Investigation into survey techniques of large mammals: surveyor competence and camera-trapping vs. transect-sampling

Rigorous and cost-effective methods are essential to efficiently assess wildlife populations and obtain accurate data to inform conservation and management decisions. In the UK, available data on terrestrial mammal species are distinctly lacking, many populations are in decline and survey methods are technically demanding and labour-intensive. There is, therefore, much need to investigate alternative methodologies to ensure that resource use is efficient and data are reliable. Camera-trapping presents a relatively new approach for surveying mammals, though in the UK, the extent to which camera traps have been used has not been quantified and their performance has not yet been compared relative to existing methods. This study uses biological parameters and economic and logistic costs to assess the efficiency and reliability of camera-trapping and transect-sampling during winter field trials. Tracks and sign surveys and sightings surveys were conducted simultaneously and where appropriate, investigated independently. In addition, a nationally-distributed questionnaire was used to investigate surveyor competence and identify temporal trends in method use in the UK. Field trials concluded that camera-trapping was the most labour-efficient method for producing a species inventory, and frequently recorded more species per sampling site than did transect-sampling. However, when the total sampling period was limited, species were encountered at a faster rate by the detection of tracks and signs than by the alternative methods investigated. The single density estimate derived from camera trap data was higher than that from transect-sampling, and no differences were observed within the three alpha diversity index estimates derived by each survey method. The questionnaire suggests that the reliability of species presence/absence data derived from tracks and signs surveys is probably compromised by surveyor confidence of species identification. A multi-evidence approach is, therefore, recommended for less-competent surveyors. Despite greater initial economic costs, it is advocated that camera-trapping may be an efficient, rigorous and cost-effective method for large-scale long-term monitoring programmes. Furthermore, data suggest that camera trap use will become increasingly frequent in the UK. More research is required to investigate the relationships between method efficiency and season, species density and habitat, and to assess the accuracy of species density estimates.