Observing young wolves at play, glimpsing river otters as they slip off the bank into river currents, viewing a cluster of hundreds of migratory trumpeter swans and listening to their faint cooing.
These are the kinds of experiences visitors dream of when they visit the United States national parks. But being in the right place at the right time - especially with some of the parks' shyer creatures - is not always easy. That's why many visitors choose to sign up for courses taught by experienced guides.
For Yellowstone National Park in Wyoming, the summer catalog (www.yellowstoneassociation.org) lists dozens of weekend and weeklong courses dealing with the history, cultural resources, wildlife, and ecology of the park. Offerings include "Alpine Flowers," "Fly-fishing for Women I and II," and "Trails through Yellowstone." Some courses even include lodging in the park.
Gordon Langlie recently participated in his third Yellowstone Institute course, this one devoted to wolves.
During the four-day class, Mr. Langlie - a security specialist for the Department of Energy who traveled to Yellowstone from Kensington, Md., with his brother, Gary - saw a pronghorn antelope that had just given birth to two fawns. They also saw three grizzlies, numerous wolves, a silver fox, coyotes, and hundreds of bison and elk.
Students in the wolf program set out at 5 a.m. for field observation; after several hours they return to the Lamar Buffalo Ranch in the beautiful Lamar Valley for classes and meals. Then at 6 p.m., the group goes out again with spotting scopes, binoculars, and cameras.
Linda Yetz, another student in this season's wolf course, says she relishes the opportunity to see such a variety of wildlife in a short time span.
"In the classes, we learned about the 'ripple effect' of reintroducing wolves to Yellowstone and how it's affected the entire park ecosystem, not only other animals but even trees and plants."
But Ms. Yetz, who works in Boston at a high-tech business-development company, says she also attends the courses because she's a "big wildlife lover" and enjoys the experience of spending time with so many like-minded people.
While wolves and grizzlies are a big draw at Yellowstone, people flock to the Smokies to learn more about salamanders and wildflowers.
The Institute at Tremont in the Great Smoky Mountains National Park east of Knoxville, Tenn., offers residential learning programs for students during the school year and camps for youngsters during the summer. For adults, Naturalist Weeks and Weekends are offered in the fall and spring. Participants can choose from four topics, which change seasonally: wildflower identification, butterflies and moths, the ecosystems of salamanders, or Smoky Mountain history and crafts.
People come from all over America as well as from other countries, says Amber Parker, educational director at the Institute at Tremont. The week and weekend naturalist courses at Tremont change yearly, so people can return without repeating the same material.
On the other side of the country, Yosemite National Park (www.yosemite.org) in California hosts nearly 3.4 million visitors a year. The vast majority spend only a day or two driving or hiking through this park's spectacular scenery. But other park visitors gain a much more in-depth experience of the flora and fauna by attending the Outdoor Adventure Program.
These range from short-guided hikes such as "A Dome in a Day," which covers three miles and ends at Sentinel Dome and offers spectacular views of the valley, to the four-day "Family Camping Jamboree." Another popular course is "Introduction to Backpacking and Wilderness Ethics for Teenage Girls," where girls get the chance to ask a variety of questions before taking off into the wild.
Why are such park educational tours and courses becoming so popular? People are "feeling less connected with nature in their day-to-day lives and jobs, so they really want that experience for their vacation," says Ms. Parker.
For Matt and Carol Millenbach, who live close to Yellowstone and have always frequented the park, it's all about the wildlife. "People tell me they come to the park and don't see anything. They talk about missing the days when bears used to come up to the car to beg for food," says Mr. Millenbach. "But nowadays we never come to the park that we don't see bears or wolves or coyotes or something because we know what to look for and where to go."