Linnell, J.D.C., Fiske, P., Herfindal, I., Odden, J., Brøseth, H. & Andersen, R. 2007: An evaluation of structured snow-track surveys to monitor Eurasian lynx Lynx lynx populations. - Wildl. Biol. 13: 456-466.
Counts of tracks that passively accumulate on a suitable substrate are commonly used to derive indices of large carnivore abundance. In this study we evaluate the suitability of a similar survey using multiple 3-km long transect-lines to detect changes in population size for Eurasian lynx Lynx lynx in central Norway. We used GIS methods to simulate the crossing of transect lines by lynx using real telemetry data from the study area. We compared the effect of transect-line placement (deliberate vs random), transect-line density, and the number of nights over which tracks can accumulate in the snow. For each scenario we evaluated both the probability of detecting lynx that are present in the survey area, and the power of the index to detect changes between consecutive surveys. Deliberately placed lines performed significantly better than randomly placed lines, and as expected, increases in line density and the period of track accumulation improved the outcome. Using three nights of track accumulation and the highest density of deliberately placed lines that we simulated (1/38 km2) indicated that both the probability of detecting individual lynx present within the survey area, and the power to detect a 33% change in population size between two surveys, were . 80%.
Key words: Eurasian lynx, large carnivore, Lynx lynx, monitoring, population indices, snow-tracking