The distinctive, explosive sound of a deer “blowing” or snorting is a well-known alarm signal across many species, including the common white-tailed deer and mule deer. This sharp, sudden noise instantly signals that an animal has detected a threat. This behavior is a fundamental part of the deer’s survival strategy, revealing the sophisticated nature of their anti-predator communication. The sound is a calculated action with complex purposes that extend beyond simply expressing fear.
How the Alarm Call is Produced
The deer alarm call is not a true vocalization, as it does not originate from the vibration of the larynx. Instead, the sound is a non-vocal, forced expulsion of air through the nostrils, similar to a greatly magnified sneeze. The resulting “snort” or “blow” is produced when the rapid, forceful flow of air causes the closed or pinched nostrils to vibrate.
The type of sound produced often depends on the distance and imminence of the threat. A deer startled at very close range, such as one beginning its immediate escape, typically produces a single, short, and explosive snort. Conversely, a deer detecting danger at a safer distance will often emit a series of drawn-out “whooshes” or longer blows, which can be repeated multiple times.
Immediate Triggers for the Call
The snort is typically triggered after a deer has moved past simple alertness and has begun actively assessing a potential threat. The alarm sequence is often initiated by olfactory detection, such as smelling the unfamiliar scent of a human or a predator. A deer may also be triggered by visual confirmation of a threat or by sudden, unexpected movement or noise.
When a deer senses a potential problem but cannot immediately confirm it, it often enters an assessment phase before blowing. During this period, the deer will stand rigid, stomp its front hoof, and use its nose and ears to try to identify the source of the danger. This stomping behavior can vibrate the ground, helping other deer detect the disturbance, and it also serves to urge the perceived threat to move and reveal itself.
The Dual Purpose of the Alarm
The primary function of the deer’s alarm snort is communication, serving a dual purpose: it works within the deer’s own species and is also directed toward the predator itself.
Intra-Species Communication
The first function is intra-species communication, serving as an immediate warning to nearby deer that danger is present. Since the sound can travel a considerable distance, it efficiently alerts group members, allowing them to freeze, become vigilant, or flee. This warning is particularly prevalent in social groups, such as the matriarchal family units of does and their fawns. By warning their kin, the deer increases the survival rate of its relatives.
Inter-Species Communication
The second function is inter-species communication, often referred to as the pursuit-deterrence hypothesis. In this scenario, the snort is a signal directly aimed at the predator, informing it that it has been detected. The loud, sudden noise communicates to a stalking predator, such as a coyote or bobcat, that the element of surprise is gone. Signaling that the threat has been identified may convince the predator to abandon the hunt, saving the deer the energy required for a full-speed chase. The act of blowing may also be an attempt to startle a hidden threat into revealing its exact location or causing it to retreat.