Local bears pack on the pounds before they drowse

Pre-hibernation trash munching driving uptick in nuisance calls

A bear takes a nighttime walk near the Alaska State Office Building on Tuesday, Oct. 21, 2025. (Mark Sabbatini / Juneau Independent)

By Ellie Ruel

Juneau Independent

As the air cools and winter approaches, local bears’ search for sustenance is heating up. That means an uptick in human-bear conflict as they dig through garbage and scatter it across streets in search of food.

“We get more calls later in the year in the downtown area, for example, because the fish runs and things like that have sort of calmed down,” said Alaska Department of Fish and Game Area Management Biologist Carl Koch. 

Koch’s main advice to people looking to avoid bear conflict is to secure their bird feeders and trash, and to keep attractants out of their vehicles. He said nuisance calls should slow down in November and December, but ADF&G sometimes receives bear calls year-round.

In the fall, bear dining habits are driven by a period of extreme appetite known as hyperphagia. Increased caloric intake builds fat reserves to fuel their normal bodily functions during hibernation. During the feeding frenzy, black bears transition from their usual 8,000-calorie diets to consuming 15,000-20,000 calories daily. At least twenty hours of a bear’s day are dedicated entirely to devouring whatever is in sight.

“When they're in this hyperphasia, there’s hormones that tell you when you're full, and they kind of are inhibited a little bit so that they'll pack on more weight,” Koch said. 

Once they retreat to higher-altitude dens to wait out the winter, those fat stores provide the energy they need. Water harvested from the breakdown of previously stored protein groups is used to metabolize body fat, and waste like urea is broken down, with the resulting nitrogen used to build proteins to bulk up muscle mass and organ tissues. 

Their natural food sources become scarcer as salmon runs decline, grasses become less nutritious later in the year, and berry season comes to a close. This leads bears to shift to anthropomorphic sources like trash, food scraps and bird feeders to satiate their hunger.

“They'll keep on going after food when it's available and until they're burning more calories than they're taking in, and then they shift into sort of like this pre-hibernation,” Koch said.

When bears eat more human food than natural food, they tend to hibernate less, which in turn can impact their health. A wildlife ecology study tested the proportion of carbon-13, a stable isotope of carbon found in corn and cane sugars, present in bear tissue samples, against how long that bear hibernated. They found higher concentrations of the isotope was correlated with shorter hibernation.

The researchers also tested how reduced hibernation impacted how the animals were aging. They measured how fast telomeres — the compound structure at the end of a chromosome that shortens during cell division — were shrinking. Bears with shorter slumbers had faster rates of telomere shrinkage compared with their better-rested counterparts.

Since bears are attracted to high calories and strong odors, they can become conditioned to searching for snacks in populated areas. Bears rooting through a garbage can or dumpster might be what comes to mind when imagining bears eating trash, but reports of them opening car doors have also increased in the past few years. 

“Some bears seem to learn how to open car doors,” Koch said. “It used to be a rare occurrence, and I guess it is still somewhat rare because people, not everybody keeps stuff in their vehicles, but it's picked up in the last few years.”

A 2018 paper from Colorado noted high availability of human food sources can cause bears to change their behavior, increase human-caused bear mortality and reduce population growth rates, while also creating more situations that cause property damage and threaten human safety. 

During the study, researchers selected treatment areas where they distributed bear-resistant trash containers and enhanced education and enforcement efforts. They found that trash-related conflicts were 60% less likely in those areas, where resident compliance with local wildlife ordinances requiring trash to be locked away was 39% higher.

According to the City and Borough of Juneau, ways to keep bears out of the trash include using bear-resistant containers, keeping garbage in a garage or other enclosure until 4 a.m. on trash pickup days, deodorizing cans with bleach or ammonia, and freezing fish and meat scraps before disposal. 

• Contact Ellie Ruel at ellie.ruel@juneauindependent.com.