Stress and the city: urbanization and its effects on the stress physiology in European blackbirds

Blood transcriptome analysis of common kestrel nestlings living in urban and non-urban environments

Urbanisation is one of the main anthropogenic forms of land cover affecting an ever-increasing number of wild animals and their habitats. Physiological plasticity represents an important process through which animals can adjust to the novel conditions of anthropogenic environments. Relying on the analysis of gene expression, it is possible to identify the molecular responses to the habitat conditions and infer possible environmental factors that affect the organismal physiology. We have quantified for the first time the blood transcriptome of common kestrel (Falco tinnunculus) nestlings living in urban sites and compared it to the transcriptome of kestrel nestlings inhabiting rural and natural environments. We found mild differences in the expression of genes among sites, indicating adaptability or acclimation of the birds to the urban habitat. We identified 58 differentially expressed genes between urban and natural kestrels, and 12 differentially expressed genes between urban and rural kestrels. The most striking differences among sites involved inflammatory-immunological, metabolic, apoptosis, DNA repair and development genes. In particular, we found that (i) urban kestrel nestlings had higher expression of genes linked to inflammation, repair of DNA damage, or apoptosis than natural kestrel nestlings, and (ii) natural and rural kestrel nestlings had higher expression of genes linked to the development and activation of immune cells, type I interferon response, or major histocompatibility complex than urban kestrel nestlings. Finally, the KEGG enrichment analysis identified the insulin signalling as the main pathway that differed between natural and urban kestrel nestlings. This is one of a limited number of studies on vertebrates that revealed habitat-associated differences in the transcriptome. It paves the way for further in-depth studies on the links between physiological variation and habitat structure at different spatial and temporal scales.

Seasonal Hair Glucocorticoid Fluctuations in Wild Mice (Phyllotis darwini) within a Semi-Arid Landscape in North-Central Chile

Mammals in drylands face environmental challenges exacerbated by climate change. Currently, human activity significantly impacts these environments, and its effects on the energy demands experienced by individuals have not yet been determined. Energy demand in organisms is managed through elevations in glucocorticoid levels, which also vary with developmental and health states. Here, we assessed how anthropization, individual characteristics, and seasonality influence hair glucocorticoid concentration in the Darwin's leaf-eared mouse (Phyllotis darwini) inhabiting two areas with contrasting anthropogenic intervention in a semi-arid ecosystem of northern Chile. Hair samples were collected (n = 199) to quantify hair corticosterone concentration (HCC) using enzyme immunoassays; additionally, sex, body condition, and ectoparasite load were recorded. There were no differences in HCC between anthropized areas and areas protected from human disturbance; however, higher concentrations were recorded in females, and seasonal fluctuations were experienced by males. The results indicate that animals inhabiting semi-arid ecosystems are differentially stressed depending on their sex. Additionally, sex and season have a greater impact on corticosterone concentration than anthropogenic perturbation, possibly including temporal factors, precipitation, and primary production. The influence of sex and seasonality on HCC in P. darwini make it necessary to include these variables in future stress assessments of this species.

Diversity and Distribution of Avifauna in the Northeast of Addis Ababa, Central Ethiopia

Exploring avian species diversity and distribution patterns is vigorous for conservation efforts in biodiversity-rich countries such as Ethiopia. Compared to other species, birds are relatively well-known and easily observed, making them great markers of productivity or biodiversity. Although bird species are found all across the world, their survival and range have been negatively impacted by habitat loss, fragmentation, and destruction. Thus, the goal of this study is to provide baseline data on avifaunal diversity in the Northeast of Addis Ababa, including species richness, distribution, and relative abundance in various habitats conducted from January 2023 to September 2023 using a stratified sampling design into three habitat types: settlement, farmland, and abattoir. A fixed-width line transect sampling method was used at the farmland and settlement, and a point transect was employed at the abattoir site to collect the bird data. The data were compared using Mann-Whitney and Kruskal-Wallis statistical tests in both seasons and habitat types. A total of 42 bird species belonging to twenty-three families, and nine orders were recorded during the study period. Of these, blue-winged goose and wattled ibis are endemic to Ethiopia. Hooded vultures and White-backed vultures are critically endangered species. The mean abundance of bird species significantly varied in the three habitat types (χ2 = 13.6, df = 2, p=0.001). The abundance of bird species was nonsignificant difference between wet and dry seasons (U = -0.874, p=0.381). The highest diversity (H' = 2.74) was recorded at settlement, and the lowest diversity index (H' = 1.09) was recorded at the abattoir in the dry season. In the wet season, the highest diversity (H' = 2.66) was recorded in the farmland, and the lowest (H' = 1.08) was recorded at the abattoir. The highest evenness (J = 0.94 and J = 0.93) was recorded on the farmland in the wet and dry seasons, respectively. In the study area, urbanization is extremely impacting the environment and altering ecosystem services upon which human civilization depends. Most of the avian species observed in the study area are capable and tolerant of human-induced habitats in the city. Therefore, city planners must consider conserving urban bird species' habitats and feeding sites.

A blood-based multi-biomarker approach reveals different physiological responses of common kestrels to contrasting environments

The increase of urbanization and agricultural activities is causing a dramatic reduction of natural environments. As a consequence, animals need to physiologically adjust to these novel environments, in order to exploit them for foraging and breeding. The aim of this work was to compare the physiological status among nestling common kestrels (Falco tinnunculus) that were raised in nest-boxes located in more natural, rural, or urban areas in a landscape with a mosaic of land uses around Rome in Central Italy. A blood-based multi-biomarker approach was applied to evaluate physiological responses at multiple levels, including antioxidant concentrations, immunological functions, genotoxicity, and neurotoxicity. We found lower concentrations of glutathione and GSH:GSSG ratio values and higher proportions of monocytes in urban birds compared to the other areas. We also found higher DNA damage in rural compared to urban and natural krestels and inhibition of butyrylcholinesterase activity in urban and natural birds compared to rural area. Finally, we found similar values among study areas for respiratory burst, complement system, bactericidal capacity, and plasma non-enzymatic antioxidant capacity. These results suggest that (i) city life does not necessarily cause physiological alterations in kestrels compared to life in other habitats, and (ii) environmental pressures are likely to differ in typology and intensity across habitats requiring specific responses that a multi-biomarker approach can help to detect. Further studies are needed to assess which factors are responsible for the physiological differences among city, rural, and natural birds, and whether these differences are consistent across time and space.

