LEWISTON – You know what they say: What happens in Thorncrag stays in Thorncrag.

At the bird sanctuary Friday night, dozens of people gathered around a pool to watch nature in its most private moments. Frogs having sex, salamanders collecting the sperm of their mates, pregnant critters of all varieties.

Love was in the air at Thorncrag, and about 60 people turned out to witness it.

“Everything is breeding like mad right right now because it’s warm enough,” said Susan Hayward, president of the Stanton Bird Club and leader of this voyeuristic event.

Not that “herping,” as it is called, is at all lascivious. Much of the observation is done with the ears, listening for amphibians and other creatures expressing their amorous moods. Learning to tell the difference between the love song of the wood frog and the spring peeper. Examining critters from the vernal pool to look for signs of pregnancy.

“I really like nature,” said 11-year-old John Pettingill of Lisbon Falls. He was among roughly 30 kids who took part in the observation exercise. He examined every vertebrate and invertebrate plucked from the cool water, with a particular eye out for the wood frog.

“They mate in the ponds because their eggs need to be in water,” Pettingill said.

Ten minutes into the foray, a bullfrog was spotted by itself, clinging to a log. One girl thought the creature looked kind of sad, perhaps because he was alone while all that mating was going on around him.

“He has no date,” said Alan Seamans, a coordinator with the Stanton group. “He’s not talking right now, either. He’s kind of shy.”

The vernal pool is not a good place for shyness. Frogs mate there, male salamanders leave packets of sperm for females to collect, and it seemed like just about everything alive there was pregnant or mating.

But don’t feel bad for the salamander and the detached efficiency with which it goes about its business of getting into a family way.

“They do a nuptial dance,” Hayward said. “They rub their bodies together.”

Frogs, too. The polite word for it is amplexus.

“That’s frog sex,” Hayward said. “He’s on top, she’s on the bottom.”

Some frogs are required by nature to do their breeding in the pool. Others can be more discreet. The wood frog, which sounds somewhat like a duck when it gets to chattering, is obligate, meaning it does its sexy business in the pool or not at all.

The spring peeper, on the other hand, has more options.

“They don’t need a vernal pool to mate,” Seamans said. “They can do it pretty much anywhere.”

The group examined a variety of fauna plucked from the pond. There was dragonfly larvae, there were sideswimmers and there were backswimmers. There were sperm packets and egg masses. All living things seemed to rejoice in the arrival of spring, creating a happy place out of a pool that will be gone in another month or so.

The fact is, the people who gather to watch the perennial romance going on in the pools at Thorncrag never know exactly what they will find there.

“Every year,” Hayward said, “is a different surprise.”