HIS YEARS of tracking, with plenty of time to think, have given O'Brien an interesting perspective on wildlife in general and predators, specifically.
He doesn't buy the conventional wisdom that humans have encroached on the animals' habitat, a theory that is supposed to explain why coyotes diminished the once-booming sheep industry in the county or why mountain lions are turning up close to urban areas.
He thinks it's just the opposite.
"The lions are coming into our territory. When I started working here in '74, except for the area along the Lake County border, there were, for all practical purposes, no mountain lions in Sonoma County.
"The old-timers, like Jim Modini, agree with me on this. And I wish the late George Charles (who raised sheep in the northwestern part of the county) were here to attest to that. We didn't ever have a lion involved in sheep preditation back then.
"There were no lions out there, or coyotes for that matter — no coyotes on the coast when I started."
O'Brien's theory is that the "groceries," as he puts it, are scarcer in the high country. There seem to be fewer deer, he says, although he's not certain why this is.
"It may be cyclical," he suggests. "Or something we just don't understand."
It's true, of course, that some hunters stalked mountain lions purely for sport, but O'Brien does not agree with those who blame the California law that protects non-predatory lions on the increased numbers.
"The lion boom is all over the Western states," he says, including states that don't have protection laws.