An ocular technique for estimating utilization of karoo bushes

Abstract

A subjective technique for estimating utilization of karoo bushes is evaluated and guidelines for its use are proposed. Taking the average utilization from estimates on 30–40 bushes, 20% differences in utilization could be distinguished as significant ‐ even when different operators were used. Zero and 100% levels of utilization were judged with greater accuracy and precision than intermediate levels. However, if more than 30 bushes are taken per sample the precision and accuracy at all levels is adequate. Acceptable levels of accuracy were obtained with fewer bushes than that required for adequate precision. Using similar sample sizes the ocular‐estimation technique was more precise and more accurate than objective techniques. Furthermore, this technique was far more efficient than any of the objective techniques.