Details

Autor(en) / Beteiligte

• Oliveira, Alexandra
• Medinas, Denis
• Craveiro, João
• Milhinhas, Catarina
• Sabino-Marques, Helena
• Mendes, Tiago
• Spadoni, Giulia
• Oliveira, André
• Guilherme Sousa, Luís
• Tapisso, Joaquim T.
• Santos, Sara
• Lopes-Fernandes, Margarida
• da Luz Mathias, Maria
• Mira, António
• Pita, Ricardo

Titel

Large-scale grid-based detection in occupancy surveys of a threatened small mammal: A comparison of two non-invasive methods

Ist Teil von

• Journal for nature conservation, 2023-04, Vol.72, p.126362, Article 126362

Ort / Verlag

Elsevier GmbH

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •Efficient species detection over large scales is key to infer distribution changes.•We compare method-specific occupancy detection of Cabrera voles in large grid cells.•Sign surveys provided higher detectability at lower cost than owl pellet analysis.•Large scale monitoring of certain small mammals may rely on sign survey methods. Monitoring the status and trends of wildlife is key to understand how species respond to natural and human-derived threats, and to evaluate and improve conservation planning and management. Large-scale, grid-based assessment of species distribution, abundance, and population trends over time is an important component of biodiversity monitoring. However, such assessments still present important challenges related, for instance, to how the choice of the sampling method may affect species detectability and thus, overall data accuracy. Here, we address this issue, focusing on the Cabrera vole (Microtus cabrerae), a threatened small mammal, listed in the Habitats Directive (Annexes II and IV), hence requiring regular evaluation of its population status and trends. We used occupancy modelling to estimate method-specific detection probability of the species over large-scale, grid-based (10 × 10 km2) surveys relying on two non-invasive sampling techniques: sign surveys and owl pellet analysis. Results provided evidence for a greater cost-effectiveness of sign surveys compared to owl pellet analysis for detecting the species in occupancy surveys, suggesting that large-scale population monitoring of Cabrera voles (or other species also producing easily identifiable signs of their presence) may fairly rely on sign-surveys. Overall, our study supported the view that while owl pellet analysis provides a valuable option when the aim is to assess small mammal assemblages (i.e. multiple species) in a region, other complementary methods may be required to increase the detection probability of certain species that because of their secretive behaviour or rarity remain less predated by owls. We thus argue that the choice of the sampling method should be context-dependent and evaluated based on the study aims, the surveyed area (i.e. local factors), the target species (i.e. life history traits) and the available resources. Based on our results we recommend that researchers and managers explore survey-design trade-offs to ensure the proposed designs have sufficient power to detect real population trends.