Marko Anđelković

Reptiles rely on behavioural thermoregulation to maintain optimal body temperature (Tb), essential for many physiological functions. However, thermal biology remains poorly studied in many snake species, including the Caspian whipsnake (Dolichophis caspius, Gmelin, 1789). This study examined the thermal biology of the Caspian whipsnake under natural and laboratory conditions. In the field, we investigated the influence of sex, age category, season, time of day, air temperature, detection status, feeding status, and shedding phase on Tb. Under controlled conditions, we assessed preferred Tb variation and its relationship to active thermoregulation. In the field, Tb was significantly affected by sex, season, time of day, air temperature, feeding status, and shedding phase, but not age category, body size or detection status. Males had lower Tb than females and snakes with food in their stomachs exhibited higher Tb. Tb increased from March to June and from morning to afternoon, and air temperature had a positive effect on Tb. In the laboratory, mean Tb (24.5 ± 4.9 °C) was lower than in the field (26.9 ± 5.2 °C) and was significantly associated with body posture and terrarium part, indicating active behavioural thermoregulation. In the laboratory, males had lower Tb than females, and juveniles had lower Tb than adults. The lower thermal preference suggests a cooler thermal niche than many colubrids, potentially increasing their susceptibility to climate warming. However, the broad Tb variation and behavioural thermoregulation indicate some flexibility in responding to environmental changes. These findings highlight the role of behavioural thermoregulation in snake thermal responses to environmental variation.

Wildlife-vehicle collisions (WVCs) represent an important ecological and road-safety problem, yet the influence of short-term meteorological variability on their occurrence remains insufficiently understood. This study investigated the associations between temperature extremes, abrupt temperature changes, and broader hydro-meteorological conditions and reported WVC frequency in Serbia over a 10-year period (2016–2025). A municipality-day dataset comprising 6281 police-reported WVCs was analyzed using an event-based methodology. Exploratory analyses were complemented by Poisson regression models to evaluate prolonged temperature episodes, abrupt temperature shocks, and broader hydro-meteorological conditions, while additional regional analyses examined the consistency of the observed associations across Serbia. The results demonstrated pronounced seasonal variation, with the highest reported WVC frequencies occurring during spring and late autumn. At the national level, prolonged cold episodes were associated with significantly lower reported WVC frequencies during their onset and middle phases, whereas heat episodes showed no significant associations. Abrupt cool-down shocks were associated with a short-term increase in reported WVC frequency on the day of the temperature decrease, while warm-up shocks showed no significant effects. Moderate and heavy precipitation, snow-day conditions, and prolonged dry spells were associated with reduced reported WVC frequency, whereas daily mean temperature and atmospheric pressure were not independently associated with reported WVC frequency. Regional analyses generally supported the national findings, although no regional associations remained statistically significant after false discovery rate correction. These findings demonstrate that short-term meteorological variability is associated with reported WVC frequency in a temporally dependent manner and highlight the importance of considering both environmental events and regional variability when investigating wildlife-vehicle collisions.

Some animals successfully inhabit anthropogenic environments but are often exposed to negative impacts such as habitat destruction, disturbance and pollution. Lizards frequently occupy stone walls, abandoned buildings and cultural monuments, including fortresses, where crevices provide important sites for hiding, thermoregulation, and hibernation. However, urbanisation and restoration activities can negatively affect animal populations by restricting movement and dispersal and by reducing reproductive success, growth, and survival, potentially leading to population declines or local extinctions. The main objective of this study was to assess the impact of cultural monument restoration on Common Wall Lizard (Podarcis muralis) populations by analysing body condition index and population structure. The study was conducted at Kalemegdan Fortress, located in the urban centre of Belgrade, Serbia. This three-year-long research showed that at the locality Kalemegdan 1, fortress restoration caused local population extinction due to habitat destruction and the killing of lizards, with no evidence of lizards migrating to the neighbouring locality - Kalemegdan 2. Interestingly, lizards from Kalemegdan 1 consistently exhibited a higher body condition index than those from Kalemegdan 2, suggesting more favourable hibernation conditions at the former locality. However, body condition index values at Kalemegdan 1 showed a declining trend over the study period, likely as a consequence of restoration activities. Overall, the results indicate that restoration of historic fortresses can result in habitat loss and population declines in urban lizards. Given that urban populations are often small and fragmented, the absence of appropriate mitigation measures during restoration may increase the risk of local extinction.

