The use of sighting data to analyse Iberian lynx habitat and distribution

Authors


Dr Pedro Beja (fax + 351 89 818353; e-mail pbeja@ualg.pt).

Summary

1. Over a large part of its very restricted and fragmented range, Iberian lynx Lynx pardinus occur in remote mountainous country at low density, where the only information about the species comprises records of incidental sightings obtained by inquiry. In this study we developed an approach for quantifying lynx–habitat relationships and distribution patterns from sighting data, using records from western Algarve (Portugal) in 1990–95.

2. Habitat was described in terms of land cover, topography, human disturbance and rabbit abundance, in 25-km2 cells surrounding lynx sightings and at random locations within the study area.

3. Lynx sightings were consistently associated with predictable habitat features. Sighting probabilities estimated from a logistic regression model increased with the abundance of rabbits and the proportion of land covered by tall Mediterranean maquis, and declined with road density and the amount of developed land. This model identified correctly 85·7% of lynx sightings; at the same time only 20·7% of the random locations were misclassified.

4. Indices of human presence were never associated positively with lynx sightings, suggesting that observation patterns were not influenced by the spatial distribution of potential observers.

5. Kriging was used to interpolate spatially between sighting probabilities derived from the logistic model in order to produce a map of sighting potential for the Iberian lynx in western Algarve. Jack-knife resampling assessed the accuracy of this map. Three well-defined areas of high sighting potential were identified, probably representing the lynx core areas in this region.

6. Our analysis of lynx sighting records suggests that these data may provide a first approximation to lynx habitat and distribution when further information is lacking. The application of this approach to other rare and reclusive species is discussed.

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