Estimating age of carnivores from the Pantanal region of Brazil

Abstract

Conservation and management of animal populations often require knowledge about the age structure, but this information is usually difficult to discern. We propose a method to estimate the age of carnivores based on dental condition and body size measurements, and we apply the method to populations of brown‐nosed coatis Nasua nasua and crab‐eating foxes Cerdocyon thous in the Brazilian Pantanal. We sexed, weighed and measured 31 coatis and 45 foxes of known‐age, and characterized and quantified their pattern of dental eruption and wear for the construction of a teeth condition index. Scores of the first factors of a principal component analysis including data on six body size measurements and the teeth condition index of the individuals were then used in a discriminant analysis to generate functions that can be used for estimating age of animals of unknown age. Models were validated using subsets of individuals of known age through a 3‐fold cross validation process. The first functions accounted for over 90% of the discriminatory power for both species. Whereas in coatis, the first function was mainly explained by the body size measurements, in crab‐eating foxes it was represented mainly by the teeth condition index. During model validation, individuals were on average classified with 88 and 80% average confidence for coatis and foxes, respectively. Our method is as accurate as other methods that are commonly applied to assess age, but less subjective. While it requires animal capturing, it is less invasive than methods requiring tissue removal such as analyses of teeth cementum annuli. The method we outlined can be used for age estimation of other populations, as long as the models are validated with a subset of animals from the region studied. It could also be useful as a model for estimating age of other carnivore species.

Quantifying the age- and sex-dependent morphological variation in two syntopic mustelids: Martes martes and Martes foina

“…The PCA clearly showed a high correlation between body mass, head-and-body length, tail length, and neck circumference, with the notable exception of the posterior foot length. The overall reassignment success rate of the discriminant analysis seemed to be fairly good (85.24%) when compared to studies on other carnivores where accuracy of age determination ranged from 31 to 100% (Gerasimov, 1985;Olifiers et al, 2010). In all cases, the main errors were the misclassification of adults in the subadult class or the reverse.…”

Applicability of Age-Based Hunting Regulations for African Leopards

“…The factor scores of the first PCA axes that explained >80% of the cumulative data variation were then applied in a discriminant analysis (DA) to determine whether the phenotypic traits could be reliably used to assign male leopards to their respective age classes [26]. The discriminant model was built using a randomly selected 70% of the dataset.…”

Relationship Between Tooth wear and Age in the Japanese Black Bear in Hiroshima Prefecture, Japan

“…Use of distinguishable wear categories following Olifiers et al (2010) allowed us to limit subjectivity when evaluating tooth attrition, which likely improved the repeatability of our assessments. Moreover, the constant increase of tooth attrition with fox age indicated the relevance of a linear model to predict age of individuals, whereas the strong relation (r 2  0.64) between tooth wear notation and known age indicates that individuals could be reliably aged from tooth wear in our studied population.…”

“…Most of the times, tooth wear was used in dead (Harris 1978, Smuts et al 1978, Harris et al 1992, Gay and Best 1996, Hewison 1999, Gipson et al 2000, Rosatte and Silver 2007, anesthetized (Stander 1997, Van Horn et al 2003, Olifiers et al 2010, Delahay et al 2011 or captive (Grau et al 1970) animals. To our knowledge, only Lohr et al (2011) used tooth wear to age non-anesthetized wild mammals, in their case, the brushtail possum Trichosurus vulpecula.…”