A Crivitz landowner says the experience two teens had with a bear on his property over the weekend is proof you can't leave food around your campsite.

"They're pretty much city boys, so they didn't want to come out and have too much to do with the bear," Wayne Franzen said.

Franzen received a call Sunday morning from his nephew and one of his friends.

"They called and said, 'What do we do? There's a bear outside the camper.' I said, 'Well, don't go outside.'"

Instead, the boys grabbed a cell phone and camera and started taking pictures of the bear roaming around the campsite and sniffing a cooler.

"Had they been in a tent, yeah, they would have been panicky, but they we're in a motor home so they felt a little bit confident there."

Franzen says just 20 years ago a sight like this was almost unheard of around Crivitz.

"Never saw a bear hunting. It would be like if you saw one driving, it was like big news, everybody talked about it, 'I saw a bear.'"

According to Department of Natural Resources wildlife biologists, the black bear population in Wisconsin's Northwoods has more than doubled in the past decade from 15,000 to 35,000.

Sheriff's department dispatchers say calls about bears in back yards and knocking over garbage cans increases every year.

"They're just like you and I -- they're lazy. Instead of making the sandwich we'll stop at McDonald's. Instead of them foraging for blueberries that aren't ripe yet, they're gonna go to what's easiest, and obviously a cooler full of food in a campground is pretty easy," Franzen said.

"We're in its environment," Franzen said, "so it had no problem -- that cooler was part of its domain."

Wildlife biologists say many campers need to do a better job of keeping food and garbage in places bears can't get to.