Photo analysis
To estimate the extent of winter coat shed, we compared pixel counts of
shed versus unshed areas of mountain goats’ coats in each photograph
using Adobe Photoshop. First, we outlined the entire animal, typically
using a combination of the quick selection and lasso tools (omitting
hooves, eyes, nose, mouth, and horns), copied the animal, separated from
its background, into a new layer (total layer). Second, we duplicated
this layer, and outlined the shed and unshed areas and cut these as new
layers (shed and unshed layers). We selected all pixels in the layers
and used the histogram tool to obtain counts of both shed and unshed
areas. Lastly, to create quick visuals, we filled the unshed area with
red and the shed area with black; a video tutorial of one of our
approaches can be found here:
https://www.youtube.com/watch?v=h9cWl9Z1Odw. Our non-invasive,
photo-based moult analysis is not without precedent: Vieira et al.
(2017) used photos to evaluate feather moult in black skimmers
(Rynchops niger ) and Beltran et al. (2019) used photos to study
moult in Weddell seals (Leptonychotes weddellii ).