The giving-up density (GUD) of gray squirrels feeding on college campuses tends to be higher than that of squirrels feeding in suburban back yards. Which of the following hypotheses is consistent with this result? a. Squirrels perceive predation risk to be higher in suburban back yards.
b. Squirrels perceive predation risk to be higher on college campuses.
c. Squirrels are better fed in suburban back yards, and thus feed less intensively.
d. Squirrels benefit less by foraging in suburban back yards than on college campuses.

The correct answer is option b. "Squirrels perceive predation risk to be higher on college campuses".

Explanation:

According to the article "Giving-up densities of gray squirrels in a forest and suburban environment and the effect of substrate depth" by Thomas Pospiech and colleagues, the giving-up density (GUD) is defined as the percentage of food left unconsumed by gray squirrels. In this case, it is stated that the GUD score is higher in college campuses than in suburban back yards. This is consistent with the hypotheses that squirrels perceive predation risk to be higher on college campuses. This would explain why squirrels leave before finishing their food, they fear to be predated more in college campuses than in suburban back yards.