Data for plot in Figure 2 (30-by-3 matrix). Column 1 = Year; Column 2 = Encounter rates of sperm whales off the Galapagos Islands (calculated as number of groups of female and immature whales encountered divided by the total hours of acoustic and visual search (i.e. total effort minus time following whales)); Column 3 = Standard Error of the Mean for encounter rates (calculated as [Squareroot(number of encounters)/total hours of sampling effort], assuming Poisson distribution).