Standard Operating Procedures for Wild Horse and Burro Double-Observer Aerial Surveys

Techniques and Methods 2-A16
Prepared in cooperation with the Bureau of Land Management
By: , and 



The U.S. Geological Survey has been collaborating with the Bureau of Land Management to develop statistically reliable methods for wild horse and burro aerial survey data collection and analysis for more than a decade. In cooperation with Colorado State University, the U.S. Geological Survey tested several methods in herds with known abundance, resulting in two scientifically defensible aerial survey and population estimation techniques. These methods are now being applied by the Bureau of Land Management across the western United States, enabling better management of wild horses and burros. The purpose of these Standard Operating Procedures (SOPs) is to provide detailed instructions to the Bureau of Land Management wild horse and burro specialists who need to fly aerial surveys for management.

This report provides multiple SOPs that are related to Equus caballus (wild horse) and Equus asinus (wild burro) double-observer aerial surveys, along with datasheets, pre-survey checklists, and a quick-guide to the methods. SOP 1 describes how to carry out wild horse and burro aerial surveys as an aviation crew member. SOP 2, SOP 3, and SOP 4 relate to data management, and are important for the wild horse and burro specialist or other lead staff who will be responsible for documenting and archiving records from the survey. SOP 5 details double-observer reporting via a data entry spreadsheet and provides reference for analyzing double observer data to obtain population estimates. SOP 6 presents general principles for preparing aerial survey flight lines. SOP 7 provides instructions for using abundance estimates from aerial surveys to project population size forward in time. The appendixes provide survey datasheets, pre-survey checklists, and a quick-guide to SOP 1.

Suggested Citation

Griffin, P.C., Ekernas, L.S., Schoenecker, K.A., and Lubow, B.C., 2020, Standard operating procedures for wild horse and burro double-observer aerial surveys: U.S. Geological Survey Techniques and Methods, book 2, chap. A16, 76 p.,

ISSN: 2328-7055 (online)

Table of Contents

  • Preface
  • Acknowledgments
  • Introduction
  • Standard Operating Procedure 1—Conducting Aerial Surveys with the Simultaneous Double-Observer Method
  • Standard Operating Procedure 2—Global Positioning System Use
  • Standard Operating Procedure 3—File Folder Structure
  • Standard Operating Procedure 4—Processing Digital Photographs
  • Standard Operating Procedure 5—Reference for Analyzing Double-Observer Data
  • Standard Operating Procedure 6—Preparing Flight Lines for Aerial Surveys
  • Standard Operating Procedure 7—Principles for Projecting Population Size
  • Appendix 1. List of Herd Codes, by State
  • Appendix 2. Examples of Percent Concealing Vegetation, 0–80 percent
  • Appendix 3. Blank Data Forms
  • Appendix 4. Pre-Survey Checklists
  • Appendix 5. Quick-Guide to Double-Observer Surveys
Publication type Report
Publication Subtype USGS Numbered Series
Title Standard operating procedures for wild horse and burro double-observer aerial surveys
Series title Techniques and Methods
Series number 2-A16
DOI 10.3133/tm2A16
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Fort Collins Science Center
Description Report: viii, 76 p.; Data Release
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details