Ecological traits such as behaviour, physiology and morphology mediate an organism's interaction with its environment, and understanding their joint contribution to reproductive fitness is essential for predicting biological responses to global change. We addressed how urbanization shapes trait-function relationships across natural, suburban or urban areas to advance the functional and mechanistic understanding of ecological processes in changing environments. We investigated how interactions among ecological (urbanization, season) and phenotypic (body mass, personality) traits influence reproductive fitness in female Eurasian red squirrels (Sciurus vulgaris) across a natural-urban gradient in Italy. Using 204 records of 72 female squirrels across 12 sites, we found that body mass, mediating the effect of the spring season, was the main factor affecting the probability to reproduce in female red squirrels. Further, our results suggest a direct effect of urbanization on squirrels' reproduction: The probability of reproducing was higher in natural habitats than in the urban and suburban sites. Female red squirrels in natural sites also engaged more frequently in explorative behaviours than their conspecifics in urban sites, but this did not translate into either direct or significant indirect effects of personality on reproductive success. Finally, body mass of females tended to be slightly higher in urban and suburban than in natural habitats, but this did not result in a higher reproductive rate. While body mass emerged as the dominant predictor of reproduction, its functional role was context-dependent, shaped by seasonality, environmental resource distribution and potentially by altered energetic dynamics in urban environments. In contrast, personality traits varied with habitat but did not mediate reproduction, highlighting how trait expression does not equate to ecological function unless matched with the appropriate environmental context. This work underscores the importance of integrating multiple levels of biological organization, behaviour, body mass, life history and environmental context to understand how global change alters ecological and evolutionary trajectories. As urbanization continues to transform natural habitats, studies that disentangle direct and indirect pathways from phenotype to fitness will be essential not only for predicting wildlife persistence but also for linking individual-level processes to population and community dynamics.Read the free for this article on the Journal blog.

Anthropogenic disturbances, such as habitat fragmentation and pollutants, can act as stressors limiting wildlife persistence and adaptation, and mammals are particularly vulnerable to airborne pollutants and pesticides that disrupt glucocorticoid (GC) signalling. The synergic impact of pollution and chronic GCs exposure may cause genomic damage reducing genetic diversity and adaptative potential. Using the invasive Eastern grey squirrel (Sciurus carolinensis), we assessed genomic damage, micronuclei (MNi) and nuclear buds (NBUDs), along a gradient from urban centres to agricultural areas, with increasing air pollution, and related this to faecal glucocorticoid metabolites (FGMs). Genomic damage varied significantly among study areas, with lower MNi and NBUDs in a hilly urban area. In the central urban area, MNi frequency was lower than in the agricultural areas. Conversely, in the peripheral urban area, near major roadways, MNi and NBUDs were comparable to those in agricultural areas, suggesting a similar exposure to genotoxic stressors, likely originating from different sources. A curvilinear relationship was observed between air pollutants and genomic damage: MNi and NBUDs levels remained stable at low pollution levels and decreased as pollution increased. Sex, body condition and age had no significant effects. FGMs did not significantly influence MNi or NBUDs across urban and agricultural areas. Our results show that squirrels in a hilly urban area had less genomic damage than those in high-traffic peripheral or agricultural areas. These findings highlight the importance of urban planning that incorporates refuges capable of mitigating environmental stressors and strategies that limit genotoxic effects in urban and agricultural areas.

