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 ).