Estimating body mass of wild pigs (Sus scrofa) using body morphometrics.

Abstract

Wild pigs (Sus scrofa) are invading many areas globally and impacting biodiversity and economies in their non-native range. Thus, wild pigs are often targeted for eradication efforts. Age- and sex-specific body measurements are important for informing these eradication efforts because they reflect body condition, resource availability, and fecundity, which are common indicators of population trajectory. However, body mass is often difficult to collect, especially on large individuals that require specialized equipment or multiple people to weigh. Measurements that can be rapidly taken by a single land or wildlife manager on any size wild pig without aid from specialized equipment would be beneficial if they accurately infer wild pig body mass. Our goals were to assess whether morphometric measurements could accurately predict wild pig body mass, and to provide tools to directly input these measures and estimate wild pig body mass. Using linear models, we quantified the relationship between body mass and morphometric measurements (i.e., body length, chest girth, ear length, eye to snout length, hindfoot length, shoulder length, and tail length) from a subset (n=102) of wild pigs culled at the Mississippi Alluvial Valley, Mississippi, USA. We evaluated separate models for each individual morphometric measurement. We then used the model coefficients to develop equations to predict wild pig body mass. We validated these equations predicting body mass of 1592 individuals collected across eight areas in Australia, Guam, and the USA for cross-validation. Each developed equation remained accurate when cross-validated across regions. Body length, chest girth, and shoulder length were the morphometrics that best predicted wild pig body mass. Our analyses indicated it is possible to use the presented equations to infer wild pig body mass from simple metrics.