A hot, dry summer spread across the Midwest in 2012. Biting midges that spread epizootic hemorrhagic disease flourished in the drying mud at shrinking water holes. By autumn, dead deer were being found near ponds and in creek bottoms from Illinois to Iowa. The virus did not remain in the herd, but the harvest record still bears the mark fourteen years later. A steep drop separated the 2012 and 2013 harvests. Harvest totals remained lower for a while, then Illinois recovered to nearly its level before the sudden drop by 2024. Iowa DNR also reports severe outbreaks in 2013 and 2019, and Iowa's harvest line shows another dip in 2019. The record offers an example of a harvest drop over one season that occurred in the same year as severe EHD, followed by a period when harvest totals in both states quit falling.
KEY FINDINGS
- A season brought a 17.4% harvest loss in Illinois (155,584 during 2012 fell to 128,572 during 2013); Iowa's loss was 14.0% (115,608 fell to 99,414) over that same season. Harvest dropped steeply in each state that fall.
- The change forms an abrupt step instead of a gradual slope. From 2008 through 2012, Illinois harvest eased downward slightly; Iowa’s total declined 18.7%. A steep seasonal drop followed in each state, although the harvest record by itself cannot determine why.
- A continuing decline did not follow. Beyond 2013, harvest in each state leveled out at a lower baseline. Illinois later recovered to roughly its earlier line by 2024. Iowa failed to regain its former level, but its downward movement ended.
- The signature is visible, although it varies across counties: EHD acts locally. Harvest in Monona County, Iowa, fell 18.5%, and Allamakee lost 17.6% during 2012 to 13. Dubuque changed very little. Disease tied to shrinking watering holes affects counties unevenly.
IA SHOCK, NOT A TREND
How harvest records reflect a summer outbreak
Harvest records distinguish a slow decline from an abrupt seasonal loss. Much of the analysis lies in recognizing that difference. A downward slope means harvest decreases in successive years. Establishing either a population decline or its cause requires accounting for permits, hunting effort, and other factors that affect harvest. A shock produces a step: harvest plunges during a single season, and subsequent totals continue at that lower baseline. Such a harvest step coincided with the 2012 outbreak involving epizootic hemorrhagic disease, a virus transmitted by biting midges that multiply during hot, dry conditions late in summer. Iowa DNR says hemorrhagic disease generally grows worse during dry years as deer congregate near remaining water. It normally ends with the first hard frost, which kills the midges. No persistent herd infection continued into 2013. The records show an abrupt seasonal harvest loss, yet they cannot distinguish deaths caused by disease from other factors affecting harvest.
IITHE SAME NOTCH IN TWO STATES
Comparing indexed harvest for 2012 and 2013
Set the harvest index for each state at 100 for 2010, then compare their paths. Across 2008 through 2012, Illinois shows a slight downward drift, whereas Iowa harvest is already declining. Each plunges into 2013: the index moves from 98 down to 81 for Illinois, a seasonal loss of 17.4%, and from 91 down to 78 for Iowa, a loss of 14.0%. Iowa's downward harvest movement preceded 2013: its total went from 142,194 during 2008 to 115,608 during 2012, a decline of 18.7%, while Iowa DNR sought to shrink the herd. The abrupt 2013 loss, at 14.0%, exceeded every individual yearly decrease across 2009 through 2012 and coincided with a severe EHD year. Still, harvest figures by themselves cannot apportion that loss between disease and licensing. Both states experienced the same weather and the midges those conditions produced.
- Illinois
- Iowa
An ongoing decline forms a slope; a sudden shock leaves a step. The step is easiest to see in the Midwest's harvest history at the 2012 outbreak: a drop over one season, followed by a lower level that stayed steady.
IIIPATCHY BY COUNTY
Disease associated with drying water holes has a local reach
Moving from statewide totals to individual Iowa counties breaks the signature into uneven pieces, just as an EHD outbreak would. Biting midges transmit EHD, whose outbreaks affect places differently. A county may suffer heavily while neighboring counties escape. Outbreak severity has been associated with dry years. In Iowa, Monona County, along the Missouri River bottomlands, recorded a harvest loss of 18.5% between 2012 and 2013. The losses were 17.6% for Allamakee and 15.5% for Madison. Meanwhile, Dubuque changed little, rising 1.4%, and Jackson declined just 4.2%. County harvest changes span a broad range. Those differences fit an uneven outbreak, although a statewide policy can affect counties differently too. Harvest differences by themselves cannot quantify the intensity of local outbreaks.
