*Norris, K. S., and T. P. Dohl (1980a) “Behavior of the Hawaiian Spinner Dolphin, Stenella longirostris.” Fishery Bulletin, U.S. 77:821- 49.
*———(1980b) “The Structure and Functions of Cetacean Schools.” In L. M. Herman, ed., Cetacean Behavior: Mechanisms and Functions, pp. 211–61. New York: Wiley- InterScience.
*Norris, K. S., B. Wursig, R. S. Wells, and M. Wursig (1994) The Hawaiian Spinner Dolphin. Berkeley: University of California Press.
*Ostman, J. (1991) “Changes in Aggressive and Sexual Behavior Between Two Male Bottlenose Dolphins (Tursiops truncatus) in a Captive Colony.” In K. Pryor and K. S. Norris, eds., Dolphin Societies: Discoveries and Puzzles, pp. 304-17. Berkeley: University of California Press.
Patterson, I. A. P., R. J. Reid, B. Wilson, K. Grellier, H. M. Ross, and P. M. Thompson (1998) “Evidence for Infanticide in Bottlenose Dolphins: an Explanation for Violent Interactions with Harbor Porpoises?” Proceedings of the Royal Society of London, Series B 265:1167–70.
*Saayman, G. S., and C. K. Tayler (1973) “Some Behavior Patterns of the Southern Right Whale, Eubalaena australis.” Zeitschrift fur Saugetierkunde 38:172–83.
Samuels, A., and T. Gifford (1997) “A Quantitative Assessment of Dominance Among Bottlenose Dolphins.” Marine Mammal Science 13:70–99.
Shane, S. H. (1990) “Behavior and Ecology of the Bottlenose Dolphin at Sanibel Island, Florida.” In S. Leatherwood and R. R. Reeves, eds., The Bottlenose Dolphin, pp. 245-65. San Diego: Academic Press.
Shane, S. H., R. S. Wells, and B. Wursig (1986) “Ecology, Behavior, and Social Organization of the Bottlenose Dolphin: A Review.” Marine Mammal Science 2:34–63.
*Tavolga, M. C. (1966) “Behavior of the Bottlenose Dolphin (Tursiops truncatus): Social Interactions in a Captive Colony.” In K. S. Norris, ed., Whales, Dolphins, and Porpoises, pp. 718-30. Berkeley: University of California Press.
*Tayler, C. K., and G. S. Saayman (1973) “Imitative Behavior by Indian Ocean Bottlenose Dolphins (Tursiops aduncus) in Captivity.” Behavior 44:286-98.
*Wells, R. S. (1995) “Community Structure of Bottlenose Dolphins Near Sarasota, Florida.” Paper presented at the 24th International Ethological Conference, Honolulu, Hawaii.
*———(1991) “The Role of Long-Term Study in Understanding the Social Structure of a Bottlenose Dolphin Community.” In K. Pryor and K. S. Norris, eds., Dolphin Societies: Discoveries and Puzzles, pp. 199–225. Berkeley: University of California Press.
*———(1984) “Reproductive Behavior and Hormonal Correlates in Hawaiian Spinner Dolphins, Stenella longirostris.” In W. E Perrin, R. L. Brownell, Jr., and D. P. DeMaster, eds., Reproduction in Whales, Dolphins, and Porpoises, pp. 465–72. Report of the International Whaling Commission, Special Issue 6. Cambridge, UK: International Whaling Commission.
*Wells, R. S., K. Bassos-Hull, and K. S. Norris (1998) “Experimental Return to the Wild of Two Bottlenose Dolphins.” Marine Mammal Science 14:51–71.
*Wells, R. S., M. D. Scott, and A. B. Irvine (1987) “The Social Structure of Free-ranging Bottlenose Dolphins.” In H. Genoways, ed., Current Mammalogy, vol. 1, pp. 247–305. New York: Plenum Press.
