1. Field studies on many aspects of killer whale reproduction are not available, yet much has been learned at marine life parks. Studies of killer whales in marine zoological facilities suggest that females become sexually mature when they reach 4.6 to 4.9 m (15-16 ft.), at about 6 to 10 years.
2. Males usually become sexually mature when they reach about 5.5 to 6.1 m (18-20 ft.), at about 10 to 13 years. In the SeaWorld Adventure Park system, one male successfully mated at approximately 7.5 to 8 years of age. In the wild, social factors greatly influence a male's breeding success. Males may not successfully reproduce until they are much older, larger, and more able to compete with other males.
B. Mating activity.
1. Killer whales are considered polygamous as they tend to mate with any number of partners.
2. Females come into estrus or 'heat' several times during the year. Observations of females in zoological parks indicate that killer whales undergo periods of multiple estrus cycling (polyestrus), interspersed with periods of non-cycling. This period is highly variable, as is the period of non-cycling, both for one whale over time, and between whales.
3. Breeding may occur in any season, but it is most common in the summer. In the North Atlantic, mating seems to peak in October and November; in the western North Pacific, mating seems to be at its highest between May and June.
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