The hot ticket for biologists these days? Watching monkeys do it. Every batch of new published studies seems to include simian sex. Consider Dana Pfefferle, a researcher at the German Primate Center in Göttingen, who spent two years counting monkey thrusts at Gibraltar's Upper Rock Nature Reserve to find that when the female screamed during mating, the male partner climaxed 59 percent of the time. Or Paul Vasey of the University of Lethbridge in Alberta, who has discovered that female Japanese macaques are often bisexual and will choose a female partner over a male more than 92 percent of the time. Monkey mating is everywhere. Vasey says primate prurience is essential to human sexuality research. "There are very few situations in which you can watch humans have sex," he explains, noting that monkey sex has also shed light on several other species. To eavesdrop on the macaques, Vasey travels to the outskirts of Kyoto, Japan, in the fall and winter. For up to three months, six days a week, he hikes up a small mountain to the monkey's habitat and records who mounts whom and for how long, what positions they use and what pelvic movements are employed, which he tracks using a notation system designed to record the movements of dancers. He's not at all inhibited about discussing his research with the public. After all, he says, "people like monkeys, and people like sex."