Most studies assessing amphibian presence and abundance are conducted during the reproductive season, focusing primarily on aquatic and semi-aquatic breeding sites. Consequently, the terrestrial habitats where these species spend the majority of the year remain significantly undersampled. Given the vital role these sites play in species survival, there is an urgent need for new, minimally-invasive monitoring techniques to detect amphibians during the post-breeding season.

Recently, Acta Herpetologica published a study assessing the feasibility of using PVC pipes as artificial shelters for sampling Hyla arborea outside the breeding season. Conducted from July 2022 to December 2024 in Slovenia’s Škocjanski Zatok Nature Reserve, the research tested 60 cm PVC pipes of two different diameters (40 mm and 50 mm) as artificial shelters within the terrestrial habitat of the European treefrog.

The method proved effective for monitoring hylids in the study area outside their breeding period. While both shelter types were utilized and no correlation was found between body size and shelter diameter, the frogs showed a clear preference for the narrower pipes. These smaller shelters likely provide better microhabitat conditions, improved moisture retention, reduced visibility, and better protection against predators. However, shelter occupancy declined over the years, possibly due to the disturbance caused by researcher manipulation.

A significant number of juveniles used the shelters in 2022, though this trend was not observed in subsequent years. While this might suggest habituation (with 2022 hatchlings returning to the pipes over in the following years), it demonstrates that the pipes are suitable for monitoring both juveniles and adults. Given the low impact on non-target species, this method is highly suitable for long-term monitoring in ecologically sensitive areas. Future developments may involve capture-recapture protocols to investigate population structure and interannual variations, while the use of narrower pipes may further clarify microhabitat preferences across different life stages.

Read the full paper to find out more.

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