Noise and light pollution elicit endocrine responses in urban but not forest frogs

Urban areas are characterised by the presence of sensory pollutants, such as anthropogenic noise and artificial light at night (ALAN). Animals can quickly adapt to novel environmental conditions by adjusting their behaviour, which is proximately regulated by endocrine systems. While endocrine responses to sensory pollution have been widely reported, this has not often been linked to changes in behaviour, hampering the understanding of adaptiveness of endocrine responses. Our aim was, therefore, to investigate the effects of urbanisation, specifically urban noise and light pollution, on hormone levels in male urban and forest túngara frogs (Engystomops pustulosus), a species with reported population divergence in behaviour in response to urbanisation. We quantified testosterone and corticosterone release rates in the field and in the lab before and after exposure to urban noise and/or light. We show that urban and forest frogs differ in their endocrine phenotypes under field as well as lab conditions. Moreover, in urban frogs exposure to urban noise and light led, respectively, to an increase in testosterone and decrease in corticosterone, whereas in forest frogs sensory pollutants did not elicit any endocrine response. Our results show that urbanisation, specifically noise and light pollution, can modulate hormone levels in urban and forest populations differentially. The observed endocrine responses are consistent with the observed behavioural changes in urban frogs, providing a proximate explanation for the presumably adaptive behavioural changes in response to urbanisation.

Mitigating Human Impacts on Wild Animal Welfare

Human activities negatively impact the welfare of wild vertebrates in many different contexts globally, and countless individual animals are affected. Growing concern for wild animal welfare, especially in relation to conservation, is evident. While research on wild animal welfare lags behind that focused on captive animals, minimising human-induced harm to wild animals is a key principle. This study examines examples of negative anthropogenic impacts on wild animal welfare, how these may be mitigated and what further research is required, including examples from wildlife management, biodiversity conservation, wildlife tourism and wildlife trade. Further, it discusses the relationship between animal welfare and biodiversity conservation, and synergies that may be achieved between these. Ultimately, it is discussed how the welfare of wild animals may be balanced with other priorities to ensure that welfare is afforded due consideration in interactions between people and wildlife.

Future directions in urban endocrinology - The effects of endocrine plasticity on urban tolerance

After twenty years of studies of endocrine traits in animals living in cities, the field of urban endocrinology has built a robust literature including numerous studies looking for signatures of the effects of urban living, usually in mean circulating hormone concentrations. The findings of this past research have primarily demonstrated the absence of any generalizable endocrine responses to city life. In this opinion paper, I suggest that a strong route forward would include investigations of the role of variation in endocrine plasticity in determining the degree to which organisms tolerate urban challenges (i.e., urban tolerance). Achieving this research aim will require creative experimental and comparative studies, consideration of alternative study systems, and teasing apart of sources of variation in plastic phenotypes (plasticity, sorting, and contemporary evolution). Insight into the role of endocrine plasticity in influencing urban tolerance could help us better understand and predict impacts of expanding urbanization on biodiversity across the globe.

The singing activity of the Yellowhammer (Emberiza citrinella) under traffic noise around highways

Steadily increasing human population is changing the environment in many ways. One of the most disturbing impacts is the development of anthropogenic noise pollution connected to ever-growing traffic intensity. The road network can have both positive and negative effects on biodiversity and populations. Many bird species use acoustic communication to establish and maintain their territories and for intra-pair and adult–young communication. Noise pollution can impact negatively on breeding success and biorhythm if this communication is masked by noise and the individuals must adjust their singing activity. Yellowhammer (Emberiza citrinella) is a common bird species of agricultural landscapes whose population is declining due to agricultural intensification. It is found also in habitats near highways with forest steppe-like characteristics, where it is affected by the high levels of anthropogenic noise pollution. This study aimed to determine how this species adapts to noise from highway traffic by adjusting its singing activity. The influence of locality type, immediate and long-term impact of traffic noise on the average and total length of song sequences in the birdsong, and influence on the total number of recorded song sequences during the second hour after sunrise were evaluated in this study. Our results showed that Yellowhammer’s singing activity changed in localities close to highways compared to agricultural landscape. With increasing long-term traffic intensity on highways, song duration of the Yellowhammer song was decreasing. The present traffic intensity led to later onset of dawn chorus and decreasing strophe length with increasing number of passing vehicles. Furthermore, in the agricultural landscape, Yellowhammer’s song duration increased with increasing distance from the nearest road.

Past and future: Urbanization and the avian endocrine system

Urban environments are evolutionarily novel and differ from natural environments in many respects including food and/or water availability, predation, noise, light, air quality, pathogens, biodiversity, and temperature. The success of organisms in urban environments requires physiological plasticity and adjustments that have been described extensively, including in birds residing in geographically and climatically diverse regions. These studies have revealed a few relatively consistent differences between urban and non-urban conspecifics. For example, seasonally breeding urban birds often develop their reproductive system earlier than non-urban birds, perhaps in response to more abundant trophic resources. In most instances, however, analyses of existing data indicate no general pattern distinguishing urban and non-urban birds. It is, for instance, often hypothesized that urban environments are stressful, yet the activity of the hypothalamus-pituitary-adrenal axis does not differ consistently between urban and non-urban birds. A similar conclusion is reached by comparing blood indices of metabolism. The origin of these disparities remains poorly understood, partly because many studies are correlative rather than aiming at establishing causality, which effectively limits our ability to formulate specific hypotheses regarding the impacts of urbanization on wildlife. We suggest that future research will benefit from prioritizing mechanistic approaches to identify environmental factors that shape the phenotypic responses of organisms to urbanization and the neuroendocrine and metabolic bases of these responses. Further, it will be critical to elucidate whether factors affect these responses (a) cumulatively or synergistically; and (b) differentially as a function of age, sex, reproductive status, season, and mobility within the urban environment. Research to date has used various taxa that differ greatly not only phylogenetically, but also with regard to ecological requirements, social systems, propensity to consume anthropogenic food, and behavioral responses to human presence. Researchers may instead benefit from standardizing approaches to examine a small number of representative models with wide geographic distribution and that occupy diverse urban ecosystems.

