up to seven individuals.
Description
Behavioral Expression: Male Verreaux’s Sifakas sometimes mount other males during the mating season. The mounted animal—usually a younger adult or adolescent male— often snaps at the mounter and tries to wriggle free (as do females trying to escape from unwelcome heterosexual advances). In Lesser Bushbabies, females occasionally mount and thrust against each other when in heat. Like other species of Bushbabies, the genitals of female Lesser Bushbabies are unusual in several respects. The clitoris is long and pendulous, greatly resembling the male’s penis, and the urethra extends through to the tip of the organ, so that females urinate through the clitoris rather than through a urethral opening near the vagina. Females do not menstruate, and in fact the vagina remains closed at all times except during the mating season (which lasts no more than two to three weeks and occurs twice a year).
Frequency: Homosexual mounting probably occurs only occasionally in Ver-reaux’s Sifakas and Lesser Bushbabies. However, one study of wild Verreaux’s Sifakas found that 3 out of 21 mountings (14 percent) were between males.
Orientation: Lemurs and Bushbabies that participate in same- sex mounting probably also engage in heterosexual activity, although too little is known about individual life histories in these species to draw any firm conclusions.
Nonreproductive and Alternative Heterosexualities
Many heterosexual copulations in Verreaux’s Sifakas—more than two-thirds in some populations—do not involve penetration or ejaculation, often because the female resists the mating attempt and wriggles free. Females sometimes also mate when they are not in heat: for some individuals, 30–80 percent of their sexual activity is nonprocreative, taking place during times when they cannot conceive. In some populations females also delay reproducing for several years, and only slightly more than half of all adult females reproduce each year. Infanticide occurs occasionally in this species, and possibly also abortions. In Lesser Bushbabies, heterosexual copulations can be lengthy—more than nine minutes in some cases—and a female often bites the male, “boxes” him with her hands, and tries to push him off or get away from him during mating.
Sources
*asterisked references discuss homosexuality/transgender
*Andersson, A. B. (1969) “Communication in the Lesser Bushbaby (Galago senegalensis moholi).” Master’s thesis, Witwatersrand University.
Bearder, S. K., and G. A. Doyle (1974) “Field and Laboratory Studies of Social Organization in Bushbabies (Galago senegalensis).” Journal of Human Evolution 3:37- 50.
Brockman, D. K., and P. L. Whitten (1996) “Reproduction in Free-Ranging Propithecus verreauxi: Estrus and the Relationship Between Multiple Partner Matings and Fertilization.” American Journal of Physical Anthropology 100:57–69.
Butler, H. (1967) “The Oestrus Cycle of the Senegal Bush Baby (Galago senegalensis senegalensis) in the Sudan.” Journal of Zoology, London 151:143–62.
Dixson, A. F. (1995) “Sexual Selection and the Evolution of Copulatory Behavior in Nocturnal Prosimians.” In L. Alterman, G. A. Doyle, and M. K. Izard, eds., Creatures of the Dark: The Nocturnal Prosimians, pp. 93–118. New York: Plenum Press.
*Doyle, G. A. (1974a) “Behavior of Prosimians.” Behavior of Nonhuman Primates 5:154–353.
———(1974b) “The Behavior of the Lesser Bushbaby.” In R. D. Martin, G. A. Doyle, and A. C. Walker, eds., Prosimian Biology, pp. 213–31. Pittsburgh: University of Pittsburgh Press.
Doyle, G. A., A. Pelletier, and T. Bekker (1967) “Courtship, Mating, and Parturition in the Lesser Bushbaby (Galago senegalensis moholi) Under Semi-Natural Conditions.” Folia Primatologica 7:169-97.
Kubzdela, K. S., A. F. Richard, and M. E. Pereira (1992) “Social Relations in Semi-Free-Ranging Sifakas (Propithecus verreauxi verreauxi) and the Question of Female Dominance.” American Journal of Primatology 28:139–45.
Lipschitz, D. L. (1996) “Male Copulatory Patterns in the Lesser Bushbaby (Galago moholi) in Captivity.” International Journal of Primatology 17:987– 1000.
Lowther, F. D. L. (1940) “A Study of the Activities of a Pair of Galago senegalensis moholi in Captivity, Including the Birth and Postnatal Development of Twins.” Zoologica 25:433-65.
Richard, A., (1992) “Aggressive Competition Between Males, Female-Controlled Polygyny, and Sexual Monomorphism in a Malagasy Primate, Propithecus verreauxi.” Journal of Human Evolution 22:395–406.
———(1978) Behavioral Variation: Case Study of a Malagasy Lemur. Lewisburg, Pa.: Bucknell University Press.
*————(1974a) “Intra-specific Variation in the Social Organization and Ecology of Propithecus verreauxi.” Folia Primatologica 22:178–207.
*———(1974b) “Patterns of Mating in Propithecus verreauxi verreauxi.” In R. D. Martin, G. A. Doyle, and A. C. Walker, eds., Prosimian Biology, pp. 49–74. London: Duckworth; Pittsburgh: University of Pittsburgh Press.
Richard, A., P. Rakotomanga, and M. Schwartz (1991) “Demography of Propithecus verreauxi at Beza Ma-hafaly, Madagascar: Sex Ratio, Survival, and Fertility, 1984–1988.” American Journal of Physical Anthropology 84:307–22.
Marine Mammals
DOLPHINS AND WHALES
IDENTIFICATION: An 8-foot-long dolphin with a long, toothed beak and light blue or even bright pink skin. DISTRIBUTION: The Amazon and Orinoco River systems; vulnerable. HABITAT: Slow-moving streams and tributaries, flooded forests, lakes. STUDY AREAS: Duisburg Zoo, Germany; Aquarium of Niagara Falls, New York; subspecies l.g. humboldtiana, the Orinoco Dolphin.
Social Organization
Although little is known about their social organization, it appears that Botos are largely solitary animals that occasionally associate in groupings of up to a dozen or more individuals. Larger aggregations generally occur at feeding areas, and Botos may even coordinate their fishing attempts with other species, such as the giant river otter (Pteronura brasiliensis). The Boto mating system is probably polygamous.
Description
Behavioral Expression: Male Botos participate in a wide variety of homosexual interactions, including mating with each other using fully three different types of penetration: one male may insert his erect penis into the genital slit of the other, into his anus, or into his blowhole. When engaging in anal or genital-slit intercourse, one male swims upside down beneath the other one as in heterosexual copulation; blowhole mating occurs with the inserting male above the other one. If there is an age difference between the males, typically the older one penetrates the younger one. Males also rub their genital openings or erect penises against each other; alternatively, one male might rub his head against the other’s genitals,
