Population Ecology of European Tortoises: Review of Field Techniques

Field techniques used in recent studies of the population ecology of European tortoises are discussed. An efficient marking system suitable for large sample sizes is described. The dual problems ofageing adults and sexing juveniles are highlighted. The relative merits of sampling techniques are dependent on habitat and population density. Mark-recapture techniques are most suitable when sampling is conducted within a grid system which enables results to be stratified, allowing for differential ease of location. However, grid sampling is only practical where tortoise densities are high. At low density sites, or for brief surveys, recording numbers observed per man hour along random paths is the most convenient method, but allowances must be made for differential observer skill. Existing sampling methods bias against finding inactive animals and where these form a large proportion of the population, sample size is strongly influenced by habitat type.