Assessing unverified observation data used for estimating Iberian lynx distribution

Abstract

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.

Comparing interview methods with camera trap data to inform occupancy models of hunted mammals in forest habitats

“…Where camera trap data are available, estimates of occupancy informed by both hunter diaries and interviews often agree with estimates derived from camera traps at the village scale (e.g., estimates fall within the CIs of the camera trap estimates). As such, our findings contradict those of Garrote and Pérez de Ayala (2015) who found that estimates from interviews overestimate occurrence and distribution (Garrote & Pérez de Ayala, 2015).…”

“…Locally informed monitoring methods are also potentially biased. Several articles have warned against the use of unverifiable data from interviews due to concerns over species misidentification (McKelvey et al, 2008; Molinari‐Jobin et al, 2012), which in some studies has resulted in overestimations of occupancy compared to camera trap data (Garrote & Pérez de Ayala, 2015). Bias is sometimes associated with the stakeholder that gathers information.…”

“…We predict that species that are of particular interest to hunters, such as pangolins, will be well detected within the hunter diaries. We also expect both locally informed methods to be more cost‐effective than camera traps (Garrote & Pérez de Ayala, 2015; Hausser et al, 2017).…”

Estimating bobcat and Canada lynx distributions in British Columbia

“…We stress that citizen science reports must be accompanied with an image or physical evidence of the animal to be verifiable (Aubry and Jagger , Roy et al ). Unverified sighting records are unreliable for rare or secretive species and often overestimate their distribution because of a bias towards misclassifying more common species as the rare species (McKelvey et al , Garrote and Ayala ). For example, in response to our outreach for images, we received a few emails without images notifying us of bobcat sightings in northern British Columbia, hundreds of kilometers from the nearest verifiable image or physical record; such reports are extremely unlikely to be accurate.…”

“…Another approach is citizen science, such as sending surveys to people with knowledge of local species (e.g., trappers; Bridger et al ), or soliciting public sighting reports (Palma et al , Reed et al ). However, images or physical evidence must accompany public sighting reports to be verifiable (Aubry and Jagger , McKelvey et al , Garrote and Ayala , Roy et al ). Although there are concerns over the standardization and reliability of data collected using citizen science (Kosmala et al ), the volume of data, and their spatial and temporal coverage, cannot be obtained by any other method.…”