Fluctuations in annual weaning mass of pups. a) Least squares regression shows a significant decline in weaning mass over the entire study period. b) A Loess plot smoothes the data and reveals two functions, a declining slope and an increasing slope with the breakpoint between the two occurring in the late 1990s. c) A Least squares regression line reveals a significant decline in weaning mass from 1975 to 1999 (solid circles); the regression line from 1999 to 2004 (open circles) shows increasing weaning mass values. The dotted lines are the 95% confidence limits in kilograms.