Novel pressures derived from urbanisation can alter native habitats and ultimately impact wildlife. Coping with such human-driven changes might induce shifts in species phenotypic traits, such as physiological responses to anthropogenic stressors. Preadaptation to face those challenges has been suggested to favour settlement and spread of invasive alien species in urbanised areas which, consequently, might respond differently than ecologically similar native species to stressors posed by urbanisation. The activation of the hypothalamic-pituitary-adrenal (HPA) axis and the subsequent release of glucocorticoids (GCs) has been suggested to mediate responses to anthropogenic disturbance in vertebrates. Furthermore, intraspecific competition, in conjunction with stressors related to urbanisation, might affect invasive and native species physiological stress responses differently. Using a parallel pseudo-experimental study system we measured faecal glucocorticoid metabolite (FGM) concentrations of the native Eurasian red squirrel and the invasive alien Eastern grey squirrel along a rural-urban gradient and in relation to conspecific density. The two species responded differently to challenges posed by the synergic effect of urbanisation and intraspecific competition. Association of FGMs and conspecific density in native red squirrels varied between rural and suburban sites, potentially depending on differential HPA axis responses. In urban sites, this relationship did not differ significantly from that in rural and suburban ones. Conversely, invasive grey squirrels' FGMs did not vary in relation to conspecific density, nor differed along the rural-urban gradient. Improving knowledge about native and competing invasive species' physiological responses to anthropogenic stressors can support conservation strategies in habitats altered by man. Our findings suggested that the invasive squirrels might be preadapted to cope with these challenges in urbanised areas, potentially increasing their success under the future global change scenario.

Public attitudes towards the management of invasive squirrel species: lessons learned from Iran

Adeleorid apicomplexan parasites of the genus Hepatozoon Miller, 1908 are broadly distributed among the rodents. Broader molecular data on Hepatozoon from Palaearctic squirrels are necessary for evaluation of diversity and origin of Hepatozoon in Eurasian red squirrel Sciurus vulgaris populations, considering ongoing invasion by Gray squirrel S. carolinensis. Our report brings a set of molecular data from a population of S. vulgaris in the Czech Republic, non-invaded by any invasive squirrel species. Cadavers of 41 Eurasian red squirrels were examined using nested PCR targeting 18S rRNA gene; 30 animals tested positive for the presence of Hepatozoon spp. DNA in at least one tissue. Phylogenetic analysis of obtained sequence types revealed relatedness to sequences of Hepatozoon sp. from S. vulgaris from Spain and the Netherlands, forming a sister clade to Hepatozoon isolates from other European rodents. The fact that all available 18S rRNA gene sequences form a monophyletic clade is interpreted as a presence of a single Hepatozoon species in S. vulgaris in continental Europe, most probably Hepatozoon sciuri. The presented molecular data on the Hepatozoon from European squirrels provides a basis for future studies on possible exchange of Hepatozoon species between Eurasian red and gray squirrels.

Successful management of an invasive species requires in depth knowledge of the invader, the invaded ecosystem, and their interactions. The complexity of the species-system interactions can be reduced and represented in ecological models for better comprehension. In this study, a spatially explicit population model was created using the RAMAS software package to simulate the past and future invasion dynamics of the eastern grey squirrel (Sciurus carolinensis) in the fragmented habitat in case study areas in Ireland. This invasive squirrel species causes economic damage by bark stripping forest crops and is associated with the decline of its native congener (S. vulgaris). Three combinations of demographic and dispersal parameters, which best matched the distribution of the species shortly after introduction, were used to simulate invasion dynamics. Future population expansion was modeled under scenarios of no control and two different management strategies: fatal culls and immunocontraceptive vaccination programmes. In the absence of control, the grey squirrel range is predicted to expand to the south and southwest of Ireland endangering internationally important habitats, vulnerable forest crops, and the native red squirrel. The model revealed that region-wide intensive and coordinated culls would have the greatest impact on grey squirrel populations. Control strategies consisting solely of immunocontraceptive vaccines, often preferred by public interest groups, are predicted to be less effective. Complete eradication of the grey squirrel from Ireland is not economically feasible and strategic evidence-based management is required to limit further range expansion. Ecological models can be used to choose between informed management strategies based on predicted outcomes.

