Researchers believe that the interaction of older and younger whales serves to strengthen the community and to pass on learned behavior - such as hunting techniques essential to survival. If the population of southern residents continues to fall, researchers likely will see further failures in orca blood lines. Eventually, they say, the population will reach a point of no return.
The southern residents are on a "knife edge" between endurance and extinction, according to an analysis by the Center for Biological Diversity in Tucson, Ariz. If the population continues on a downward spiral, it will reach a point where it can no longer sustain itself without dangerous risks of inbreeding. How the whales might respond to this critical state has been the subject of speculation. Genetic studies show that individuals from J, K or L pod will mate with whales from either of the other two pods but not within their own pod.
This adaptive behavior helps protect the whales from inbreeding, said Kieran Suckling of the Center for Biological Diversity. But it also limits their opportunities to breed at all. At the moment, the distribution of males and females in the three pods is out of balance, which could hinder the ability to recover.
J-Pod, for example, has no males of reproductive age. K-Pod has only two. So, there are just two males to mate with 13 females in L-Pod. It isn't clear whether one male will mate with multiple females in a given year, Suckling said. If not, that could limit the rate of recovery for the population. Another factor that could slow recovery compared to some animals is that females space out their births to every three to five years to give care to their young. Time may improve the prospects, since J-Pod contains two males approaching adolescence, Blackberry and Mike.
Three younger males were born in the past six years. Southern resident orcas occupy a specific geographic territory from South Puget Sound up into British Columbia, though they also travel out to sea.
A group of similar whales, the northern residents, occupy a territory to the north, including Northern British Columbia and Southeast Alaska. The two whale communities overlap around Vancouver Island. Both northern and southern residents eat fish.
In contrast, the transients, a separate, wide-ranging group of orcas, prey on seals and other marine mammals. Transients differ in other ways, too, including their outward appearance and social relationships. While the two resident communities produce similar squeaks and squeals, acoustic researchers have discovered unique variations, or dialects between the groups. Under study is how much emotional or intellectual information is conveyed through their language.
A striking difference between the two orca communities is that the northern residents continue to grow in number while the southern residents have declined. According to the Columbia Basin Fish and Wildlife News, a study found that whale feces is filled with rich nutrients that include nitrogen, which stimulates the growth of plants. Organisms, such as plankton, that feed the ocean food chain also benefit from tons of whale feces floating on the ocean's surface.
The disappearance of this source of natural nitrogen is likely to have a negative effect on plant and food production. An overpopulation of sea lions would quickly be evident as soon as the whales that prey on them vanished. Likewise, the economies of Canada and the United States would suffer from a lack of tourist dollars because whale watching is very popular.
World View. The scientists have been looking at the levels of PCBs found in various whales around the planet and putting that data into computer models to predict how many calves are likely to be born over the next 50 years as a result. This could build up a detailed image of how the cetaceans will likely fare if nothing is done. The only resident pod of killer whales in the UK is down to just eight individuals and has not had a calf in over 25 years.
Dr Chiara Giulia Bertulli, sighting officer for the Sea Watch Foundation, says, 'The waters around the UK are one of the places where killer whale populations have been affected the most, being halved during the last century where PCBs have been detected. PCBs dissolve in fat and in milk and the new generations of killer whales will keep on carrying this heavy chemical burden.
The whales in higher latitudes, thus further from contaminated water, are predicted to do much better. Populations that live off Norway, Iceland, Canada and the Faroe Islands are still doing reasonably well and may act as refuges for the species to repopulate the regions in which the whales went extinct. Cleaning up these chemicals once and for all is possible. Europe on the other hand simply introduced a ban, then seemingly hoped the chemicals would go away.
If we actually followed the Stockholm Convention and tackled the issue, the whales would be in a much better situation to deal with other threats they may be facing, such as the loss of major prey such as shark and tuna, as well as underwater noise pollution. Research on communities of killer whales reveals there might be more to menopause than simply old age. Get email updates about our news, science, exhibitions, events, products, services and fundraising activities.
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By Josh Davis.
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