Complex sentence: The area between the forehead and antlers contains a large number of apocrine sweat glands, and leave a scent that communicates a challenge to other male deer while also attracting potential mates.
Split into simpler sentences: The area between the forehead and antlers contains a large number of apocrine sweat glands. The scent left by deer rub communicates a challenge to other male deer, and attracts potential mates.