A Sex-Specific Affiliative Contact Behavior in Indian Ocean Bottlenose Dolphins, Tursiops sp

With the evolution of social living came the problem of forming, maintaining, advertising, and repairing social bonds between individuals (e.g. de Waal 1986, 1993). Affiliative contact behaviors such as grooming and socio-sexual behavior play an important role in the expression and negotiation of social bonds. In rare cases an affiliative contact behavior may be restricted largely to one sex. Perhaps the best known example is found in bonobos (Pan paniscus). Female bonobos engage in a behavior, genital–genital or ‘G–G’ rubbing (Kuroda 1980), where ‘usually two, but sometimes more, females clasp each other ventro-ventrally and rapidly rub the anteriors of the external genitalia together with a repeated lateral motion’ (White 1996). Genital–genital rubbing is thought to play an important role in conflict mediation and bond formation (Kuroda 1980; de Waal 1987; Hohmann & Fruth 2000). Genital–genital rubbing can be viewed as an extension of male–female ventro–ventro sexual behavior. What might be the male equivalent, ‘penis fencing’, is apparently much less common (de Waal 1989). Sexual anatomy does not play a role in contact swimming, a gentle contact behavior described among bottlenose dolphins in captivity (Tavolga & Essapian 1957; Samuels & Tyack 2000) and in Shark Bay, Western Australia (Richards 1996; Mann & Smuts 1999; Connor et al. 2000a). In contact swimming, one dolphin rests its pectoral fin against the flank of another dolphin, behind the other dolphin’s pectoral fin and below or just posterior to the dorsal fin. Contact swimming is a highly distinctive and visible behavior with no relative movement between the two dolphins; this lack of relative motion between the body of one individual and the pectoral fin of the other distinguishes contact swimming from other forms of pectoral fin Correspondence Richard Connor, Biology Department, UMASSDartmouth, 285 Old Westport Rd., North Dartmouth, MA 02747, USA. E-mail: [email protected]