Judging a reindeer by its teeth: A user‐friendly tooth wear and eruption pattern recording scheme to estimate age‐at‐death in reindeer (Rangifer tarandus)

Abstract

Reindeer (Rangifer tarandus) have shaped the cultures and provided livelihood to peoples of the Northern Hemisphere for thousands of years. They are still the socio‐economic cornerstone of many northern cultures. Insight into reindeer mortality patterns is important for understanding past human–reindeer interactions and reindeer population fluctuations in relation to climatic and environmental change. Beyond archaeology, assessing the age structures of modern reindeer populations is important for developing wildlife management strategies. This paper presents a quick, non‐destructive and cheap method to estimate age in reindeer in both modern and ancient populations based on tooth wear and eruption patterns of mandibular teeth. We devised the method using a large sample of Svalbard reindeer (Rangifer tarandus platyrhynchus) of known age. We blind‐tested the method and tested its applicability on another known‐age Svalbard reindeer mandible assemblage. The tests demonstrate our methods' user‐friendliness and reliability to generate reproducible, reusable datasets and accuracy in estimating reindeer age‐at‐death.

Tooth Wear Age Estimation of Ruminants from Archaeological Sites

“…These methods are divided into three overarching categories: Crown Height, Visual Wear Pattern, and Wear Trait Scoring Methods. Usually, researchers can easily tell which animals are younger or older relative to one another using tooth wear (Aitken 1975;Gifford-Gonzalez 2018;Lowe 1967;Spinage 1973;van den Berg, Loonen, and Çakırlar 2021). The greatest challenge is to relate relative age to an estimation of age in years or months (Miller 1974).…”

“…The 'absolute scheme' is only for Svalbard reindeer mandibles (van den Berg, Loonen, and Çakırlar 2021). The 'relative scheme' could be applied to any reindeer or caribou population but requires the user to calibrate this scheme themselves using either known age or accurately ageing reindeer mandibles from the relevant region (van den Berg, Loonen, and Çakırlar 2021). There are also separate tooth wear illustrations for each scheme demonstrating the variation of wear between Svalbard reindeer and other Rangifer populations (van den Berg, Loonen, and Çakırlar 2021, 4-6).…”

“…There are also separate tooth wear illustrations for each scheme demonstrating the variation of wear between Svalbard reindeer and other Rangifer populations (van den Berg, Loonen, and Çakırlar 2021, 4-6). Unfortunately, this method leaves the potential user outside the Svalbard region with three options: apply the 'absolute scheme' with the assumption that the accuracy will be close enough to be meaningful, apply the 'relative scheme' without assigning ages in their analysis, or calibrate the 'relative scheme' themselves (van den Berg, Loonen, and Çakırlar 2021). Not only would time be needed to calibrate this scheme, but if known-age specimens are unavailable, destructive and time-consuming cementum annulation may be required (van den Berg, Loonen, and Çakırlar 2021) and is not as reliable as true known-ages (Miller 1974).…”

“…The popularity of the Visual Wear Pattern Method suggests that this approach is relatively easy to use while providing meaningful results. This method is straightforward to adapt to new ruminant species (Bowen et al 2016;van den Berg, Loonen, and Çakırlar 2021;Lubinski 2001). Although Visual Wear Pattern Methods work for loose teeth or incomplete mandibles, the accuracy is severely reduced (Twiss 2008, 349).…”

“…Tooth wear age estimation is more efficient and easier to learn than cementum annulation and can be adapted to additional species with some work and access to knownage specimens (Gifford-Gonzalez 2018;Lyman 2017;Miller 1974;Spinage 1973). This method has been developed for and applied to age a variety of mammals in zooarchaeology (Bowen et al 2016;Dudley Furniss-Roe 2008;Grant 1982;Greenfield and Arnold 2008;Halstead 1985;Hambleton 1998;Klein and Cruz-Uribe 1983;Lubinski 2001;Morrison and Whitridge 1997;Mutze et al 2021;Pasda 2009;Payne 1973;1987;Pike-Tay, Morcomb, and O'Farrell 2001;Steele and Weaver 2012;Tomé and Vigne 2003;Twiss 2008;van den Berg, Loonen, and Çakırlar 2021), in wildlife management (Brown and Chapman 1990;1991;Høye 2006;Lowe 1967;Miller 1972;1974;Pérez-Barbería et al 2014), and in veterinary studies (Aitken 1975). For mammals, mandibles and teeth survive well against taphonomic processes, and are therefore more likely available for archaeological research compared with fragile maxillae (Gifford-Gonzalez 2018, 125;Pasda 2009;Spiess 1979, 77;Winkler and Kaiser 2015).…”