Deer travel in groups. One deer means there are probably more, so even if the one you see is off the road and going away, slow way down immediately.
Heed deer-crossing signs, particularly in the seasons and times of day when deer are active. Slow down, use your high beam, and cover the brakes.
The Wisconsin DOT says that deer collisions peak in October-November, with a smaller peak in May-June. Such crashes between April and August are most likely to occur between 8 pm and midnight. Between November and January, 5 to 10 pm were the danger times.
Additional good, powerful driving lights are worth their weight in gold on a deserted road at night. Alternatively, fit a bulb with a 100-watt high-beam.
Noisea horn, revving your engine, etc.may drive deer away. (Don't count on it though. My son and I recently went out to plink not far from that Sierra Nevada road, and after we set up, a doe and fawn appeared perhaps 30 yards away between us and our targets. I figured they would be gone at the first gunshot, so we fired it in a different direction. They didn't move then or when we fired into the tree above them several times, dropping debris around them. We finally had to shoo them away.)
Flashing your headlights may break the spell that seems to cause deer to freeze.
Deer and other wild animals are designed to be hard to see. Aside from the flickering white tail of some species or reflection from an eye, they simply disappear. However, this absence of reflected light can also tip you off. A "hole" in a white fence or wall or "missing" roadside reflectors at night might be an animal. A reflector that "blinks" might also indicate an animal passing between you and it.
Don't challenge large animals by approaching them. A buffalo, moose, elk, mountain lion, bear, or large deer might attack to drive you off. Stay away and consider turning and riding farther away. A rider and his Harley were thrown high into the air by a bison last summer when he tried to ride through a herd crossing a road.
If an animal has been injured, stay away. It may attack or injure you unintentionally if it comes to and tries to escape.
If a collision appears imminent, do not swerve. Braking hard right up to the point of impact is good, but you want to be stabilized if you do collide, which will give you the greatest chance of remaining upright.
If riding in a group, spread out. This will keep one rider who hits a deer from taking other riders down with him.
Wear protective gear. As with other crashes, no one plans to hit an animal. The only way to be ready when it happens is to be ready on every ride. Wearing a helmet for a relaxing evening ride may seem unnecessary, since you are taking it easy, but the deer won't care. A few years ago, a rider told me of a deer leaping over him and catching him hard enough with a hoof to leave a significant gouge in the side of his helmet and wrench his neck a bit. That rider was very pleased he was wearing a good helmet. A collision with a deer that leaves you lying injured or unconscious in the road is also one of those occasions when you will appreciate reflective material on your gear.
On hot muggy nights when there are a lot of mosquitoes, moose and deer head out of the woods to escape the fly bites. If you have a thick film of bugs on your eye protection, clue in that the animals are getting eaten alive and their situational awareness is impaired.
If you are driving at night and see the oncoming headlights "twinkle", that is probably a moose or a deer legs intersecting the headlight beams. They are rarely alone and may be with young. Slow down and keep your eyes open.
During the spring time, deer and moose congregate along side of roads to lick the salt applied during the winter months to control road ice.
Watch for dips in a road where the surrounding land is swampy or a brook crosses under the road. These are usually trails used by animals. Transportation departments are getting better at labeling animal crossings but usually as a result of tragic animal collisions at that location in the past. It is a sobering thought to realize the price that was paid for the DOT to incur the expense of installing and maintaining that sign.
Small animal motorcycle collisions with raccoons and porcupines can also be deadly. A fast-moving motorcycle with the brakes locked is a recipe for disaster. A glancing hit can veer a motorcycle off the road. These animals are low and have a round body structure that doesn't "crush," causing the body to roll under an undercarriage. You will have to replace those tires after striking a porcupine!
Finally, there is the skunk. You don't want to slow down close to one, they will let you know that they are not happy that you invaded their personal space._