LAPORTE, Colo. - When Dean Biggins was only 5, he brought his mother a black widow in a jar.

His mother, Lee, sighed and released the spider, just as she did with all the frogs, snakes and dozens of other creatures her son had to show her. He even brought home a jar full of mosquito larvae he thought were fish.

Usually boys will shift their interest to girls or cars or bad rock bands as they get older, but not Biggins.

"I'm afraid I never outgrew that," Biggins said.

Biggins, now a 58-year-old married father of two, never outgrew his interest in wildlife. He used snowmobiles to study elk while earning his master's degree at the University of Montana. He went on to earn a doctorate and chose a career studying a much smaller animal: the endangered black-footed ferret.

Although he would have enjoyed any career working with animals, it's doubtful it would have been as important. Biggins, a wildlife research biologist with the U.S. Geological Survey, is often credited with helping ensure the ferret's continued existence.

Biggins knew he wanted to be a biologist when he was in elementary school. He would walk with his mother and talk about all the things they would see along the way while growing up in Alaska and California. When he wasn't taking nature walks with his mom, he was fishing and exploring.

"It really was born in him," said his mom.

Biggins found his calling in 1981, when 46 adult ferrets were discovered in Meeteetse, Wyo. Biologists believed the ferrets were extinct. When the small population was discovered, Biggins was tapped for the project of making sure they didn't fade away again.

He had worked with a well-known ferret expert in the late 1970s to develop radio transmitters to study ferrets in the wild. He also helped develop radio technology to assist him with his elk studies. Biggins became known as the "ferret transmitter guy," so scientists called him in when the black-footed ferrets were discovered.

Biggins was thrilled.

"It was really intriguing in the sense that here's a fascinating animal that we don't know much about," he said. "We don't understand them at all because they are nocturnal and extremely rare. It was up to us to figure the animal out."

Biggins first traveled to China several times to study the Siberian polecat, the black-footed ferret's closest cousin. But in 1985, four years after their discovery, the ferrets were in danger of disappearing again because of distemper and plague.

Biologists knew they had to take drastic measures. They began capturing the ferrets for breeding, but the plan was so controversial one biologist backed out and in some ways attempted to block the program.

"We had that nagging at us, that these really were the last of this animal," Biggins said. "We didn't know if we would be contributing to their extinction or their salvation. It was one of the most depressing times of my life."

He needed some help. What he didn't know was salvation would come from the ferrets themselves, especially an overactive male that they nicknamed Scarface.

In the winter of 1985, biologists started capturing the ferrets. The program didn't appear promising until summer, when the biologists went back to the Wyoming site. They discovered the original den had grown to 18, thanks to a busy male.

"We brought him in, and he bred like crazy," Biggins said. "He made a huge difference."

So much of a difference, in fact, that in the early 1990s, biologists wanted to minimize his contribution so the entire black-footed population wasn't a bunch of little Scarfaces. By that time, things were much more comfortable with several breeding populations in Wyoming and at zoos in Omaha, Neb., and Virginia.

The captive population is now 250, though it's hardly thriving. Wild ferret populations are continually fluctuating, and Biggins believes chronic plague has something to do with it. Black-footed ferrets are dependent on prairie dogs for food and their burrows, yet prairie dog colonies also attract plague.

"Ferrets are about as specialized a carnivore as we have in the U.S.," he said.

While plague wipes out colonies, the ferrets seem to have just enough resistance to it for it to be a chronic problem, such as cancer in humans. It's just that the margin of error is much thinner for ferrets.

Biggins is now leading a study on plague, just as he led dozens of studies that helped scientists rescue the population. Late last year, he was recognized for his work with the ferrets when he was given the Denver Zoological Foundation Conservation Award.

His biggest reward, however, is in South Dakota, where a thriving, plague-free population lives on some grassland. There are more than 150 adults, and more than 100 litters are born each year, Biggins estimated.

Scientists are taking ferrets from that den and transporting them to dens in Utah, Colorado and Montana. Studies have shown transported wild ferrets have a greater chance to survive than those bred in captivity.

"I just feel like I've been extremely fortunate," Biggins said. "That's very rewarding to make a difference. That's just an extra reward placed on top of a very satisfying career."