Individuals in a group may gain protection from I predators because of the dilut
ID: 3130073 • Letter: I
Question
Individuals in a group may gain protection from I predators because of the dilution effect: when o predator stocks', the larger the number of prey individuals in the group, me smaller the chance that any particular member of the group will be the victim. Foster and Treherne" tested whether the dilution effect occurred when o predatory fish attacked groups of a marine insect, ine ocean skater. A subset of their data is presented in the table, which shows the number of predator attacks (per 5 minutes) on ocean skater groups differing in size. Calculate the average number of attacks (per 5 minutes! for each group size. Do the fish predators show a clear preference for attacking small groups over large groups [or vice versa)? Explain. For each group size, convert the average that you calculated for question 1 into the average number of attacks per individual (per 5 minutes) Is there a consistent relationship between the overage number of per individual (per 5 minutes) and group size? Explain. Are these results consistent with the dilution effect?Explanation / Answer
Part 1-Average Number of attacks for each group size
Group Size Average No.of attacks Per group
1 10.33
4 12
6 9.33
15 8.5
50 13
70 10.5
No,we donot see a clear preference on the number of attacks per group because as the group size increased,the number of attacks per group were not monotonic either in a increasing or a decreasing fashion.It is more like a sinusoidal movement of the distribution.
Part b- Average nu,ber of attacks per individual
Group Size Average No.of attacks Per individual
1 10.33
4 3
6 1.55
15 0.567
50 0.26
70 0.15
Yes there is a consistent relationship between the attacks per individual and the group size.As the group size increased,the number of attacks per individual decreased monotonically.
Part c
Yes the results are consistent with the dilution effect for the second case as the number of individuals increased overall and the number of attacks per individual decreased clearly representing the dilution effect