Chuck Zukowski was in the middle of discussing Colorado cattle mutilations when he paused to reflect.

The Colorado Springs UFO researcher had just recounted an investigation he conducted in March near Walsenburgin which a cow turned up dead with its udder missing and the animal’s newborn calf was found nearby, unharmed.

“What kind of predator would go after an 1,100-pound cow and leave a calf?” he continued. “(The ranchers) bottle-fed the calf to keep it alive.”

But the livestock owners, like many others Zukowski has met, were less willing to talk about the case publicly.

“The reason ranchers don’t talk about (cattle mutilations) is the giggle factor (concerning UFOs),” he said. “And we all know about the giggle factor.”

Several people in the audience nodded knowingly, and a few smiled faintly, but no one laughed. It was a moment that illustrates the no-nonsense — dare we say down-to-earth? — attitude that Zukowski and other UFO researchers who spoke Thursday at the 40th Annual International UFO Symposium in Denver bring to their work.

The lectures were meant to teach the audience of about 60 fellow researchers how to be better volunteer field investigators for the Fort Collins-based Mutual UFO Network, a national, nonprofit group that studies sightings of unidentified flying objects and is hosting the four-day conference at the Denver Marriott Tech Center. Topics the first day ran the spectrum from photo analysis and basic astronomy to evidence collection and interviewing techniques.

As one speaker put it, the presentations were designed to show investigators how to “discern the normal things from the abnormal things.”

Granted, the speakers belong to an organization with “UFO” in its name and many of them said flatly that they believe extraterrestrials exist. But they also spoke passionately about not wanting an investigator’s belief in flying saucers, or the beliefs of a witness, to cloud a case and lead it somewhere that the evidence doesn’t.

“The public is very good at observing things; they’re not good with scientific things — we have to be the scientific people in this community,” said Jan Harzan, MUFON’s assistant state director for Southern California, who led a discussion about the organization’s formal investigation process. ” … There are about 5 percent of the cases where we really don’t know what happened.”