Fitting the von Bertalanffy growth equation to polar bear age–weight data

Abstract

Heavy sea ice in the Canadian Arctic in the winter of 1973–1974 reduced seal populations; polar bears, preying principally on seals, consequently lost weight. The nature and degree of this weight loss was investigated by examining the parameters of von Bertalanffy growth curves, fitted by direct minimization of a sum of squares using the simplex algorithm of Nelder and Mead. Growth rates were lower for both males and females tagged in 1974–1975 than for bears tagged in 1971–1973. Weights of mature bears were unaffected.