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One of the taxonomical milestones regarding the Ibiza Wall Lizard, Podarcis pityusensis, the doctoral dissertation “Revisión taxonómica de las subespecies del lacértido Podarcis pityusensis BOSCÁ, 1883” by ANTÒNIA MARIA CIRER COSTA (CIRER 1987), has remained quite underexposed to date. One of the possible causes that led to the underexposure is the form in which the material was preserved in the 1980s: As a microfiche. To solve this, we compiled a searchable, text based, bilingual and annotated version of the original text, making this dissertation more accessible.

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This is our fifth report in a series on our whereabouts while collecting data for a future revision of the present subspecific order of the endemic Balearic sisterspecies Podarcis lilfordi (GÜNTHER, 1874) and Podarcis pityusensis (BOSCÁ, 1883), which data are stored in our free accessible database at www.pityusensis.nl (VAN DEN BERG & ZAWADZKI 2011 ; VAN DEN BERG et al. 2013 ; VAN DEN BERG et al. 2014a ; VAN DEN BERG et al. 2014b). During this trip from the 9th of May until the 23rd of May 2015, we were able to collect data on a few mainland Ibiza locations, as well as the following adjacent islands: Punta Galera, Es Canaret, Illa de la Xanga (Sal Rossa), Pouet de Ses Illetes, Formentera, Purroig, Es Vedrà, Rates, Malví Pla (North), Malví Rodó (South), S’Espardell, Calders, Penjats and Ses Margalides. We continue with the ventral coloration as a possible determining key as introduced in our 2014 trip report (VAN DEN BERG et al. 2014b). Images of the anal shields are presented of each lizard for purposes of illustration.

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Hemorrhois hippocrepis arrives at the beginning of the twenty-first century to the Pityusic Islands, like an invasive species and it has placed the endemic lizard Podarcis pityusensis at serious risk of extinction in the two major islands. It makes urgent to have an estimated population density of lizards in the various islets of the Pityusas. It has been used personal field notes with the indications that allow us to estimate the population density in the different visits realized to the islets from 1979 to 2024.

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In this study we compile data regarding lizard densities of the island populations of the Ibiza wall lizard, Podarcis pityusensis, which can serve as a baseline for future research and control of the invasive snakes, and in particular the horseshoe whip snake Hemorrhois hippocrepis, in the Pityusic Islands. Special attention has been given to the correct official spelling of 96 locations of which 89 are real rocks, islets and islands. For each island a short description, toponymy, faunal and floral aspects and some herpetological history is given, and a lizard density value was assigned. The results are very disturbing, with two confirmed- and three most likely extinct island populations of Podarcis pityusensis, and we call for coordinated action.

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Observations on Podarcis pityusensis consuming herbivorous food on Eivissa and the surrounding islands are summarized and compared with the existing literature. The advantages of a herbivorous diet on small islands is briefly discussed.

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The Ibiza wall lizard (Podarcis pityusensis), has a very limited distribution, being located only in the Pitiusas Islands of Balearic Islands, which are Ibiza and Formentera. In the Red List of Threatened Species of IUCN (International Union for the Conservation of Nature), this species went from being classified as `Near Threatened` (NT) and became `Endangered` (EN) on the 27th of June. This change in its category is due to a population decrease of more than 50% since 2010. The main reason for this population reduction is due to predation by invasive snake species, especially the horseshoe whip snake (Hemorrhois hippocrepis), which was accidentally introduced into the islands in 2003 and has since been a major threat to the lizard. Because its conservation status has recently been rectified, the recovery plan that it should have as being classified as an endangered species by IUCN has not yet been published. Thus, in this end-of-degree work it is intended to carry out this recovery plan for the Ibiza wall lizard (Podarcis pityusensis). This will include a review of the current status of the species (population status, critical areas, threats, etc.), definition of a set of objectives for the plan and identification of measures necessary to achieve the objectives, eliminate the threats facing the species, to restore their populations and ensure their long-term viability.