Range expansion of Pallas's squirrel (Callosciurus erythraeus) introduced in southern France: Habitat suitability and space use

Several squirrel species are biological invaders and their establishment in an area is often marked by ecological and economic costs to native species and forest crops. The eastern grey squirrel (Sciurus carolinensis Gmelin 1788) has been intentionally introduced multiple times outside of its native range but its success in establishing and spreading has not been consistent. An intensive live-trapping programme was designed to investigate the demography and population dynamics of populations of this species on the invasion frontier in the Republic of Ireland, a region marked by the slow but steady invasion of the grey squirrel. Low densities and high breeding rates distinguished these frontier populations. These results were placed in context with other frontier and established grey squirrel populations throughout their introduced and native ranges. As expected, variations in invasion speed and impact severity between regions were reflected in population demography. The highest densities, survival rates and breeding rates were recorded in Britain where the grey squirrel invasion has been most damaging. Careful comparative demographic study of invading populations could improve management outcomes, indicate differential invasibility of invaded communities, and offer clues to enhance the design of conservation reintroduction projects.

Context Improved knowledge of changing species distributions is critically important for conservation managers in the face of increasing species invasions, habitat disturbance and climate change. Efficient monitoring of the location of advancing species invasion frontiers is especially crucial for effective species community and habitat management. Aims To compare the cost-effectiveness and efficiency of two survey methods, a citizen science survey and a traditional hair-tube survey, in their abilities to locate the current southern invasion frontier of grey squirrels (Sciurus carolinensis) in Ireland. Methods In the citizen science survey, we collected sighting reports of the grey squirrel and its native congener, the red squirrel (S. vulgaris), from the geographic region of the invasion frontier from untrained members of the public over a 2-year period. Hair-tube surveys were carried out in 14 woodlands (=30 ha) in the same geographic area to test the ability of this indirect field method to identify colonising grey squirrel populations. The costs, efficiency and cost-effectiveness of each method were compared. Key results The citizen science sighting reports resulted in the clear delineation of the southern frontier of the zone invaded by the grey squirrel. The hair-tube survey ascertained the presence of grey squirrels in 4 of 14 sites, but did not detect this species close to the invasion frontier defined by the citizen science survey. Even though the total cost of the citizen science survey was higher, it was more cost-effective and efficient on a per detection basis for the purposes of detecting the presence of grey and red squirrels. Conclusions The citizen science survey detected invasive squirrels in sites where the hair-tube survey did not. As such, the citizen science survey provided a more comprehensive snapshot of the location of the grey squirrel invasion frontier more efficiently and cost-effectively than did traditional field techniques. Implications In the face of increasing ecological and economic costs of biological invasions, we recommend straightforward citizen science surveys, over indirect field surveys, to managers and researchers seeking to efficiently track progressing invasions of readily observable animals cost-effectively.

Effects of the invasive Barbary ground squirrel (Atlantoxerus getulus) on seed dispersal systems of insular xeric environments

This contribution aimed to predict the invasive Barbary ground squirrel (Atlantoxerus getulus) potentiality for invading the Canary Islands and western Mediterranean region, by determining firstly the climatic suitable areas in its native range and secondly, using presence data in the invaded range. Nineteen environmental variables submitted to a Principal Components Analysis selected those variables with higher factor loadings, which represent the main environmental conditions of the Northern African region (temperature in the coldest quarter, seasonal temperature, precipitation in the coldest quarter, temperature in the wettest quarter). After selecting hundred times more pseudo-absence points than presence observations (n = 6600 at a 0.083° resolution), Generalized Additive Models and Single-hidden-layer Neural Networks fitted in R were used to calibrate the model. Model results were extrapolated for the Canary Islands and the western Mediterranean region. In order to select between the two techniques, we calculated three accuracy measures (specificity, sensitivity and AUC) after using a Jack-knifing procedure and models were repeated ten times. The GAM model was less accurate than the NN model. Suitable areas did not have mean temperatures in the coldest quarter lower than −5°C and precipitation in the coldest quarter higher than 300 mm, respectively. We predicted favorable climatic areas across almost all the Maghreb, the European western Mediterranean region and in all the Canary Islands. Nevertheless, the seven islands differed significantly in the mean favorability scores, with El Hierro, Lanzarote and Gran Canaria being the most suitable. Same methodological analysis was applied to predict A. getulus distribution in other Canarian islands based on presence data from the invaded Fuerteventura. In this case, only Lanzarote and Gran Canaria appeared to be climatically suitable for the species. Our predictive model is an applicable tool to establish the invasive potential of A. getulus and to prioritize management strategies, within and outside the Canarian archipelago, to impede the expansion of this invasive squirrel out of Fuerteventura Island.