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Difference in radionuclide contamination among genetic populations of Asian black bear in Fukushima
Yui Nemoto, Rie Saito, Natsuko Ito Kondo, Masahiko Kabeya, Kenji Inami, Kosuke Kanda, Yoshiki Morimitsu, Masanori Tamaoki
Ursus 2025 (36e12), 1-15 (2025). https://doi.org/10.2192/URSUS-D-24-00019R1
KEYWORDS: Asian black bear, Cs-137, Fukushima, genetic structure, Radiocesium, single-nucleotide polymorphisms, SNP, Ursus thibetanus
Since the Fukushima Daiichi Nuclear Power Plant accident in 2011, radionuclides have been detected in the tissues of Asian black bears (Ursus thibetanus). Some bears had higher concentrations of radiocesium (Cs-134 and Cs-137) activity than others, despite their capture in the same area. Migration from areas with different Cs-137 contamination levels may explain this disparity. Therefore, we used single-nucleotide polymorphisms (SNPs) with a MIG-seq analysis to identify the genetic populations of the bears and assessed the migration of populations and variations in the Cs-137 activity concentrations in the muscle of the distinct populations in Fukushima Prefecture, Japan, 2015–2018. The SNP analysis identified 2 populations, with population distributions suggested to have been affected by geographic features and land use. The Cs-137 activity concentrations indirectly differed by the genetic populations via correlation between the Cs-137 activity concentrations and the Cs-137 contamination levels at the capture sites. Migration occurred between the genetic populations, and their migration rates were similar. Therefore, migration may explain why Cs-137 activity concentrations in the muscles of the bears differed despite being captured in the same area. This study is the first to report the genetic structure of the Asian black bear in Fukushima Prefecture on a regional scale, the migration rates between populations, and the effect of migration on Cs-137 activity concentrations in these bears.
Quantifying recovery of British Columbia’s South Selkirk grizzly bear population
Michael F. Proctor, John Boulanger, A. Grant MacHutchon, David Paetkau, Wayne F. Kasworm
Ursus 2025 (36e13), 1-26, (8 December 2025) https://doi.org/10.2192/URSUS-D-24-00012
KEYWORDS: connectivity, DNA, grizzly bears, population recovery, SECR, South Selkirks, Spatially explicit capture–recapture, Ursus arctos
Small, isolated wildlife populations are often at great conservation risk. Quantitative monitoring of their conservation status over time and evidence of recovery is relatively rare. We carried out population surveys of grizzly bears (Ursus arctos) pre– (2005) and post– (2020–2021) conservation management, to assess the efficacy of strategic measures applied to the at-risk Canadian South Selkirk grizzly bear population in southeastern British Columbia. We evaluated our management outcomes by comparing our recent survey results with recovery targets outlined in a 2016 Recovery Management Plan, which included abundance, trend, number and distribution of females, distribution of reproductive females, mortality rates, and inter-population connectivity. Surveys consisted of remote genetic sampling where DNA from hair roots generated genotypes identifying individuals, sex, and family units. In 2020–2021, we identified 73 individuals (41 females, 32 males) that were used in a spatially explicit capture–recapture (SECR) density estimate, and 8 individuals sampled opportunistically at rub sites that were used in our connectivity analysis. We estimated the average number of bears using the area at any one time to be 69 (95% CI = 56–86). This estimate exceeded our closure-corrected recovery target of 60 bears. Densities were highest in the northern and central portions of the area, but the average density was estimated to be 17 grizzly bears/1,000 km2(95% CI = 14–22). Female distribution and evidence of reproduction varied spatially but occurred in all 6 delineated subunits, which exceeded our target of occurring in 5 subunits. Human-caused female mortality reported over the past 6 years was 0.5 bears/year, well below our target of 1 bear/year. We identified 9 immigrants (1F, 8M) from the Purcell Mountains who bred 27 offspring (12F, 15M) with other South Selkirk mates. This level of connectivity and gene flow represented a substantial increase for this previously fragmented population. Our results suggest that 15 years of conservation management have significantly improved the status of the Canadian South Selkirk grizzly bear population.