Assessing unverified observation data used for estimating Iberian lynx distribution

Anecdotal occurrence data are often used to assess the current and historical ranges of elusive species. However, the use of such data can lead to misidentifications that may result in the overestimation of the species’ range and thus have potentially negative consequences for species conservation and management. Despite being a widely criticized practice, anecdotal sighting data have been used to establish the range of the Iberian lynx. We assessed the accuracy of anecdotal sighting data by drawing comparisons with non-invasive standard sampling methods that depend on verifiable physical evidence of the presence of the Iberian lynx to establish its range. The study was carried out in the central and northern part of the Iberian lynx populations that were believed to exist in the 1980s. The study area was divided into 10 × 10 km Universal Transverse Mercator (UTM) squares, in which interviews regarding sightings and scat and camera trapping surveys were conducted. A total of 82 lynx sightings were obtained in 44 different squares, but only one scat was located and no photographs were obtained. Our results show that the use of sighting data overestimates the range of the species when compared to the range obtained using physically verifiable data. Anecdotal data are considered to be notoriously unreliable by most scientists, yet, in the case of the Iberian lynx, this type of data continues to be used. Iberian lynx conservation and management decisions must be taken based solely on verified existing records to avoid wasting the limited resources available for conservation and to prevent inappropriate management decisions from being taken.