Minnesota home hosts denning bear and her cubs under porch

Crosslake, Minn. — At a home near Crosslake, it isn’t obvious who a resident is hosting. Soon it’s revealed: a sow bear and two cubs beneath the residential porch.

“I don’t think we’ll be coming over to this part of the house, you know, we’ll just go in and out through the garage,” Tim Greer said.

While the Greers spotted the sow just before leaving town for about a month, the DNR’s bear project leader, Andy Tri, suspected she arrived in November, at the latest.

That revelation surprised the Greers, as they have lived business-as-usual throughout the fall and winter, playing with their grandkids in the snow on the front lawn or going in and out the front doors.

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A research opportunity

After discovering the bear’s nest under the porch in late-January, Tim Greer installed a camera below the deck. Upon monitoring the bear more, the Greers discovered there were also two cubs tucked away with her.

Once Tri’s team heard there was a reproductive female black bear in the area, they knew they wanted to add her to the current study roster on reproduction in the Brainerd area.

Researchers put a radio collar on the sow because she meets the criteria of a new study the team is running to try to discern how early in life bears in the Brainerd area are having their first litter.

“So if we’re able to get new females on air (collared) and get their age of first reproduction, that’s a new data point for us,” said Hannah Leeper, a DNR wildlife biologist.

After spending the past two weeks working 11-hour days while tracking down collared and uncollared black bears, Tri’s team is a well-oiled machine in gathering data on the bears.

“This is our go time for the year, because (with) cubs (there’s) kind of a short window of when we can handle them. So, they’re all packed into the end of February, beginning of March,” Leeper said.

Quietly, the team approached the porch and prepared to inject the sow with an anesthetic. When it was determined she was safe to handle, she was pulled from the den and placed on the porch, and the researchers got down to business.

They worked to collect various information including weight, a tooth inspection, a blood draw, body temperature reading, the tread on the animal’s pads, and other details, while also fitting her with some new jewelry – a collar and ear tags.

Because there were two cubs inside the den, some measurements were taken on them, too. In this case, the two cubs – one male and female – were some of the biggest the researchers had seen all season. The female weighed 8.2 pounds, while the male was 9.4 pounds.

“He’s more than twice the size of most of the cubs we’ve seen this year,” Leeper said.

Dumpster diving

Even though a more typical litter size is around three cubs, the weight of the cubs depends on access to food provided by their mother. In this case, the sow is doing OK.

The night before the researchers arrived on Sunday, March 9, Tim Greer saw the sow – via his doorbell camera – dart toward a neighbor’s house and return with a bag of trash. Once the team got into her den, they discovered she likely had done that often.

“She has a palace of trash under there,” Leeper joked.

Tim Greer’s neighbor said he saw her three times the previous week. After the researchers tagged her and cleared out some of her hoarded trash, Greer said she left her den early on Monday morning, hoping to restock at his neighbor’s house again, but returned empty-handed.

Tri estimates the sow gave birth sometime in mid-January and will be leaving the Greer residence in coming weeks.

Because the cubs will remain with their mother for roughly another year, the team will also plan to collar the female cub to add her data points to the research on reproductive cycles.

The current method for calculating when the bears reproduce is possible via rings in their teeth. Similar to a tree’s rings, each ring offers a clue as to what happened that year. When there is a thin ring on a tooth, it signifies that the female likely had a litter that year since more nutrients went to the cubs instead of herself.

A thicker ring on the tooth implies that the sow retained nutrients rather than losing some to cubs. Over time, however, that methodology has come under more scrutiny with Tri and the team wondering about its true accuracy.

“Reading them is not perfect. The bears don’t always lay down lines when they’re supposed to,” Tri said.

And over time, researchers have begun to suspect the age of first reproduction in the Brainerd area is getting younger. The best way to track that will be to collar younger bears and gather information on when that is happening.

As the field work portion of the researchers’ job this season wraps up later in March, they’ll begin to comb through the data they have collected.