Innate immune function and antioxidant capacity of nestlings of an African raptor covary with the level of urbanisation around breeding territories

Urban areas provide breeding habitats for many species. However, animals raised in urban environments face challenges such as altered food availability and quality, pollution and pathogen assemblages. These challenges can affect physiological processes such as immune function and antioxidant defences which are important for fitness. Here, we explore how levels of urbanisation influence innate immune function, immune response to a mimicked bacterial infection and antioxidant capacity of nestling Black Sparrowhawks Accipiter melanoleucus in South Africa. We also explore the effect of timing of breeding and rainfall on physiology since both can influence the environmental condition under which nestlings are raised. Finally, because urbanisation can influence immune function indirectly, we use path analyses to explore direct and indirect associations between urbanisation, immune function and oxidative stress. We obtained measures of innate immunity (haptoglobin, lysis, agglutination, bactericidal capacity), indices of antioxidant capacity (total non-enzymatic antioxidant capacity (tAOX) and total glutathione from nestlings from 2015 to 2019. In addition, in 2018 and 2019, we mimicked a bacterial infection by injecting nestlings with lipopolysaccharide and quantified their immune response. Increased urban cover was associated with an increase in lysis and a decrease in tAOX, but not with any of the other physiological parameters. Furthermore, except for agglutination, no physiological parameters were associated with the timing of breeding. Lysis and bactericidal capacity, however, varied consistently with the annual rainfall pattern. Immune response to a mimicked a bacterial infection decreased with urban cover but not with the timing of breeding nor rainfall. Our path analyses suggested indirect associations between urban cover and some immune indices via tAOX but not via the timing of breeding. Our results show that early-life development in an urban environment is associated with variation in immune and antioxidant functions. The direct association between urbanisation and antioxidant capacity and their impact on immune function is likely an important factor mediating the impact of urbanisation on urban-dwelling animals. Future studies should explore how these results are linked to fitness and whether the responses are adaptive for urban-dwelling species.

The development of behavioral and endocrine coping styles in nestlings from urban and rural sites

Urbanization is increasing globally and altering the stressors that animals face in their everyday lives. Organisms often differ in their coping styles-both behavioral and endocrine-across urban to rural habitats. For example, urban animals are often bolder, more exploratory, and mount stronger glucocorticoid stress responses compared to their rural counterparts. While these coping styles are important in shaping fitness across the urban-to-rural gradient, it remains unclear when these differences arise in the life of organisms. We explore the development of coping styles in European starling nestlings (Sturnus vulgaris), an urban-adapted species. We test whether breathing rate, handling struggle rate, and bag struggle rate differ across sites and find no difference in the behavioral coping styles of nestlings raised in urban versus rural sites. We also explore differences in baseline and stress-induced glucocorticoids, finding that urban nestlings develop a stronger stress response than rural birds before fledging the nest. We find no significant correlations between behavioral and endocrine traits for urban or rural birds, which supports the two-tiered model of coping styles. One possibility is that behavioral and endocrine differences develop at different times over the lives of organisms. Our findings support prior work suggesting that behavioral and endocrine coping mechanisms act independently of one another, and suggests that endocrine coping mechanisms develop in early life and before differences in behavioral coping styles might arise. Future work on the mechanisms leading to early-life differences in coping styles-from genetics to maternal effects to environmental effects-is needed to best predict how urban-adapted organisms cope with environmental change. Studies across a greater number of sites will help disentangle site from urbanization effects.

Compensatory recruitment allows amphibian population persistence in anthropogenic habitats

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages could compensate for reduced adult survival, corresponding to "compensatory recruitment". To date, evidence of compensatory recruitment in response to habitat modification is restricted to plants, limiting understanding of its importance as a response to global change. We used the yellow-bellied toad (Bombina variegata), an amphibian occupying a broad range of natural and anthropogenic habitats, as a model species to test for and to quantify compensatory recruitment. Using an exceptional capture-recapture dataset composed of 21,714 individuals from 67 populations across Europe, we showed that adult survival was lower, lifespan was shorter, and actuarial senescence was higher in anthropogenic habitats, especially those affected by intense human activities. Increased recruitment in anthropogenic habitats fully offset reductions in adult survival, with the consequence that population growth rate in both habitat types was similar. Our findings indicate that compensatory recruitment allows toad populations to remain viable in human-dominated habitats and might facilitate the persistence of other animal populations in such environments.

Optimal hormonal regulation when stressor cues are imperfect

The endocrine system uses information about the environment and the individual's state to regulate circulating concentrations of hormones, and then those hormones, through receptor binding, cause changes in the phenotype. How quickly individuals can up- and down-regulate their hormones can affect baseline and elevated hormone levels and presumably affects how successfully individuals can cope with a varying environment. To respond to environmental change, individuals first need to perceive and process cues about the state of the environment. Individuals may receive imperfect cues about the environment due to perceptual errors, variation in cues, or inexperience with novel stressors. In this paper we use a mathematical model to ask how these imperfect cues should affect how individuals regulate their glucocorticoid concentrations. We find imperfect cues can lead to changes in hormone regulation with individuals generally having higher baseline and lower elevated hormone levels as environmental cues become less reliable. Informational constraints and physiological constraints appear to have generally additive effects, with informational constraints having less of an impact as physiological constraints increase. Our results highlight the different means by which imperfect information can affect hormone regulation. We find that mistakes caused by imperfect cues are commonly responsible for changes in average hormone levels, but imperfect cues also cause individuals to be slower and less certain in their updated estimates of the environmental state, which affects hormone regulation. We also demonstrate the separate effects of false positive and false negative cues and how these are shaped by the relative fitness consequences of baseline and stress-induced hormone levels. Our model shows how given our assumptions imperfect stressor cues should affect endocrine flexibility and regulation, and we hope provides a piece for future conversations and models of endocrine regulation.

