WAUSAU, Wis. -- The popple stand in this section of Marathon County Forest seems pretty typical -- just 7 years old, it's a vertical, gray maze of trunks.
Some are just six feet tall and thick as a broomstick. Others tower overhead and are more like baseball bats.
The trees are spaced tightly enough to require a human visitor to side-slip between trunks every few feet.
Every so often, too, the ground is mounded with an old stump or a pile of slash from the previous timber harvest.
An average stand of regrowth in the north central Wisconsin? Yes, except for one, very big difference: the dark, cooing mass ahead.
"She's got four cubs," says Karl Malcomb, a University of Wisconsin researcher, nodding at a circular clearing in the aspen.
There, sprawled on its side, is a sow black bear with four suckling cubs. The cubs emit soft squeals and purrs as they jostle for position and take nourishment in the cold, winter air.
Malcomb and a team of researchers, including Karl Martin and Dave MacFarland of the Department of Natural Resources, have visited the sow to evaluate its health and reproductive success and to change its radio collar. They inject a tranquilizer with a long jab stick; 10 minutes later the sow is immobilized and ready for handling.
The cubs are plucked off the sow and held by assistants like squirmy toddlers.
At about 8 weeks old, they are perfect little bears, with full, black coats, strong forearms and tiny claws.
The mom isn't too bad, either. At about 275 pounds, the sow is large and healthy looking, even after a winter in which it has given birth and provided milk to the newborns.
The sow has a track record of success, too.
"When I first saw her two years ago, she had four cubs, too," says Terry Lane of Mosinee, one of the other guests on the den visit. "She seems to be a pretty good mom."
Lane was rabbit hunting this section of public land two years ago when he heard a squealing noise in an adjacent thicket.
He crept closer, thinking perhaps it was a raccoon.
What he found was something else entirely. Like this year, the sow had denned on top of the ground. The four cubs were happily nursing.
The bears are part of a growing population of the large omnivores at the edge of Wisconsin's forest and farming landscape.
The Wisconsin population of bears is estimated at between 26,000 and 40,000. Though the population is considered healthy and expanding, it was not always the case.
Prior to 1985, unlimited and increasing harvests caused the bear population to decline; the bear hunting season was closed in 1985.
With the cooperation of major hunting organizations and new legislation, a new system of bear hunting and harvest control began in 1986. Since then, the bear population in Wisconsin has nearly tripled according to DNR estimates.
Most bears are found in the northern third of the state, but bears are being sited more frequently in counties farther south and southwest.
Bears, probably dispersing young adults, have even been sighted in suburban Milwaukee in recent years.
This area west of Wausau is a mixture of hardwoods, aspen and pines surrounded by agricultural land.
Malcomb, working in collaboration with the DNR, is trying to learn how bears move through fragmented forest habitat and where they are likely to set up breeding populations. The work is funded by a grant from the U.S. Department of Agriculture and logistical support from the Wisconsin Bear Hunters Association.
The radio collars allow researchers to closely follow the movements of the bears.
Dispersers are important from an ecological and management perspective because their behavior and survival determines how a population expands into unoccupied territory, according to a research paper on the project.
Some data indicate agricultural areas south of traditional bear habitat will sustain populations of bears, perhaps because of changing farming practices or farms being converted into recreational land and managed for wildlife.
It's also possible that, due to abundant food resources in the agricultural areas, sows will have larger litters. Studies on Wisconsin bears have shown average litter sizes from 2.5 to 4 cubs.
"If this one is any indication, these bears around here will definitely have more," says Lane, looking down at the sow he found two years ago.
Lane and his fellow members of the Mosinee Sportsman's Alliance have become more than observers. They have donated thousands of dollars to the project to pay for drugs and other supplies.
The club keeps the den location a secret to help protect the sow and cubs. It is, however, within 50 yards of a public trail and 500 yards of a subdivision.
Another aspect of the research is to see how well bears and people coexist in areas like this near Wausau. Yet another is to evaluate the degree of crop damage caused by bears in these areas.
Malcomb and the other researchers take measurements of the sow's temperature, respiration and evaluate tooth wear. A new radio collar is also attached.
The cubs are weighed and quickly evaluated.
Once the work is done, the cubs are placed back on the sow. Within seconds, they work into position and begin suckling.
In the coming weeks the sow will arise from its slumber and lead its four new charges into the Wisconsin spring. For now, though, it's time to rest.
The group of researchers and assistants picks up its clipboards and tools and walks out through the popples.
From 25 yards away, the den is obscured by the fence-like aspen, its presence betrayed only by a sweet, soft yelping.