Urbanization is a major form of land use change, entailing the creation of novel environments where unique dynamics and selective pressures can shape wildlife phenotypes, with behaviour being especially affected. These environmental changes can shape animal personality, resulting in differences between populations along an urbanization gradient. To fill the knowledge gap about the role of personality traits in population persistence in cities, we investigated whether the mean expression of activity, exploration and social tendency, as well as their among-individual variance and within-individual variance, changed between urban, suburban and rural populations. We conducted 490 repeated arena tests on 169 Eurasian red squirrels, Sciurus vulgaris, to estimate personality trait expression through an open field test followed by a mirror image stimulation test. We found no differences in the mean expression of activity, exploration and social tendency between populations living at different degrees of urbanization, even if exploration decreased at higher population densities. However, we observed minor changes in the variance components of all the personality traits. Rural populations tended to be more heterogeneous (higher among-individual variance) in the expression of exploration and social tendency, and individuals in suburban populations were more flexible (greater within-individual variance) in activity than rural conspecifics. Our findings provide insights into how the variance components change along an urbanization gradient, a topic still largely unexplored despite its implications for ecology, evolution and management of populations, as it could support population response to the highly dynamic urban environments. (c) 2026 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Mast seeding, the variable and intermittent production of seeds, has cascading effects on ecosystem functioning. This study explores its influence on the brown bear populations in the Italian Alps, focusing on beechnuts (Fagus sylvatica L.), the primary food source for bears in the region. Using historical data and field sampling, we estimated and mapped the annual seed biomass from 2007 to 2021 for the province of Trento. The energy content of beechnuts was assessed through high heating values, providing the caloric resources available. Data on beechnuts production, records of damages and GPS data from 16 Eurasian brown bears were integrated to perform a temporal and spatial analysis at home range and at landscape level. Standardised damages to beehives and livestock decreased during mast years, suggesting that bears met their trophic needs through natural food sources. In fact, bears used more agricultural areas and less beech forest during years of beech crop failure. At landscape level, agriculture and pasture areas close to beech forests and distant from cities showed a higher risk of damage, providing a tool to anticipate management actions. This work provides insights on the ecological dynamics and conservation implications of brown bears in the study area by mapping the spatial and temporal aspects of mast seeding and bear-related damages.

Climate change is predicted to drive geographical range shifts that will result in changes in species diversity and functional composition and have potential repercussions for ecosystem functioning. However, the effect of these changes on species composition and functional diversity (FD) remains unclear, especially for mammals, specifically bats. We used species distribution models and a comprehensive ecological and morphometrical trait database to estimate how projected future climate and land-use changes could influence the distribution, composition, and FD of the European bat community. Future bat assemblages were predicted to undergo substantial shifts in geographic range and trait structure. Range suitability decreased substantially in southern Europe and increased in northern latitudes. Our findings highlight the potential for climate change to drive shifts in bat FD, which has implications for ecosystem function and resilience at a continental scale. It is important to incorporate FD in conservation strategies. These efforts should target species with key functional traits predicted to be lost and areas expected to experience losses in FD. Conservation strategies should include habitat and roost protection, enhancing landscape connectivity, and international monitoring to preserve bat populations and their ecosystem services.

According to Bergmann's and Allen's rules, climate change may drive morphological shifts in species, affecting body size and appendage length. These rules predict that species in colder climates tend to be larger and have shorter appendages to improve thermoregulation. Bats are thought to be sensitive to climate and are therefore expected to respond to climatic changes across space and time. We conducted a phylogenetic meta-analysis on > 27 000 forearm length (FAL) and body mass (BM) measurements from 20 sedentary European bat species to examine body size patterns. We assessed the relationships between body size and environmental variables (winter and summer temperatures, and summer precipitation) across geographic locations, and also analysed temporal trends in body size. We found sex-specific morphological shifts in the body size of European bats in response to temperature and precipitation patterns across space, but no clear temporal changes due to high interspecific variability. Across Europe, male FAL decreased with increasing summer and winter temperatures, and BM increased with greater precipitation. In contrast, both FAL and BM of female bats increased with summer precipitation and decreased with winter temperatures. Our data can confirm Bergmann's rule for both males and females, while females' BM variations are also related to summer precipitation, suggesting a potential link to resource availability. Allen's rule is confirmed only in males in relation to summer temperature, while in females FAL and BM decrease proportionally with increasing temperature, maintaining a constant allometric relationship incompatible with Allen's rule. This study provides new insights into sex and species-dependent morphological changes in bat body size in response to temperature and precipitation patterns. It highlights how body size variation reflects adaptations to temperature and precipitation patterns, thus providing insights into potential species-level morphological responses to climate change across Europe.

Ecological theory predicts that coexisting species should exhibit realized niche differentiation to minimize competition. However, little is known about patterns of niche differentiation when ‘newcomer’ species spontaneously colonize a new region, leading to novel sympatric conditions. Over the past 15 years, three closely related and ecologically similar falcon species (Common Kestrel Falco tinnunculus , Lesser Kestrel Falco naumanni and Red‐footed Falcon Falco vespertinus ) have expanded their ranges as the result of land‐use and climate changes in the intensively cultivated agroecosystems of the Po Plain (Northern Italy). This is a unique condition in the European range of these species and provides an excellent opportunity to investigate patterns of foraging and trophic niche partitioning during the initial phases of sympatry. We assessed species‐specific patterns of foraging habitat selection and interspecific differences in diet composition. Our findings showed that falcons selected largely overlapping foraging habitats, yet exhibited significant differentiation among species regarding vegetation height, structure and crop types. Overall, diet composition was similar, though some degree of trophic niche differentiation was detected. In line with the niche partitioning hypothesis, the three species slightly partitioned their foraging and trophic niches, probably playing a key role in making syntopic coexistence possible. Our study provides insights into the mechanisms of niche partitioning when ‘newcomers’ appear in a guild, a process that is likely to become increasingly relevant because of the rapid and often uneven distributional shifts caused by global change.

