Corn Acreage Does Not Measure Nutrition: Illinois Counties and Big Bucks

Feeding experiments at Mississippi State brought Lower Coastal Plain bucks raised on one nutritious diet up to the size of wild bucks from the Delta. County corn acreage, however, does not measure that food supply. When Illinois listings are divided by county land area, counties with more cropland have lower big-buck densities: the rank correlation is -0.44 for 102 counties. Dividing by huntable acres reverses that relationship to +0.40 across the 101 counties with a recorded huntable-acre value. Because the divisor changes the answer, cropland share is not a suitable proxy for deer diet.

Buck size varies among Mississippi's soil regions. At age 3, harvested bucks from the Delta exceed those from the Lower Coastal Plain by 41 pounds in weight and by 25 inches in antler score, according to the Extension account of Mississippi State University's experiments. That account describes extensive Delta agriculture, where soybeans provide summer food and wheat supplies forage during fall and winter. Timber production is the main use in the Lower Coastal Plain, where a thick canopy limits forage growth. To distinguish nutrition from ancestry, researchers collected pregnant does in the Delta, in Thin Loess and in the Lower Coastal Plain. Their young received one nutritious diet.

Across the three regions, the first generation increased body size and antler size by about 6 percent, although gains differed among regions. The second generation showed much larger gains; their mothers had grown up eating the experimental diet. Bucks from the Lower Coastal Plain weighed 36 pounds more than wild bucks native to that region, reaching the weight of wild Delta bucks. Their antler scores increased by 28 inches. According to the publication, two generations receiving improved nutrition brought bucks from the Lower Coastal Plain and from Thin Loess up to the size of wild bucks native to the Delta. The authors conclude that an individual animal's growth depends on genetics, while genetics do not account for the differences among regions.

Three qualifications accompany those findings. Sample sizes are absent from the publication. Its reported measurements cover weight and antler score, without molecular measurements. The lab interprets the effect as epigenetic: environmental conditions change gene expression without changing the DNA itself. Our conclusion does not require that interpretation. The experiment also covered two generations, and the authors describe 5 to 10 years with consistently better nutrition as the time needed for deer to show more of their genetic potential. The experiments establish that size differences among wild deer from different regions do not demonstrate a genetic limit. Better nutrition changed the measured results.

Illinois offers a straightforward test of the familiar belief that corn country produces large bucks. We analyzed FDR's big-buck listing series, compiled from three trophy-listing programs. We removed duplicates across programs so that a deer appearing in multiple programs contributes only once. We calculated listings relative to county land area for all 102 counties, then rescaled that density to put the statewide county median at 100. The result is an index of density rather than a listing total. We calculated cropland's portion using the 2022 Cropland Data Layer, including corn, alfalfa, soybeans, winter wheat and other hay.

The rank correlation between that density index and the cropland portion is -0.44. Its 95 percent bootstrap interval spans -0.61 to -0.25. Rank correlations use a scale extending from -1 to +1. A value of 1 indicates matching rankings, -1 indicates reversed rankings, and 0 indicates no overall association between ranks. The forest relationship is +0.55, with an interval spanning 0.37 to 0.69. Grouping counties into thirds shows the same pattern, with a qualification: density drops in the top third rather than declining steadily.

Changing what divides the listings changes the result. The Illinois Index divides trophy listings by huntable acres using a county value recorded in the Index workbook. Our analysis did not audit how that value was calculated or what land it includes. As cropland expands, huntable acreage contracts. In the third with the most cropland, the median huntable portion of county land is 13.7 percent; in the third with the least, it is 43.8 percent. The cropland portion and the huntable portion correlate by rank at -0.84. A smaller divisor increases the calculated density in crop-heavy counties, reversing the sign.

With huntable acreage as the divisor, median density index values are 61.0 for the third with the least cropland, 86.6 for the middle group and 126.4 for the third with the most. That ordering reverses the result based on total land. With deer registrations as the divisor, the relationship with cropland is +0.23 and the relationship with forest is -0.41. Thus, more heavily forested counties have fewer listed big bucks relative to registered harvests.

These relationships do not measure the food available to deer. Both divisors that reverse the sign, huntable acreage and deer registrations, change with land cover. The forest portion also fails as a food measure: the Mississippi State publication describes thick canopy blocking the light needed for deer forage.

Registered deer represent the county harvests reported by hunters. We averaged those reports annually across 2005 to 2024, using the 99 counties that supplied at least 15 seasons of records. Hunting effort influences registrations along with deer abundance, so registrations measure reported harvest rather than the entire herd. In Illinois, registrations per square mile have strong relationships with land cover: -0.62 for cropland and +0.89 for forest. This agrees with Forest, Not Corn, which identified the same relationship between forest and harvest density. Big-buck density correlates with registrations per square mile at +0.43 as well. For the 99 counties supplying registration records, the cropland relationship is -0.44 before adjustment. Holding registered deer per square mile constant brings the correlation to -0.25, indicating that part of the land-area association varies with registered deer density.

Our checks support the result based on county land. Excluding the six counties around Chicago, Cook, DuPage, Kane, Lake, McHenry and Will, produces -0.46. Accounting for developed land also produces -0.46. Restricting crops to corn plus soybeans yields -0.45. Land-cover data from 2020 and 2024 yield -0.44 and -0.43, respectively. Removing counties individually puts the result between -0.48 and -0.42. Using listings grouped into three kill-year windows produces -0.43, -0.39 and -0.38.

Pike, Brown and Calhoun lead this density measure, followed by Lake and Schuyler. Four of these five counties fall within the ten farthest west among Illinois's 102 counties. This calculation differs from the Illinois Index. For its trophy component, that Index uses huntable acres as the divisor and includes a trend covering 2015 to 2024. Agreement between the two density measures is weak (0.37). Where the Giants Live describes how the Index works. The Trophy-Count Trap describes how reporting effort combines with deer numbers in listing totals.

A listed deer has been scored and submitted by someone. Listing density therefore reflects both large bucks and submission habits, along with the number of bucks surviving long enough to reach a large size. According to the Mississippi State Deer Lab, a buck's first set of antlers is 10 to 25 percent as large as its eventual antlers. Roughly 80.2 percent of listings with dates fall within kill years 1987 to 2012, whereas the land-cover data describe 2022. We excluded the 0.3 percent of listings lacking a county.

The cropland portion classifies land use. In Illinois, the Cropland Data Layer identifies corn and soybeans accurately: NASS gives producer's accuracy as 92.9 and 92.6 percent, respectively, in 2022 (the agency's metadata). Those crops account for 99.2 percent of cropland for the median county. These results apply only within Illinois. We did not separate rivers or urban edges, and an association does not establish a cause. The analysis does not show that cropland alters antler size.

The county comparison gives no basis for spending extra on corn-acre percentage as a proxy for antler size. A quoted big-buck density remains incomplete until its divisor is identified. Ask what acreage or count was used to divide the listings, and request the county's harvest registrations per square mile alongside the result.

On your property, measure what Mississippi State managed: the forage available each season and deer numbers relative to that supply. The publication emphasizes summer, when fawns and antlers are growing, and describes shaded woods producing little forage. It also reports that individual deer show a short-term response to better nutrition, while greater expression of their genetic potential takes 5 to 10 years of consistently improved nutrition. Food plots and timber thinning were outside the experiments, leaving the response time for your property unknown. We would follow forage supply and deer abundance over multiple years rather than judge the outcome from one season's bucks.