Survey tools to predict and monitor the presence of brown bears (Ursus arctos) in Greece: A case study integrating spatial analysis and invertebrate-derived DNA

Increasing populations of brown bear (Ursus arctos) in Greece have resulted in recolonisation of areas previously unoccupied for decades. Large carnivore recolonisation often threatens hard-established human-wildlife coexistence efforts, therefore the need to monitor and predict bear presence and movement becomes more apparent as the animals make use of corridors existing between their current range and other suitable habitats. The challenge of carrying out surveys in infrequently used areas, such as wildlife corridors, is compounded by limited funds for wildlife conservation. This calls for the exploration of alternative monitoring techniques that are more cost and time-efficient than the standard methods such as scat surveys. This study explored the use of habitat suitability modelling techniques in mapping brown bear ecological networks in Greece throughout their current range and sites of potential future recolonisation. Using these suitability maps as a guide, the study utilised an innovative non-invasive genetic monitoring technique, invertebrate-derived DNA (iDNA), to survey the species in the field. A single-species targeted qPCR approach was used and method development experiments were conducted to form a protocol to optimise its performance in the field. Next, iDNA surveys combined with scat surveys were conducted to model bear distribution in northern Greece using occupancy modelling. These models describe the probability of bear detection in a landscape that incorporates a core brown bear habitat, a presumed corridor and a recently recolonised area. A review of the laboratory experiments and a comparison of the resulting occupancy models indicated that iDNA can effectively monitor the presence of a species as well as be subsequently used in occupancy modelling analyses. iDNA can be seen as an effective and complementary method of assessing brown bear distribution to inform conservation strategies and has the potential to assist with the conservation monitoring of other bear species