Chin whiskers tell deer precisely how far their lips are from the ground when they feed. I also read that they may determine air movement.

How I Got The Photo – Why Whitetail Deer Have Chin Whiskers
This Whitetail Doe was near the road and I pulled up close to her to get this photo. I had my camera and lens resting on a bean bag draped over the open window of my pickup.
Gear Used:
- Camera: Canon EOS 1D Mark III
- Lens: Canon EF 500 mm f/4L IS USM
Technical:
- Location: Sequoyah National Wildlife Refuge (Oklahoma)
- Date Taken: August 13, 2009
- Aperture Priority
- Aperture: f5.6
- Shutter speed: 1/250 sec. (as determined by the camera)
- ISO: 800
- White Balance: Auto
- Metering Mode: Evaluative
- Exposure Compensation: 0 EV
- Back-button Focus
- Single Point Focus
- Focal Length: 500 mm
- Processed With Luminar 4