Kotschy’s gecko, Mediodactylus kotschyi, is native to the Eastern part of the Mediterranean Basin and a successful colonizer, with an extensive distribution across the Balkans and outside its native range. In Serbia, it was presumed native in Prizren (Kosovo and Metohija province) and introduced across the remaining territory. To explore the origin of Serbian Kotschy’s gecko, we collected specimens from most of the Serbian populations where the species was recorded and assessed their phylogenetic relationships based on three mtDNA markers (COI, cytb, 16S rRNA) under Maximum Likelihood (ML) and Bayesian Inference (BI) approaches. First, our results support that the specimens found in Serbia belong to M. kotschyi. Second, all populations except Prizren belong to the subspecies M. kotschyi skopjensis. Furthermore, the Italian populations are sister to the specimens from Prizren, suggesting a Balkan origin for these populations, which settled in Apulia likely through ancient human-mediated dispersion. The small genetic differentiation found suggests that Kotschy’s gecko rapidly colonized the Central Balkans, originating from Northern Greece and North Macedonia. The results also suggest a story of multiple, complex (most likely) human-mediated introductions. However, further studies should be conducted to properly elucidate the colonization pathways, and to truly disentangle the potential fast natural range expansion from an anthropogenic dispersion of this gecko species.

Alpine habitats are exposed to increasing anthropogenic pressure and climate change. The negative impacts can lead to chronic stress that can affect the survival and reproductive success of individuals and even lead to population extinction. In this study, we analyse different morphological and ecological traits and indices of abiotic and biotic stressors (such as head size and shape, fluctuating asymmetry, body condition index, tail autotomy, and population abundance) in alpine and subalpine populations of two lacertid species (Zootoca vivipara and Lacerta agilis) from Serbia and North Macedonia. These lizards live under different conditions: allotopy/syntopy, different anthropogenic pressure, and different levels of habitat protection. We found differences between syntopic and allotopic populations in pileus size, body condition index (in both species), pileus shape, fluctuating asymmetry (in L. agilis), and abundance (in Z. vivipara). Differences between populations under anthropogenic pressure and populations without it were observed in pileus shape, body condition index (in both species), pileus size, fluctuating asymmetry, tail autotomy and abundance (in L. agilis). On the basis of our results, it is necessary to include other stress indicators in addition to fluctuating asymmetry to quickly observe and quantify the negative effects of threat factors and apply protective measures.

Insular populations offer excellent opportunities to study the factors that influence phenotypes. We observed island dwarfism in a widespread snake, the nose-horned viper (Vipera ammodytes). Island vipers were ~20% smaller than mainland individuals. They also produced fewer and smaller offspring. In snakes, food availability has a positive influence on body size, fecundity and offspring size. Consequently, low energy intake is a plausible explanation for insular dwarfism. The diet of island vipers was principally represented by lizards and centipedes, whereas the most profitable prey items (e.g. rodents) were regularly found in the stomach of mainland vipers. Furthermore, the proportion of individuals captured with a full stomach and good body condition were lower on the island compared with the mainland. Thus, island vipers were likely to be experiencing permanent energy restriction, with cascading effects on adult body size and reproductive output. Large prey promotes high relative jaw length in snakes. Island vipers displayed smaller relative jaw length compared with mainland populations, suggesting that plasticity played a role in insular dwarfism. But the difference in relative tail length between island and mainland populations, a trait not subjected to food-induced plasticity, indicates local adaptation. Both plasticity and adaptation might influence the phenotype of island vipers.

Amphibians and reptiles are the most threatened vertebrates by traffic, especially near ponds and wetlands. The main aim of this study was to examine seasonal and spatial patterns of amphibian and reptile road mortality in Special Nature Reserve “Obedska bara” (Serbia). We chose a road section of 4.2 km near the largest wetland in Serbia, with two different habitat types (forest-pond and agricultural area-pond). During 2018 (32 fieldwork days) and 2019–2020 (three control fieldwork days), we found 20,457 and 2231 road-killed animals, respectively. We recorded nine amphibian and eight reptile species. Amphibians (93%) were more vulnerable to traffic than reptiles (7%). The number of killed amphibians and reptiles varied between the seasons. Generally, amphibian roadkill was most frequent during the summer, whereas reptile roadkill was most frequent in spring and at the end of the summer. Furthermore, different roadkill patterns were observed during the examined months. In addition, we found that habitat type significantly affects the vulnerability of animals towards the roads. For both amphibians and reptiles, there were significant aggregations of roadkill, and most hotspots were located at the forest pond habitat type where mitigation measures must be applied (construction of tunnels and fences).