STUDENT INSTRUCTIONS

In the previous section, you figured out the nature of the relationship between army ants and ant-following birds. But how important is this interaction to the army ants? To figure this out, work with a partner or in a small group to answer the following questions.

• Describe the graphs in Figure 2 and what they show.
• Why is the trial with the large Rufous-vented Ground Cuckoo present shown with a special symbol? How did this trial influence how the researchers analyzed and presented their data?
• Interpret the data. Given your previous analysis of Figure 1, what new information does Figure 2 provide to increase your understanding of the interaction between ants and birds?
• Do ant-following birds represent a significant energy cost to army ant colonies? To figure this out, recall that army ants forage through daylight hours (always about 12 hours in the tropics), and the experimental trials lasted only 10 minutes. On average, an army ant colony consumes about 46 g (dry mass) of arthropods per day. The arthropods that ant-following birds remove are on average 1-1.5 cm long and have a dry mass of about 0.035 g. How significant is the removal of prey by birds to the energy intake of an army ant colony? That is, what proportion of a colony’s normal daily food intake do birds remove?