In resource-limited producer-consumer systems, environmental variables such as weather, habitat structure, and resource availability interact to shape consumer dynamics. We conducted a comparative analysis on territorial Fremont's squirrel (Tamiasciurus fremonti) in Arizona mountain ranges (three sites) and non-territorial Eurasian red squirrel (Sciurus vulgaris) in the Italian Alps (five sites) to investigate the effects of forest composition, pulsed seed resources, weather, and climate change-induced forest disturbances on population density. We also explored potential synchrony in spatial and temporal dynamics between squirrel populations, driven by endogenous and exogenous processes. Our long-term, multi-site datasets revealed shared density-dependent patterns: annual oscillations in Fremont's squirrel populations and biennial oscillations in Eurasian red squirrels. Both species exhibited strong bottom-up responses, with higher densities following tree-seed production and warmer spring temperatures. Despite the absence of synchronized trends in population density across time or regions, we found consistent responses to resource availability and abiotic conditions, demonstrating shared mechanisms across ecologically distinct systems. By integrating field data, remotely sensed forest disturbances, and multi-factorial modeling, this study highlights the role of climate, forest dynamics, and climate change-induced forest disturbance in shaping population processes in pulsed resource systems. Our findings underscore the importance of understanding producer-consumer interactions under climate change, providing globally relevant insights into the interplay of abiotic drivers, species-specific behaviours, and ecological resilience. These results contribute to advancing strategies for wildlife conservation and forest management in the face of ongoing environmental change.

The current, rapid urbanisation process impacts global biodiversity and can be a driver for phenotypic changes in mammals that persist in cities. Animals display different response strategies in urban environments compared to natural areas, but patterns may differ among species. To better comprehend this process, we focused on a limited number of species that are present in many urban green spaces around the globe.The aim of this systematic review is to investigate which response strategies chipmunks, arboreal and flying squirrels use to cope with urban environments, exploring whether there are general response patterns, and to reveal potential adaptations to life in urban areas. We included studies that compared trait differences among conspecifics living in different areas along an urbanisation gradient (rural-urban) and studies comparing individuals or populations between urban areas with different environmental characteristics.The effects of urbanisation on chipmunks, arboreal and flying squirrels, at the individual and at the population levels, were identified in nine topics. Included articles explored at least one of these topics and their key findings were described.Effects of urbanisation are evident in all considered topics. However, we found contrasting patterns between species or even among individuals of the same species studied in different geographical areas. Overall, we reported two knowledge gaps: some phenotypic traits were considered in few studies, and many species, especially those living in the Global South, where urban growth rate is higher, have not been studied.This systematic review suggests that urbanisation can be an important driver for adaptation in small mammals, underlining the complexity and differentiation of response patterns. Since target species have important ecological and social roles, additional comparative studies, increasing our understanding of processes that determine their presence in cities, are essential for urban green planning which aims to conserve biodiversity. image

Abstract Studying nocturnal bird migration is challenging because direct visual observations are difficult during darkness. Radar has been the means of choice to study nocturnal bird migration for several decades, but provides limited taxonomic information. Here, to ascertain the feasibility of enhancing the taxonomic resolution of radar data, we combined acoustic data with vertical‐looking radar measurements to quantify thrush (Family: Turdidae) migration. Acoustic recordings, collected in Helsinki between August and October of 2021–2022, were used to identify likely nights of high and low thrush migration. Then, we built a random forest classifier that used recorded radar signals from those nights to separate all migrating passerines across the autumn migration season into thrushes and non‐thrushes. The classifier had a high overall accuracy (≈0.82), with wingbeat frequency and bird size being key for separation. The overall estimated thrush autumn migration phenology was in line with known migratory patterns and strongly correlated (Pearson correlation coefficient ≈0.65) with the phenology of the acoustic data. These results confirm how the joint application of acoustic and vertical‐looking radar data can, under certain migratory conditions and locations, be used to quantify ‘family‐level’ bird migration.

