A drone caused 1,500 elk to stampede for half a mile in western Wyoming.
The incident occurred at the National Elk Refuge after a man flew a drone over a resting herd.
Food is put out to help elk, which are one of the largest species of deer, survive for the winter.
Due to the harsh weather conditions, where more than three feet of snow has piled up, the animals often congregate at the refuge.
Disturbing wildlife is a serious offence in the United States and those who are found guilty can receive a fine of up to $5,000 (£4,000).
The man, who has not been identified, is thought to be from Washington DC and was given a fine of $280 from a US Fish and Wildlife Service officer.
It is believed he launched the drone from a highway pullout, according to ABC News.
No-one at the National Elk refuge was immediately available for comment.
