Question

Fiddler crabs are so called because males have a greatly enlarged “major” claw, which is used to attract females and to defend a burrow. Darnell and Munguia (2011) recently suggested that this appendage might also act as a heat sink, keeping males cooler while out of the burrow on hot days. To test this, they placed four groups of crabs into separate plastic cups and supplied a source of radiant heat (60-watt light bulb) from above. The four groups were intact male crabs; male crabs with the major claw removed; male crabs with the other (minor) claw removed (control); and intact female fiddler crabs. They measured body temperature of crabs every 10 minutes for 1.5 hours. These measurements were used to calculate a rate of heat gain for every individual crab in degrees C/log minute. Rates of heat gain for all crabs are provided below. Female: 1.9, 1.6, 1.4, 1.1, 1.6, 1.8, 1.9, 1.7, 1.5, 1.8, 1.7, 1.7, 1.8, 1.7, 1.8, 2.0, 1.8, 1.7, 1.6, 1.6, 1.5 Intact male: 1.9, 1.2, 1.0, 0.9, 1.4, 1.0, 1.3, 1.4, 1.1, 1.0, 1.4, 1.2, 1.4, 1.4, 1.5, 1.5, 1.1, 1.4, 1.3, 1.3, 1.3 Male minor removed: 1.2, 1.0, 0.9, 0.8, 1.2, 0.9, 1.1, 1.1, 1.3, 1.3, 1.3, 1.1, 1.4, 1.5, 1.4, 1.4, 1.2, 1.4, 1.3, 1.2, 1.4 Male major removed: 1.2, 0.9, 1.4, 1.2, 1.2, 1.6, 1.9, 1.4, 1.4, 1.4, 1.6, 1.4, 1.7, 1.3, 1.5, 1.2, 1.3, 1.6, 1.5, 1.5, 1.5

a) Use Bonferroni to compare intact males to females, males minor removed and males major removed.

Answer 1

Arrange the data where in one column you will have the group name as in Intact males, females, males minor removed, males major removed and in another column you will have rate of heat gain in degree C/ log minute.

Use the below R Code:

d=read.csv("data1.csv",header=T)
pairwise.t.test(d$Heat.gain,d$Treatment.Group, p.adjust = "bonferroni")

Output:

Pairwise comparisons using t tests with pooled SD

data: d$Heat.gain and d$Treatment.Group

Female Intact Male Male Major removed

Intact Male 2.4e-07 - -

Male Major removed 0.00064 0.29264 -

Male Minor removed 1.3e-09 1.00000 0.01231

P value adjustment method: bonferroni

P value for Intact males vs female is significant but intact males vs other groups is not signifcant.

Also see that p-value for females vs all other groups are significant, hence we might infer that "major claw" does not act as heat sink.