The video was taken at night using a trailcam. It uses infrared which shows up as a red glow on the camera. However this Chital though it must be aware of the camera shows no alarm until it is opposite. Then you can see it starts smelling the air as it twitches its nose. I have come to the conclusion is that what it is smelling is the human scent on the trailcam and hence its alarm - there are poachers around in the jungles of India so wildlife has to be on the lookout.....