This Valentine's weekend some American zoos are offering an adults-only opportunity to discover animals' amorous antics, and perhaps pick up a few tips.

This Valentine's weekend some American zoos are offering an adults-only opportunity to discover animals' amorous antics, and perhaps pick up a few tips.

For 75 dollars per person, including champagne and brunch, a Philadelphia Zoo is providing a three-hour romantic tour, dubbed "Lovin' on the Wild Side."

Sadly -- although the tour is for over 21's only -- it is not guaranteed that every visitor will get lucky.

"We don't guarantee that the animals will have intimate moments when we see them," the zoo's Laura Warner cautioned.

But with a bit of luck, Warner said, guests might see an array of unusual overtures.

Tortoises, Warner explained, "like to nibble their toes to get to know each other."

"Bats, since they sleep upside down, there are other things they do upside down," she added. "The giraffes like to rub each other's neck."

But the most unusual -- and brutal -- mating rite may come in the spiders' enclosure.

"After their intimate moment, the female often bites off the male's head," she said.

But for lessons in attentiveness and trust visitors need look no further than the rhinoceros hornbill.

According to Dean Noble, director of marketing at Santa Barbara Zoo in California -- which is also offering tours -- this black-bodied bird is the master of post-coitus care.

"The male of the species seals the female in a hollow tree with mud and then feeds her through the hole and removes the excrement until the chicks are ready to fly," he said.