Organisms often face the choice of whether or not to pursue a prey item. As we saw in Chapter 5 of the textbook, optimal foraging theory predicts that evolution by natural selection will shape organisms such that they forage in an optimal manner, given the constraints of their environment. In the absence of increased risk due to foraging, optimally-foraging organisms will forage so as to maximize net energy gain per unit of time. Net energy gain is the energy acquired by metabolizing the food item minus the costs incurred. These costs can arise from many sources, including energy spent traveling to the food item, energy spent digesting the food item, and energy spent searching for the food item. If the food item is an animal, additional costs may be spent pursuing, fighting, and killing the prey item.
In the simulations that follow, you will act as an organism in search of food, following different strategies and testing which provide the highest net energy gain. These simulations consider only costs associated with traveling to the prey and digesting it.
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Question 1
In the first exercise, you will make the animal go after all prey items regardless of how far they are away. Set the repeat value to 10 and run the simulation 20 times. Record the gain or loss of net energy of each replicate, and total the net energy gain. Describe your results.
Question 2
Next, follow the rule that you will pursue all items that are 20 meters or less away and ignore those that are greater than 20 meters away. Set the repeat value to 10 and run the simulation 20 times. Record the gain or loss of net energy of each replicate, and total the net energy gain. Describe your results.
Question 3
Finally, follow the rule that you will pursue all items that are 40 meters away or less, and ignore those that are greater than 40 meters away. Set the repeat value to 10 and run the simulation 20 times. Record the gain or loss of net energy of each replicate, and total the net energy gain. Describe your results.
Question 4
In the exercises above, all of the prey items provided the same amount of energy gain. Suppose prey items varied in how much energy they contained, and that the predator could detect differences in this quality. How would this alter the optimal foraging rule?
