Procedures for Estimating Pronghorn Abundance in Wyoming Using Aerial Line Transect Sampling
by Richard J. Guenzel
This manual is a basic presentation of current procedures used by the Wyoming Game and Fish Department to conduct aerial line transect surveys of pronghorn populations. It is not a complete reference on line transect sampling, nor is it a cookbook on how to conduct aerial line transect surveys.
Users will have to adapt these procedures to their own circumstances based upon their familiarity with populations to be sampled. Those not familiar with line transect sampling should consult referenced texts, statisticians, and other experienced persons before designing their own surveys. The only dumb question is the one that isn't asked. Users should check for additional improvements implemented after publication of this manual.
The purpose of this manual is to supplement and not replace existing texts on line transect sampling and analysis by explaining this application to aerial pronghorn surveys. This manual should be used in conjunction with the books, Introduction to Distance Sampling: Estimating Abundance of Biological Populations (Buckland et al. 2001), and DISTANCE 5.0 Release 2 User's Guide (Thomas et al. 2006).
As with all aerial surveys, SAFETY IS THE PRIMARY CONCERN. Although all low level survey work is potentially dangerous, surveys should not be performed under unusually hazardous conditions. Under those circumstances, pilots have difficulty flying designed transects and observers are less attentive to surveying. You can come back later to complete a survey. Special care should be taken in placing equipment to facilitate distance measurements and record data on aircraft.
The user is responsible for conducting the survey properly, meeting assumptions, and critically examining results. Aerial line transect procedures require a great deal of quality control. The line transect technique provides an estimate of density which is subject to variability. This uncertainty should be considered in its interpretation and application.
Detailed procedures for setting up aircraft for line transect surveys are beyond the scope of this manual. The marking of aircraft for line transect surveys requires extreme care and special calculations. Those interested should contact the author.
Persons who will participate as observers or pilots in these surveys should be properly trained prior to the survey. Practice runs prior to the survey are very helpful to allow participants to get comfortable with protocols and ask questions about procedures.
This manual deviates from accepted standards for scientific writing by mixing Metric and English units. The use of mixed units facilitates analysis because of aircraft instrumentation and the set-up for the Wyoming Technique.
Users of these procedures should use the program DISTANCE 5.0 Release 2 for analysis. We do not recommend the use of earlier versions of DISTANCE and its predecessor TRANSECT-II for data analysis.
Unlike the previous system, observers and pilots must be familiar with the set- up, operation, and data management of the CyberTracker data capture system. These responsibilities fall on the survey crew.