Question 4. Monkeys will often actively search for fruit trees, feeding on the f

Question

Question 4. Monkeys will often actively search for fruit trees, feeding on the fruit within a tree until it is mostly gone and then leaving to look for another tree in which to feed. Optimal foraging theory makes predictions about which behaviors should be favored by natural selection. Consider the following figure showing cumulative energy gain per minute for monkeys feeding in different fruit trees (green lines): Tree 1 Tree 2 0 5 10 5 20 25 30 35 4045 Time (T) Tree 1 Tree 2 0 5 10 15 20 25 30 35 40 45 Time (T) A. What is the key assumption upon which optimal foraging theory is based? B. Using the marginal value theorem (MVT) as a framework, how do the fruit trees in panel (a) above differ from each other from the perspective of a monkey? For how long should a monkey forage in each tree before leaving? Be specific.

Explanation / Answer

A] Foraging mean searching for food in the wild by animals. It affects an animal's fitness and the population as it plays an important role in their ability to survive and reproduce.

Optimal Foraging Theory [OTF] helps to predict how an animal will behave while searching for food. Animals will look for gaining maximum energy for the lowest cost during foraging so that it can maximise its fitness. OFT helps to predict the best strategy that an animal can use to achieve this goal.

The ke assumptions on which OTF is based are currency, constraints and appropriate decision rule.

Here, currency means the animals ability to get maximum food per unit time so that they can maximum energy and lose as little energy as possible while foraging for food. This will help them to devote more time in activities like looking for a mate, nurturing the young etc.

Constraints are the conditions of the environment where the animal lives. The ready availability of food in the environment will directly affect the currency as the net gain of energy [ i.e energy gained from food -- energy spent in searching and hunting for food ] will be higher.

The optimal decision rule is the animal's best foraging strategy. It is defined as the decision that maximizes the currency under the constraints of the environment. Identifying the optimal decision rule is the primary goal of the OFT.

B] The marginal value theorum describes the strategy that will maximize gain per unit time in systems where resources decrease with time. This model weighs benefit and costs and is used to predict giving up time and giving up density.

The graph in panel [a] clearly shows thatthe cumulative energy gain of the monkeys is decreasing with time. This is clearly because the availability of fruits has decreased due to continuous foraging by the monkeys. As a result, the time and energy spent by the animals has become more and hence the net gain of energy has decreased.

From the perspective of a monkey, tree 1 has more 'currency' than tree 2. The cumulative energy gain is more for tree 1.

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