Post-Natal Growth and Sustained Lactational Effort in the Aardwolf: Life- History Implications

Abstract

Earlier life-history studies suggested that the mammalian iteroparous/semelparous gradient may be particularly important in shaping patterns of post-natal development in the hyaenids. Apparent anomalies between Aardwolf metabolic rates and post-natal development patterns are investigated. Age-specific post-natal growth in the Aardwolf supports sexual size monomorphism in the species and no statistical difference in goodness of fit was evident among various growth curves. Nevertheless, the Gompertz equation consistently provided the better fit and is recommended. Significant seasonal trends in adult body weights were evident with low weights at the end of winter (August). Seasonal adjustment of growth data failed to improve the goodness of fit of growth curves. Asymptotic weight is approached by 1.8 years of age but may be reached as early as 3.6 months by some individuals. Maximum growth rate is achieved at 3 months of age. The power coefficient (c) which scales growth between birth and independence is 0.61, and falls below the mean value of 0.81 for carnivores. However, previous life-history analyses and the implementation of the Charnov (1991) model suggests that the Aardwolf has an above average weight and a below average age at maturity. In addition, this species reached final weight before sexual maturity, an uncharacteristic feature for mammalian species. This peculiar suite of life-history characteristics suggests that the Aardwolf tends towards an iteroparous life style, which serves to reduce juvenile mortality. However, species-specific constraints do not allow it to pursue this strategy by maximizing growth rate. Instead growth is sustained using an extended lactation period and intensive parental care to enable final body size to be reached as soon as possible. 8. These results not only suggest that the adoption of a universal growth power coefficient (c) to model mammalian life histories is unrealistic but also that c should also be interpreted within the broader context of the complete suite of species specific life-history constraints and characteristics.