How giant are giant armadillos? The morphometry of giant armadillos (Priodontes maximus Kerr, 1792) in the Pantanal of Brazil

摘要

Morphometrics is the quantitative study of organisms shape and size. Intrinsic (e.g. age and sex) and extrinsic (e.g. abiotic conditions) factors can be related to morphological diversity and can aid in the study of species biology and ecology. Giant armadillos have rarely been captured in the wild and very little is known about the species. Here we aimed to characterize body measurements of free-living giant armadillos (Priodontes maximus) in mid-western Brazil and evaluate how these measurements vary between sexes and age classes to gain insights on the species biology and ecology. We captured 28 armadillos in the study area, 18 adults (9 males, 9 females) and 10 subadults (6 males, 4 females) and assessed twenty-five different morphometric measurements for each captured armadillo. To evaluate if age class and sex of adult individuals can be differentiated by a concise set of morphometric measurements we used Linear Discriminant Analyses. We encountered significant morphometric differentiation between age classes and report seven parameters that best discriminate individuals between age classes which may allow the identification of individual's age class in future studies. The wide morphometric variation in subadults could indicate that individuals have a long developmental process between weaning and sexual maturity. Morphometric differentiation between sexes was possible through the association of three morphological parameters and adult males are larger and heavier than females. Although we were limited by the number of animals sampled in previous studies, females presented similar body mass across studied sites, while males presented variation of up to ten kilos across the species distribution. This indicates that the degree of sexual dimorphism can vary among localities and raises interesting ecological questions regarding the species reproductive system. This variation can be related to abiotic factors (e.g. latitude, temperature and topography), differences in productivity among biomes (i.e. resource abundance and distribution), population density, and/or genetic variation between populations and should be explored further. We propose the measurements used here be used as standard measurements for this species since it encompasses all of the most distinctive features of the species and allows a full morphological characterization, enabling the future comparison between populations of this widely distributed species. (C) 2018 Published by Elsevier GmbH on behalf of Deutsche Gesellschaft fur Saugetierkunde.