Terrestrial mammal three‐dimensional photogrammetry: multispecies mass estimation

Abstract

Assessing body mass in mammals is of importance as it influences virtually all aspects of mammal physiology, behavior and ecological parameters. However, the assessment of body mass of large mammals is potentially dangerous and logistically challenging. Photogrammetry (measurements through the use of photographs) is a well‐established science. In zoology it has been used with varying success to estimate the size and mass of some marine and terrestrial mammal species. However, photogrammetric body mass estimation of terrestrial mammals has received comparatively little attention. This is largely due to species' variable morphological attributes which complicates measurement especially if, for 3D orientation, photogrammetric models are dependent on identifiable features on the animals themselves. Ninety‐two individuals belonging to 16 terrestrial mammalian species were weighed and photographed for body mass estimation using a volumetric photogrammetry method, purposely applied with commercially available software. This method is not dependent on identifiable body features for 3D orientation. Measured body mass ranged from 25 kg to 4060 kg. Photogrammetric mass estimates versus physically weighed mass was plotted and the goodness of fit assessed for each species. Body size, shape and physiological attributes influence the accuracy of body mass estimation between species (although consistent within species), largely attributed to morphological features (e.g., hair length and posture). This photogrammetric method accurately estimated the body mass of several terrestrial mammal species. It represents innovative use of photographs to create calibrated three‐dimensional imagery for accurate quantification of mammalian metrics, specifically body volume and mass. Advances of a method that is not subject to species, sex or age is advantageous and suitable for wide application in our effort to model population demography.

Measuring Complex Morphological Traits with 3D Photogrammetry: A Case Study with Deer Antlers

“…Photogrammetry is a cheap and simple method to obtain 3D data from sets of 2D digital photographs (Falkingham 2012;Katz and Friess 2014). It has been successfully used to estimating body size in the field for a variety of species (Breuer et al 2007;Waite et al 2007;Chiari et al 2008;de Bruyn et al 2009;Postma et al 2015;Beltran et al 2018; see also Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s1169 2-020-09496 -9) contains supplementary material, which is available to authorized users. Christiansen et al 2019) or shape of marine colonial organisms (Lavy et al 2015;Gutierrez-Heredia et al 2016;Roth et al 2019).…”

Exploring South Africa’s southern frontier: A 20-year vision for polar research through the South African National Antarctic Programme

“…This research area offers unique opportunities for innovative and leading engineering studies; within the South African context this field is largely unexplored. Furthermore, the challenging field conditions for biological research also promote creativity and ingenuity in the use and development of novel technologies 33 that can be applied more broadly 34 .…”

Body-Mass Estimation in Paleontology: A Review of Volumetric Techniques

“…Initial studies employed a dual parallel-laser approach as a means of measuring linear dimensions in the field (Durban and Parsons, 2006;Bergeron, 2007;Rothman et al, 2008), and 3-D photogrammetric techniques are becoming increasingly popular (Waite et al, 2007;de Bruyn et al, 2009;Postma et al, 2013). A recent interspecific analysis of modern African mammals reported reasonable success in mass prediction using a volumetric approach (Postma et al, 2015). Mass predictions were invariably overestimates, however, ranging from 11% to 49% of recorded body mass.…”

“…Perhaps more of a concern, the degree of overestimation differed considerably between digestive groups (e.g., carnivores, ruminants, fermenters). Thus, despite setting out to devise a single technique applicable to multiple mammal groups, the authors acknowledge species-specific calibration still remains necessary to achieve reliable mass estimates for some modern species (Postma et al, 2015). Therefore, the assumption that broad modern calibration equations (e.g., for quadrupedal mammals, Sellers et al, 2012;for birds, Brassey and Sellers, 2014) can perform well when applied to distantly related and/or functionally dissimilar fossil taxa has been further weakened.…”