Vol. 20 No. 2 (2025)
Articles

Occupancy of artificial shelters by European tree frog (Hyla arborea) in Škocjanski zatok Nature Reserve: A non-invasive sampling method in ecologically sensitive habitats

PDF
  • Martin Senič,
  • Matic Jančič,
  • Jure Jugovic,
  • Kevin Rečnik,
  • Sara Zupan,
  • Martina Lužnik
Martin Senič
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
Matic Jančič
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
Jure Jugovic
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
Kevin Rečnik
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
Sara Zupan
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
Martina Lužnik
University of Primorska, Faculty of Mathematics, Science and Information Technology, Koper, Slovenia
DOI: https://doi.org/10.36253/a_h-18266

Published 2025-11-19

Keywords

  • Hyla arborea,
  • artificial shelters,
  • PVC pipes,
  • amphibian monitoring,
  • protected areas

How to Cite

Senič, M., Jančič, M., Jugovic, J., Rečnik, K., Zupan, S., & Lužnik, M. (2025). Occupancy of artificial shelters by European tree frog (Hyla arborea) in Škocjanski zatok Nature Reserve: A non-invasive sampling method in ecologically sensitive habitats. Acta Herpetologica, 20(2), 175–184. https://doi.org/10.36253/a_h-18266

Copyright (c) 2025 Martina Lužnik, Martin Senič, Matic Jančič, Jure Jugovic, Kevin Rečnik, Sara Zupan

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Crossref
Scopus
Google Scholar
Europe PMC

Abstract

Monitoring amphibians in non-breeding habitats is constrained by low detectability and potential disturbance to sensitive ecosystems. We tested the effectiveness of artificial shelters - PVC pipes - as a non-invasive method for monitoring the European tree frog (Hyla arborea) outside the breeding season in Škocjanski zatok Nature Reserve (Koper, Slovenia). Over three years (2022–2024), we installed 40- and 50-mm diameter shelter pipes at 24 sites and conducted regular inspections. A total of 338 encounters of the focal species were recorded, with frogs of all sizes using the shelters. Overall shelter occupancy declined across years, possibly reflecting a combination of factors including reduced recruitment, vegetation changes, demographic fluctuations, and weather conditions. A statistically significant trend was observed, with narrower (40-mm) shelter pipes having 1.6 to 1.7 times more captures than wider (50-mm) ones, despite no significant difference in the body size of frogs occupying each type. By using PVC artificial shelters, we greatly enhanced the detectability of H. arborea in the Škocjanski zatok Nature Reserve compared to classical monitoring methods such as acoustic surveys or dip-netting. Importantly, a non-invasive approach using artificial shelters minimized the risk of disturbance to breeding and migratory birds, which is essential in areas with high avifaunal conservation value. Our results support the broader use of artificial shelters for monitoring arboreal amphibians in ecologically sensitive areas and suggest future research should explore finer-scale shelter design to improve detection and ecological interpretation across life stages.

