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.