Population density mediates induced immune response, but not physiological condition in a well-adapted urban bird

Thriving under high population density is considered a major feature of urban exploiter species. Nevertheless, population density appears to be a surprisingly overlooked factor in urban ecology studies. High population numbers observed in urban species might promote pathogen transmission and negatively affect health or condition, thus requiring investments in immunocompetence. The feral pigeon Columba livia domestica is an example of a successful city-dweller, found in great abundance in large cities across the globe. We investigated the effects of population density on induced immune response (phytohaemagglutinin skin test) and body condition (blood haemoglobin concentration and size-corrected body mass) in 120 feral pigeons, captured along population density gradient in Łódź (central Poland). We found that stronger immune response was associated with higher population density, but was not related to physiological condition and physiological stress (heterophil/lymphocyte ratio). Moreover, condition indices were not associated with population density. However, since pigeon population density was highly correlated with the level of habitat urbanization, we cannot exclude that any density-dependent effects may be mediated by habitat variation. Our results indicate that urban environment, via population density, might exert different selective pressures on immunocompetence and body condition in this successful urban exploiter.

Chronic Stress Indicators in Canines

With a growing number of dogs abandoned, living in shelters, and being rehomed, it is important to distinguish behavioural responses due to stress in our domestic companions. Cortisol is involved in the stress responses in animals which generally enters the individual’s body into a “state of emergency”. Prolonged stress can lead to exhaustion, disease, and death. Chronic stress can be detected by evaluating cortisol concentration in hair. Most domesticated dogs respond well to hair collection, thus avoiding further stressors. The method is simple, relatively inexpensive, and non-invasive. Our experiment focused on assessing multiple parameters using a modified Canine Behavioural Assessment and Research Questionnaire to evaluate their significance with cortisol in hair samples from a diverse range of dogs. Each stress parameter was tested against cortisol concentration using a t-Test, i. e., the Paired Two Sample for Means. The effect of weight on cortisol levels was statistically significant (P = 0.03). This fact revealed that an increase in body weight correlated with an increase in cortisol levels.

Urbanization’s Effects on Problem Solving Abilities: A Meta-Analysis

Cognitive abilities are often assumed to be advantageous in urban habitats, but relatively few studies tested this assumption. In a meta-analysis, we tested whether urban animals have better problem-solving abilities compared to their less urbanized conspecifics. After screening 210 papers we collected by keyword search and forward search, we found 12 studies that compared the ability to solve food-extraction or obstacle-removal problems between urban and non-urban populations of the same animal species. These studies were published between 2009 and 2021, and were performed mostly on birds, whereas a quarter of them used mammals as study species. We found a statistically non-significant trend that urban animals are more successful and faster problem-solvers compared to their less urbanized conspecifics. However, both solving success and solving latency effect sizes were highly heterogeneous, therefore hard to generalize. Though the sample was too low to test the factors explaining this high heterogeneity, we suggest that it may be explained by variation in task types, study species, definitions of urbanization, whether the study was performed on captive or free-living animals, geographical location, or publication bias in both directions. Altogether, more studies are needed to either confirm or disprove this trend.

The Behavioral Responses of the Chiguanco Thrush to Urbanization in a Neotropical City Comes From Preadapted Behavioral Traits

Several animal species can survive within cities by changing their behavior; such changes could be the result of evolutionary adaptation, epigenetic effects, or come from preadapted traits through phenotypic plasticity or non-random dispersal. Exploring whether behavioral preadapted traits are present in non-urbanized populations could improve our understanding of the processes that allow animals to cope with urbanization. We compared the boldness, neophobia, and solving-test skills of adult individuals of the Chiguanco Thrush (Turdus chiguanco) between urban and extra-urban habitats in La Paz (Bolivia), a high-altitude Neotropical city. The urban Chiguanco Thrushes were bolder, less neophobic, and performed better in problem-solving tests. Extra-urban individuals varied significantly more among them in boldness and neophobia, and although a smaller proportion of individuals were able to solve the simplest problem-solving test, they did so in the same way as the urban ones. This evidence suggests that the behavioral responses of the Chiguanco Thrush to urbanization in La Paz come from preadapted traits.

Fatty acids composition in yellow-legged (Larus michahellis) and lesser black-backed (Larus fuscus) gulls from natural and urban habitats in relation to the ingestion of anthropogenic materials

Urban habitats offer spatially and temporally predictable anthropogenic food sources for opportunistic species, such as several species of gulls that are known to exploit urban areas and take advantage of accessible and diverse food sources, reducing foraging time and energy expenditure. However, human-derived food may have a poorer nutritional quality than the typical natural food resources and foraging in urban habitats may increase birds' susceptibility of ingesting anthropogenic debris materials, with unknown physiological consequences for urban dwellers. Here we compare the fatty acids (FA) composition of two opportunistic gull species (the yellow-legged gull, Larus michahellis, and the lesser black-backed gull, Larus fuscus) from areas with different levels of urbanization, to assess differences in birds' diet quality among foraging habitats, and we investigate the effects of ingesting anthropogenic materials, a toxicological stressor, on gulls' FA composition. Using GC-MS, 23 FAs were identified in the adipose tissue of both gull species. Significant differences in gulls' FA composition were detected among the three urbanization levels, mainly due to physiologically important highly unsaturated FAs that had lower percentages in gulls from the most urbanized habitats, consistent with a diet based on anthropogenic food resources. The deficiency in omega (ω)-3 FAs and the higher ω-6:ω-3 FAs ratio in gulls from the most urbanized location may indicate a diet-induced susceptibility to inflammation. No significant differences in overall FA composition were detected between gull species. While we were unable to detect any effect of ingested anthropogenic materials on gulls' FA composition, these data constitute a valuable contribution to the limited FA literature in gulls. We encourage studies to explore the long-term physiological effects of the lower nutritional quality diet for urban dwellers, and to detect the sub-lethal impacts of the ingestion of anthropogenic materials.

