Sound is very important to animals living in aquatic environments as the visibility is often very poor underwater. Researchers have discovered a lot about family relationships of killer whales by listening to the sounds they make. A great deal of information about the social relationships in resident killer whales has been revealed through this acoustic research. Whales communicate with one another through a wide variety of whistles, squeaks and whines. Canadian researchers have discovered that in resident pods, each whale has the same set of calls, or DIALECT, as other pod members. The only other mammals known to have true dialects are humans, some monkeys, and the sperm whale. Groups of whales that share the same "dialect" are related to each other. Pods of whales with related dialects are called CLANS.

While killer whales have good eyesight and can see both above and below the water. This sense has limitations depending on time of day and water clarity. However, the use of underwater sounds to communicate is unaffected by these limitations. Sound travels very well through water going further and faster than the same sounds produced above water. Underwater sounds can be heard and recorded using an underwater microphone, called a hydrophone. Hydrophones have been placed at strategic locations along the British Columbian coastline to monitor for whale vocalizations.

hydrophone

Killer whales produce three types of underwater sounds:

	echolocation used to navigate and find food
	calls and whistles used to communicate between group members.

Calls can be analyzed using spectrograms. They allow researchers to identify different pods through acoustic means as well as visual clues (i.e. photo identification). Each call is given a specific name (i.e. n4) and whales that use the same calls are related to each other in some way.
Below are the spectograms associated with five different calls. Click on the calls below to hear the differences between them.
n4	n7
n9	n8
n13

Killer whales have a fatty organ at the front of the head called a melon, which focuses emitted sounds into a beam ahead of the animal. The whale produces a beam of rapidly emitted echolocation clicks to help it navigate and find food. As the clicks are projected forward, they bounce back to the whale from objects in its path.

Resident Killer Whales
Resident killer whales are very vocal whales that echolocate frequently and use vocalizations to keep within earshot of each other while foraging. This makes the use of hydrophones to track their location very useful. In fact, resident killer whales have group-specific dialects so recordings can identify not only that resident killer whales made the vocalizations, but also the pod(s) to which the whales belong.

click here to learn more about the social structure of resident killer whales

Unlike transients, resident killer whales have a large repertoire of distinct calls, averaging about 12 per pod. Whales that sound similar belong to the same clan and share a unique set of related dialect among them. In the northern resident community there are three clans (A, G, and R) and in the southern resident community there is the single J clan. 

Resident killer whale vocalization

Transient Killer Whales
Transient killer whales tend to be very quiet while travelling and foraging, and can often pass by a hydrophone without being detected. This is because their prey (i.e. porpoises, sea lions, seals) have ears and would be able to hear the whales approaching if they were making noise. However, when they are attacking and killing prey, transients become quite vocal, and can be easily identified by their unique calls.

Transient killer whale vocalization

Transients have a very fluid social structure, which may explain their lack of group-specific dialects, as heard in resident killer whales. Instead of a wide variety of dialects, most transient calls belong to the same repertoire of 4 to 6 distinct call types. It should be mentioned, however, that there is some variation between the call repertoires of B.C., Alaskan and Californian transients. All transient whales along the Pacific Northwest coast appear to share the same dialect.

Offshore Killer Whales
Little is known about the vocal patterns of offshore killer whales, however it appears that their calls are completely different from those produced by either the resident or transient killer whales. Whether all offshore killer whales produce the same calls, as in the case of the transients, or if they have distinct dialects like the residents, remains to be discovered. 

Offshore killer whale vocalization