PDF

References

  1. Agasyan, A., Avci, A., Tuniyev, B., Andrén, C., Cogălniceanu, D., Crnobrnja-Isailović, J., Poboljšaj, K., Halpern, B., Wilkinson, J., Ananjeva, N.B., Üzüm, N., Orlov, N.L., Lymberakis, P., Podloucky, R., Litvinchuk, S. (2024): Hyla arborea. In The IUCN Red List of Threatened Species 2024.
  2. Alford, R.A., Richards, S.J. (1999): Global amphibian declines: A problem in applied ecology. Annu. Rev. Ecol. Evol. Syst. 30: 135-165.
  3. Bartareau, T.M. (2004): PVC pipe diameter influences the species and sizes of treefrogs captured in a Florida coastal scrub community. Herpetol. Rev. 35: 150-152.
  4. Bégaud, B., Martin, K., Abouelfath, A., Tubert-Bitter, P., Moore, N., Moride, Y. (2005): An easy to use method to approximate Poisson confidence limits. Eur. J. Epidemiol. 20: 213-216.
  5. Boughton, R.G., Staiger, J., Franz, R. (2000): Use of PVC pipe refugia as a sampling technique for hylid treefrogs. Am. Midl. Nat. 144: 168-177.
  6. Campbell, K.R., Campbell, T.S., Johnson, S.A. (2010): The use of PVC pipe refugia to evaluate spatial and temporal distributions of native and introduced treefrogs. Fla. Sci. 73: 78-88.
  7. Carlson, A., Edenhamn, P. (2000): Extinction dynamics and the regional persistence of a tree frog metapopulation. Proc. R. Soc. B Biol. Sci. 267: 1311-1313.
  8. Cowan, M.A., Callan, M.N., Watson, M.J., Watson, D.M., Doherty, T.S., Michael, D.R., Dunlop, J.A., Turner, J.M., Moore, H.A., Watchorn, D.J., Nimmo, D.G. (2021): Artificial refuges for wildlife conservation: What is the state of the science? Biol. Rev. 96: 2735-2754.
  9. Cruickshank, S.S., Bergamini, A., Schmidt, B.R. (2021): Estimation of breeding probability can make monitoring data more revealing: A case study of amphibians. Ecol. Appl. 31.
  10. do Vale, R.L., Torres, I., Gomes, S., Fonseca, C., Ferreira, E. (2018): Ecological preferences of Hyla molleri in the colonisation of arboreal refuges in a human-shaped wetland. Amphib.-Reptil. 39: 51-61.
  11. Dytham, C. (2011): Choosing and using statistics: A biologist’s guide (3rd ed.). Wiley-Blackwell.
  12. Falaschi, M., Manenti, R., Thuiller, W., Ficetola, G.F. (2019): Continental-scale determinants of population trends in European amphibians and reptiles. Glob. Change Biol. 25: 3504-3515.
  13. Ferreira, E., Gomes Rocha, R., Malvasio, A., Fonseca, C. (2012): Short notes pipe refuge occupancy by herpetofauna in the Amazonia/Cerrado ecotone. Herpetol. J. 22: 59-62.
  14. Forks, K. (2015): Use of PVC pipes of different diameters as artificial refuges by green tree frogs (Hyla cinerea) in Texas. Unpublished Undergraduate Research Scholars Thesis. Texas A&M University.
  15. Glorioso, B.M., Waddle, J.H. (2014): A review of pipe and bamboo artificial refugia as sampling tools in anuran studies. Herpetol. Conserv. Biol. 9: 609-625.
  16. Goin, O.B. (1958): A comparison of the nonbreeding habits of two treefrogs, Hyla squirella and Hyla cinerae. Q. J. Fla. Acad. Sci. 21: 49-60.
  17. Granatosky, M.C., Krysko, K.L. (2011): Ontogenetic behavioral shifts in habitat utilization of treefrogs (Hylidae) in North-central Florida. Reptil. Amphib. 18: 194-201.
  18. Gvoždík, V., Moravec, J.Í., Kratochvíl, L. (2008): Geographic morphological variation in parapatric Western Palearctic tree frogs, Hyla arborea and Hyla savignyi: Are related species similarly affected by climatic conditions? Biol. J. Linn. Soc. 95: 539-556.
  19. Hoffmann, K.E., Johnson, S.A., McGarrity, M.E. (2009): Interspecific variation in use of polyvinyl chloride (PVC) pipe refuges by hylid treefrogs: A potential source of capture bias. Herpetol. Rev. 40: 423-426.
