Zachary Salonek heard some rustling outside his home in south-central Minnesota around midnight recently and was startled to find a black bear rummaging through his dumpster.

Brown County, where Salonek and his fiancée, Cecily Eichhorn, live, is far from the 40 percent of the state that makes up Minnesota bear country. Or so they thought.

The bear they photographed rolling contentedly around their yard in early June was one of seven sightings in the county since May that have been plotted on a new online map that lets Minnesotans report bear sightings outside of the bears' traditional range across the forests of north and northeastern Minnesota.

Salonek's family lives a couple miles out of Springfield. He said the day after he saw the bear on his property he learned that his neighbor's bird feeder had been tipped over. And another bear — possibly the same one — was spotted about 15 miles to the west, around Lamberton.

Many more sightings have been pinned to the map around the Twin Cities since the tool went live in May, including more than 40 in Anoka County.

"We didn't expect to see this many sightings in the Twin Cities area or south of there," said Dave Garshelis, a research biologist with the Minnesota Department of Natural Resources. He cautioned against reading too much into the data, however.

"This is the first chance for people to actually report stuff in a formal way, and so obviously we're seeing what appears to be a lot of sightings compared to — nothing. We don't have a baseline," Garshelis said. "It's not really clear that this is represents any kind of an increase. When you look at the map you think, 'Oh, wow, it seems like a lot of bear sightings. It must be that there's bears moving in.' But we don't really know that."

He said if the map had been available a decade ago it might have revealed the same distribution. It's also possible that multiple people are plotting sightings of the same bear.

That issue could be compounded in more populated counties, such as the metro area.

Garshelis said it will be interesting to compare the sightings reported on the map to the number of calls the Department of Natural Resources gets — the previous method for gauging bear range. "It's possible that all of these sightings that you see on the map only generated a dozen calls," he said.

Minnesota has an estimated 12,000 to 15,000 bears. While some posit that the bears in southern Minnesota are juvenile males pushed out of their territory in the north by an expanding population, Garshelis suspects that a number of the bears sighted near the Twin Cities and farther south wandered into the state from Wisconsin. He says Wisconsin's bear population has been growing for years, and the state has a "very restrictive" harvest by hunters — the bears' only natural enemy.

Wisconsin has an estimated 29,000 bears, up from just over 9,000 in the late 1980s, which has pushed more bears farther south. Scott Walter, large-­carnivore specialist with the Wisconsin Department of Natural Resources, said for the past couple of decades bears have been moving from their typical range in the north to the southern part of the state, a trend that has accelerated in the past five to 10 years. He said when male bears reach about 18 months of age, they get pushed out to find their own territory.

"It's probably a population that is now established and is going to, from here on out, increase," Walter said. "The big issue is getting people used to the idea."

That means bear-proofing trash cans, bringing pet food indoors and keeping bird feeders inaccessible, he said.

Asked what he thinks of Minnesota's interactive bear map, Walter said, "We tracked bear sightings in southern Wisconsin for a number of years until it became commonplace, and we no longer track that."

Now, he said, the state collects photographs of wildlife contributed by Wisconsinites who set up trailside (or backyard) cameras. While the project is not limited to bears, he expects it will contribute valuable data to understanding their range.

Walter said Wisconsin's Driftless area is great bear habitat because it provides a mix of bountiful forest and agricultural land.

"Dave [Garhelis] might be right: Your bears may be coming from Wisconsin," Walter said. "It's an interesting idea; one I had not heard. It makes sense to me. They've certainly got a corridor along the Wisconsin side, and they're excellent swimmers. Getting across the Mississippi [River] is not a problem at all."

Minnesota is not alone. News reports in the Charlotte (N.C.) Observer, Pensacola (Fla.) News Journal and the Buffalo (N.Y.) News have reported increased bear sightings attributable to growing bear populations. Bear experts advise learning to live with the animals.

Salonek said that's the approach he's taking. He has chained down his dumpster lid to keep bears out and set up a trail camera in case one returns. As of Tuesday, none had.