ORIGINAL PAPER Accuracy and repeatability of moose (Alces alces) age as estimated from dental cement layers Christer M. Rolandsen & Erling J. Solberg & Morten Heim & Frode Holmstrøm & May I. Solem & Bernt-Erik Sæther Received: 30 June 2006 / Revised: 23 March 2007 / Accepted: 29 March 2007 / Published online: 20 April 2007 # Springer-Verlag 2007 Abstract Optimal research and management of species with age structure often depends on estimates of age- specific population parameters, which in turn depends on reliable methods for age determination. By counting annuli in the cementum of incisor root tips from 51 known-age moose (Alces alces) between 1 and 12 years old, we examined the variation in accuracy and repeatability of age estimates provided by three research technicians with different experiences of aging moose. The most experi- enced technician estimated the moose age correctly in up to 90% of the cases, while the technician with no prior experience estimated age correctly in up to 73% of the cases. The medium-experienced technician achieved a lower accuracy (up to 53%), indicating that experience alone is not sufficient if the basic training or lack of routine checks against other colleagues or a known-age material are not undertaken. The percentage moose aged within ±1 year from correct age was significantly higher in all technicians (94–98%). After the generally high accuracy, we also found high repeatability (0.980–0.994) within technicians. We conclude that this method of age-determination provides reliable estimates that can be used by management and research to gain information about age-specific patterns in moose populations. However, to obtain estimates of high accuracy the technicians should be well trained, have gained the necessary experience, and most preferably, have access to a sample of teeth from known-age moose. Keywords Age estimation . Alces alces . Known-age . Moose . Tooth sections Introduction Estimates of age-specific population parameters are impor- tant for optimal research and management of species with age structure (e.g., Sæther 1997; Gaillard et al. 1998; Solberg et al. 1999, 2004; Festa-Bianchet et al. 2003; Mysterud et al. 2005), and accordingly there is a constant need for relatively accurate age estimates. In moose and other mammals, age estimates are often provided by counting the number of growth layers (annuli) deposited in the dentine and/or cementum of their teeth. This method was first developed for marine mammals (Laws 1952; Scheffer 1950), but a few years later it was also applied for moose (Sergeant and Pimlott 1959) and other cervids (Low and Cowan 1963; Gilbert 1966; Reimers and Nordby 1968). The rationale is that annuli of teeth varies over time due to slow and fast growth associated with climate and/or nutritional stress (e.g., winter/dry season vs summer/wet season), although the exact understanding of what deter- mines the formation of annuli in different species and regions is not fully understood (Grue and Jensen 1979). Thus, by counting the annual cementum and/or dentine layers in permanent incisors or molars, while correcting for missing layers that has been deposited in deciduous teeth, a reasonable accurate age estimate can be provided for a number of animals. Eur J Wildl Res (2008) 54:6–14 DOI 10.1007/s10344-007-0100-8 Communicated by H. Kierdorf C. M. Rolandsen (*) : E. J. Solberg : M. Heim : F. Holmstrøm : M. I. Solem : B.-E. Sæther Norwegian Institute for Nature Research, Tungasletta 2, 7485 Trondheim, Norway e-mail: christer.rolandsen@nina.no B.-E. Sæther Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway