Which deer species raises its white tail as an alarm signal to warn others?

The white-tailed deer is the deer species known for raising its white tail as an alarm signal when it detects danger.

This behavior is called tail-flagging. When alarmed or fleeing, a white-tailed deer lifts its tail and exposes the bright white underside, creating a conspicuous visual flash. The display is especially noticeable as the deer runs through vegetation, where it can help a fawn or nearby deer track its movement.

White-tailed deer also communicate danger through forceful exhalations called blowing or snorting, foot-stomping, scent, and body posture. Tail-flagging is therefore one part of a larger communication system rather than the animal’s only alarm response.

A common mix-up is mule deer, whose tail has a dark or black tip and whose rump pattern is different. Scientists have debated whether tail-flagging primarily warns other deer, tells a predator that it has been detected, or helps keep a group together. That debate concerns the signal’s function, not the species associated with the raised white tail.