Aging Sambar (Rusa unicolor) Using Cementum Annuli and Eruption and Wear: Implications for Predicting Populations

Sambar (Rusa unicolor), one of 6 deer species introduced to Australia, are poorly studied and declared vulnerable in their native range of India and southern Asia. In southeastern Australia sambar are increasing in abundance and distribution despite commercial venison harvest and unlimited public hunting. The ability to accurately age individuals is important for management of cervid populations because many life history events are age dependent. The techniques most widely used to estimate the age of cervids involve tooth eruption and molar wear (EW), and interpretation of cementum annuli (CA) in incisors. Aging techniques based on teeth are influenced by diet, body condition and metabolic stressors such as disease and reproduction. We compared age estimation derived by both EW and CA techniques and applied age estimates from both methods to lifetables and the Euler-Lotka equation to predict population growth. Sambar have CA that are discernible and correspond to midwinter despite calving throughout the year in a temperate environment. Age estimation by eruption times of molar teeth appears reliable in sambar but estimation based on wear patterns of molar teeth is less accurate than CA. Assuming CA is accurate, aging by EW was less than 30% for sambar 3 years and older. For management purposes, however, estimation of rates of population growth using either the Euler-Lotka equation or a lifetable provided similar outputs using ages estimated by either CA or EW.