After an Acorn Shortfall: Deer Harvest in Missouri's Wooded Counties

Registered harvest in Missouri's wooded counties increased during 2023-24 following a weaker acorn crop, then decreased during 2024-25 following an abundant crop. County-level tables reveal how closely those shifts followed the amount of forest. Across the three season pairs beginning with 2022-23, counties in the highest forest third posted median changes of 19 to 24 percent each time: a rise, a fall, and another rise. Counties in the lowest forest third changed less than 5 percent. Acorn development follows different schedules in white oaks and red oaks. A diet study from the southern Appalachians found that the substitute food deer relied on supplied about half an acorn's energy. We tested whether added firearms seasons, opening dates, or location would undo the county pattern. It held through each check.

Annual oak mast surveys by the Missouri Department of Conservation (MDC) began in 1960. Surveyors assess developing acorns in sampled tree crowns using an index running from 0 to 300. The agency's report for 2013 assigns separate ratings to each oak group: white oaks produce an acorn within one growing season, whereas red oaks need two. Its explanation suggests weather in the current growing season has a stronger connection to white oak production. Red oak production may reflect weather from the current year as well as the preceding year.

Those ratings can differ. The combined oak rating reached its lowest point in the survey's 53-year record during 2012, with scores of 42 for white oaks and 78 for red oaks. Both groups reached about 150 the following year. The wildlife agency in Virginia recorded a similar split during 2023: white oak survey routes reached their lowest rating on record, while red oak production matched the long-term median. Group ratings also conceal differences among individual trees. Researchers examining 200 white oaks across two sites in the southern Appalachians found that a third produced about 75 percent of all acorns, while half produced about 10 percent. An acorn failure reported by a survey leaves questions about the oak group involved and the particular trees affected.

Deer collected in the southern Appalachians between 1983 and 1988 were examined by Wentworth, Johnson and Hale. Following productive crops, acorns occupied 49.6 percent of fall rumen volume, 65.2 percent in early winter, and 44.1 percent in late winter. Following weak crops, the corresponding shares fell to 5.0 percent, 3.8 percent, and 0.0 percent. Leaves from broadleaf evergreens then dominated the diet, with rosebay rhododendron supplying most of them. The replacement supplied less energy. Each gram of rhododendron foliage yielded 1.27 kcal of digestible energy, compared with 2.32 from white oak acorns, or about 55 percent of that amount.

Tests of doghobble foliage returned 2.51 kcal per gram, and galax foliage returned 2.32, both close to acorns. Rosebay rhododendron nevertheless supplied most of the leaf-based diet. In the same research, early-winter kidney fat indexes were significantly greater following abundant acorn years across every age and sex group other than yearling males. During poor years, researchers examined yearling does after January 16 and found that 7 of 31 had not ovulated. None of the studies included here measured the replacement diet of Missouri deer following an oak crop failure. This energy comparison is limited to the tested Appalachian foods, specifically white oak acorns and rosebay rhododendron foliage. The energy supplied by substitute foods in Missouri remains unresolved.

Research using collars complicates the assumption that an acorn failure sends deer farther afield. A Virginia study found that collared does expanded their home ranges between summer and autumn during productive acorn years; that expansion did not occur during the poor year. In a Georgia study, deer used larger ranges during fall and winter in the abundant-mast year. Neither of these two studies connects range area with the number of deer hunters observe.

Using the 2022 USDA Cropland Data Layer, we ordered Missouri counties by the fraction of their land covered by forest. We then tracked county deer harvest using MDC's harvest tables, covering 2016-17 to 2025-26. The land-cover data lack a row for Sainte Genevieve County, leaving 113 counties included out of 114. Our previous paper, Two Missouris, explains the regional shifts. Here, we add measurements at the county level.

Forest cover had little connection with county harvest changes before 2022. After that, the correlation switched between negative and positive annually. With a negative correlation, counties with greater forest cover experienced larger losses or smaller gains. A positive correlation indicates the opposite relationship.