IDENTIFICATION: The largest member of the dolphin family (16–26 feet in length); a tall dorsal fin and distinctive black-and-white markings. DISTRIBUTION: Seas and oceans worldwide. HABITAT: Often found in coastal waters. STUDY AREAS: Johnstone Strait, Vancouver Island, British Columbia, Canada; Puget Sound, Washington.
Social Organization
Killer Whales live in a complex society based on a female-centered social unit called the MATRILINEAL GROUP. This is made up of an adult female, the matriarch—usually reproductively active, but sometimes older and postreproductive—her young, and any adult sons of hers. Sometimes her mother or grandmother is also present, and possibly her brothers or uncles. Matrilineal groups usually contain three or four Orcas (although some have up to nine); these groups are organized into larger social units known as PODS, which tend to socialize together and share a common dialect in their vocalizations. Some populations of Killer Whales are TRANSIENTS, who travel widely in smaller groups (occasionally singly) and are less vocal. Unlike nontransient or RESIDENT Orcas, they feed primarily on marine mammals rather than fish.
Description
Behavioral Expression: Homosexual interactions are an integral and important part of male Orca social life. During the summer and fall—when resident pods join together to feast on the salmon runs—males of all ages often spend the afternoons in sessions of courtship, affectionate, and sexual behaviors with each other. A typical homosexual interaction begins when a male Killer Whale leaves his matrilineal group to join a temporary male-only group; a session can last anywhere from a few minutes to more than two hours, with the average length being just over an hour. Usually only two Orcas participate at a time, although groups of three or four males are not uncommon, and even five participants at one time have been observed. The males roll around with each other at the surface, splashing and making frequent body contact as they rub, chase, and gently nudge one another. This is usually accompanied by acrobatic displays such as vigorous slapping of the water with the tail or flippers, lifting the head out of the water (SPYHOPPING), arching the body while floating at the surface or just before a dive, and vocalizing in the air. Particular attention is paid by the males to each other’s belly and genital region, and often they initiate a behavior known as BEAK-GENITAL ORIENTATION, which is also seen in heterosexual courtship and mating sequences. Just below the surface of the water, one male swims underneath the other in an upside-down position, touching and nuzzling the other’s genital area with his snout or “beak.” The two males swim together in this position, maintaining beak-genital contact as the upper one surfaces to breathe; then they dive together, spiraling down into the depths in an elegant double-helix formation. As a variation on this sequence, sometimes one male will arch his tail flukes out of the water just before a dive, allowing the other male to rub his beak against his belly and genital area. When the pair resurfaces after three to five minutes, they repeat the sequence, but with the positions of the two males reversed. In fact, almost 90 percent of all homosexual behaviors are reciprocal, in that the males take turns touching or interacting with one another. During all of these interactions, the Orcas frequently display their erect penises, rolling at the surface or underwater to reveal the distinctive yard-long, pink organs. One male may even attempt to insert his penis—which has a prehensile tip that can be independently moved—into the genital slit of another male (although this has yet to be fully verified).
Although males of all ages participate in homosexual activities, this behavior is most prevalent among “adolescent” Orcas (sexually mature individuals 12–25 years old). More than three-quarters of all sessions involve males who are more than five years apart in age, although age-mates also interact together (especially among adolescents). Occasionally, adult-only homosexual activity (i.e., between males 25 years and older) takes place. Some males have favorite partners with whom they interact year after year, and they may even develop a long- lasting “friendship” or pairing with one particular male. Other males seem to interact with a wide variety of different partners. Most participants in homosexual activity come from different matrilineal groups and are therefore not related; however, more than a third of the sessions include brothers or half brothers (along with other participants), while 9 percent are entirely incestuous.
Frequency: Homosexual interactions are common in Orcas during the summer and fall, especially during August and September—anywhere from 6 to 30 or more sessions of same-sex activity may occur each season in some populations. On average, each male participates in one or two
