Inbreeding Puts Endangered Killer Whales at Further Risk
Endangered killer whales off the west coast of Canada and the U.S. are facing an additional threatinbreeding.
A research team headed by the U.S. National Oceanic and Atmospheric Administration (NOAA) has found that orca whales that frequently visit Washingtons Puget Sound and the coast of British Columbia are mating within the same pods, or the same social groups.
This could lead to a significant reduction in the genetic diversity of the already perilously small population of southern resident killer whales, which currently numbers only about 85 animals.
Although the reasons for the inbreeding are not known, Ford suspects that the small size of the population might have something to do with it.This behaviour may be unique to the southern resident population, perhaps related to the populations small size.
A research team headed by the U.S. National Oceanic and Atmospheric Administration (NOAA) has found that orca whales that frequently visit Washingtons Puget Sound and the coast of British Columbia are mating within the same pods, or the same social groups.
This could lead to a significant reduction in the genetic diversity of the already perilously small population of southern resident killer whales, which currently numbers only about 85 animals.
We were surprised that, in many cases, the father was from the same pod as the mother. Based on earlier studies, we didnt think killer whales mated within their own pod, said Dr. Michael Ford, lead author of the study and a scientist with NOAAs Northwest Fisheries Science Center in Seattle.Based on earlier studies, we didnt think killer whales mated within their own pod.Dr. Michael Ford
Although the reasons for the inbreeding are not known, Ford suspects that the small size of the population might have something to do with it.This behaviour may be unique to the southern resident population, perhaps related to the populations small size.
Inbreeding could reduce southern resident killer whales' genetic diversity, say U.S. researchers. (Valery Hache/AFP/Getty Images) Three different pods have been observed in the southern resident group, whose habitat ranges from B.C. to as far South as Monterey Bay in California. The researchers analyzed 78 individual whales and determined the paternity based on 26 DNA marker traits from 15 mother-calf pairs.Observations of other groups of whales have shown that inter-pod breeding is a rare and abnormal occurrence, an example being the northern resident killer whaleswhose habi! tat rang es from Washington to southern Alaskain which inbreeding has never been detected. The two groups are distinct and do not socialize with each other.
Although southern residents do not mate outside their population, the whales do tend to avoid mating with their more close relatives, found the study, which was published in the Journal of Heredity.
Even though some of the fathers were in the same pod as the mothers, none of them were really closely related to each other. Our results suggest that Southern Residents avoid mating with their siblings or parents, but we arent really sure of the social process that results in this avoidance, Ford said.
Although southern residents do not mate outside their population, the whales do tend to avoid mating with their more close relatives, found the study, which was published in the Journal of Heredity.
Even though some of the fathers were in the same pod as the mothers, none of them were really closely related to each other. Our results suggest that Southern Residents avoid mating with their siblings or parents, but we arent really sure of the social process that results in this avoidance, Ford said.
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This may reflect the difficulty male killer whales have in controlling other males access to females.
However, the study also showed that the older and larger males appeared to be responsible for most of the successful matings, indicating that females may choose to mate only with older males, or that older males may prevent the younger males from breeding successfully.
The southern resident group was listed as endangered under the U.S. federal Endangered Species Act in 2005.
According to Fisheries and Oceans Canada, southern residents are heavily contaminated with toxic chemicals such as organochlorine, which can lead to reproductive problems. Water pollution is also affecting the whales food supply, and there is the ongoing problem of ocean traffic near major centres like Seattle and Vancouver that interferes with the animals.
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This may reflect the difficulty male killer whales have in controlling other males access to females.
However, the study also showed that the older and larger males appeared to be responsible for most of the successful matings, indicating that females may choose to mate only with older males, or that older males may prevent the younger males from breeding successfully.
The southern resident group was listed as endangered under the U.S. federal Endangered Species Act in 2005.
According to Fisheries and Oceans Canada, southern residents are heavily contaminated with toxic chemicals such as organochlorine, which can lead to reproductive problems. Water pollution is also affecting the whales food supply, and there is the ongoing problem of ocean traffic near major centres like Seattle and Vancouver that interferes with the animals.
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