  20. Houlahan, J.E., Findlay, C.S., Schmidt, B.R., Meyer, A.H., Kuzmin, S.L., Kuzmink, S.L. (2000): Quantitative evidence for global amphibian population declines. Nature, 404: 752-755.
  21. Hutton, J.M., Warne, R., Macedo, A.D. (2024): Factors influencing the occupancy and detection of nonbreeding Hyla chrysoscelis within artificial polyvinyl chloride refugia. Herpetologica, 80: 221-233.
  22. Johnson, J.R. (2005): A novel arboreal pipe-trap designed to capture the gray treefrog (Hyla versicolor). Herpetol. Rev. 36: 274-276.
  23. Johnson, J.R., Mahan, R.D., Semlitsch, R.D. (2008): Seasonal terrestrial microhabitat use by gray treefrogs (Hyla versicolor) in Missouri oak-hickory forests. Herpetologica, 64: 259-269.
  24. Kovács, É.-H., Sas, I., Covaciu-Marcov, S.-D., Hartel, T., Cupsa, D., Groza, M. (2007): Seasonal variation in the diet of a population of Hyla arborea from Romania. Amphib.-Reptil. 28: 485-491.
  25. Liner, A.E., Smith, L.L., Golladay, S.W., Castleberry, S.B., Gibbons, J.W. (2008): Amphibian distributions within three types of isolated wetlands in Southwest Georgia. Am. Midl. Nat. 160: 69-81.
  26. Luedtke, J.A., Chanson, J., Neam, K., Hobin, L., Maciel, A.O., Catenazzi, A., Borzée, A., Hamidy, A., Aowphol, A., Jean, A., Sosa-Bartuano, Á., Fong G.A., de Silva, A., Fouquet, A., Angulo, A., Kidov, A.A., Muñoz Saravia, A., Diesmos, A.C., Tominaga, A., … Stuart, S.N. (2023): Ongoing declines for the world’s amphibians in the face of emerging threats. Nature, 622: 308-314.
  27. Lukanov, S., Kolev, A., Dyugmedzhiev, A., Slavchev, M. (2024): The lateral stripe - a reliable way for software assisted individual identification for Hyla arborea. Acta Herpetol. 19: 69-73.
  28. Mahan, R.D., Johnson, J.R. (2007): Diet of the gray treefrog (Hyla versicolor) in relation to foraging site location. J. Herpetol. 41: 16-23.
  29. Marsh, D. M., Trenham, P.C. (2001): Metapopulation dynamics and amphibian conservation. Conserv. Biol. 15: 40-49.
  30. McGhee, J.D. (2020): Assessing summer pond and lake inlet use by gray treefrogs (Hyla versicolor/chrysoscelis complex) using PVC pipe traps in Northwest Missouri. Trans. Mo. Acad. Sci. 48: 17-21.
  31. Ministry of Environment, Spatial Planning and Energy (2002): Pravilnik o uvrstitvi ogroženih rastlinskih in živalskih vrst v rdeči seznam. Official Gazette of Republic of Slovenia, 82/2002. https://www.uradni-list.si/_pdf/2002/Ur/u2002082.pdf [Rules on the inclusion of endangered plant and animal species in the Red List. In Slovenian]
  32. Moravec, J. (1990): Postmetamorphic growth in the European tree frog (Hyla arborea). Acta Univ. Carolin. Biol. 34, 359-370.
  33. Moulton, C.A., Fleming, W.J., Nerney, B.R. (2009): The use of PVC pipes to capture hylid frogs. Herpetol. Rev. 27: 186-187.
  34. Mozetič, B., Lipej, B. (2014): Zeleno srce Kopra - vodnik po Naravnem rezervatu Škocjanski zatok (2nd ed.). Društvo za opazovanje in proučevanje ptic Slovenije DOPPS. (The Green Heart of Koper - A Guide to the Škocjanski Zatok Nature Reserve (2nd ed.). Society for the Observation and Study of Birds of Slovenia (DOPPS)).
  35. Myers, C.H., Eigner, L., Harris, J. A., Hilman, R., Johnson, M.D., Kalinowski, R., Muir, J.J., Reyes, M., Tucci, L.E. (2007): A Comparison of ground-based and tree-based polyvinyl chloride pipe refugia for capturing Pseudacris regilla in Northwestern California. Northwest. Nat. 147-154.
