YOSEMITE -- It's called the "cascade effect" -- a catchy name for the way one mistake leads to another, and a quick explanation for how a hiker who takes one step off an established trail is one step closer to trouble.
Park rangers and search and rescue experts say that hundreds of hikers take that one wrong step each year. The key, they say, is where their next step takes them -- back to the trail or further down a perilous path.
Ron Hoggard, Corcoran city manager, became lost two weeks ago after leaving the trail for only a few minutes. When he tried to find the path again, he went the wrong way and spent the next three days with no food and little water, trying to find help.
Hoggard, 58, had never heard of the cascade effect, but said after he was found that he believes it can happen to anyone.
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He also said he believes he was lucky.
In the case of Ottorrina "Terrina" Bonaventura, the cascade effect led a hiker with decades of experience down a wrong trail, and what should have been a short walk with friends turned deadly.
Bonaventura, 80, was on a day hike July 30 when she apparently headed the wrong way down a trail. Another hiker spoke to her later in the day, several miles from her destination, but she did not say she was lost or ask for help.
Her body was found two weeks later, miles from her campsite.
When hikers such as Hoggard or Bonaventura become lost, officials mount massive search and rescue efforts that include rangers searching trails and wilderness areas. Less known, but equally important, is the background work of building a profile of the missing person that helps officials narrow the search area and find their quarry as soon as possible.
"It's like running two separate cases -- a search and rescue and an investigation for a missing person's case," said Dave Pope, a search and rescue expert at Yosemite National Park. "People know about the searchers on the trails, but the work done off the trail can be just as important."
'Unknowing witnesses' help
That off-trail work includes interviews with friends and family members and other hikers along the trail. Searchers also write down license plate numbers of vehicles at trail heads to help them locate people who may have seen the lost hikers.
"Even if they haven't seen the person we are looking for, they can be helpful," Pope said. "We call them unknowing witnesses, and they have helped us solve cases in the past. They let us eliminate areas from the search. It's all part of building a profile of the person we are looking for."
That profile tells searchers how experienced the hiker is, whether he or she is a risk-taker or someone likely to stop once lost. It also tells them how prepared that hiker is for extra time in the wilderness.
"The more information we have, the smaller the search area can be," said Yosemite spokeswoman Adrienne Freeman. "When you are talking about a park the size of Rhode Island, narrowing down the search area is vital."
Experts said that while rookies and experienced hikers alike experience the cascade effect, it can be easily avoided.
"No one sets out for the day planning to get lost, but it happens," Pope said. "Most of the time, a person who is reported late will turn up on their own, or we will find them with a sprained ankle somewhere on the trail. It just depends on the choices they make."
Pope said that Yosemite's search and rescue team is sent out as many as 250 times a year. Most of the time, lost hikers are found quickly, and some calls are to help hikers with minor injuries.
Yosemite isn't the only park in the area where hikers get lost. Kings Canyon and Sequoia national parks see about 70 searches per year, and local sheriff's departments conduct hundreds of searches in national forest areas.
Most searches end quickly and on a positive note, officials said.
Major searches, such as those conducted for Hoggard or Bonaventura, happen only a few times a year at Yosemite, Pope said. When they do happen, there are few similarities.
"Each incident is different, always different," Pope said. "There's not an area of the park that sees a higher number of cases than anywhere else. But what they all have in common are the choices the hiker made before setting out.
"Did they have a plan? Did they tell someone where they were going? There are a lot of factors that don't play a part in a hiker getting lost but play a huge part in what happens next."
Stopping not always best advice
Sometimes, Pope said, lost hikers will follow advice that is either not accurate or doesn't apply to them, such as the idea that moss grows only on the north side of trees, or that if they become lost, the best thing to do is stop.
"The teaching is to stop," Pope said. "But for that to work, it assumes we knew where you were headed to begin with. If we didn't, and you are an experienced hiker, it might be better for you to try and get yourself out. If you are really far out there, it could take us a while to get to you."
Pope said that in Hoggard's case, even though he had not prepared to be out overnight, he did many things that helped him survive. Hoggard, a former Boy Scout, knew how to make rudimentary shelters, and left signs for searchers, including a note written to his family when he began to believe he might not survive.
"You have a lot of time to reflect in that situation," Hoggard said. "Not only was I disap- pointed and upset that I was putting people through the search, I was also worried I wouldn't be found."
After he was located, Hoggard vowed not only to learn from his mistakes, but also to help others avoid similar experiences.
"I would say to take a pack with the essentials they recommend, even on a day hike," Hoggard said. "I had said where I was going, but it would have also been a good idea to have a second person with me, just in case."