Another female. I have noticed over time. Slight head differences between male vs female head. The female has a tapered/sleek forehead, between the muzzle & forehead. The demarcation between the muzzle & forehead of a female is not as abrupt. Males also tend to have a wider muzzle & face.
I never tried to kill any of these fox. I just observed them in their natural setting. As I sought to learn their behaviors. Same with most coyotes I've laid eyes on.