were based on bias against homosexual women. 29.6% were based on anti-homosexual bias without regard to gender. The 1998 murder of Matthew Shepard, a gay student, is a notorious such incident in the U.S. LGBT people, especially lesbians, may become the victims of "corrective rape", a violent crime with the supposed aim of making them heterosexual. In certain parts of the world, LGBT people are also at risk of "honor killings" perpetrated by their families or relatives. In Morocco, a constitutional monarchy following Islamic laws, homosexual acts are a punishable offence. With a population hostile towards LGBT people, the country has witnessed public demonstrations against homosexuals, public denunciations of presumed homosexual individuals, as well as violent intrusions in private homes. The community in the country is exposed to additional risk of prejudice, social rejection and violence, with a greater impossibility of obtaining protection even from the police. Homosexual behavior in other animals Homosexual and bisexual behaviors occur in a number of other animal species. Such behaviors include sexual activity, courtship, affection, pair bonding, and parenting, and are widespread; a 1999 review by researcher Bruce Bagemihl shows that homosexual behavior has been documented in about 500 species, ranging from primates to gut worms. Animal sexual behavior takes many different forms, even within the same species. The motivations for and implications of these behaviors have yet to be fully understood, since most species have yet to be fully studied. According to Bagemihl, "the animal kingdom [does] it with much greater sexual diversity—including homosexual, bisexual and nonreproductive sex—than the scientific community and society at large have previously been willing to accept". According to Bailey et al., humans and domestic sheep are the only animals conclusively proven to exhibit a homosexual orientation. A review paper by N. W. Bailey and Marlene Zuk looking into studies of same-sex sexual behaviour in animals challenges the view that such behaviour lowers reproductive success, citing several hypotheses about how same-sex sexual behavior might be adaptive; these hypotheses vary greatly among different species. Bailey and Zuk also suggest future research needs to look into evolutionary consequences of same-sex sexual behaviour, rather than only looking into origins of such behaviour. See also LGBT rights by country or territory LGBT rights at the United Nations Anti-LGBT rhetoric Biology and sexual orientation Fraternal birth order and male sexual orientation Gay sexual practices Gender dysphoria Hate speech Human male sexuality List of nonfiction