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A systematic program of research into the reproductive physiology of killer whales by a team of scientists from SeaWorld, the National Zoological Park, and the Zoological Society of San Diego has culminated in the first live births of any cetacean--the group of marine mammals that includes whales and dolphins--by means of artificial insemination.
In a report set for publication in the journal Biology of Reproduction, the team, headed by Dr. Todd R. Robeck, based at SeaWorld San Antonio, notes that their research will allow sperm of killer whales in zoological facilities to be stored by a technique known as "genome resource banking" or GRB. GRB, used in conjunction with artificial insemination, could play an important role in ensuring the genetic vitality of captive marine mammals.
Robeck's team studied one male and five female killer whales to evaluate the reproductive physiology of these animals. The females were between 13 and 20 years old and weighed about 5,000 pounds. The male was 20 years old and weighed more than 11,000 pounds. All were trained to cooperate in a variety of procedures involved in the research.
Noninvasive techniques were used to collect data on reproductive hormonal patterns of the killer whale, and ultrasound exams helped establish the time of ovulation.
Semen collected from the male orca for use in the artificial insemination trials was either liquid-stored for up to three days or preserved by freezing and later thawed.
Eight attempts at artificial insemination over the course of two years led to three pregnancies, one from thawed sperm and two from liquid-stored sperm. One male calf and one female calf were born. The third pregnant female, who died of unrelated causes, was carrying a male fetus. Paternity tests confirmed that all three calves resulted from artificial insemination.
Although killer whales are common throughout the oceans of the world, the population in zoological facilities numbers only 48, mostly in small, genetically isolated groups. Since 1985, natural breeding of captive killer whales has led to 27 births, but natural breeding sometimes requires moving animals between facilities.
Robeck and his team point out that artificial insemination capabilities will help maintain their genetic diversity.
Journal
Biology of Reproduction