For 12 years, the San Francisco Zoo has brought lovers and singles alike an inside look at the love lives of animals.

The zoo's penguinkeeper, Jane Tollini, developed the idea when she discovered that penguin breeding habits corresponded with Valentine's Day. Tollini invited some friends to watch the penguins, cut out paper hearts, and played some Johnny Mathis.

The copulation celebration became a full-fledged sex safari and, more than a decade later, tourists are charged $50 a person for a 45-minute tour, movie, champagne, and truffles.

An extra $50 adds wine, hors d'oeuvres, and a tango session to the February 14 itinerary. Called "Patagonian Passion," the zoo's first-ever evening tour has already sold out for this year, says zoo spokesperson Nancy Chan.

Amorous Animal Antics

Tourtakers shouldn't expect to see any wild animal antics in person. In the past, the closest thing tourists saw to a peep show was a rhino courtship display and two newborn baby goats, says Chan.

Tollini makes up for the lack of live action by giving away animals' most intimate secrets: use of foreplay, preferred times and positions—nothing is off-limits for tour participants.

One of Tollini's favorite tidbits is the giant millipede, which mates "belly to belly" with 250 legs wrapped around each other and the male equipped with a pair of penises to do the job, says Chan. "[Tollini] says it is very lovely…and very efficient."

The tour also showcases sexual adaptations unique to each type of animal. "Eagles have this amazing sexual flight in the air," says Chan. "Orangutans do it upside down."

In addition to courtship rituals and the faithfulness of animal couples, the tour covers the size and shape of animals' sex organs.

Gorillas, Chan explains, are not as well endowed as they put on. And, she adds, "A tortoise has a spade-shaped penis…I think people are really interested in that for some reason."

Touring the Natural Way

The San Francisco Zoo Valentine's Day Sex Tour is limited to guests 18 and older, who will travel around the zoo in rented cable cars.

"We have a real variety of people that go on the tour," says Chan. "A lot of older adults and couples come on the tour—it's very sweet."

Although overviews of animal mating are now offered throughout the country (and the world: an Amsterdam zoo offers a homosexual zoo tour), Chan says the San Francisco Valentine's Day Zoo Sex Tour has a loyal following.

"Ours is the original. Ours is probably the most colorful and graphic," she says. "People have come back every year."