This Tech Note provides practical in-field measurement 

methods for estimating wildlife damage at planting to 

row crops, such as peanuts, corn, soybeans, and sugar 

beets. The methods are suitable for estimating damage 

to row crops caused by a variety of wildlife species, 

including feral swine.

Sampling for Damage

The example data sheet at the end of this Tech Note 

can be used to record damage observations.

1. Select fields to be sampled for damage at planting.

2. Assign each field a unique identification number or

name.

3. Note whether any feral swine management has

occurred on or near the property within the last year.

4. Estimate the area of the field to be sampled for

damage. The perimeter of the field can be defined

using a Global Positioning System (GPS), and the

area can be calculated using the GPS or Geographic

Information System (GIS) software. Alternatively,

Goodle Earth may be used to trace the field

perimeter and calculate the area.

Feral swine damage to row crops at planting can be 

assessed using the following information gathered 

from each agricultural field:

1. field size (area),

2. distance between rows, and

3. total combined lengths of segments of damage

across all rows.

Tech Note

October 2017

Estimating Feral Swine Damage 

to Row Crops Just After Planting

Feral swine cause 

more than $190 

million in damages 

to agricultural crops 

each year.

The method below describes how to estimate these 

three numbers from each field.

Measure the distance between two adjacent rows.

Note: This distance should be representative of

the average distance between all adjacent rows.

Sample for damage at least twice in the first 10 

days following planting. It is recommended 

sampling occurs 5 and 10 days post planting.

Locate damage by slowly driving the perimeter of 

the field. Using a measuring wheel, tape measure

or GPS, record the length of each segment of

rooting damage found in each row. 

Record if/when a field is replanted, if damage 

occurs between observation periods, and if 

damage occurs to a replanted crop.

5.

6.

7.

8.

Wildlife Services

Protecting People 

Protecting Agriculture 

Protecting Wildlife Part of the WS Damage Assessment Series
Note: Each observed damage segment is measured during each observation period, including damage segments 

that were measured during previous observation periods. This avoids having to keep track of locations and lengths 

of damage segments across observation periods and helps assess the total damage if crops are replanted. 

Calculating the Damage

The amount of damage to the field is calculated as 

the summed length of all damage segments divided 

by the total summed length of all rows in the field. To 

simplify the calculations, the total summed length of 

all rows in the field is estimated using the field area 

and row width from Steps 4 and 5 page 1, Sampling 

for Damage.

1. Add the lengths of all damage segments together

to get the DAMAGE TOTAL.

2. Convert the size of the field to square feet (or

square meters) to get the FIELD AREA.

3. Make sure the ROW WIDTH estimate (from Step 5

on page 1) is in units (feet or meters) consistent

with the square units for FIELD AREA.

4. Divide FIELD AREA by the ROW WIDTH. This will

provide the estimate of the total summed length of

all rows in the field.

TOTAL ROW LENGTH = FIELD AREA

ROW WIDTH 

Divide DAMAGE TOTAL by TOTAL ROW 

LENGTH to estimate the proportion of the crop 

that was damaged. 

PROPORTION DAMAGED = DAMAGE TOTAL 

TOTAL ROW LENGTH

5.

Note: This procedure is based on Thomas, J., 

Engeman R.M., Tillman, E.A., Fischer, J.W., Orzell, 

S.L., Glueck, D.H., Felix, R.K. Jr., and Avery, M.L. 

2013. Optimizing line intercept sampling and 

estimation for feral swine damage levels in 

ecologically sensitive wetland plant communities. 

Environmental Science and Pollution Research 

20:1503-1510. 

Additional Information

For more information on estimating feral 

swine damage, please contact:

Richard Engeman

USDA-APHIS-Wildlife Services 

National Wildlife Research Center 

4101 LaPorte Avenue

Fort Collins, CO 80521

(970) 266–6000

United States Department of Agriculture

Animal and Plant Health Inspection Service

The U.S. Department of Agriculture (USDA) is an equal opportunity provider and employer. 
Estimating Feral Swine Damage to Row Crops After Planting

(Example Data Sheet) 

Date: Observer: Field ID: Crop: _________

Days since planting: Distance between rows: Field area: ___________ 

Has this field been replanted (all or part) due to feral swine damage? Yes No

Has this area received WS operations control? Yes No 

If yes, when? ____________________ 

Damage measurements units: Feet Meters

Obs

#

Length of damage 

segment

Had this portion of the 

row been replanted?

Obs

#

Length of damage 

segment

Had this portion of the 

row been replanted?

1 2

3 4

5 6

7 8

9 10

11 12

13 14

15 16

17 18

19 20

21 22

23 24

25 26

27 28

29 30

31 32

33 34

35 36

37 38

39 40

41 42

43 44

45 46

47 48

49 50

51 52

53 54

55 56

57 58

59 60