6.40 Prey attract predators. Here is one way in which kii nature regulates the size of animal populations: high popu lation density attracts predators, who remove a higher propor tion of the population than when the density of the prey is low.

One study looked at kelp perch and their common predator, the kelp bass. The researcher set up four large circular pens on sandy ocean bottom in Southern California. He chose young perch at random from a large group and placed 10, 20, 40, and 60 perch in the four pens. Then he dropped the nets protecting the pens, allowing bass to swarm in, and counted the perch left after 2 hours.: Here are data on the proportions of perch eaten in four repetitions of this setup:^'

Do the data support the principle that "more prey attract more predators, who drive down the number of prey"?
|4 6.41 Predicting foot problems. Metatarsus adductus ■Ir (call it MA) is a turning in of the front part of the foot that is common in adolescents and usually corrects itself.

Table 6.4 gives the severity of MA ("MA angle") as well. Doc tors speculate that the severity of MA can help predict the severity of HAV. Describe the relationship between MA and HAV. Do you think the data confirm the doctors' speculation?
Why or why not?

40 60 Perch 10 20 2248 Proportion killed 8: 0.0 0.1 0.3 0.2 0.3 0.3 0.075 0.3 0.517 0.55 2288 0.3 0.6 0.6 0.725 0.7 0.817