Auditory Alarm Signals in Mammals

Alarm signals are vital to the majority of mammal species. Auditory alarm signals alert all the mammals in the group to the presence of predators or danger and allow them the opportunity to retreat. Some mammals appear to produce different noises to alert their groups to different sorts of danger. Marine mammals as well as terrestrial and arboreal mammals all use auditory alarm systems.

  1. Meerkats

    • Meerkats are part of the mongoose family. Meerkats live in large social groupings called mobs or gangs. Each member of the group is reliant on every other member for survival. Most mongoose species are nocturnal, but meerkats are diurnal, meaning that they are active during the day. They are also small animals that weigh very little. They forage together in large numbers during the day. Their size, feeding habits and environment mean that they have many predators, both terrestrial and airborne. Meerkat colonies are also at risk from other meerkat gangs. During the day, meerkats take turns standing sentry while the remainder of the group continue with their activities. If there is no imminent threat, the sentry makes soft chattering or peeping noises, but if the sentry detects the presence of potential danger, he makes loud barking or whistling sounds, which alerts the rest of the community to the threat.

    Velvet Monkeys

    • Velvet monkeys have different auditory alarm calls for different threats, and the behavior displayed by the monkey troop in response to hearing the alarm calls differs according to which threat the call represents. Three different alarm calls have been distinguished, which are for snakes, aerial predators and large terrestrial predators. One member of the troop vocalizes the specific threat, alerting the other troop members to potential danger. A snake alarm call results in the troop standing tall and looking around. An aerial predator vocalization results in the troop quickly exiting the trees and taking cover in bushes. A terrestrial predator warning signal results in the troop taking shelter in surrounding trees.

    Dolphins

    • Dolphins are marine mammals, and are highly intelligent, having a larger brain-to-body-weight ratio than any other mammal except humans. Dolphins live in groups called pods and have complex vocal communications. A dolphin produces distinct squeals and whistling sounds to alert the pod to potential threats.

    Elephants

    • Although elephants have few predators or other animals that threaten their survival, they still produce auditory alarm signals. The University of Oxford in the United Kingdom carried out a research project, published in 2010, regarding elephant alarm calls in the presence of bees. The study involved playing recordings of disturbed African killer bees in the presence of elephant groups. The study recorded evidence of the elephants making rumbling noises, thought to be alarm signals, alerting the rest of the group to the threat. The rumbling vocalizations resulted in other group members retreating and covering themselves in dust. Recordings of the warning rumbles were then played back to the elephant group without any disturbed bee sounds. This resulted in the group displaying the same behavior as when bee sounds were played. The study theorized that this behavior suggested that the elephants not only understood the rumbling vocals as a general warning but that they recognized the specific rumbling sound related to the threat posed by bees.