Disentangling the roles of social and individual effects on cadmium tolerance in the ant Temnothorax nylanderi

Urbanization brings new pressures for individuals. Among them, trace elements, such as cadmium, are important stressors. A recent study highlights a weaker negative effect of cadmium on city colonies relative to their forest counterparts in the ant Temnothorax nylanderi. Here, we aim to test whether the better tolerance of city colonies in this species results from a better ability of workers to rear larvae despite stressful conditions and/or a better ability of larvae to develop properly despite stressful conditions. We performed a cross-fostering experiment of workers and larvae from city and forest colonies, in common garden conditions in the laboratory. Colonies were fed using cadmium-enriched or cadmium-free food for 2 months, and we measured four life-history traits. As expected, cadmium had a negative impact on all traits. Unexpectedly, we did not observe a better tolerance of city colonies to cadmium, contrary to our previous study, which prevented us from disentangling the respective contributions of workers and larvae to cadmium tolerance. Interestingly, forest colonies seemed to be of better quality in our laboratory conditions. Finally, colony size increased adult survival, but only in the absence of cadmium, suggesting that social buffering could collapse with strong external disturbances.

Feather, But Not Plasma, Glucocorticoid Response to Artificial Light at Night Differs between Urban and Forest Blue Tit Nestlings

Urbanization drives phenotypic variation in many animal species. This includes behavioral and physiological traits such as activity patterns, aggression, and hormone levels. A current challenge of urban evolutionary ecology is to understand the environmental drivers of phenotypic variation in cities. Moreover, do individuals develop tolerance to urban environmental factors, which underlie adaptative responses and contribute to the evolution of urban populations? Most available evidence comes from correlative studies and rare experiments where a single urban-related environmental factor has been manipulated in the field. Here we present the results of an experiment in which we tested for differences in the glucocorticoid (CORT) response of urban and rural blue tits nestlings (Cyanistes caeruleus) to artificial light at night (ALAN). ALAN has been suggested to alter CORT response in several animal species, but to date no study has investigated whether this effect of ALAN differs between urban and rural populations. Immediately after hatching, urban and forest broods were either exposed to 2 lux of ALAN (using an LED source mounted inside the nestbox) or received no treatment (dark control). The experiment lasted until the chicks fledged. When the chicks were 13 days old plasma samples were collected to measure baseline CORT concentrations, and feather samples to provide an integrative measure of CORT during growth. Forest birds had higher plasma CORT (pCORT) concentrations than their urban counterparts, irrespective of whether they were exposed to ALAN or not. Conversely, we found population-specific responses of feather CORT to ALAN. Specifically, urban birds that received ALAN had increased feather CORT compared with the urban dark controls, while the opposite was true for the forest birds. pCORT concentrations were negatively associated to fledging success, irrespective of population and treatment, while feather CORT was positively associated to fledging success in broods exposed to ALAN, but negatively in the dark control ones. Our results demonstrate that ALAN can play a role in determination of the glucocorticoid phenotype of wild animals, and may thus contribute to phenotypic differences between urban and rural animals.

Urban environment alter the timing of progression of testicular recrudescence in tree sparrow (Passer montanus)

Urbanization is a rapidly growing phenomenon that affects wildlife. Laboratory studies show the effects of night light on the physiology of the organisms. Limited studies have been conducted on birds in their natural habitat. Here, we studied the effects of the urban environment on reproduction-linked phenomenon and molecules involved in the regulation of seasonal breeding. Birds (N=5/time/site) were procured from urban and rural sites at specific times, i.e., in March (stimulatory phase), June (reproductive phase), September (refractory phase), and December (sensitive phase) of 2018. Immediately after procurement, birds were brought to the laboratory. Bodyweight, bill color, molt in body feathers, and testes size were recorded. The next day, all the birds were sacrificed in the middle of the day. Blood was collected and serum was used for ELISA of corticosterone, triiodothyronine (T3), and thyroxine (T4). mRNA levels of thyroid-stimulating hormone-β (Tshβ), type 2 deiodinase (Dio2), type 3 deiodinase (Dio3), gonadotropin-releasing hormone (GnRh), and gonadotropin inhibitory hormone (GnIh) were measured in hypothalamic tissue. Urban birds showed higher levels of corticosterone during the stimulatory phase. There was a delay in the initiation of testicular growth in urban birds and it was supported by reduced levels of T3 in blood plasma and relatively lower transcription of Dio2 and GnRH mRNA in urban birds. Our findings suggest that the urban environment delays the timing of reproduction in birds and could be the consequence of local environmental conditions.

Continent-wide genomic signatures of adaptation to urbanisation in a songbird across Europe

Urbanisation is increasing worldwide, and there is now ample evidence of phenotypic changes in wild organisms in response to this novel environment. Yet, the genetic changes and genomic architecture underlying these adaptations are poorly understood. Here, we genotype 192 great tits (Parus major) from nine European cities, each paired with an adjacent rural site, to address this major knowledge gap in our understanding of wildlife urban adaptation. We find that a combination of polygenic allele frequency shifts and recurrent selective sweeps are associated with the adaptation of great tits to urban environments. While haplotypes under selection are rarely shared across urban populations, selective sweeps occur within the same genes, mostly linked to neural function and development. Collectively, we show that urban adaptation in a widespread songbird occurs through unique and shared selective sweeps in a core-set of behaviour-linked genes.

Little parental response to anthropogenic noise in an urban songbird, but evidence for individual differences in sensitivity

Anthropogenic noise exposure has well-documented behavioral, physiological and fitness effects on organisms. However, whether different noise regimes evoke distinct responses has rarely been investigated, despite implications for tailoring noise mitigation policies. Urban animals might display low responsiveness to certain anthropogenic noise regimes, especially consistent noise (e.g. freeway noise), but might remain more sensitive to more diverse noise regimes. Additionally, whether individuals differ in noise sensitivity is a rarely explored issue, which is important to fully understand organismal responses to noise. To address these knowledge gaps, we used a field experiment to measure how urban great tits (Parus major) altered parental behaviors in response to two noise regimes: consistent freeway noise, and a diverse anthropogenic noise regime that incorporated variability in noise type and temporal occurrence. We also evaluated whether sex, age, or a well-described personality trait, novel environment exploration behavior, were associated with responses to noise, although our power to assess individual differences in responses was somewhat limited. We found no evidence for mean population-level changes in nestling provisioning behaviors during either noise treatment. However, despite this overall canalization of behavior, there was evidence for individual differences in noise sensitivity, particularly during the diverse noise treatment. Females and birds that explored a novel environment more rapidly (fast explorers) reduced nestling provisioning rate more relative to baseline levels than males and slow explorers during the diverse urban noise, but not during the consistent freeway noise. Furthermore, first year breeders and fast explorers displayed larger increases in latency to return to the nest box relative to baseline conditions during the diverse noise only. Results suggest that urban animal populations might become overall tolerant to anthropogenic noise, but that certain individuals within these populations nonetheless remain sensitive to certain types of noise exposure. CAPSULE: In an urban songbird, we found no population-level changes in nestling provisioning behavior during noise exposure, but did find evidence for individual differences in noise sensitivity.