Written descriptions of acorn production appear in MDC deer status reports for 2022, 2023, and 2024. The agency described acorn output during 2022 as especially high and the 2023 crop as weaker than the 2022 crop. It also listed abundant acorns among the explanations for declining harvest during 2024-25. Regarding 2025-26, its news release from January 2026 reports only a harvest recovery, particularly through much of Missouri's southern region. Whenever MDC characterized the crop, the direction of the forest-cover relationship agreed with that description.

The magnitude becomes clear in 2024-25. Each of the 38 counties in the highest forest third recorded fewer deer than during the preceding year. Combined, they registered 36,674 fewer deer, a decline of 25.7 percent. Harvest in the lowest forest third declined 4.6 percent. Across the 113 included counties and the hunting portions summed here, with managed hunts excluded, the highest forest third supplied 44 percent of registered deer during 2023-24 and 73 percent of the subsequent decline. During the following season, that group contributed 83 percent of the recovery across 113 counties, supplying 20,507 of the additional 24,666 deer. Its harvest nevertheless remained 11.3 percent beneath its 2023-24 total.

We challenged the pattern with three checks. Added hunting seasons presented the largest complication. In 2023, MDC introduced early antlerless and CWD portions. Together they produced 28,260 registered deer that year, including 8,282 early antlerless deer from counties in the highest forest third. Excluding both portions across every year reduces the correlation for 2022-23 to 2023-24 from +0.74 to +0.61. Added seasons therefore explain part of the forest-related gain in that pair. Results for the remaining three pairs barely shift.

Our next check considered opening dates. In 2021, the November portion began on Nov 13. Its opening moved a day earlier annually through 2023, shifted five days later during 2024, then moved a day earlier during 2025. The calendar for the 2025-26 pair was nearly identical to the preceding year's. Even so, forest cover and harvest changes within the November portion alone had a correlation of +0.77. Archery received no additional portions and also produced alternating correlation signs, though the relationships were weaker: -0.56, followed by +0.43, then -0.59, then +0.48.

Location provided the final check. County latitude has a -0.47 correlation with forest cover, reflecting the greater amount of timber farther south. Accounting for each county center's latitude and longitude leaves partial correlations of -0.72, then +0.65, then -0.82, then +0.76. These represent the forest relationship remaining after the effects explained by location are removed. MDC also mentions warmth and wind during 2024-25. Every county experienced weather during the same year as the acorn crop, leaving these tables unable to distinguish the effects of weather from those of acorns.

We calculated county harvest by adding archery and every firearms portion listed in MDC's county tables, excluding managed hunts. Adding managed hunts back to those sums reproduces the agency's published Grand Total for all six seasons spanning 2020 to 2025. The 2016 total also matches. Pages covering 2017 to 2019 contain unexplained differences of 1,362 deer, 1,569 deer, and 1,646 deer. Forest cover comes from a snapshot taken in 2022. Substituting the 2020 map or the 2024 map shifts every correlation by no more than 0.02.

County correlations describe a relationship without establishing its cause. Adjacent counties share similarities, meaning the 113 counties provide less independent evidence than the correlations imply. Our search of public documents found no MDC mast index later than 2013. As a result, the connection to acorn production depends on agency descriptions covering three seasons. The pattern would fail if forested counties lost harvest during a poor-crop year, or if MDC's own survey showed a bumper crop for 2025. Harvest measures reported deer rather than the living population.

Consider acorn reports alongside the cover on your hunting ground. Counties in the highest forest third have at least 46.5 percent forest cover. Across the latest three shifts, their median registered harvest change ranged from 19 to 24 percent. According to MDC, plentiful acorns lead deer to remain in timber longer and make fewer trips in search of food. A heavy crop therefore gives hunters reason to scout wooded areas with falling acorns before checking edges. Counties in the lowest forest third have less than 20 percent forest cover. Across those same shifts, harvest for the median county changed less than 5 percent. We did not measure the additional influence of opening day or weather. These totals measure reported harvest; they do not measure sightings.

Whichever approach fits your county, first inspect white oaks and red oaks during September. Statewide averages form the crop report. In the Appalachian research, a third of sampled white oaks supplied about 75 percent of all acorns.