## What Do We Really Mean by Optimal Foraging?

Earlier in this module, we defined optimal foraging theory, which states that organisms focus on consuming the most energy while expending the least amount of energy. It is important to take this abstract concept and figure out how it relates to crows dropping whelks. First, recall the definition of work.

Recall that work done is the same thing as energy expended. We can now alter our definition of optimal foraging to say that organisms focus on consuming the most energy while doing the least amount of work. Now recall the following formula you have learned in physics:

where W is work, F is a constant force, and D is the direction that the force is acting in.

Note that equation 1 applies to a system in which an object is moving in a constant direction, and is acted on by a constant force parallel to the direction of motion.

Now we can start to make our definition for optimal foraging theory specific to this module. That is, the optimal foraging of crows refers to breaking open and consuming the biggest whelks while flying the shortest total vertical distance.

Exercise 3: When the crows are flying up to the height they want to drop the whelks from, what is the force that is opposing them?