TESTS OF DIFFERENT METHODS FOR MEASURING AND ESTIMATING UTILIZATION RATE OF HEATHER (CALLUNA-VULGARIS) BY VERTEBRATE HERBIVORES

1. The precision of four methods for measuring utilization rate of the ericaceous dwarf shrub heather (Calluna vulgaris), was examined to determine which was most suitable for assessing when given stands are at risk of damage from overbrowsing. 2. The percentage of shoots browsed gave almost as precise a measure of utilization rate (to +/-10%) as a more complex measure (for utilization rates below 40%). Utilization rate was equal to 0.67 times the percentage of shoots browsed. 3. Measuring the percentage of shoots browsed seems to be an appropriate method of determining utilization rate by sheep on moorland. 4. The other two, more subjective, methods were found to be less accurate. Both were visual estimates, one of percentage of canopy cover closely browsed and the other of percentage of shoots browsed. The latter was quick and might be useful for preliminary surveys. 5. The results are discussed in relation to their applicability to other sites. Previously used methods are assessed in relation to current findings.