Orca Communication System
If you have listened to live orcas or in documentaries or movies, you will know that their sound is too loud, tuneful and sharp. Humans have vocal cords in the larynx to make sounds, but orcas don’t. They have a compact tissue in the nasal region that produces the sound. As a highly social species, they undoubtedly require an effective communication system.
Although not readily visible, the ears of orcas are small openings located behind their eyes and are very well developed. When hunting in the dark or highly turbulent waters, sighting is not very useful, so they rely entirely on their sense of hearing to navigate, communicate and hunt.
Killer whale pods have a very complex communication system, and most components of it have not been deciphered by researchers yet. However, experts have reached some conclusions like that one pod produces a completely different set of sounds than other pods; thus, each individual can recognize the group where it belongs. Such sounds are learned and transmitted from generation to generation among the members of the community and have been called dialects. Calves are born with a limited repertoire of sounds that slowly expand as they learn from their mother and other adults in the pod. The dialects are essential for the identification and cohesion within the group.
Among different pods some similar vocalizations can exist, but there are not two different pods with the same repertoire of sounds. Although we believe that everything sounds the same, scientists have carefully studied the characteristics of each of these sounds like duration, volume, frequency and moments in which they use them and more.
As an example, the sounds of a pod in Norwegian waters were compared with those from a pod living in waters close to Iceland; that is, they had some geographical proximity. The residents of Iceland had 24 different sounds, while those from Norway had only 23, however what surprise them more, is the fact that not a single sound was repeated in both groups, all were unique to each pod.
Scientist have classified three types of sound communication: whistles, discrete calls and clicks. Whistles and discrete calls are usually employed in the pod communication and clicks when performing echolocation, a technique used to detect elements of their environment.
Research about orca communication is made with underwater microphones called hydrophones, which have provided valuable data to scientists. At the same time, they have triggered the curiosity of specialists in whether beside these complex conversations between the orcas there are other vocalizations at very low frequency that require more sophisticated hearing devices.
Studies show that the resident populations of the Pacific Ocean tend to be noisier than transient, even though they share the same waters. Orcas sound frequencies vary according to the prey they wish to hunt as marine mammals such as pinnipeds can easily detect those sounds. Some use very short sounds and others remain silent. They know that when dealing with fish noise does not matter, but when hunting other marine mammals they should remain silent.
Echolocation
This sensory capability allows better navigation and more efficient hunting for orcas. During echolocation, sound travels through the water and bounces back from the fish or any other species of interest, making such vibrations return to the orca with valuable information that will give them accurate details on the prey. The size of the victim, their proximity, the depth of the water and the possible presence of other predators are found out through echolocation. Once an orca collects such data, it decides whether hunting that prey or better looking for a less complicated food that time.
The questions still unanswered make orcas yet interesting animals. Hopefully, global warming or ocean pollution does not threaten these beautiful mammals before we can fully understand them.
