Monkeys are just like the vast majority of human beings when it comes to sex - when they go ape, they want privacy.
Among long-tailed mac-aques, the urge for hanky-panky was dampened when they were being watched by other monkeys, according to an experiment reported in the journal Behavioral Ecology and Sociobiology.
Scientists from the Biomedical Primate Research Centre in the Netherlands monitored 15 female and seven male macaques in an enclosure for four months. They installed everything for perfect mating - the simian equivalents of Barry White, satin sheets and mirrored ceilings.
The monkeys had tyres and ladders for courting rituals and even a swimming pool.
But the animals' main requirement was a quiet spot, to avoid interference from other monkeys, especially dominant alpha males.
"By concealing sexual behaviour, females and subordinate males try to reduce harassment from group members," scientist Anna Overduin-de Vries said.