APPENDIX 2. Smoothed components (solid line) of four explanatory variables (x-axes) used in the fitted GAM and the response variable, density of humpback whale schools. Each explanatory variable was allowed up to 9 df, and degree of smoothing was automated by mgcv. Each x-axis contains a rugplot, where small ticks mark locations of observations. Regions of high whale density are identified by values above zero on the y-axis. Note the different scale of each y-axis, which is labeled s(covariate name, estimated degrees of freedom). The dashed lines represent ±2 standard errors, or roughly 95% confidence intervals.