BACKGROUND: Researchers often document wildlife surveys using images. These images contain data that can be used to understand alterative research objectives, even years after they were originally captured. We have developed a method to measure age and morphology (body size measurements and
tusk size) from survey image databases and future surveys, without the availability of a known subject distance or a scale in each image. African savanna elephants (Loxodonta africana) serve as an ideal model species to develop a non-invasive, image-based morphometric methodology: as handling these animals is particularly invasive and expensive, involving anaesthesia and because of their IUCN \'vulnerable\' status. We compare in situ measurements, taken during collaring events, to
tusk-to-body-size ratios, measured from the images.
RESULTS: We provide evidence that relative morphological measurements, musth timing, and age of male African savanna elephants can accurately be obtained from a survey image database of over 30,000 images, taken over an 18-year period. Of the 11
tusk to body size ratios calculated, we recommend the use of two in particular for future measurement in African elephants to determine size and age: 1)
tusk length to
tusk diameter and 2)
tusk length to body height.
CONCLUSIONS: We present a practical, non-invasive measure to estimate morphometrics, including both age and
tusk size from photographs, which has conservation applications to the protection of elephants and is relevant to a range of other taxa.