National parks nature lab: hike, paddle, and camp your way through nature's best laboratories: America's national parks.

DID YOU KNOW?

* By 1975, grizzly bears inhabited less than 2 percent of their original range and thus were listed as a threatened species under the Endangered Species Act.

* Adult male elk sport antlers that can reach a span of 1.5 meters (5 feet)!

* Python Pete isn't the first dog to sniff out non-native species. Jack Russell terriers are regularly used to detect brown tree snakes in airport cargo entering Guam.

CRITICAL THINKING:

* When estimating the grizzly bear population in and around Glacier National Park, why might researchers prefer to collect fur samples rather than physically capturing the bears?

CROSS-CURRICULAR CONNECTIONS:

HISTORY: The artist George Catlin is generally credited with the idea of creating a national park. While on a trip to the Dakotas in 1832, Catlin wondered what would happen to America's open lands in the face of continued expansion. Forty years later, Congress designated Yellowstone the world's fast national park. Imagine you are a member of Congress in 1872. Research to write a speech declaring Yellowstone protected.

RESOURCES

* To learn more about elk and to view a quick video of the animals being released into the Great Smoky Mountains in APRIL 2001, visit: www.nps.gov/grsm/pphtml/highlights529.html

Climbing, rafting, snorkeling, and ... scientific research? To the millions of people who visit one of the 57 national parks in the U.S. each summer, the more than 50 million acres of land are an action-packed vacation spot. But to scientists who study ecosystems, or the interactions between living and nonliving things, the parks are also an ideal place to do research. That's because many of the open spaces have been mostly untouched since 1872. That's when the U.S. government set aside land for the first national park--Yellowstone.

Another protected area, Great Smoky Mountains National Park, is "one of the few places you can go and get some idea of how things might have been 100 or 200 years ago," says Joseph Clark, a wildlife biologist for the U.S. Geological Survey (USGS). That means scientists can study the park's pristine ecosystem to figure out how a healthy forest should function. This information could help researchers devise ways to restore other wooded areas that have been cut down.

And that's not all. Science is happening in each national park--from endangered falcons breeding in Big Bend to a beagle pup that's helping to save the Everglades. Read on to learn what's taking place in a park near you. These outdoor labs make a summer of "studying" look fun!

THE GRIZZLY NUMBERS

Glacier National Park, Montana

Wildlife biologist Katherine Kendall has a grizzly task: Her team of researchers is counting a threatened population of grizzly bears that roams in and around Glacier National Park. How to cover an 8-million-acre site? Kendall has devised a way to count the bears without ever setting eyes on one.

Grizzlies often scratch their backs against trees to mark their territory--and relieve an itch. Result: Tufts of fur get stuck on the trunk's bark. Kendall snatches the fur from collection sites spaced throughout the park. Then she extracts DNA (chemical that carries hereditary information) from the sample and analyzes it to determine the species, gender, and identity of the bear. By counting the number of unique samples, researchers can estimate how many grizzlies live in the park.

With a count in hand, scientists can better protect the grizzly population from shrinking. The park's beat's are most threatened by habitat loss and encounters with humans. Lured close by people's food and garbage, the bears are viewed as a threat to human safety. Result? Wildlife managers have to remove or kill the grizzlies. How can you help? Follow the park's rules: Secure items out of the bears' reach.

FOR THE BIRDS

Big Bend National Park, Texas

A peregrine falcon's nest perched high in the canyon cliffs along the Rio Grande River is causing a stir. It's even prompted park officials to close a section of Big Bend National Park to springtime hikers.

Why? "[It's important] to give the animals the opportunity to lay their eggs and raise them [in peace]," says Miguel Mora, a biologist at Texas A&M who studies the birds with the USGS.

Peregrine falcons (Falco peregrinus) were removed from the U.S. Endangered Species List in 1999. But their population isn't off the hook: Only 12 nesting pairs of falcons live in Big Bend. Mora believes water pollution is to blame.

He's sampled for toxins in the water and soil along the Rio Grande, as well as in the birds' prey, such as swallows. "We found three contaminants that may be causing reproductive failures in falcons," he says. Mercury from nearby mines and selenium from the park's own rocks leak into the water, along with leftover DDT, a chemical in pesticides that was banned from use in 1972. "[DDT] is so pervasive it has stayed in the environment," says Mora.

CALL OF THE WILD

Great Smoky Mountains National Park, Tennessee and North Carolina 

Five years ago, autumn visitors to Great Smoky Mountains National Park would have heard mostly birds singing. Now, they can hear a distinctive high-pitched whistle followed by a loud grunt. The sound, called bugling, signals mating season among the park's newcomers: A population of wild elk.

The Eastern Elk, or Cervus elaphus canadensis, which grazed the park's fields in the early 1900s, was hunted to extinction. But beginning in 2000, researchers have released 52 elk of a closely related subspecies into the Great Smokies.

Clark, of the USGS, monitors the elk with radio collars and counts calves born in the park every spring. So far, the herd is surviving. But many calves have been killed by predators. And some adult elk have succumbed to a deadly brain parasite.

Soon, biologists will determine "whether the elk will survive the park and if the park can survive the elk," says Clark. The answer will help the park service decide if the elk should stay. Meanwhile, visitors have a rare chance to hear sounds from the past.

SNAKE SNIFFER

Everglades National Park, Florida

Everglades National Park recently added a new member to its staff: a beagle nicknamed "Python Pete." Wildlife biologist Lori Oberhofer is training Pete to track Burmese pythons (Python molurus), an invasive (nonnative) species threatening to take over the park. "We tell him 'Pete find it,' and he'll go bounding ahead sniffing the trail," she says. "So far, he's doing really well finding the snakes."

The dangerous snakes wormed their way into the park when pet owners released them into the wild. Burmese pythons may start as harmless pets, but they eventually grow to 6 meters (20 feet) long. Now, the snakes, which lay up to 100 eggs in a clutch, have started to breed in the park.

That's bad news for native wildlife. Florida bobcats, for example, must compete with the snakes in the hunt for a meaty dinner. And the park's raccoons and squirrels--tops on the menu--face a new enemy. But with Python Pete's help, Oberhofer hopes to rid the park of the pesky snakes before they damage the fragile ecosystem.

WEB EXTRA

To find out more about a national park near you, visit www.nps.gov

NATIONAL PARKS NATURE LAB

Directions: Defend or dispute the following statements. (Hint: Defend means to explain why a statement is correct. Dispute means to explain why a statement is incorrect.)

1. Wildlife biologist Katherine Kendall studies grizzly bears by visiting their caves in Glacier National Park.

2. Python Pete of Everglades National Park is helping to protect the park from invasive species.

ANSWERS:

1. Dispute: Grizzlies often scratch their backs against trees to mark their territory-and relieve an itch. Result: Tufts of fur get stuck on the trunk's bark. Katherine Kendall snatches the fur from collection sites spaced throughout Glacier National Park. Then, she extracts DNA from the sample and analyzes it to determine the species, gender, and identity of the bear. By counting the number of unique samples, researchers can estimate how many grizzlies live in the park.

2. Defend: Python Pete is helping scientists track Burmese pythons, an invasive species threatening to take over Everglades National Park. The snakes wormed their way into the park when pet owners released them into the wild. Burmese pythons can grow to 6 meters (20 feet) long. Now, the snakes-which lay up to 100 eggs in a clutch-have started breeding in the park. Native wildlife such as Florida bobcats must now compete with the snakes in the hunt for a meaty dinner. And the park's raccoons and squirrels--tops on the snake's menu-face a new enemy.