Suppose a Crow Normally Uses 50 Energy Units to Extract

Multiple Choice

Suppose a crow normally uses 50 energy units to extract larvae from holes in trees and only 5 energy units foraging for nuts. The crow can get 60 energy units from eating larvae and 15 energy units from eating nuts. The crow can decrease the amount of energy used to extract larvae from holes to 5 energy units, but only if it first spends 15 energy units building a tool. Under which conditions would tool use in these crows be adaptive?

A) The larvae suddenly decrease in size so that crows gain only 5 energy units from each larva.
B) Nuts become very abundant and the amount of energy spent foraging for each nut decreases to 1 energy unit.
C) One year the nut trees fail to produce any nuts and larvae burrow deeper holes in trees so that the only way that crows can catch them is through tool use.
D) Crows take so long to learn to make and use tools that, by the time they are successful, they are past reproductive age.