Validation of gum-line recession as a reliable technique to age tigers

Abstract

Like other members of the Panthera genus, tigers are threatened throughout their range. Given their conservation status research focused on their population dynamics in the wild is needed, including population growth, lifespan, and breeding success, which requires reliable estimates of age. Current techniques to estimate age in tigers are either not reliable and/or difficult to apply in the field. Gum-line recession accurately estimates age for mountain lions, but has never been tested for tigers. The goal of this study was to determine whether gum-line recession of the upper canine teeth is a reliable indicator of age in tigers and if so, to define the equation that enables age estimation. We measured gum-line recession in 12 individuals of known ages and performed linear regression analysis to investigate the validity of this technique for tigers. We found a strong relationship between gum-line recession and age, where the model provided reliable age estimates for animals within 1-year age classes in 10 out of 12 tigers measured, providing increased accuracy over current methods.

Evaluation of Gum‐line Recession for Aging Lynx (Lynx canadensis)

“…Age estimates using GLR have been shown to correlate well with age estimates obtained from cementum analyses in some felids (Laundré et al 2000, Fàbregas and Garcés‐Narro 2014, Hiller and Tyre 2014). However, for Canada lynx, we found that GLR was not an accurate method, nor did it correspond well with age estimates using cementum annuli.…”

“…The latter was demonstrated by a weak predictive capacity even after the removal of kittens and yearlings. The poor correlation of GLR with age in Canada lynx, relative to other felids (Fàbregas and Garcés‐Narro 2014, Hiller and Tyre 2014), may stem from differences in diet among species, and therefore the degree of tooth wear (Galbany et al 2014).…”

“…The low repeatability of the measurement among observers further reduced the utility of GLR for ageing lynx. Differences between observers may occur because of the relatively small amount of recession that exists in lynx species (<3 mm) relative to other felids (i.e., <6 mm in cougars, <9 mm in tigers; Laundré et al 2000, Fàbregas and Garcés‐Narro 2014) making it difficult to accurately and reliably quantify. Although training occurred for each observer, the degree that further training and experience can improve repeatability in GLR measurements should be examined.…”

“…In this study, our goal was to determine if GLR could be used as a cost‐effective approach to aging individuals in harvest monitoring programs that utilize trapper‐submitted carcasses (Kukka et al 2017, Jung et al 2020). Additionally, GLR may potentially be applied in live‐trapping studies of lynx, similar to that for other felids (Laundré et al 2000, Fàbregas and Garcés‐Narro 2014). Specifically, we assessed 1) the relationship between GLR and age estimates obtained from cementum analysis, 2) differences in GLR measurements between age classes of lynx, and 3) the variation in GLR measurements within and among observers.…”

“…Another metric of dental characteristics for aging felids is gum‐line recession (hereafter, GLR), where the distance between the juvenile and current gumline is measured and used to estimate age. Although GLR is correlated with known age in large felids, such as cougars ( Puma concolor ; Currier 1979, Laundré et al 2000, Hiller and Tyre 2014), and tigers ( Panthera tigris ; Fàbregas and Garcés‐Narro 2014), it has not been widely validated across species. Furthermore, for smaller felids with less pronounced distinctions between previous and current gumline, such as lynx ( Lynx spp.…”