Agriculture is the dominant land use throughout the Indiana landscape with over 65% of Indiana's land area in farmland. In both 2004 and 2005, producers in Indiana harvested approximately 900 million bushels of corn and 275 million bushels of soybeans. But farmers know that they aren't the only ones cashing in on their crops. One researcher estimated wildlife-related economic losses to agricultural producers (farmers and ranchers) in the U.S. exceed $4.5 billion annually. Wildlife damage to field crops is a widespread concern in the U.S., especially in midwestern states such as Indiana.

But what is really going on in those fields? Determining the answer may seem like a natural resources version of CSI. To help find the answer to this, Purdue University Department of Forestry and Natural Resources conducted a research project to estimate the extent and timing of corn and soybean damage caused by wildlife in Indiana. Researchers and technicians spent thousands of hours surveying 160 corn and soybean fields in portions of the Upper Wabash River Basin in northern Indiana. We also surveyed local crop producers about wildlife damage. Hundreds of hours were also spent observing the feeding behavior of wildlife in crop fields.

 Several key points emerged in a comparison between landowner perceptions on crop damage and actual field data. Field crews found wildlife damage in 93% of the fields they sampled. Only 73% of landowners reported wildlife damage to either corn or soybeans within the past year; thus, minor damage may be overlooked by landowners. But landowners tended to overestimate the value lost due to wildlife damage, especially in terms of dollars lost rather than percent of total crop lost. Farmers reported averages that exceeded observed damage and their highest values often exceeded $1,000. However, regardless of the amount of damage, whether real or perceived, landowners varied on the level of damage that was tolerable to them. Some considered any damage intolerable whiles others tolerated damage of $500 or more. What is tolerable damage to one individual may not be tolerable to another, and thus, should not be dismissed as insignificant.

Crop producers correctly identified the wildlife species that caused the most damage for each crop type--raccoon and deer for corn, and deer and groundhog for soybeans. While farmers believed that deer caused the most damage to corn, field surveys indicated that raccoons were responsible for the vast majority of the damage to corn (Figure 1). This level of raccoon damage was higher than in other studies. The highly fragmented landscape and locally high raccoon populations are plausible explanations for this observation. Even though they perceived them to cause the most damage, only about 1 in 5 farmers considered deer a nuisance (2.5 times more landowners thought raccoons were a nuisance and 4 times more thought groundhogs were a nuisance).

Understandably, negative feelings by farmers towards deer and raccoons were related to the amount of perceived damage. This fact reinforces the importance of proper identification of wildlife damage. Misidentification of wildlife damage to crops can lead to negative feelings which in turn may lead to unnecessary and unwarranted management objectives for some wildlife species.

Surveys of 160 agricultural fields yielded no cases of measurable crop depredation by wild turkey. Turkey sign was evident in several fields and turkeys were observed often in fields we surveyed. Turkeys are perceived to damage crops likely because they are easily observed compared to other species. Due to their size, flocking behavior, and daytime activity, wild turkeys often are seen foraging in crop fields; however, they are usually foraging on waste grain and insects rather than damaging crops. Our study supports previous research and suggests that the occurrence of crop depredation by wild turkey is very low, even though they often occupy agricultural lands throughout the year. Anecdotal evidence of wild turkeys feeding on newly emerged soybeans was observed in a couple fields during a separate investigation of wildlife damage. However, this observation does not necessarily translate to measurable damage since light damage to soybeans rarely affects yield.

The bottom line is that wildlife damage is a common occurrence in Indiana crop fields. The good news is that the result damage is almost always light to moderate, although severe damage can and does occur. The potential for severe wildlife damage to field crops varies greatly and depends on several factors including animal densities across the landscape, field characteristics (size and proportion of edges adjacent to woodlands), and landscape-level habitat features (for example, percent woodland in the landscape surrounding those fields). Proper identification of the species responsible for crop damage is vitally important so that landowners can implement proper management strategies. In most cases this will include lethal control. Preliminary research suggests that the density of local raccoon populations is positively related to the amount of damage to field corn caused by raccoons.

Densities of raccoons were very high in our study area. For example, six individual raccoons were captured and marked in a single 10-acre woodland. Although this research is ongoing, it strongly supports the premise that local population control should decrease crop damage, at least in the short term. The immigration rate of new animals into an area likely is dependent upon the landscape configuration and surrounding population characteristics (e.g., density, sex ratio), which should dictate the length of time control efforts would be effective.

For more information about wildlife damage to crops, visit www.purdue.edu/cropdamage.