Black tailed deer only breed once a year, in the late fall.
As the days shorten, hormone levels increase in buck deer, causing them to start rubbing their antlers on trees and bushes. They begin to fight with other male deer, pushing and shoving with their antlers to determine who is strongest.
These battles can be loud and aggressive but the bucks are only interested in other deer and don't pose a threat to people, however as you would with any wildlife, keep your distance.
The real risk is that bucks are extremely intent on finding and chasing females, so much so that they may blindly run into traffic. Be extra vigilant when driving at this time of year – slow down and scan ahead for deer. Rutting activity occurs at any time of the day or night.
When out walking your dog close to areas where deer are known to be, it’s extremely important that you keep your dog on a leash. Occasionally a buck will lower his antlers and take a step toward a person or dog. Just walk slowly away and he'll leave you alone. Be prepared to change your route if you are concerned.
By mid-December, bucks will drop their antlers and the rut is over.