When the beech nuts fail, the bears come down
In the years the beech crop failed, people in five Tohoku prefectures reported 28,884 bear sightings in autumn. In the good years, 1,211. Over 18 years, bear captures and the crop move against each other with a correlation of -0.87.
Bears caught, year by year
Asian black bears in northern Japan eat beech nuts in autumn to get through the winter. The Forestry Agency scores each year's beech crop in the five Tohoku prefectures from 0 to 5; under 1 the crop has failed. The Ministry of the Environment counts the bears caught and the bears seen.
| Year | Beech crop, 0 to 5 | Bears caught | In all Japan |
|---|---|---|---|
| 2026, so far | 3.64 | 1,531 | 4,687 |
| 2025 | 0.10, failed | 7,205 | 14,741 |
| 2024 | 3.24 | 1,255 | 5,345 |
| 2023 | 0.06, failed | 4,665 | 9,271 |
| 2022 | 2.56 | 1,381 | 3,875 |
| 2021 | 1.02 | 1,716 | 4,484 |
| 2020 | 1.32 | 2,175 | 7,248 |
| 2019 | 0.24, failed | 1,770 | 6,281 |
| 2018 | 2.22 | 1,102 | 3,586 |
| 2017 | 0.84, failed | 1,665 | 3,953 |
| 2016 | 0.14, failed | 1,371 | 3,786 |
| 2015 | 2.98 | 482 | 1,950 |
| 2014 | 0.46, failed | 966 | 4,167 |
| 2013 | 3.48 | 553 | 1,859 |
| 2012 | 0.71, failed | 1,100 | 3,369 |
| 2011 | 1.44 | 511 | 1,800 |
| 2010 | 0.48, failed | 769 | 4,015 |
| 2009 | 1.40 | 554 | 1,717 |
| 2008 | 1.46 | 376 | 1,492 |
Sightings move the same way.
Bears seen in September, October and November, summed over the five prefectures. The crop failed in 2023 and 2025 and was good in the years between.
| Year | Mean beech crop | Bears seen |
|---|---|---|
| 2022 | 2.56 | 452 |
| 2023 | 0.06 | 7,120 |
| 2024 | 3.24 | 759 |
| 2025 | 0.10 | 21,764 |
Within each prefecture, a failed crop year raised captures by 95% (95% range +51% to +152%), and each point on the beech index cut them by 26% (20% to 32%). Last year's crop adds nothing: +4% (-7% to +18%).
The forecast comes in August.
The Forestry Agency counts the beech flowers in summer and publishes the year's index before the bears come down. 2026's crop scored 3.64, a good year, and 1,531 bears have been caught so far, against 7,205 in 2025, when the crop scored 0.10. The count is out months before the season it describes.
Method and caveats
- Year is the fiscal year (April to March), matched to the beech crop of the same calendar year, whose autumn is when the bears come down. The five Tohoku prefectures are Aomori, Iwate, Miyagi, Akita and Yamagata; the beech crop is their mean index (0 to 5, under 1 is a failed crop). 2026 is to date.
- Captures rose about 8-fold on the trend from 2008 to 2025 (376 to 7,205 counted), so a straight-line trend is taken out of the log of captures before they are set against the beech index. Raw, without that step, r is -0.51 (95% range -0.79 to -0.05). With it, r is -0.87 (95% range -0.98 to -0.28). The range is wide because good and failed years alternate, which leaves about 6 independent years in 18.
- Log captures on the mast index, 90 prefecture-years (5 prefectures, FY2008 to FY2025), prefecture fixed effects and a linear trend per prefecture, errors clustered by year. Computed in Python (tickerz-kit Research/correlations-2026-11-12), not recomputed here.
- Sightings in September, October and November, by prefecture and fiscal year, with that year's prefecture mast index. Each prefecture counts sightings its own way. Beech crops fail together across the region, so in four years of sightings the crop is almost the same thing as the year. The 18 years of captures are the stronger test.
- Captures also depend on how hard each prefecture culls, which rose after 2023. The trend absorbs a steady change, not a sudden one.
- Bears are counted, not people. Correlation is not cause; the explanation here is the one forest researchers already give, and the numbers agree with it.
Sources
- Ministry of the Environment, bear captures by prefecture and fiscal year (FY2008 to FY2026 to date, updated Nov 10 2026). Read in full.
- Ministry of the Environment, bear sightings by prefecture and month, last five fiscal years. Read in full.
- Forestry Agency, Tohoku Regional Forest Office, beech flowering and fruiting index by prefecture since 1989. Read in full.
No corrections. First published November 12, 2026.