Avian corticosteroid-binding globulin: biological function and regulatory mechanisms in physiological stress responses

Corticosteroid-binding globulin (CBG) is a high-affinity plasma protein that binds glucocorticoids (GCs) and regulates their biological activities. The structural and functional properties of CBG are crucial to understanding the biological actions of GCs in mediating stress responses and the underlying mechanisms. In response to stress, avian CBGs modulate the free and bound fractions of plasma corticosterone (CORT, the main GC), enabling them to mediate the physiological and behavioral responses that are fundamental for balancing the trade-off of energetic investment in reproduction, immunity, growth, metabolism and survival, including adaptations to extreme high-elevation or high-latitude environments. Unlike other vertebrates, avian CBGs substitute for sex hormone-binding globulin (SHBG) in transporting androgens and regulating their bioavailability, since birds lack an Shbg gene. The three-dimensional structures of avian and mammalian CBGs are highly conserved, but the steroid-binding site topographies and their modes of binding steroids differ. Given that CBG serves as the primary transporter of both GCs and reproductive hormones in birds, we aim to review the biological properties of avian CBGs in the context of steroid hormone transportation, stress responses and adaptation to harsh environments, and to provide insight into evolutionary adaptations in CBG functions occurred to accommodate physiological and endocrine changes in birds compared with mammals.

The effect of urbanization on innovation in spotted hyenas

Urbanization represents a dramatic form of evolutionary novelty in the landscapes inhabited by many extant animals. The Cognitive Buffer Hypothesis suggests that innovation, the process by which animals solve novel problems or use novel behaviors, may be key for many animals when adapting to novel environments. If innovation is especially beneficial in urban environments, then we would expect urban animals to be more innovative than their non-urban counterparts. However, studies comparing innovative problem-solving between urban and rural habitats have produced mixed results. Here, we hypothesized that these findings result from comparing only two levels of urbanization when related research suggests that the stage of invasion of urban habitats likely has a strong effect on demand for innovation, with demand being highest during early establishment in a novel environment. To test this hypothesis, we assessed innovation in three locations where spotted hyenas experienced varying degrees of urbanization. Spotted hyenas are relatively innovative compared to other carnivores and, although many large carnivores in Africa are endangered, spotted hyenas remain abundant both inside and outside protected areas. We measured innovation with a multi-access puzzle box with four different doors through which hyenas could obtain a food reward. We predicted that hyenas in a transitional, rapidly urbanizing habitat would be more innovative, measured by the number of unique doors opened, than those in rural or fully urban habitats. Contrary to our predictions, hyenas in the rural habitat were the most innovative. These results challenge the idea that the evolutionary novelty associated with urbanization favors greater innovativeness.

Which Traits Influence Bird Survival in the City? A Review

Urbanization poses a major threat to biodiversity worldwide. We focused on birds as a well-studied taxon of interest, in order to review literature on traits that influence responses to urbanization. We review 226 papers that were published between 1979 and 2020, and aggregate information on five major groups of traits that have been widely studied: ecological traits, life history, physiology, behavior and genetic traits. Some robust findings on trait changes in individual species as well as bird communities emerge. A lack of specific food and shelter resources has led to the urban bird community being dominated by generalist species, while specialist species show decline. Urbanized birds differ in the behavioral traits, showing an increase in song frequency and amplitude, and bolder behavior, as compared to rural populations of the same species. Differential food resources and predatory pressure results in changes in life history traits, including prolonged breeding duration, and increases in clutch and brood size to compensate for lower survival. Other species-specific changes include changes in hormonal state, body state, and genetic differences from rural populations. We identify gaps in research, with a paucity of studies in tropical cities and a need for greater examination of traits that influence persistence and success in native vs. introduced populations.

Stressed tadpoles mount more efficient glucocorticoid negative feedback in anthropogenic habitats due to phenotypic plasticity

Coping with anthropogenic environmental change is among the greatest challenges faced by wildlife, and endocrine flexibility is a potentially crucial coping mechanism. Animals may adapt to anthropogenic environments by dampening their glucocorticoid stress response, but empirical tests of this hypothesis have provided mixed evidence. An alternative hypothesis is that a non-attenuated stress response and efficient negative feedback are favored in anthropogenic habitats. To test this idea, we non-invasively sampled corticosterone release rates of common toad (Bufo bufo) tadpoles in agricultural, urban, and natural habitats, and quantified their stress response and negative feedback by a standardized stress-and-recovery protocol. We repeated the same sampling with tadpoles raised from eggs from the same ponds in a common-garden experiment to infer if the differences observed between populations in different habitats were due to individual phenotypic plasticity rather than microevolution or transgenerational effects. We found that, compared to tadpoles in natural ponds, urban tadpoles had higher baseline and stressed corticosterone release rates, and tadpoles in agricultural ponds had similar corticosterone release rates but greater stress-induced change, indicating stronger stress responses in both types of anthropogenic habitats. As predicted, tadpoles in both agricultural and urban ponds showed more efficient negative feedback than did tadpoles in natural ponds. Water pollution levels, as indicated by the concentrations of carbamazepine and corticoid-disrupting compounds in pond water, contributed to elevating the stress response regardless of land use. Infection by neither Batrachochytrium dendrobatidis nor Ranavirus was detected in free-living tadpoles. No habitat-related glucocorticoid differences persisted in the common-garden experiment. These results suggest that toad tadpoles in anthropogenic habitats increased their glucocorticoid flexibility via phenotypic plasticity. The coupling of stronger stress response and stronger negative feedback in these habitats supports the importance of rapidly "turning on and off" the stress response as a mechanism for coping with anthropogenic environmental change.

