Grizzlies in the region have so far suffered unusually high mortality rates this year, likely because of a dearth of natural food sources, the area’s most prominent grizzly bear researcher said Wednesday.

Interagency Grizzly Bear Study Team leader Chuck Schwartz said officials tallied 25 known and probable grizzly mortalities. Twenty-two of those mortalities were human-caused, two of the deaths resulted from natural causes, and the cause of one death was undetermined. For every bear that was reported dead, two more deaths likely went unreported, Schwartz said.

“This is not a good year for bears, as far as mortality is concerned,” Schwartz said.

Schwartz was speaking to a group of wildlife managers and conservationists at the annual meeting of the Yellowstone Grizzly Coordinating Committee at Snow King Resort in Jackson.

Schwartz’s Interagency Grizzly Bear Study Team is a group of researchers that has monitored grizzlies in Yellowstone since the bears were put on the endangered species list. It is funded by the U.S. Geological Survey.

Nine female grizzlies older than 2 years were among the reported dead: three from management actions, four from hunting incidents, and two from natural causes. Wildlife managers say these so-called “independent age females” have the biggest impact on the grizzly populations.

In all, Schwartz said a conservative estimate for the overall grizzly population in Yellowstone is 571 bears. This year, Schwartz’s team documented 50 females with cubs of the year. The average litter size was 2.16 cubs.

Black bears in the area also had a tough year. Wyoming Game and Fish Department officials say they have responded to roughly 175 bear conflicts in the Jackson Hole area so far, exceeding the last five years combined.

Wildlife managers have killed nine black bears and relocated more than 25. Officials say black bears throughout the region continue to explore human-populated areas in search of food as they make the final push for calories before hibernating for the winter. Homeowners have been asked to take care to secure human food sources such as garbage, bird seed and pet food.