Transgender pornography features performers who cross-dress for sexual gratification, either for themselves or for their partners. The arousal from being desperate comes from the sensation of having a full bladder. Animal masturbation has been observed in many horny milfs species, both in the wild and in captivity. Rape pornography features performers simulating rape. Sadomasochism is practiced in isolation relatively rarely, though some masochists report biting, pinching, or even stun-gunning themselves as a prelude to, or as part of, masturbation. Lesbianism has been a theme in erotic art since at least the time of ancient Rome, and many regard depictions of lesbianism to be erotic. Gay-for-pay describes male or female actors, pornographic stars, or sex workers who self-identify as heterosexual but who are paid to act or perform as homosexual professionally. In general, BDSM play is usually structured such that it is possible for the consenting partner to withdraw his or her consent during a scene; for example, by using a safeword that was agreed on in 3d hentai advance. A survey by the New York City Department of Health and Mental Hygiene found that heterosexual women are more likely to bareback when engaging in anal sex than homosexual and bisexual men. The term applies to the depiction of the act rather than the act itself, and so does not include live exhibitions like sex shows and striptease. Snuff pornography involves the actual death of any of the participants, consenting or otherwise, simulated death is not considered snuff. For example, in Australia gaysex it is rated Refused Classification . Klaw ran an international mail-order business out of his store, Movie Star News, selling cheesecake pinups and bondage/spanking photos. Some women who engage in same-sex sexual activity may reject not only identifying as lesbians but as bisexual as well, while other women self-identification as lesbian may not align with their sexual orientation or sexual behavior; sexual identity is not necessarily the same as one sexual orientation or sexual behavior, due to various reasons, such as the fear of identifying their sexual orientation in a homophobic setting.