APPENDIX 3. One two-dimensional (LonMid, LatMid) and two one-dimensional (depth + mindist) smoothing splines (solid line) of the fitted GAM (x-axes) and the response variable, density of fin 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 observed values. 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.