Yellowstone-area grizzly bear deaths have reached a record number. This year researchers have documented the most known and probable grizzly mortalities in a single year, with removals associated with cattle depredations increasing, according to a U.S. Geological Survey biologist.

Currently there have been 70 known or probable mortalities as of Nov. 4, surpassing 2018 as the highest number of deaths according to Frank van Manen, a supervisory research wildlife biologist with the US Geological Survey and team leader of the Interagency Grizzly Bear Study Team, which addresses monitoring and research needs for the Greater Yellowstone Ecosystem grizzly bear population.

With more than a month left before most grizzly bears are hibernating, the number of mortalities is likely to rise considering bears are currently in hyperphagia while storing up fat for their long nap.

The majority of deaths of the species are the result of management decisions by the U.S. Fish and Wildlife Service. This year, all categories of mortality causes are “essentially at the average of the previous 10 years,” van Manen said, with the exception of removals associated with cattle depredations.

“There is sometimes a cyclic pattern with livestock depredations; removing depredating bears tends to be an effective strategy and typically reduces such conflicts in several subsequent years, after which new bears may move into the same area and the cycle starts anew,” he said in a Monday interview with the Tribune. “This year may be the peak of such a cycle, and with possible added effects of drought conditions, depredations become a major challenge for managers.”

There have been 43 deaths inside the Demographic Monitoring Area (DMA) in 2024. The DMA is a 20,000 square miles area that has been determined to be suitable habitat for the species. The previous record for the total number of mortalities was in 2018, when 47 deaths occurred inside the DMA and about 22 outside the DMA. The Interagency Grizzly Bear Study Team doesn’t have a mandate or the funds to count grizzlies outside the DMA, van Manen said in a previous interview with the Tribune.

More than 50 of the 70 deaths in 2024 occurred in Wyoming, and 27 deaths were outside the DMA. Grizzly bears are increasing in population outside the DMA, van Manen said, with some reaching as far as Byron and the Ten Sleep area to the east and Red Lodge in Montana, according to previous reports.

“A large proportion of management removals are from outside the DMA. We counted 19 management removals outside the DMA based on the provisional data,” he said, or about 27% of all 2024 mortalities.

“Although we did not document expansion of occupied range from 2020 to 2022, we did document continued population growth,” he said. “This likely translates to a higher density of grizzly bears in occupied range outside the DMA, where mortality risks are higher compared with areas inside the DMA.”

This trend of more conflicts and mortalities outside the DMA started around 2010 and continues to date. The reason for the higher mortality risk is that habitat quality in areas outside the DMA is lower and there are higher levels of human influence, he said.

The study team has been estimating populations since 1975. There are currently an estimated about 1,000 grizzly bears inside the DMA, and, according to a 2022 U.S. Fish and Wildlife Service report, grizzly bears currently occupy about 98% of suitable habitat in the DMA and 30% of the current estimated distribution is occurring beyond the DMA.

“The Interagency Grizzly Bear Study Team is currently evaluating the feasibility of implementing an integration population model,” the report said.

Full data for 2024 won’t be updated until 2025.

Climate change may be extending the time the species is active, according to a paper, of which the authors included van Manen.

“Climate change poses a pervasive threat to humans and wildlife by altering resource availability, changing co-occurrences, and directly or indirectly influencing human-wildlife interactions,” the paper reports. “For many wildlife agencies in North America, managing bears and human-bear interactions is a priority, yet the direct and indirect effects of climate change are exacerbating management challenges,” they reported. “Understanding the underlying ecological drivers of bear responses to climate variability and change, and the implications for conflict, will be critical for maintaining human-bear coexistence in North America.”

Other categories of mortalities in the Yellowstone ecosystem species include: Killed by another bear (two), killed by a vehicle (two), electrocution in Yellowstone National Park (two), drowning in cement-side irrigation canals (three) and one that was killed in a human/grizzly conflict in self defense. Eighteen of the 70 deaths are still under investigation and Wyoming leads the category by a broad margin with 11 of the 18 still being investigated, according to the provisional data.