The European ground squirrel (Spermophilus citellus) is an endangered species, endemic to Central and Southeastern Europe, inhabiting burrow colonies in grassland and agricultural ecosystems. In recent years, agricultural land-use changes and increased urbanization have largely contributed to a severe population decline across its range, particularly in its southernmost edge. Assessing the population and habitat status of this species is essential for prioritizing appropriate conservation actions. The present study aims to track population size changes and identify habitat characteristics of the species in Greece via a literature search, questionnaires, and fieldwork for assessing trends in population size as well as spatial K-means analysis for estimating its relation to specific habitat attributes. We found that both distribution size (grid number) and colony numbers of the species decreased in the last decades (by 62.4% and 74.6%, respectively). The remaining colonies are isolated and characterized by low density (mean = 7.4 ± 8.6 ind/ha) and low number of animals (mean = 13 ± 16 individuals). Most of the colonies are situated in lowlands and did not relate to specific habitat attributes. Habitat aspect and system productivity (NDVI) were the main factors contributing mostly to the clustering of the existing colonies. These results demonstrate that the species is confined to small, isolated anthropogenic habitats. Specific conservation actions such as population reinforcement, habitat improvement, and specific common agricultural policy measures could effectively improve agroecological zones that are suitable for the maintenance and protection of existing and potential habitats for populations of the species.
The European ground squirrel (Spermophilus citellus) is an endangered semifossorial small mammal of grassland/agricultural ecosystems. In the last few decades, the species’ population has declined throughout its range in Europe. The Greek populations represent the southernmost limit of the species’ range and are notably small, scattered, and located mainly in human-modified areas. The goal of the present research is to understand the environmental and anthropogenic variables associated with its distribution in the Mediterranean habitats, assess possible drivers of observed local extinctions, and propose conservation and land-use management actions in light of near-future climate change scenarios. We used presence records since 2000 across all known populations (107 colonies) and maximum entropy conditional probability models (MaxEnt) to calculate both the habitat suitability (bioclimatic variables) and habitat availability (anthropogenic/land-use variables) within the European ground squirrel’s historical range in northern Greece. We report a projected 39% to 94.3% decrease in habitat suitability by 2040–2060 due to climate change. Based on our findings, we provide guidance by proposing nascent conservation actions to protect the few existing colonies in Greece via improved land management practices and identify in situ climate refugia that could be prioritized as sites for future reintroductions.
Urban forests impose significant challenges to the animals that inhabit them due to the altered properties of available substrates from anthropogenic interventions. To cope with these structural peculiarities, urban species exhibit behavioral adjustments to successfully exploit the urban habitat. The present study examined habitat use and positional behavior of northern palm squirrels (Funambulus pennantii) in the urban forests of Kathmandu, Nepal, to test such behavioral modifications. Between July and August 2018, we collected focal animal instantaneous data on the behavior, locomotor/postural mode, forest layer, tree crown part, and substrate type, size, and inclination use of four different individuals. Our results indicated a primarily arboreal species, mostly using the middle canopy layers and the intermediate and central tree parts. Moreover, tree branches and artificial substrates were commonly used that were mainly large and horizontal. Locomotion was dominated by quadrupedalism and claw climb, whereas postures by quadrupedal stand, and, to a lesser extent, sit and claw cling. Most of our initial predictions were only partly supported by our findings. This behavioral idiosyncrasy most likely reflects the adaptive flexibility of the species to human-modified habitats. In this way, northern palm squirrels apparently expanded their ecological niche and successfully persisted against anthropogenic pressures throughout their range. As urban expansion is inexorable, more research is required to understand the behavioral and ecological flexibility of animals that effectively exploit these impacted habitats.
The current publication gives a detailed assessment of the results from a population reinforcement of a European ground squirrel's (Spermophilus citellus) colony in south-eastern Bulgaria. The reinforcement was planned and implemented along with multidisciplinary research of the adaptation process (including radiotelemetry, parasitological study and assessment of the stress in the animals) and regular monitoring (yearly burrow counting). Although the donor and recipient populations were genetically similar, morphometrical data indicated variations in the body size probably due to the difference in population densities in the two sites. The monitoring revealed that the burrows were aggregated and there was a positive correlation in the spatial distribution of the ground squirrels’ burrow holes and the colonies of Harting's vole (Microtus hartingi) - another social ground-digging rodent that co-inhabits the study area. The first results showed successful reinforcement according to the three classical evaluation criteria: the individuals survived the translocation process, they successfully reproduced and an initial population growth was observed, based on the burrow entrances’ count - from 36 in 2017 to 280 in 2020. In 2021, however, a considerable decline in the abundance of the population was recorded - 58.5% decline in the burrow number and 36% decline in the colony area. A decrease was also observed in the abundance of the Harting's voles' colonies. A review of all the collected information suggests it is unlikely that the decrease is due to helminth parasites, translocation stress or other behaviour issues. The most probable explanation is the bad weather conditions - unusually high rainfalls combined with relatively high temperatures in January 2021. In conclusion, we strongly emphasise the need for detailed and long-term monitoring after conservation translocation and careful evaluation of all the influencing factors before, during and after such actions.
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