Prey attract predators.
Problem: Here is one way in which nature regulates the size of animal populations: high population density attracts predators, who remove a higher proportion 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:
|
Perch
|
Proportion killed
|
|
10
|
0.0
|
0.1
|
0.3
|
0.3
|
|
20
|
0.2
|
0.3
|
0.3
|
0.6
|
|
40
|
0.075
|
0.3
|
0.6
|
0.725
|
|
60
|
0.517
|
0.55
|
0.7
|
0.817
|
Do the data support the principle that "more prey attract more predators, who drive down the number of prey"?