Growth Curve Models and Age Estimation of Young Cougars in the Northern Great Basin

Abstract

We analyzed mass growth of 96 cougars (Puma concolor) from south-central Idaho and northwestern Utah with a Richards growth curve, tested the applicability of the curve for total body length and tail length, and tested whether changes in mass, total length, and tail length could be used to predict ages of young animals. The Richards curve provided good fits of the data for mass (M: R 2 = 0.986; F: R 2 = 0.966), total length (M: R 2 = 0.961; F: R 2 = 0.958), and tail length (M: R 2 = 0.949; F: R 2 = 0.948). The mass growth model analysis indicated differences in sex for adult mass, growth rate, and birth weight. The growth model for total length indicated a sex effect for adult total length. The model for tail length was free of any sex effects. Separate simple linear regressions of the log e (age) to the log e (mass), log e (total), and log e (tail length) provided good fits of the data for males and females (r 2 mass = 0.957 and 0.938, r 2 total length = 0.939 and 0.968, and r 2 tail length = 0.918 and 0.955, respectively). We propose that models based on body mass, total length, and tail length are useful in studying the biology and ecology of cougar populations and developing sound management policies for this species.