Rare behaviors are often missing from published papers, hampering phylogenetic analyses. Here, we report, for the first time, masturbation and same-sex sexual behavior (SSB) in both male and female black-and-white colobus monkeys. We recorded these behaviors during 32 months of observation (1573 h of focal animal sampling) on Colobus vellerosus collected at the Boabeng–Fiema Monkey Sanctuary in Ghana. Males were observed masturbating and involved in SSB more than females. Subadult males were the age-sex class that engaged in both of these behaviors most often and a third of all SSB observed in young males occurred when they were forming an all-male band (AMB), which are temporally transient social groups in this species. Our data support that masturbation in males may be a sexual outlet for individuals that do not have a current sexual partner, while in females it may function in mate attraction by advertising receptivity. SSB may occur as an evolutionary byproduct but given the temporal clustering of observed events in males prior to AMB formation, our data best support the hypothesis that these behaviors facilitate male-male bonding (i.e., act as social glue). Within AMB’s, males engage in coalitionary behavior to take over social groups containing females and strong bonds are important for success and later access to females, which could have selected for SSB in C. vellerosus.

已发表的论文中经常会遗漏罕见的行为，从而阻碍了系统发育分析。在这里，我们首次报告了雄性和雌性黑白疣猴的手淫和同性性行为（SSB）。我们在对加纳 Boabeng-Fiema 猴子保护区采集的疣猴进行 32 个月的观察（1573 小时的重点动物采样）期间记录了这些行为。据观察，男性自慰和参与 SSB 的程度高于女性。亚成年雄性是最常从事这两种行为的年龄性别类别，在年轻雄性中观察到的所有 SSB 的三分之一发生在他们形成全雄性群体 (AMB) 时，这是该物种中短暂的社会群体。我们的数据表明，男性手淫可能是目前没有性伴侣的个人的性出口，而女性则可能通过广告接受性来吸引配偶。SSB 可能作为进化的副产品出现，但考虑到 AMB 形成之前男性中观察到的事件的时间聚类，我们的数据最好地支持这些行为促进男性与男性之间的联系（即充当社会粘合剂）的假设。在 AMB 中，雄性会采取联盟行为来接管包含雌性的社会群体，而牢固的联系对于成功以及随后获得雌性非常重要，而雌性可能会在C. vellerosus中选择 SSB 。