Orcinus orca: our neighbors with fins
A blog by Howard Garrett first posted on Orcasphere.net
The astounding natural history of Orcinus orca
: First, a bit of history to set up the seismic shift in our perception of the orca. When NOAA Fisheries listed the Southern Resident orca community, native to Washington State and British Columbia waters, as endangered under the Endangered Species Act (ESA) in November, 2005, a new definition of the orca emerged from the process that officially revised our basic understanding of the species. Before NOAA could list J, K and L pods as endangered, they first had to establish that this community of orcas is a "distinct population segment" (DPS), as defined by the ESA. In 1978, in response to the need to protect particular runs (not just species) of salmon in the Pacific Northwest, the ESA was amended so they could list a subspecies, and if necessary, a loosely defined "distinct population segment." Congress instructed the Secretary to exercise this authority "...sparingly and only when the biological evidence indicates that such action is warranted. And...
"To be considered a distinct population segment, a population must be reproductively isolated from other conspecific (same species) populations, and it must be important for the evolutionary legacy of the species."
Until the Southern resident orcas were listed, only geographic separation, at least during breeding, could cause a population to be reproductively isolated from other populations of the same species. For example, Sacramento River Spring run Chinook salmon are geographically, and therefore reproductively, separated from Upper Columbia River Spring run Chinook, and so are listed separately. (Southern Resident orcas have historically depended on both Chinook runs to survive, and both are engandered.)
Trouble is, Southern Resident orcas cross paths every day with Transient orcas, and in fact are in no way separated from Northern resident orcas, or Offshore orcas for that matter. The various populations could easily interbreed, but they don't. The field of biology doesn't account for this kind of willful reproductive separation. It tells us something is at work here determining behavior that has never before been found in any animal other than humans. That factor is culture.
NOAA has never before had to deal with an animal that demonstrated culture, so in June, 2002, NOAA partially dodged the issue by designating the Residents as "depleted" under the less stringent Marine Mammal Protection Act (MMPA), thus avoiding the troublesome ESA language. NOAA stated that although the Southern Residents "compose a distinct population," and "face a relatively high risk of extinction," they were not significant to the species worldwide. If they went extinct, NOAA said, another orca community could simply move in and occupy their habitat. The MMPA listing triggered a lawsuit in which the judge was presented with a wealth of evidence that Southern residents are a unique and irreplaceable cultural community, which prompted the judge to instruct NOAA to review it all and reconsider their decision not to list the orcas under the ESA. NOAA did reconsider, and concluded that the Southern residents are indeed a cultural community, and needed protection under the ESA.
The evidence, and what it all adds up to
The strongest evidence for culture lies in the vocal dialects of resident pods; each pod has a distinctive set of 7-17 `discrete' calls (Ford 1991a; Strager 1995). These dialects are maintained despite extensive associations between pods. Some pods share up to 10 calls and pods which share calls can be grouped together in acoustic 'clans,' suggesting another level of population structure. Ford found four distinct clans within two resident communities (Northern and Southern), and suggested that these call variations are a result of dialects being passed down through vocal learning, and being modified over time. Thus, given the lack of dispersal, acoustic clans may reflect common matrilineal ancestry, and the number of calls any two pods share may reflect their relatedness. In addition to these pod-specific calls, orcas make a wide variety of "variable" calls, especially during intense socializing, that defy description. No similarities have been found in the calls made by different communities.
Other evidence for culture includes
Unlike any other mammal known, both male and female offspring remain with their mother and her family their entire lives. There is no dispersal. Diet is strictly limited. Though they are the top marine predator, Southern Residents eat only fish, mainly chinook salmon.
Reproduction is strictly limited. Mating occurs only within the community, and between, but not within, pods. Orcas live in family groups believed to be led by elder matriarchs. Two or more matrilines may form a pod. Female orcas may live more than four decades after birthing their last calf at about age 40-45. Only orcas and humans exhibit such long post-reproductive lifespans.
A similar pattern of distinct and separate cultural orca communities has been found worldwide, demonstrating unique vocalizations, diets, social systems and habitat usage. A landmark paper published in 2001
summed it all up thusly:
"The complex and stable vocal and behavioural cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans and represent an independent evolution of cultural faculties" (Rendell and Whitehead).
All of the above leaves little doubt that for Southern Resident orcas, cultural traditions transcend instinct, genetics, environment, or individual learning, and to some extent actually determine evolutionary development. In years to come scientists may be describing not just physical attributes and interesting behaviors in our friendly neighborhood orcas, but their cultural identities as well.
The fact of orca culture is showing up in all sorts of media, from Nature magazine to the Seattle Times, but so far scientists and thinkers have remained generally silent about any revision of our understanding of orcas. For more depth on the implications of orca cultures without parellel except in humans
see: Do Orcas Use Symbols."