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The fast-growing expansion of urban areas pose severe pressures on wildlife. However, some generalist native mammals thrive in urbanized landscapes, while invasive alien species (IAS) are often more abundant in cities than in rural habitats. Variation in phenotypes—such as differences in personality traits—can influence the probability to colonize anthropized areas, especially in the case of IAS where certain traits are related to invasion success. Here, we investigated the expression of activity, exploration, and social tendency in the invasive alien Eastern Gray Squirrel (Sciurus carolinensis) in replicated study sites along a rural–urban gradient in Northern Italy. Personality traits expression was estimated using an open field test (OFT) followed by a mirror image stimulation (MIS) test. We found that squirrels were more active in urban than in suburban and rural sites, and behaved more sociable in urban than in suburban sites. Conversely, exploration did not differ along the gradient. Results also reveal the presence of a behavioral syndrome: activity (OFT), social tendency, and activity–exploration (MIS). We suggest that variation in activity level and social behavior in urban habitats could favor some species to respond positively to urbanization. This study sheds light on the underexplored personality–urbanization relationship in IAS, helping to understand the complex process of invasion. [ABSTRACT FROM AUTHOR]

Short-term elevation of glucocorticoids (GCs) is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors (stressors). However, when exposure to stressors occurs repeatedly or over a prolonged period of time, animals may experience chronic elevation of GCs, which reduces the immune response efficiency and can lead to higher intensity of parasitic infection. Here, we used invasive gray squirrels Sciurus carolinensis introduced in Northern Italy and their 2 most prevalent gastrointestinal parasites, the nematode Strongyloides robustus and coccidia of the genus Eimeria , as a model to investigate relationships among macroparasite infection and concentrations of fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs. Our results revealed an association of FGMs with infection by St. robustus , but not with coccidia. Individuals with higher FGMs appear to be responsible for the greatest St. robustus egg shedding within gray squirrel populations, thus possibly acting as superspreaders. However, FGMs were negatively associated with adult St. robustus , suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs, but is only affected by it through immune-mediated effects on its fecundity. Finally, the relationship between St. robustus (both eggs and adult parasites) and FGMs was not linear, suggesting that only high levels of physiological stress influence parasite infection. Our findings highlight that the direction and magnitude of the stress–infection relationship may depend not only on the specific host–parasite system, but also on the different life stages of the same parasite. [ABSTRACT FROM AUTHOR]

Understanding the effects of invasive alien species (IAS) on native host–parasite relationships is of importance for enhancing ecological theory and IAS management. When IAS and their parasite(s) invade a guild, the effects of interspecific resource competition and/or parasite‐mediated competition can alter existing native host–parasite relationships and the dependent biological traits such as native species' behaviour.We used a natural experiment of populations of native red squirrels Sciurus vulgaris that were colonized by the alien grey squirrel Sciurus carolinensis, comparing repeated measurements of red squirrel parasite infection and personality with those taken in sites where only the native species occurred.We explored two alternative hypotheses: (a) individual differences in personality traits (activity and/or sociability) of native red squirrel positively affect the probability of macroparasite spillover and thus the likelihood to acquire the alien's parasitic helminth Strongyloides robustus; (b) the combined effects of grey squirrel presence and parasite infection result in a reduction of costly personality traits (activity and/or exploration).Using data from 323 arena tests across three experimental (native species and IAS) and three control sites (only native species), we found negative correlations between native species' activity and infection with S. robustus in the sites invaded by the alien species. Activity was also negatively correlated with infection by its native helminth Trypanoxyuris sciuri but only when grey squirrels were present, while in the red‐only sites there was no relationship of T. sciuri infection with any of the personality traits. Moreover, individuals that acquired S. robustus during the study reduced their activity after infection, while this was not the case for animals that remained uninfected.Our results show that parasite‐mediated competition is costly, reducing activity in individuals of the native species, and altering the native host–native parasite relationships. [ABSTRACT FROM AUTHOR]

Glucocorticoids (GCs) are involved in the regulation of an animal's energetic state. Under stressful situations, they are part of the neuroendocrine response to cope with environmental challenges. Animals react to aversive stimuli also through behavioral responses, defined as coping styles. Both in captive and wild populations, individuals differ in their behavior along a proactive–reactive continuum. Proactive animals exhibit a bold, active-explorative and social personality, whereas reactive ones are shy, less active-explorative and less social. Here, we test the hypothesis that personality traits and physiological responses to stressors covary, with more proactive individuals having a less pronounced GC stress response. In wild populations of invasive gray squirrels Sciurus carolinensis , we measured fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs, and 3 personality traits (activity, sociability, and exploration) derived from open field test (OFT) and mirror image stimulation (MIS) test. Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males. Personality varied with body mass and population density. Squirrels expressed more activity-exploration at higher than at lower density and heavier squirrels had higher scores for activity-exploration than animals that weighed less. Variation in FGM concentrations was not correlated with the expression of the 3 personality traits. Hence, our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations, where animals experience varying environmental conditions, the GC endocrine response and the expression of personality are uncorrelated traits among individuals. [ABSTRACT FROM AUTHOR]

Introduction of alien species into new areas can have detrimental effects on native ecosystems and impact the native species. The present study aims to identify coccidia infecting native and introduced squirrels in Italy, to gain insight into possible transmission patterns and role of monoxenous coccidia in mediating the competition between alien and native hosts. We collected 540 faecal samples of native red squirrels, Sciurus vulgaris , invasive alien grey squirrels, S. carolinensis , and introduced Pallas's squirrels, Callosciurus erythraeus . Total prevalence of Eimeria spp. was 95.6% in S. vulgaris , 95.7% in S. carolinensis and only 4.1% in C. erythraeus . Morphological examination revealed 3 Eimeria morphotypes. Phylogenetic analyses of Eimeria DNA based on 18S, ITS, cox I markers displayed fairly distinct monophyletic clades in the microscopically indistinguishable E2 morphotype, proving indisputable distinction between the isolates from red and grey squirrels. Grey squirrels successfully introduced E. lancasterensis from their native range, but this species does not spill over to native red squirrels. Similarly, there is no evidence for the transmission of E. sciurorum from red to grey squirrels. The possible transmission and the potential role of monoxenous coccidia in mediating the competition between native and invasive squirrels in Italy were not confirmed. [ABSTRACT FROM AUTHOR]