Carnivores are doing it, marsupials are doing it, large and small animals are doing it, even insects are doing it, said Jane Tollini, founder of the San Francisco Zoo sex tour, “Woo at the Zoo.”

With photographic evidence of primates, rhinos, lions, tigers and other animals engaged in the act, patrons were greeted by these images Wednesday as they walked through the door of the zoo’s 19th annual Woo at the Zoo, just in time for Valentine's Day.

“Banana slugs are hermaphrodites,” Tollini said. “Except if the slug [in the male role] gets its penis stuck in the female, it will bite it off and become a female for the remainder of its life.”

It was detailed sexual information like that which Tollini shared to the group, who sat in front of a PowerPoint presentation inside the zoo’s great hall.

“My language is very explicit,” she said. “That’s why the tour is only for those 21 and over.”

Tollini said the crowd of 28 patrons were going to see a tasteless, tacky and kinky tour of animal sex, which aimed to educate as well as entertain.

Various animals from a Columbian boa, to a hedgehog, to a crow, to a baby alligator were brought through the hall for the group to view while eating dinner and dessert and drinking various beverages, including champagne.

According to Tollini, the event has undergone changes in its nearly two-decade existence.

“In the past we used to go outside and walk through the zoo, but February weather isn’t always the best,” Tollini said of bringing the tour indoors.

Tollini got the idea for what she still calls "the sex tour" when working with the penguins at the zoo many years ago. She had noticed that the penguins were wooing one another around Valentine’s Day.

“I even started playing Johnny Mathis for them,” Tollini said of playing mood-setting music for them.

It took several years for Tollini, who has worked at the zoo for 25 years, to convince the zoo of the sex tour idea, she said.

John Flynn, another employee at the zoo, assisted in the Woo at the Zoo, by displaying Sequoia, a 19-year-old bald eagle.

“Eagles lay about 2 to 3 eggs a year,” he said of bald eagle mating habits. “Often only two will make it.”

Of birds within the rescue program at the zoo, which Sequoia is a part of, 109 offspring have been released into the wild, he said.

A first time attendee, Sarah Smith, said she found the monogamy of certain birds to be the most fascinating.

“I found the eagle fascinating. It was interesting to learn how birds act towards one another,” she said.

Animals are into all types of sex, like bondage, Tollini said. But some birds practice monogamy, even with life spans that reach 80 years.

“When the mate [of a crown crane] dies,” she said. “The other one has been known to stop eating, wanting to follow the other [into death].”

The sex tour ended with the last power point slide and the animals went back to their different enclosures at the zoo. And although no actual animal sex was witnessed at the tour, as springtime continues to roll nearer, Tollini said this is when animals start mating, be it a bug, bird, or bear.