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Es wird über einen 1930 angesetzten Versuch berichtet, bei dem auf einem bis dahin eidechsenfreien Felseiland (Dado Grande bei Ibiza, Pityusen) Männchen einer melanistischen und Weibchen einer grünen Inselpopulation von Podarcis pityusensis ausgesetzt wurden. Die Untersuchung von sechs fünf Jahre später gefangenen Tieren ergibt, dass die Vermischung zu erhöhter Variabilität und gesteigertem Größenwuchs geführt hat. Eine erneute Kontrolle dieses noch vorläufigen Ergebnisses wird angeregt.

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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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The status of the populations of Podarcis pityusensis on about 70 islets and small islands around Ibiza and Formentera (Balearic Islands) is examined, using data from our own observations, and, to a lesser amount, other publications. Lizard populations were found on 43 islets, but data are lacking for another 13. Only 10 sites (18 %) have abundant and well-maintained populations. In 13 localities (23%), there is no geographic isolation between the populations, or this isolation is very poor and incomplete. The high probability of populations mixing, or actual observation of this mixing, in 19 islands (34%) is indicated. Human pressure on lizard populations is strong in 14 cases (25 %). And finally, 18 populations (about one third) may be considered highly endangered or already extinct by elimination or genetic mixing with other populations. Among the subspecies which became extinct through mixing are P.p. miguelensis, P.p. subformenterae, P.p. algae, P.p. sabinae and P.p. grueni. The need for adequate protective measures aimed at the conservation of the remaining populations is emphasized.

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Survey of the present known occurrences of population exposures within the Ibiza wall lizard (Podarcis pityusensis Boscà,1883). Probably more often than it has been documented in the past, lizards are transported with the help of men to other islands or islets where either no lizards live or which are inhabited by different subspecies. Therefore the mixing of populations is possible and the genetic barrier is broken which leads to complications in the taxonomy of these species. In some cases unfortunately such transported lizards have probably been described as different subspecies. In the future taxonomic studies of this specie the possible precence of such transported lizards within various populations should be given more attention.