Simian sex: Monkey seen, monkey doesn't

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 macaques, the urge for hanky-panky was dampened when they were watched by other monkeys, according to an unusual 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 a giant enclosure for four months.

They installed everything for perfect love-making -- the simian equivalents of Barry White, satin sheets and mirrored ceilings.

The monkeys had tyres and ladders for courting rituals, sawdust bedding, tasty offerings of fruit to replenish lost energy and even a swimming pool for chillout time.

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," Anna Overduin-de Vries said in an email to AFP.

"Although harassment is not frequent, it may have serious consequences such as getting injured or not being able to finish a copulation."