Wild Colorado: The beavers are back

Saturday, May 15, 2010

Beavers are common throughout North America today, despite almost being hunted to extinction in the 1800s

By Julie Sutor
summit daily news

SUMMIT COUNTY — The Colorado High Country is known for its abundance of charismatic wildlife, but there is perhaps no other species that has played as pivotal a role in its history as the beaver.

Beavers — and their thick, soft pelts — were the initial draw to Summit County for white settlers. Beaver furs were highly coveted in Europe for centuries, and the animals were hunted nearly to extinction on that continent by the mid-1500s. The North American beaver trade served as a new, seemingly endless supply, and beaver hats were all the rage again in Europe by the mid-1600s, funding the continued development and settlement of the American colonies.

“Across the entire sweep of North America, the fur trade was the cutting edge of the frontier, and the driving force behind the exploration of the country,” author Alice Outwater wrote in her book, “Water: A Natural History.”

In the early 1800s, as many as a thousand white trappers were hunting beavers in the Rocky Mountains at any given time, according to Outwater. Beaver trapping drove white settlement in Summit County through the middle of the 19th century. It is believed that beaver trappers were likely the first to discover gold in Summit County, drawing the second wave of white settlers to the area, according to Caitlin Lewis of the Frisco Historic Park and Museum.

By the mid 1800s, American beavers were on the brink of being wiped out, and their salvation and eventual recovery hinged on the whims of fashion: In the 1840s, silk top hats replaced beaver-felt hats as the must-have headwear.

By the 1870s, beaver populations began to slowly rebound in Colorado. However, their return was slowed by mining and agriculture, which infringed on their habitat and diverted and polluted their waters.

“Beavers have always had a tough time in Colorado, whether from trapping for their pelts or from development,” said Randy Hampton of the Colorado Division of Wildlife.

In the last 50 years, as environmental regulations improved water quality and habitat, beavers at last staged their comeback in the Rockies.

“Beavers have responded fairly well, and now they're found pretty much everywhere around the state where there's water,” Hampton said.

Keystone species

Beavers are a keystone species, meaning that their presence will dictate the overall health of their ecosystem. Their incessant activity in creating dams along streams and rivers fundamentally alters riparian areas, leading to the formation of pools, ponds, wetlands and meadows, which all serve as habitat for other species, including fish, plantlife, amphibians, deer and other wildlife on up the food chain. Without beavers, fish lose important breeding and spawning areas, as waters run too cold and fast for reproductive activity. That impact to fish then cascades throughout the entire ecosystem.

“Beavers do more to shape their landscape than any other mammal except for human beings,” Outwater wrote.

In 2007, Canada-based ecologist Jean Thie identified a half-mile-long beaver dam visible from space. Thie located the dam in Alberta's Wood Buffalo National Park, using Google Earth.

A mating pair of beavers creates its home by burrowing into the bank of a stream from underwater. The beavers excavate upward, creating a den above the high-water line, which they then line with vegetation. Having an underwater entrance to the den provides protection from predators. Beavers build dams in order to maintain the water level above the den's entrance.

Today, as beavers busily dam up Colorado's waters, they inevitably come into conflict with humans, altering the course of waterways and creating small floods.

“In Glenwood Canyon, CDOT is constantly dealing with beavers plugging up the streams, causing flooding concerns that could, over time, threaten the interstate. They alter the ecosystem in good ways and bad ways. It's one of those things where we have to find a balance,” Hampton said.

Tularemia likely in Colorado beaver deaths

Small numbers of beavers found dead in San Miguel and Gilpin counties in late April most likely died as the result of infection from the bacteria that causes tularemia, the Colorado Division of Wildlife has concluded. There is no evidence of tularemia infections in Summit County beavers.

Water-borne tularemia occurs naturally in Colorado, and sometimes infects beavers, muskrats and other animals that spend time in the water. Rabbits are also commonly infected. Both of the recent outbreaks in beavers appear to be localized.

“Seeing two small outbreaks in different parts of the state at the same time is probably just a coincidence,” said Dr. Lisa Wolfe, wildlife veterinarian with the Division of Wildlife. “Water-borne tularemia outbreaks tend to be reported in spring, so these seem to be pretty typical cases.”

In San Miguel County, four beavers were found dead near ponds in Telluride. Another beaver was found dead in Specie Creek, about 15 miles northwest of Telluride. In Gilpin County, three beaver carcasses were found south of Rollinsville.

After on-site investigations suggested the possibility of tularemia, DOW staff transported some of the carcasses from both counties to labs in Grand Junction or Fort Collins for postmortem examinations. Testing to confirm the diagnosis is still under way.

The causative bacterium, Francisella tularensis, poses a low threat to human health, according to the Colorado Department of Public Health and Environment.

Simple steps recommended by CDPHE to protect against tularemia include not drinking untreated water, wearing gloves when skinning game, wearing insect repellent (due to the risk of transmission through deer fly or tick bites) and preventing pets from feeding on animal carcasses.

Other beavers will likely move into the areas soon, according to wildlife officials.

http://www.summitdaily.com/article/20100515/NEWS/100519852/1078&ParentProfile=1055