Observations of amphibian, reptile and some mammal species in the area of Šaleška jezera near Velenje during the 2015–2017 period

. In this contribution we present our observations of amphibians, reptiles and some mammals from the area of Šaleška jezera (lakes) near Velenje in northern Slovenia. This area refers to three lakes – Velenjsko jezero, Šoštanjsko jezero and Škalsko jezero, which were formed in the 20th century as a consequence of underground lignite mining. The landscape is still changing due to an ongoing subsidence of the valley caused by continuous mining, which constantly affects the surface water bodies and habitats. The changes are so apparent that they could be measured in weeks if not days. New records on the occurrence of 9 amphibian, 7 reptilian and 9 mammalian species were made in the region during our field work carried out from 2015 to 2017. Three of these species are listed on Annex II of the EU Habitats Directive – Emys orbicularis, Bombina variegata and Triturus carnifex, and additional eight on Annex IV of this directive – Bombina variegata, Hyla arborea, Rana dalmatina, Triturus carnifex, Emys orbicularis, Lacerta viridis, Podarcis muralis and Natrix tessellata. We also recorded two introduced species – Dama dama and Trachemys scripta

Since the area and its lakes are fairly dynamic with constantly changing habitats, data about possible vertebrate distribution can be considered interesting.Distribution changes and succession had been noted in some former destroyed mining areas in other countries (e. g.Tischew et al. 2009).The most dynamic subsiding area, where the changes can be measured in days, is the landscape between lakes Velenjsko jezero and Šoštanjsko jezero due to still active underground mining and ash deposition from the nearest Šoštanj thermoelectric plant.Despite the records of endangered species at the European level, this landscape has currently no nature conservation status.On the other hand, the northeastern shore of Velenjsko jezero, including the patch between Velenjsko and Škalsko jezero, is designated as a valuable natural area (Ur. l. RS 2004a).Velenjsko and Škalsko jezero are also partly situated on the southwestern border of the Velenjsko-Konjiško gorovje area of ecological importance (»ekološko pomembno območje«; Ur. l. RS 2004b).The same area was also included in an initiative to establish a natural landscape park Škale, but all the attempts failed (Pokorny 1999).
In this contribution we present some amphibian, reptile and mammal species in the Šaleška jezera region, noted as chance findings between the years 2015 and 2017.

Materials and methods
Šaleška jezera (lakes) are very young, formed in the mid-20 th century in Šaleška dolina, a basin in Slovenia near the town of Velenje.The valley has natural deposits of lignite and the mining of this coal started 130 years ago, causing the subsidence of the valley, which was gradually flooded with the water from passing brooks.The flooding resulted in three notable lakes (Fig. 1) -Velenjsko jezero, Šoštanjsko jezero in Škalsko jezero (Šterbenk 2011).Due to the still active mining, the shape of the lakes and their surrounding landscape is still changing.After several decades of activity, the subsidence of the grounds is currently most significant on the northwestern shores of Velenjsko jezero and northern and eastern shores of Šoštanjsko jezero.The changes occur in short periods of time and are often accompanied by deforestation along with creation of new water bodies, marshland, reeds, shrubland and other surfaces (Šterbenk 2011).The southern, more stable shores of these two lakes are popular tourist destinations, with the smallest lake, Škalsko jezero, completely designated for human activities (Šterbenk et. al. 2017).
The fieldwork was carried out from May 2015 to October 2017 and was mainly focused on regular bird surveys (Gojznikar et al., in prep.), but we also recorded other vertebrate species encountered during our field work.The amphibian and reptile species were either caught, identified, photographed and released or only observed through binoculars or telescope and identified using some of the available literature (Veenvliet & Kus Veenvliet 2008, Speybroeck et al. 2016).Some amphibian species were also identified by sound recognition.Mammals were identified after being photographed or observed through binoculars or telescope with the aid of available literature (Kryštufek 1991, Kryštufek & Janžekovič 1999).We also identified several mammalian species via their footprints according to Krofel & Potočnik (2016).Apart from the obvious and easily determinable species, we excluded certain mammal groups from our survey, as no suitable methods for their identification were at hand.These were nearly all rodents (Rodentia) and all insectivores (Eulipotyphla) and bats (Chiroptera).

