(Host) No series about Lake Champlain and the Islands would be complete without mentioning Champ, the mythical monster said to be lurking in the lake's chilly depths. Commentator Joe Citro has a Champ update.

(Citro) Even in the 21st century, Vermont's oldest mystery remains unsolved. We still don't know whether some kind of "monster" is living in Lake Champlain. Until recently, the most convincing evidence of "Champ's" existence was the so-called "Mansi photo." It shows what appears to be the long neck and head of some unknown aquatic creature. Recently, Skeptical Inquirer magazine insisted Ms. Mansi mistook a piece of driftwood for a lake monster.

But now there's a fascinating new bit of evidence. It's not something seen, but heard.

One chilly June morning in 2003, a team of scientists, under contract to the Discovery Channel, were visiting Lake Champlain, working on a documentary about Champ. It was 8:00 in the morning. Everything was still. The water was mirror-smooth. Lead scientist Elizabeth von Muggenthaler and Dr. Joe Gregory, professor of sound and vibration at North Carolina State, had highly sensitive underwater recording equipment. They were cold, probably bored, and not too optimistic that anything remarkable would happen.

Then.... everything changed.

Very, very faintly, an unexpected sound came over the headphones. It was not the sound of frolicking fish or outboard motors. It was something they'd never heard before in the lake. But it was an animal sound.

If they'd been at sea, the series of high-pitched tickings and chirpings would have been familiar - like sounds made by dolphins or Beluga whales. But then, there are no whales or dolphins in Lake Champlain.

Liz and Joe moved to another location and heard the sounds again. If it were a whale, their trained ears and equipment would have recognized it's echolocation at once. To me, it sounds like a railroad train, but it isn't; it's the so-called "bio-sonar" whales emit to find food underwater.

But what Liz and Joe heard was very different. The pitch of the sounds was incredible - ten times higher than any known fish in the lake! What could it be?

Well, no one knows. Yet this much is certain: they've discovered a creature in Lake Champlain that produces unique and powerful bio-sonar. Quite possibly they've recorded the sound of Champ.

And this is the sound of Joe Citro. My thanks to Elizabeth Von Muggenthaler and her North Carolina-based Fauna Communications Research Institute for the use of her recordings.

Novelist Joe Citro is a native Vermonter. He lives in Burlington. His new book is "Curious New England: The Unconventional Traveler's Guide to Eccentric Destinations."

Copyright Joe Citro 2003.