to 15% of its body weight. How then do they manage to find enough energy to survive and reproduce?

Natural Selection

The answer lies in the fact that hummingbirds, just like any other organism, must constantly weigh the costs and benefits of their activities. Natural selection filters out organisms that waste time and energy that could otherwise be used to survive and reproduce. When they spend energy, they have to obtain even greater rewards.

Optimal Foraging

The secret to the hummingbird's success is that they balance the incredible costs of hovering flight against the large rewards of nectar from flowers they visit. Like tiny economists, hummingbirds forage in a way that is sensitive not just to their gross intake, but also to what economists call the marginal value: the gain in energy that just (marginally) balances costs of obtaining the energy.

What is optimal behaviour?

Now let's introduce the patch model...[next]

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