Results and discussion
In the surveyed area we noted 25 different species-level taxa from three vertebrate classes -Amphibia, Reptilia and Mammalia with 9, 7 and 9 species respectively (Tab.2).Altogether, the animals were noted on 71 different localities (Tab.1).We recorded three species found on Annex II of the EU's Habitats Directive: yellow-bellied toad (Bombina variegata), Italian crested newt (Triturus carnifex) and European pond terrapin (Emys orbicularis), and additional eight on Annex IV of this directive: yellow-bellied toad (Bombina variegata), European tree frog (Hyla arborea), agile frog (Rana dalmatina), Italian crested newt (Triturus carnifex), European pond terrapin (Emys orbicularis), European green lizard (Lacerta viridis), common wall lizard (Podarcis muralis) and dice snake (Natrix tessellata) (Official Journal of the EU 1992).The only noted species being considered endangered (E category) in Slovenia is E. orbicularis (Ur. l. RS 2002).Two introduced species for Slovenia were also observed: the pond slider (Trachemys scripta) and the fallow deer (Dama dama).We noted two subspecies of the former -T.s. scripta and T. s. elegans (Tab.2).Although there were at least 8 different individuals present in the aforementioned pond, we found no evidence of their reproduction.It is of crucial importance to ensure that the current state of the pond remains undisturbed, which might be difficult to achieve due to the continuous subsidence in the area.Another issue for E. orbicularis is the presence of the possibly competitive T. scripta in the area.Cadi & Joly (2004) suggested in their experiment that the latter could have a negative impact on the former.During our research, T. scripta was found, among other localities, in the same pond as E. orbicularis.The former is known in the area for a much longer period than the latter, with the first recorded observation at Škalsko jezero in 1995 (Gregori 1995).The subspecies T. s. elegans is known to reproduce in the wild elsewhere in Slovenia (Lipovšek 2013); the question whether it reproduces in our study area, remains unanswered.Among other reptilians we could not distinguish between L. viridis and L. bilineata due to their almost identical morphological features.The species complex is still a partial mystery in Slovenia, even though it seems that L. bilineata is more likely to be found in the west and L. viridis in the east of the country (Tome 1999).Other noted reptilian species are quite common across Slovenia (Krofel et al. 2009).
Our list of amphibian and reptilian species is more or less in concordance with other publications (Poboljšaj 2001, Poboljšaj & Lešnik 2003, Krofel et al. 2009), even though we believe that some other common Slovenian species could also occur regularly in the area (e.g. the Fire Salamander (Salamandra salamandra)).The same, however, cannot be said of our observations of mammals.The actual number of mammalian species in the area is certainly much higher owing to the fact that we excluded bats, insectivores and nearly all rodents from our records.Out of nine species of the recorded mammals, only three (Mustela erminea, M. nivalis and Sciurus vulgaris) are listed on the Slovenian Red List and fall into the O1 category.We did, however, regularly note D. dama, which was introduced to the lake area in 1973 (Krže 1975).An interesting find was a lone chamois (Rupicapra rupicapra), a species usually restrained to higher altitudes (Kryštufek 1991).
Degraded areas can offer an interesting insight into succession processes, as demonstrated in Eastern Germany, where enormous tracts of land were destroyed by open-pit coal mining (Tischew et al. 2009).Lignite mining in our area of research is, however, subterranean, which is not common on a global scale (Šterbenk 2011).Therefore, the ever changing surface offers a unique window into succession processes and species reaction to quick environmental changes as indirect consequences of human activities.We believe that further research, focused on noting the impact of the changeable surface, could be interesting.The area is also interesting from the aspect of conservation -the species listed on the Annex II or the Annex IV co-appear in several conservationally important areas elsewhere in Slovenia (Govedič et al. 2009) and offer a possible comparison insight into the effect of the aforementioned human activities.

Table 2 .
(Ur. l.EU 1992)nik 2003)me mammalian species recorded in the Šaleška jezera area between 2015 and 2017 (A -Amphibia, R -Reptilia, M --Mammalia; I -introduced species; HD -Habitats Directive(Ur.l.EU 1992), RL -Slovenian Red List(Ur.l.RS 2002), IUCN -The IUCN List of Threatened Species, E -endangered, LC -least concern, NT -near threatened, O1 -species threathened in the past but currently not threatened, V -vulnerable ; few: 2-5, many: 6 or more).Tabela 2. Vrste dvoživk, plazilcev in določenih sesalcev, zabeležene v okolici Šaleških jezer med letoma 2015 in 2017 (A -Amphibia, R -Reptilia, M -Mammalia; I -tujerodne vrste; HD -Habitatna direktiva(Ur.l.EU 1992), RL -Rdeči seznam Slovenije(Ur.l.RS 2002), IUCN -IUCN seznam ogroženih vrst, , E -prizadeta vrsta, LC -vrsta, ki trenutno ni ) on the Slovenian Red List(Ur.l.RS 2002).Bombina variegata is still considered widespread in Slovenia, but could locally be under negative impact.Its populations are, in general, under threat from urbanisation, intensive forestry, agriculture and disappearance of small water bodies, their preferred habitat(Poboljšaj & Lešnik 2003).In the research area, small water bodies are highly susceptible to geomorphological changes, which could exert pressure on the local population of the species.Triturus carnifex, on the other hand, was not seen as often as B. variegata.Although generally present throughout Slovenia, its populations are very small(Poboljšaj & Lešnik 2003) and the species is sometimes considered rare(Govedič et al. 2009).T. carnifex is threatened by multiple local negative influences, especially the devastation of suitable water bodies nationwide(Poboljšaj & Lešnik 2003), and therefore faces a similar problem in the lake area as B. variegata.Other interesting amphibian observations were Ichthyosaura alpestris and Lissotriton vulgaris, which were found only as juveniles together in the same pond, and Hyla arborea, found on four localities.The only species not listed on the Slovenian Red List is the invasive T. scripta.Emys orbicularis is also listed on the Annex II and Annex IV of the Habitats Directive(Ur.l.EU 1992).It is known to have suffered population declines throughout its range, mainly due to habitat degradation, fragmentation and destruction (Tome 2003).In the research area, E. orbicularis was discovered only recently, for the first time recorded about two years ago (CKFF 2018, leg.M. Vranič).During the time of our survey, it was noted also by other researchers (CKFF 2017, leg.N. Kirbiš & M. Vamberger) on the same locality.