Many insects depend on high-altitude, migratory movements during part of their life cycle. The daily timing of these migratory movements is not random, e.g. many insect species show peak migratory flight activity at dawn, noon or dusk. These insects provide essential ecosystem services such as pollination but also contribute to crop damage. Quantifying the diel timing of their migratory flight and its geographical and seasonal variation, are hence key towards effective conservation and pest management. Vertical-looking radars provide continuous and automated measurements of insect migration, but large-scale application has not been possible because of limited availability of suitable devices. Here, we quantify patterns in diel flight periodicity of migratory insects between 50 and 500 m above ground level during March-October 2021 using a network of 17 vertical-looking radars across Europe. Independent of the overall daily migratory movements and location, peak migratory movements occur around noon, during crepuscular evening and occasionally the morning. Relative daily proportions of insect migration intensity and traffic during the diel phases of crepuscular-morning, day, crepuscular-evening and night remain largely equal throughout May-September and across Europe. These findings highlight, extend, and generalize previous regional-scale findings on diel migratory insect movement patterns to the whole of temperate Europe. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Radar technology has emerged as a vital tool for studying bird migration, particularly due to the predominantly nocturnal and high-altitude nature of the phenomenon. Avian Vertical-looking Radars (AVLRs) offer detailed insights into migratory patterns, including flight behavior and altitude. Bird ringing, on the other hand, although useful for describing migratory phenomena at the species level, has limitations when used to quantify migration itself. In this study, radar data from the Bolle di Magadino wetland area in Switzerland were analyzed to describe and quantify the spring migration of passerine birds during 2021 and 2022. Migration activity was significantly higher during the night, with migratory peaks reached at night in mid-April in 2021 and in the second half of April in 2022. Passerine flight altitudes remained consistently higher at night than during the day. Also, the analysis of wing-flapping frequency (WFF) revealed both seasonal and diel variations, with WFF slowly increasing at night as the season went on, but remaining higher and stable during the day. A GLM did not reveal significant effects of rain and wind intensity on migratory traffic, but it did show a positive and strongly significant relationship with the number of ringed birds (beta = 0.55, p < 0.001). This confirms for the first time a positive proportionality between ground-based monitoring and radar-based monitoring in a stoHpover area, where theoretically we would have expected a weaker relationship between the number of ringed birds and MTR, compared to places where the migratory flow is uninterrupted and the birds have no means to stop.

The unequal distribution of the costs and benefits of living with wildlife is one of the causes of human-carnivore conflicts. The existence of large carnivores is valued globally, but the costs of damages and management impacts human residents. The Apennine brown bear is endemic of central Italy and, besides its ecological value, it can attract tourists in search of nature and wilderness. The Advertising Value Equivalent of the bears' appearances in the national newspaper and on television from 2015 to 2020 was used to calculate the economic value of this flagship species as a destination image. The 11 million Euro of Advertising Value Equivalent estimated largely exceeded the amount of reimbursements sustained by the Park to manage this carnivore in the same period. This evaluation of cultural value could be used to highlight the economic benefits provided by the bear and contribute to the discussions with managers and stakeholders.

Although many studies highlighted the potential of COVID-19 to reshape existing models of wildlife management, empirical research on this topic has been scarce, particularly in Europe. We investigated the potential of COVID-19 pandemic to accelerate the ongoing decline in an aging population of recreational hunters in Italy. Namely, we modelled spatiotemporal trends between 2011 and 2021 in the number of recreational hunters in 50 Italian provinces with a varying incidence of COVID-19, and temporally delayed waves of infection. Compared to projections from 2011-2019 data, we detected a lower number of hunters who enrolled for the hunting season, both in 2020 (14 provinces) and in 2021 (15 provinces). The provinces with the highest incidence of COVID-19 in the Lombardy and Emilia-Romagna regions were also those experiencing the most marked decrease in hunting participation. Our findings revealed that a wildlife management system based on recreational hunting can be rapidly destabilized by epidemics and their associated public health measures, particularly when the average age of hunters is high, like in Italy. Considered the high incidence attained by COVID-19 in many European countries, where hunters are pivotal for the management of large ungulates and where they were already declining before the pandemic, our findings call for further large-scale research about the impact of COVID-19 on hunting participation.

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.

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. To shed light on invasive alien species success in urban areas, we studied the personality-urbanization relationship in the Eastern Gray Squirrel in Italy. In cities, squirrels differed in activity and sociability levels, which may favor their response to urbanization.

