Accuracy of conventional radio telemetry estimates: a practical procedure of measurement

Telemetry triangulation is commonly used for obtaining location estimates of animals in the filed. Although this technique provides only an estimate of the animal’s true position, most authors do not report the error associated with the radio-telemetry location. We show the results of estimating error in a radio-telemetry study of roe deer in a hilly environment in central Italy. Ten VHF radio-collars were hidden in the study area by an external field operator and five field workers involved in the collection of the data were asked to locate the transmitters. The position of the radio-collars was changed three times, thus generating thirty different locations. Radio-locations were obtained using standard triangulation from settled receiving stations. We estimated linear and angular errors associated with the radio-telemetry technique, we tested the experience effect of the filed workers and the topography effect of the study area on linear and angular errors. Furthermore, we quantified the proportion of estimated locations not correctly associated with the habitat types. The mean linear and angular errors were respectively 42.9 m and 12.6°. For both linear and angular errors, no differences were detected among field operators and between the expert and not expert field operators. The linear error was strongly related to the angular error and to the mean distance between the transmitter and the receiving stations. The angular error was negatively related to the slope of transmitters. The assignation of an erroneous habitat occurred on 22.7% of the times. This study is aimed to emphasize the importance of reporting radio-telemetry error in studies were triangulation technique is used.