Orca Social Structure and (Whale) Dialects

It has been known that killer whales speak in dialects since at least March 10,1990, when Leigh Dayton published “Killer Whales Communicate in Distinct Dialects”. In Dayton’s paper, J. Ford, the curator of marine mammals at Vancouver’s Public Aquarium, discovered this through listening to the two main communities of killer whales that were then divided into pods, each with its own dialect. Based upon these facts Ford concludes that since dialect is dependent upon pod the dialect is genetic. (2) Since Leigh Dayton’s paper in 1990 more has been found about orcas (killer whales) and their dialects with respect to their social structure along with the fact that dialect is not restricted only to killer whales but many other species of whale.

The orcas Ford spoke of were orcas of the resident type as opposed to the transient and offshore types. Resident orcas live in coastal waters moving up and down specific stretches of coast and, remain in specific locations within their stretch for months at a time to feed on fish such as herring and salmon. These orcas “have a complex system of social grouping” (7) which I shall now try to explain.

The smallest unit of resident orcas consists of a matriline involving a matriarch and her descendants (about 8 orcas). The matriline is then built up into pods consisting of 18 orcas with the same dialect. Building up on that are clans, which consist of pods with similar, but not the same dialect. The largest group of orcas would be that of communities, defined as clans that mix with each other. Since pods consist of matrilines, meaning a group of orcas with one common female relative, one could come to the conclusion that dialect is dependent upon genetics. However, a look at the transient orca type would prove or disprove this.

Transient orcas are nomadic orcas (resident orcas are nomads tied to stretches of coast as opposed to the coast in general) that travel in groups of 7-8 that can but do not necessarily consist of a family group. Their diet usually consists of larger marine mammal prey such as harbor seals, sea lions, and other whales. The prey of transient orcas can hear better than that of the prey of resident orcas and as exemplified by the harbor seals of British Columbia have learned to distinguish the difference between the native orcas dialects and that of foreign dialects (usually transient orcas) and so the “seals associate all unfamiliar killer whale calls with danger and have memorized the noises that their harmless neighbors make.” (3) It is because of this that transient orcas hunt in silence until attacking or killing prey at which point they become quite vocal

While transient orcas are all genetically related each pod does not have its own dialect, instead there is one dialect spanning the entire group of transient orcas. It is believed that the transient orcas case is much the same for offshore orcas, orcas who live and eat in the deep sea, but not much is known about the third type of orca. Based upon these past two paragraphs does genetics determine dialect?

One could try and make the argument that transient orcas are all related due to the fact that they genetically mix through not living in a family pod, but the fact of the matter is that for resident orcas “matings never occur within matrilines, very rarely occur within pods and overwhelmingly occur outside clans.” (9) In fact, female orcas choose their mates based upon their having a dissimilar dialect from their own which would make transient and residential orcas about the same with respect to genetic diversity. It should be noted however, that the three types of orca located on the western coastline of North America (7) are determined by genetics, diet, and temperament, meaning that transient, resident, and offshore orcas are genetically different so much so that they probably haven’t interbred for “at least hundreds of generations.” (9) I propose and it has been implied that social structure and not genetics determines the dialects; that transient orcas pod hopping somehow results in one dialect whereas Resident orcas remaining in a matrilineal pod really only interact with each other and therefore the pods dialect remains isolated. However, no dialects in whale are as isolated than that of the finback whales of the Ligurian Sea.

The finbacks of the Ligurian Sea do not migrate and therefore do not mate with finback whales from other groups. Perhaps this group of whales dialect will in time become a whale language in it’s own right (as opposed to a dialect), incomprehensible by other finback whales. “Observations show that dialects of pods recently split apart are more similar than dialects of pods separated for many years.” (5) Another example of species isolation would be that of the blue whale.

Blue Whales off the Pacific northwest sound different than those from the western Pacific Ocean both of which sound different than the blue whales living in Antarctica, all of which sound different than the whales located just off Chile. “‘The whales in the eastern Pacific have a very low-pitched pulsed sounds followed by a tone,’ said David Mellinger of Oregon State university. ‘Other populations use different combinations of pulses, tones and pitches.’” (4) As of January 2006 researches know that whales definitely do have distinct dialects but do not know as to why the whales have dialects.

The most recent discovery in whale dialects is that not only do Narwhals speak in different dialects but individuals also have their own voices. Scientists researched this by suctioning digital recording devices to three narwhals. Of the three recordings two were retrieved. What scientists found what that each of the two whales had their own unique vocalizations involving “whistle and pulsed sounds.”(1)

Given the information that there are different “dialects” raises the question as to whether or not the blue whales really have dialects so much as languages. If a blue whale of the Pacific Northwest were to run into a blue whale of Chile would the Pacific Northwestern blue whale be able to understand the Chilean blue whale? Or, would the Pacific Northwestern blue whale recognize that the sound of the Chilean blue whale was different, but be unable to understand it, much like the Harbor seals of British Columbia.

Sources

1. Legendary ‘Unicorns’ Have Individual Voices:

http://news.yahoo.com/s/space/20060930/sc_space/legendaryunicornshaveindividualvoices;_ylt=ArSmkHnmwA26t97pwr91kjCs0NUE;_ylu=X3oDMTA3MzV0MTdmBHNlYwM3NTM-

2. Killer Whale Dialects

http://www.science-frontiers.com/sf070/sf070b06.htm

3. Seals learn songs to detect killers

http://www.newscientist.com/article.ns?id=dn3059

4. Whales Found to Speak in Dialects

http://www.livescience.com/animalworld/060103_whale_noises.html

5. Mediterranean On the Rocks: The Sea Within the Sea

http://www.pbs.org/safarchive/4_class/45_pguides/pguide_1004/44104_sea.html#answers

6. Whale Culture

http://www.sciencentral.com/articles/view.php3?article_id=218392150

7a. Orcas

http://en.wikipedia.org/wiki/Killer_whales

7b. Three Distinct Populations

http://en.wikipedia.org/wiki/Killer_whales#Three_distinct_populations

8. Whale Chat

http://www.killerwhale.org/fieldnotes/chat.html

9. Clans Pods

http://www.killerwhale.org/fieldnotes/clans.html