Co-occurrence of ecologically similar species can lead to direct agonistic interactions, including kleptoparasitism, where one individual consumes trophic resources acquired by another. We documented facultative kleptoparasitism in two similarly-sized raptors, the lesser kestrel (Falco naumanni) and the red-footed falcon (Falco vespertinus). These two species currently co-occur in Northern Italy due to recent range shifts influenced by climate and land-use changes. Multi-year focal observations revealed that single or multiple red-footed falcons were associated with 72

Animal size, a trait sensitive to spatial and temporal variables, is a key element in ecological and evolutionary dynamics. In the context of climate change, there is evidence that some bat species are increasing their body size via phenotypic responses to higher temperatures at maternity roosts. To test the generality of this response, we conducted a >20-year study examining body size changes in 15 bat species in Italy, analysing data from 4393 individual bats captured since 1995. In addition to examining the temporal effect, we considered the potential influence of sexual dimorphism and, where relevant, included latitude and altitude as potential drivers of body size change. Contrary to initial predictions of a widespread increase in size, our findings challenge this assumption, revealing a nuanced interplay of factors contributing to the complexity of bat body size dynamics. Specifically, only three species (Myotis daubentonii, Nyctalus leisleri, and Pipistrellus pygmaeus) out of the 15 exhibited a discernible increase in body size over the studied period, prompting a reassessment of bats as reliable indicators of climate change based on alterations in body size. Our investigation into influencing factors highlighted the significance of temperature-related variables, with latitude and altitude emerging as crucial drivers. In some cases, this mirrored patterns consistent with Bergmann's rule, revealing larger bats recorded at progressively higher latitudes (Plecotus auritus, Myotis mystacinus, and Miniopterus schreibersii) or altitudes (Pipistrellus kuhlii). We also observed a clear sexual dimorphism effect in most species, with females consistently larger than males. The observed increase in size over time in three species suggests the occurrence of phenotypic plasticity, raising questions about potential long-term selective pressures on larger individuals. The unresolved question of whether temperature-related changes in body size reflect microevolutionary processes or phenotypic plastic responses adds further complexity to our understanding of body size patterns in bats over time and space.

In an ever more urbanized world, animals have to cope with different challenging conditions that may shape the individual’s phenotype in the urban environment. Since body mass and body size are found to be related to fitness in many species, investigating the variation in these two morphological traits along the rural-urban gradient, is a first step to understand how animals adapt to urbanization. Here we studied two tree squirrels, the native Eurasian red squirrel ( Sciurus vulgaris ) and the invasive Eastern grey squirrel ( Sciurus carolinensis ), using a pseudo-experimental design with replicated study sites (2 rural, 2 suburban and 2 urban sites for each species). We investigated whether squirrels differed in body size and body mass along the urbanization gradient and whether the invasive alien squirrels had more marked differences along the gradient, showing a higher adaptation capacity. We did not find variation in body size in red squirrels along the gradient, but invasive grey squirrels were slightly larger in urban than in other area-types. In both species, animals of either sex were heavier in the urban than in the rural sites, while the difference between urban and suburban areas depends on species and sex. Hence, morphologically both native and invasive species showed similar changes, with higher body mass in urban habitat, which could result in higher fitness, since body mass in squirrels species is positively related to reproductive success.

The study of the relationship between animal stress and personality for free-ranging animals is limited and provides contrasting results. The perception of stressors by an individual may vary due to its personality, and certain personality traits may help individuals to better cope with them. Using non-invasive infrared thermography (IRT), we investigated the link between physiological and behavioral components expressed during an acute stress event by free-ranging Fremont's squirrels (Tamiasciurus fremonti). We expected that, during the acute stress event of being approached by the researcher, individuals that showed a fast pace-of-life syndrome (bolder, more active, and less social/more aggressive) based on an arena test would exhibit stronger sympathetic-adrenal-medullary system reactivity showing a more intense stress-induced hyperthermia (high core body temperature and low peripheral temperature) than individuals with a slow pace of life (shy, less active, and more social). We successfully employed IRT technology to images of Fremont's squirrels with identification of the individuals' body parts (eye, nose, ear, hind foot). However, we found no support for our hypothesis. Squirrels' body surface temperatures told us more about a squirrel's external environment and less about the thermal state of the body in that environment following a stressful event. Further studies need to assess how to make IRT effective and efficient in the field and improve its performance in studying the relationships between physiology and personality in wildlife.