The mysterious nighttime meetings of snakes on an Ozark hilltop have taken a puzzling new turn.

For the past two summers, dozens of Southern copperhead snakes have appeared beneath a cedar tree at Chuck Miller's rugged mountaintop home in Marion County. Like clockwork, the snakes arrived suddenly around 8 p. m., stayed for an hour or so, and then disappeared.

But things are different this summer. Instead of making their first appearance in mid-July, as they did in 2005 and 2006, the snakes began showing up in August. And their numbers are down significantly.

The latest developments make the case "more confusing and perplexing than ever," said Stanley Trauth, a professor of zoology and director of the Electron Microscope Facility at Arkansas State University in Jonesboro.

Copperheads congregate in the fall as they move toward winter hibernation sites. They also gather in the spring. Scientists haven't observed this behavior in the hot summer months, said Trauth, an expert in Arkansas snakes who has been studying the phenomenon.

"Nothing has changed - except the weather, or something we don't know about," said Miller, a construction company owner and nature lover who has worked side by side with ASU graduate students to catch, mark and study the snakes.

Some nights, there were more snakes than they could possibly grab, said ASU graduate student Bobby Neal, who is writing his master's thesis in biology about the snakes on Miller's land.

"There were animals we couldn't catch because we had our hands full," Neal said.

Neal estimated 150 to 200 copperheads on the mountain, above and below ground, during the summer months. That's an unusually high density in such a small area, he said.

Researchers caught and marked 67 snakes in 2005, notching out a scale on the belly to allow researchers to determine whether the marked snakes are returning to the property. In 2005 and 2006, 26 more were tagged with radiofrequency identity chips. A "reader" passed within a foot of the tagged snake registers the identification number embedded in the chip. Radio transmitters were implanted in six snakes, but those devices are too expensive to be widely used in the project, he said.

Of the 67 snakes marked in 2005, at least 20 returned to Miller's yard the following year, Neal said. He also documented 23 new visitors.

But this year, Neal has documented only four snakes so far - two previous visitors and two newcomers.

He said changing weather conditions might explain the new behavior.

Nighttime air temperatures in July 2005 and 2006 were much warmer. Some evenings, temperatures hovered around 100 degrees, Neal said. But a cool snap this July sent temperatures into the 50 s some nights.

"I think that kind of put of a damper on them, kind of confused them," the graduate student said.

His professor, however, isn't drawing any conclusions.

"We don't really have any clue about why they would be less numerous this year," Trauth said. "There have been other years of high temperatures, and this kind of phenomenon was not observed."

Trauth speculated in 2006 that the snakes massing around the cedar tree might be following scent trails left by other snakes.

Last year, he began developing a new theory based on temperature differences in the area.

But Trauth has always cautioned that definitive answers are a long way off. "You have to gather data for many, many years," he said last week.

Neal said he's developing a theory that the snakes might be following temperature cues to their meal of choice - cicadas.

Whatever the cause, Neal believes the summertime congregations aren't limited to Miller's 30 acres between Flippin and Yellville, based on informal conversations with colleagues at professional conferences.

"I think there's a large part of these animals' nature history that we've just scratched the surface on," he said.

Some Marion County natives don't find the snake behavior unusual.

As a child, Carolyn Vigna remembers seeing masses of copperheads at the residence of her widowed great-aunt, Alice Smith, who lived in the Mull community near the Buffalo National River in southern Marion County.

"She'd always say, ' Y'all look, because the copperheads are coming, '" Vigna, 61, recalled last week. "She'd have hundreds and hundreds. Those copperheads - it was just like they were swarming."

Vigna, who is secretary of the Yellville Area Chamber of Commerce, said news accounts of Miller's snakes have produced some phone calls to the chamber seeking more information.

The snakes are also a recurrent topic of local conversation, she said.

Miller said he fields questions about the snakes wherever he goes.

"In fact, I just went to the bank, and everybody in there crowded around, asking if we'd seen them yet," he said.

While scientists haven't closed the book on the snakes, Miller said the nocturnal visitors helped open a happy new chapter in his life.

Last summer, many area residents visited Miller's place, hoping to see the snakes. One night, the visitors included Machelle Curtis, who'd seen a newspaper article about the snakes.

Miller and Curtis hit it off immediately and have been a couple ever since. They were married Friday night on the mountaintop. The guests included 200 friends and relatives - and probably a few snakes.

Miller joked that the snakes brought him true love.

"They got me famous and everything, and I met a girl. So now I really don't care much about snakes any more."