Abstract
Lizard populations have been traditionally considered unusually stable. However, there are very few examples to verify this hypothesis on long-term studied populations. Over almost four decades, we have obtained long time series of the abundance of Lilford’s Wall Lizard, Podarcis lilfordi, from all known populations of Menorca (Balearic Islands, Spain). Lizard densities were estimated from line transects data using N-mixture models. Irregular time series were then checked for the presence or absence of a monotonic trend and for density dependence of each population. With multiple regression models we studied the relationship between weather events and the annual abundance of lizards. Density dependence was detected only in two populations: Addaia Petita and Binicodrell Gros. The analysis with EGSS and OUSS models, as well as the results with a Bayesian analysis, showed that most populations seem stable over the years, with a positive and statistically significant trend in five of the 17 populations under study. Only on Sanitja Island the population of lizards exhibits a significantly negative trend. Weather events have a very variable influence on each of these populations. In two small islets, Mel and Ses Mones, the annual number of cloudy days have a negative effect on the abundance of lizards. In Bledas Island, with an exposed geographical situation, we observe a significantly negative effect of all three weather events considered: storms, cloudy days and strong winds. Surprisingly, in Aire and Addaia Gran islands, the annual number of days with storms had a significantly positive effect, probably because the marine subsidies contributed to trophic availability of these two islands by the storms. This work is a first attempt to establish the real abundance of this species, its long-term trend and the influence of weather events on densities of a large set of populations. The relevance of weather events is strongly different on each population and depends on environmental conditions of each population, especially lizard abundance itself, the island surface, geographical location and degree of exposure to weather events.
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The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.
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Acknowledgements
In s’Albufera des Grau Natural Park, the director David Martínez, as well as the former director, Martí Escudero, Agnès Canals and Samuel Pons, facilitated the access to the populations of the Natural Park, as well as the use of their boat for access to Mel Islet. The constant support of managers of the Conselleria de Medi Ambient of the Gouvernment of Balearic Islands has been essential for decades, granting of scientific capture permits and follow-up commissions. To mention Joan Mayol, head of the Species Service and Catalina Massutí, head of the Protected Areas Service. Both always facilitated the permits and information about their areas of expertise. Likewise, Iván Ramos, Tomás Bosch and Luis Parpal have constantly supported us, as well as Dr. Samuel Pinya (University of Balearic Islands), responsible for the Boscà Plan of Amphibians and Reptiles Conservation of Balearic Islands. The work in Rei Island has always been facilitated and supported by the Foundation Illa del Rei and especially, by Luis Alejandre and José Muñoz.
Funding
Throughout the last 35 years, several research grants from the Institut Menorquí d’Estudis, allowed the two authors to carry out the studies presented here. The lizard surveys in Menorca were constant during the last 10 years thanks to the support and financing of the Agency of the Biosphere Reserve (Insular Council of Menorca), especially thanks to Félix de Pablo, Juan Juaneda and Irene Estaún.
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A P–C and V P-M obtained field data, analyzed and interpreted them. A P–C and V P-M wrote the manuscript. Both authors read and approved the final manuscript.
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Pérez-Cembranos, A., Pérez-Mellado, V. Trends and weather events in long-term densities of an insular lizard. Sci Rep (2026). https://doi.org/10.1038/s41598-025-34615-x
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DOI: https://doi.org/10.1038/s41598-025-34615-x