Consistent choice of landscape urbanization level across the annual cycle in a migratory waterbird species

Rapid urbanization has a great impact on avian distribution, ecology, habitat selection, and behavior. Recent avian studies indicated that individuals remain consistent in their behavioral responses to human disturbance across short periods of time. However, there is still little information about keeping consistent behaviors in distinct locations across different stages of the annual cycle. In this study, we aimed to test for long-term consistency in habitat selection with respect to urbanization in a migratory waterbird species, the Eurasian coot Fulica atra. For this purpose, we individually marked ca. 300 coots from four populations that varied in urbanization level and tracked their habitat preferences during the non-breeding season. We found that individuals from urban breeding populations selected habitats with a higher share of artificial areas during the non-breeding season, when compared to non-urban individuals. Also, a comparison of non-breeding sites selected by birds from our study populations with random sites showed that urban birds selected sites with higher urbanization level than resulting from random availability. Finally, we found a seasonal variation in habitat preferences in coots—individuals from all study populations selected more urbanized areas as the non-breeding season progressed. The results indicate that birds are able to remain consistent in habitat preferences not only at a large geographical scale, but also across different seasons. Marked between-population variation in habitat selection across the annual cycle may reflect personality differences of coots from urban and non-urban populations, and it stays in line with the personality-matching habitat choice hypothesis.

Effects of Urbanization and Landscape on Gut Microbiomes in White-Crowned Sparrows

Habitats are changing rapidly around the globe and urbanization is one of the primary drivers. Urbanization changes food availability, environmental stressors, and the prevalence of disease for many species. These changes can lead to divergence in phenotypic traits, including behavioral, physiological, and morphological features between urban and rural populations. Recent research highlights that urbanization is also changing the gut microbial communities found in a diverse group of host species. These changes have not been uniform, leaving uncertainty as to how urban habitats are shaping gut microbial communities. To better understand these effects, we investigated the gut bacterial communities of White-Crowned Sparrow (Zonotrichia leucophrys) populations along an urbanization gradient in the San Francisco Bay area. We examined how gut bacterial communities vary with the local environment and host morphological characteristics. We found direct effects of environmental factors, including urban noise levels and territory land cover, as well as indirect effects through body size and condition, on alpha and beta diversity of gut microbial communities. We also found that urban and rural birds' microbiomes differed in which variables predicted their diversity, with urban communities driven by host morphology, and rural communities driven by environmental factors. Elucidating these effects provides a better understanding of how urbanization affects wild avian physiology.

Lower bioenergetic costs but similar immune responsiveness under a heat wave in urban compared to rural damselflies

There is mounting evidence that the widespread phenotypic changes in response to urbanization may reflect adaptations caused by rapid evolutionary processes driven by urban-related stressors. Compared to increased habitat fragmentation and pollution, adaptations towards another typical urban-related stressor, that is higher and longer lasting very high temperatures (heat waves), are much less studied. Notably, the sensitivities to heat waves of life-history traits and important fitness-related physiological traits such as immune responsiveness and bioenergetic variables (energy availability, energy consumption and their balance) have never been contrasted between urban and rural populations. By conducting a laboratory common-garden experiment, we compared effects of a simulated heat wave on life history (survival and growth rate), immune responsiveness and bioenergetic variables between three urban and three rural populations of the damselfly Coenagrion puella. Because energy-mediated trade-off patterns may only be detected under energetically costly manipulations, all larvae were immune-challenged by simulating ectoparasitism by water mites. As expected, the simulated heat wave caused negative effects on nearly all response variables. The immune responsiveness, on the other hand, increased under the heat wave, consistent with a trade-off pattern between immune function and growth, and this similarly between urban and rural populations. A key finding was that urban larvae suffered less from the simulated heat wave compared to the rural larvae in terms of a lower heat wave-induced depletion in energy availability. This suggests an adaptation of urban populations to better cope with the stronger and more frequent heat waves in cities. Notably, this urbanization-driven evolution in the bioenergetic variables was not apparent in the absence of a heat wave. Given that changes in energy budgets have strong fitness consequences, our findings suggest that the evolved higher ability to cope with heat waves is fundamental for the survival of urban damselfly populations.

One hundred research questions in conservation physiology for generating actionable evidence to inform conservation policy and practice

Environmental change and biodiversity loss are but two of the complex challenges facing conservation practitioners and policy makers. Relevant and robust scientific knowledge is critical for providing decision-makers with the actionable evidence needed to inform conservation decisions. In the Anthropocene, science that leads to meaningful improvements in biodiversity conservation, restoration and management is desperately needed. Conservation Physiology has emerged as a discipline that is well-positioned to identify the mechanisms underpinning population declines, predict responses to environmental change and test different in situ and ex situ conservation interventions for diverse taxa and ecosystems. Here we present a consensus list of 10 priority research themes. Within each theme we identify specific research questions (100 in total), answers to which will address conservation problems and should improve the management of biological resources. The themes frame a set of research questions related to the following: (i) adaptation and phenotypic plasticity; (ii) human-induced environmental change; (iii) human-wildlife interactions; (iv) invasive species; (v) methods, biomarkers and monitoring; (vi) policy, engagement and communication; (vii) pollution; (viii) restoration actions; (ix) threatened species; and (x) urban systems. The themes and questions will hopefully guide and inspire researchers while also helping to demonstrate to practitioners and policy makers the many ways in which physiology can help to support their decisions.

A World for Reactive Phenotypes

Humans currently occupy all continents and by doing so, modify the environment and create novel threats to many species; a phenomenon known as human-induced rapid environmental changes (HIREC). These growing anthropogenic disturbances represent major and relatively new environmental challenges for many animals, and invariably alter selection on traits adapted to previous environments. Those species that survive often have moved from their original habitat or modified their phenotype through plasticity or genetic evolution. Based on the most recent advances in this research area, we predict that wild individuals with highly plastic capacities, relatively high basal stress level, and that are generally shy—in other words, individuals displaying a reactive phenotype—should better cope with sudden and widespread HIREC than their counterparts' proactive phenotypes. If true, this selective response would have profound ecological and evolutionary consequences and can therefore impact conservation strategies, specifically with respect to managing the distribution and abundance of individuals and maintaining evolutionary potential. These insights may help design adaptive management strategies to maintain genetic variation in the context of HIREC.

