Kiesha wants to know what type of food wolves prefer to eat. To answer her question, she attaches a small video camera around a wolf's neck, allows the wolf to go about its normal activities for one week, and then makes notes when she later observes the video. Kirk also wants to know what type of food wolves prefer to eat. However, Kirk chooses to perform a controlled experiment. In Kirk's experiment, he keeps a wolf in captivity, offers the wolf four different selections of food each day, and records which food item the wolf selected. What is one disadvantage of Keisha's investigation?