IVTHE PLATEAU THAT HELD
A shifted baseline, the same trend, and what later records inherit
The clearest part of this pattern is what happened after the sharp drop. Harvest did not begin falling again in either state. The shock in 2012 did not lead into a continuing decline. Illinois stayed at its lower level through the mid-2010s before rising toward its earlier harvest line. By 2024, it reached 156,338, nearly matching its 2011 level. Iowa did not recover its former highs, but harvest settled within a range of 100,000 to 110,000 and held there. Harvest totals by themselves cannot prove that disease caused the lasting change in level or confirm that the underlying management trend remained unchanged. That limit also matters where county-level harvest histories start later: Missouri’s records start in 2015, while Indiana’s start in 2013. Both begin after the harvest drop in Illinois and Iowa, so they cannot reveal whether those states had the same break. These newer baselines cannot tell us whether a summer with disease changed harvest in the years before those particular records start. This pattern warns against treating those baselines as “normal” without understanding the earlier history.
Swipe table to see every column
| Series | 2012 | 2013 | Single-season change |
|---|---|---|---|
| Illinois (statewide) | 155,584 | 128,572 | −17.4% |
| Iowa (statewide) | 115,608 | 99,414 | −14.0% |
| Monona Co., IA | 1,026 | 836 | −18.5% |
| Allamakee Co., IA | 3,654 | 3,011 | −17.6% |
| Dubuque Co., IA | 2,045 | 2,074 | +1.4% |
VREADING SHOCKS HONESTLY
What hunters gain by telling the patterns apart
A sudden shock and a continuing trend call for opposite interpretations, which makes telling them apart useful. A harvest line that drops year after year warns about what lies ahead. A sharp fall over one season followed by a level stretch describes earlier harvests without establishing how many deer are in the herd or where its population is headed. Mix up those patterns and you will mistake the 2013 bottom for the beginning of a collapse that did not follow, or brush off a true gradual decline as a harmless isolated dip. The 2012 pattern is useful because it leaves no ambiguity: one autumn, a drop at the same time across states, county differences consistent with the biology, and a level stretch that lasted. Fourteen years later, that break remains visible in the harvest record. The record alone, though, cannot establish deer numbers or determine what role earlier summer weather played.
NOTES AND SOURCES
- The one-season harvest drop across Illinois and Iowa associated with the 2012 event fits the documented severe Midwest outbreak of epizootic hemorrhagic disease (EHD) in 2012. The outbreak was associated with drought conditions that favored the Culicoides midge that carries the disease. Deer that survive EHD do not remain persistently infected. Sources come from the deer programs of Illinois DNR and Iowa DNR.
- Our statewide series add up results from one preferred reporting instrument at the county-year level (vw_county_harvest_best). Iowa county values come from harvest_county_year. Each state’s index shows its harvest as a percentage of its 2010 total.
- The county-level harvest series collected here start in 2015 for Missouri and 2013 for Indiana, both later than the 2012 shock. The discussion covers their plateau following the shock, but the sharp drop came before those county series start and is therefore absent from the charts here.
- Limits: permits govern harvest, and the figures have no adjustment for hunting effort. A permit change can, in principle, produce an abrupt seasonal loss. A synchronized harvest dip across states within a year, coupled with uneven county results, supports a shared environmental shock hypothesis. It cannot exclude state policy or other factors affecting harvest. For the period charted, figures are current through the season of 2020.
Fully Drawn Research is an independent data analysis desk, not affiliated with any state wildlife agency, transportation agency, mapping provider or outfitter. Harvest figures are Illinois DNR and Iowa DNR public records analyzed independently by FDR. The 2012 EHD attribution is an inference from the timing, cross-state synchrony, and county-level pattern of the single-season decline, consistent with contemporaneous agency reporting of the outbreak; it is not a claim of a measured cause-of-death for individual deer. FDR is an independent data analysis desk, not affiliated with any state wildlife agency. Figures current to the seasons shown.
Keep reading
FDR Scout puts county harvest history like this on the map of the ground you hunt. Open Scout →