Winter Activity of Podarcis muralis (Laurenti, 1768) and P. erhardii (Bedriaga, 1876) in Urban and Suburban Habitats in the City of Blagoevgrad, Bulgaria

Lizards in Bulgaria hibernate in winter. Yet, individuals of many species were found active in this period. Cases of winter activity of Podarcis muralis and P. erhardii in the country have been published, but this behavior has not been studied in detail. The purpose of this research was to observe and analyze the winter activity of these two species in the city of Blagoevgrad. The observations took place at two sites in days with high solar radiation in December, January, and February 2015–2017. One of the sites was a typical urban territory, inhabited only by P. muralis. The other site was a suburban area, inhabited by P. erhardii. The number of the active individuals of the Common Wall Lizard recorded was about 8.5 times higher than that of the Erhard's Wall Lizard. The lowest air temperature at which P. muralis was observed was -4°C and for P. erhardii it was +0.5°C. Individuals of both species were registered only at positive substrate temperatures. Representatives of all age groups of P. muralis were recorded often with dorsoventrally flattened bodies while basking. On the other hand, few juveniles of P. erhardii were found active and they flattened their bodies very rarely.