Ontogenetic skull variation in an Amazonian population of lowland tapir, Tapirus terrestris (Mammalia: Perissodactyla) in the department of Loreto, Peru

Walter Vasquez Mora,Richard Bodmer,Eckhard W Heymann,Ethersi Pezo Lozano,Rommel R Rojas,Emérita R Tirado Herrera

doi:10.1590/1809-4392202101382

Abstract

ABSTRACT The skulls of 54 specimens of the South American tapir, Tapirus terrestris collected in the department of Loreto, Peru were measured, analyzed and compared to investigate skull development of this species. Univariate, multivariate and allometric analyses were performed using 32 skull variables through traditional morphometrics. Significant skull shape variation was detected among ontogenetic classes. Young individuals (class I, n = 22) showed higher variation than subadults and adults (class II, n = 23 and class III, n = 9), without evidence of sexual dimorphism (males = 35, females = 19). Principal component analyses and discriminant function analysis showed almost complete separation of the age classes. Allometric analysis indicated a tendency of unproportioned cranial growth. All our samples come from the same population living under the same ecological condition, which eliminates the effect of confounding variables related to habitat on the pattern of ontogenetic variation of this anatomical structure.

Highlights

The ungulate mammal genus Tapirus Brisson, 1762 (Perissodactyla), comprises five living species: T. pinchaque (Roulin, 1829) distributed in the Andes mountains, T. terrestris (Linnaeus, 1758) and T. kabomani (Cozzuol et al 2013) in South American Amazonia; T. bairdii (Gill, 1865) in Central America and T. indicus Desmarest, 1819 in southeastern Asia
Our study investigates the skull development in T. terrestris using a large sample of skulls from the same population in Amazonia, with the aim of controlling the effect of ecological conditions on the ontogenetic and sexual dimorphism of the South American tapir
The two axes of the Principal Component Analysis (PCA) indicate a high overlap in relative skull shape between the sexes (Figure 4A)

Summary

Introduction

The ungulate mammal genus Tapirus Brisson, 1762 (Perissodactyla), comprises five living species: T. pinchaque (Roulin, 1829) distributed in the Andes mountains, T. terrestris (Linnaeus, 1758) and T. kabomani (Cozzuol et al 2013) in South American Amazonia; T. bairdii (Gill, 1865) in Central America and T. indicus Desmarest, 1819 in southeastern Asia. South American species of tapirs dispersed from North America during the Great American Biotic Interchange, which followed the formation of the Isthmus of Panama (Webb 1991; Woodburne 2010; Carrillo et al 2014; O’Dea et al 2016). Ontogenetic skull variation in an Amazonian population of lowland tapir, Tapirus terrestris (Mammalia: Perissodactyla) in the department of Loreto, Peru. ROJAS et al Ontogenetic variation in lowland tapir skulls males have long penises relative to their body size (Bodmer et al 1988; Maffei 2003). The most prominent feature of their head morphology is the presence of a short, mobile proboscis (Padilla and Dowler 1994)

Methods

Results

Conclusion