  36. Pellet, J., Hoehn, S., Perrin, N. (2004): Multiscale determinants of tree frog (Hyla arborea L.) calling ponds in western Switzerland. Biodivers. Conserv. 13: 2227-2235.
  37. Pellet, J., Rechsteiner, L., Skrivervik, A.K., Zürcher, J.-F., Perrin, N. (2006): Use of the harmonic direction finder to study the terrestrial habitats of the European tree frog (Hyla arborea). Amphib.-Reptil., 27: 138-142.
  38. Pereira-Ribeiro, J., Ferreguetti, Á.C., Bergallo, H.G., Rocha, C.F.D. (2017): Use of polyvinyl chloride pipes (PVC) as potential artificial shelters for amphibians in a coastal plain forest of southeastern Brazil. J. Coast. Conserv. 21: 327-331.
  39. Perry, G., Wallace, M.C., Perry, D., Curzer, H., Muhlberger, P. (2011): Toe clipping of amphibians and reptiles: Science, ethics, and the law. J. Herpetol. 45: 547-555.
  40. Pittman, S.E., Jendrek, A.L., Price, S.J., Dorcas, M.E. (2008): Habitat selection and site fidelity of Cope’s Gray Treefrog (Hyla chrysoscelis) at the aquatic-terrestrial ecotone. J. Herpetol. 42: 378-385.
  41. R Core Team. (2024): R: A language and environment for statistical computing. R Foundation for Statistical Computing.
  42. Schurbon, J. M., Fauth, J. E. (2003): Effects of prescribed burning on amphibian diversity in a Southeastern U.S. National forest. Conserv. Biol. 17: 1338-1349.
  43. Semlitsch, R. D., Bodie, J. R. (2003): Biological criteria for buffer zones around wetlands and riparian habitats for Amphibians and Reptiles. Conserv. Biol. 17: 1219-1228.
  44. Senič, M., Adam, K., Jakovljević, M., Jugovic, J., Lončarević, N., Možina, M., Rečnik, K., Shklyarnik, E., Zupan, S., & Lužnik, M. (2024): Using artificial shelters and photo identification for monitoring the European tree frog (Hyla arborea) in Škocjanski zatok nature reserve. In: Book of abstracts: 2nd Life Amphicon International Conference: amphibian conservation and habitat restoration, 2024.Bolčina, A., Poboljšaj, K., Levstek, S., Vertič, Ž., Kotnik, T., Eds, Podsreda, Kozjanski park.
  45. Suriyamongkol, T., Forks, K., Villamizar-Gomez, A., Wang, H. H., Grant, W. E., Forstner, M. R. J., Mali, I. (2021): A simple conservation tool to aid restoration of amphibians following high-severity wildfires: Use of PVC pipes by green tree frogs (Hyla cinerea) in central Texas, USA. Diversity, 13.
  46. Tanadini, L. G., Schmidt, B. R. (2011): Population size influences amphibian detection probability: Implications for biodiversity monitoring programs. PLOS ONE, 6.
  47. Trimble, M. J., van Aarde, R. J. (2014): A note on polyvinyl chloride (PVC) pipe traps for sampling vegetation-dwelling frogs in South Africa. Afr. J. Ecol. 52: 381-383.
  48. Van Buskirk, J. (2005): Local and landscape influence on amphibian occurrence and abundance. Ecology, 86: 1936-1947.
  49. Veenvliet, P., Kus Veenvliet, J. (2014): Monitoring dvoživk in plazilcev v Naravnem rezervatu Škocjanski zatok-končno poročilo. Nova vas, Zavod Symbiosis.
  50. Waddle, J. H., Rice, K. G., Mazzotti, F. J., Percival, H. F. (2008): Modelling the effect of toe clipping on treefrog survival: Beyond the return rate. J. Herpetol. 42: 467-473.
  51. Wyatt, J. L., Forys, E. A. (2004): Conservation implications of predation by Cuban treefrogs (Osteopilus septentrionalis) on native hylids in Florida. Southeast. Nat. 3: 695-700.
  52. Zacharow, M., Barichivich, W. J., Dodd, C. K., Jr. (2003): Using ground-placed PVC pipes to monitor hylid treefrogs: Capture biases. Southeast. Nat. 2: 575-590.
  53. Zuur, A. F., Ieno, E. N., Smith, G. M. (2007): Analysing ecological data. Springer New York, NY.