In a study published online this month in the Journal of Heredity, NOAA researchers and others, using DNA testing to fill in a missing link in the lives of killer whales that seasonally visit Washington's Puget Sound, have discovered that some of the progeny they studied were the result of matings within the same social subgroups, or pods, that are part of the overall population.
One implication of this inbreeding behavior is a significant reduction in the genetic diversity of what is already a perilously small population of animals, formally known as Southern Resident killer whales. That population numbers only about 85 animals and was listed as endangered under the federal Endangered Species Act in 2005.
Southern resident killer whales, which also visit the waters of British Columbia and are occasionally found as far south as Monterey Bay, Calif., consist of three pods called J, K and L pod. Inter-pod mating has never been detected in studies of Northern Resident killer whales, which range from Washington to southern Alaska, and until now researchers assumed that Southern Residents exhibited similar mating patterns. The two populations are distinct and do not socialize with each other.
The study, titled "Inferred paternity and male reproductive success in a killer whale (Orcinus orca) population," involved researchers from NOAA's Fisheries Service, the University of Washington, Cascadia Research Collective and the Center for Whale Research.
"We were surprised that, in many cases, the father was from the same pod as the mother. Based on earlier studies, we didn't think killer whales mated within their own pod," said Dr. Michael Ford, lead author of the study and a scientist with NOAA's Northwest Fisheries Science Center in Seattle.
"This behavior may be unique to the Southern Resident population, perhaps related to the population's small size," Ford added.
The researchers analyzed 78 i
|Contact: Vicky Krikelas |
NOAA National Marine Fisheries Service