Urban ecophysiology: beyond costs, stress and biomarkers

Natural habitats are rapidly declining due to urbanisation, with a concomitant decline in biodiversity in highly urbanised areas. Yet thousands of different species have colonised urban environments. These organisms are exposed to novel urban conditions, which are sometimes beneficial, but most often challenging, such as increased ambient temperature, chemicals, noise and light pollution, dietary alterations and disturbance by humans. Given the fundamental role of physiological responses in coping with such conditions, certain physiological systems such as the redox system, metabolism and hormones are thought to specifically influence organisms' ability to persist and cope with urbanisation. However, these physiological systems often show mixed responses to urbanisation. Does this mean that some individuals, populations or species are resilient to the urban environmental challenges? Or is something missing from our analyses, leading us to erroneous conclusions regarding the impact of urbanisation? To understand the impact of urbanisation, I argue that a more integrated mechanistic and ecological approach is needed, along with experiments, in order to fully understand the physiological responses; without knowledge of their ecological and evolutionary context, physiological measures alone can be misinterpreted. Furthermore, we need to further investigate the causes of and capacity for individual plasticity in order to understand not only the impact of urbanisation, but also species resilience. I argue that abiotic and biotic urban factors can interact (e.g. pollution with micro- and macronutrients) to either constrain or relax individual physiological responses - and, thereby, plasticity - on a temporal and/or spatial scale, which can lead to erroneous conclusions regarding the impact of urbanisation.

Stress in the city: meta-analysis indicates no overall evidence for stress in urban vertebrates

As cities continue to grow it is increasingly important to understand the long-term responses of wildlife to urban environments. There have been increased efforts to determine whether urbanization imposes chronic stress on wild animals, but empirical evidence is mixed. Here, we conduct a meta-analysis to test whether there is, on average, a detrimental effect of urbanization based on baseline and stress-induced glucocorticoid levels of wild vertebrates. We found no effect of urbanization on glucocorticoid levels, and none of sex, season, life stage, taxon, size of the city nor methodology accounted for variation in the observed effect sizes. At face value, our results suggest that urban areas are no more stressful for wildlife than rural or non-urban areas, but we offer a few reasons why this conclusion could be premature. We propose that refining methods of data collection will improve our understanding of how urbanization affects the health and survival of wildlife.

Anthropogenic Change Alters Ecological Relationships via Interactive Changes in Stress Physiology and Behavior within and among Organisms

Anthropogenic change has well-documented impacts on stress physiology and behavior across diverse taxonomic groups. Within individual organisms, physiological and behavioral traits often covary at proximate and ultimate timescales. In the context of global change, this means that impacts on physiology can have downstream impacts on behavior, and vice versa. Because all organisms interact with members of their own species and other species within their communities, the effects of humans on one organism can impose indirect effects on one or more other organisms, resulting in cascading effects across interaction networks. Human-induced changes in the stress physiology of one species and the downstream impacts on behavior can therefore interact with the physiological and behavioral responses of other organisms to alter emergent ecological phenomena. Here, we highlight three scenarios in which the stress physiology and behavior of individuals on different sides of an ecological relationship are interactively impacted by anthropogenic change. We discuss host-parasite/pathogen dynamics, predator-prey relationships, and beneficial partnerships (mutualisms and cooperation) in this framework, considering cases in which the effect of stressors on each type of network may be attenuated or enhanced by interactive changes in behavior and physiology. These examples shed light on the ways that stressors imposed at the level of one individual can impact ecological relationships to trigger downstream consequences for behavioral and ecological dynamics. Ultimately, changes in stress physiology on one or both sides of an ecological interaction can mediate higher-level population and community changes due in part to their cascading impacts on behavior. This framework may prove useful for anticipating and potentially mitigating previously underappreciated ecological responses to anthropogenic perturbations in a rapidly changing world.

Habitat urbanization and stress response are primary predictors of personality variation in northern cardinals (Cardinalis cardinalis)

Behavioral traits that vary consistently among individuals across different contexts are often termed as ‘personality traits,’ while the correlated suite formed by those traits is called a ‘behavioral syndrome’. Both personality trait and behavioral syndrome are potentially responsive to animal ‘states’, defined as strategically relevant individual features affecting the cost-and-benefit trade-offs of behavioral actions. Both extrinsic ‘states’ (e.g. urban versus rural habitats), and intrinsic ‘states’ (e.g. sex), may shape among-individual variation in personality traits, as well as behavioral syndromes. Here, we used northern cardinals sampled from four locations to examine the effect of habitat type (urban versus rural, an extrinsic state), stress hormone corticosterone (CORT) parameters, body weight and sex (intrinsic states) on personality traits and behavioral syndrome variation. We used behavioral trials to measure five personality traits. Using principal component analysis to quantify personality traits first, followed by general linear mixed models, we found that habitat type, CORT at capture and 2-day CORT response affected some personality traits, while body weight and sex did not. Cardinals inhabiting more urbanized areas had lower CORT metabolite levels at capture and were more neophilic, less neophobic and also less aggressive than their rural conspecifics. Using structural equation modeling to construct behavioral syndromes formed by our selected personality traits, we found that urban and rural cardinals varied in the models representing syndrome structure. When utilizing the shared syndrome structural model to examine the effects of states, habitat type and 2-day CORT response appear to affect syndrome variation in a coordinated, not hierarchical, manner.

Helminths of urban rats in developed countries: a systematic review to identify research gaps

Although black (Rattus rattus) and brown (Rattus norvegicus) rats are among the most widespread synanthropic wild rodents, there is a surprising scarcity of knowledge about their ecology in the urban ecosystem. In particular, relatively few studies have investigated their helminth species diversity in such habitat. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guideline to synthesize the existing published literature regarding the helminth fauna of urban rats in developed countries (North America, Europe, Australia, New Zealand and Japan). We aimed at describing the species diversity and richness of urban rat helminths, the species prevalence and associations, the methods of investigation, the pathological changes observed in the hosts, the risk factors of infection and the public health significance of rat-borne helminthiases. Twenty-three scientific papers published between 1946 and 2019 were reviewed, half of them were conducted in Europe. Twenty-five helminth species and eight genera were described from the liver, digestive tract, lungs and muscles of urban rats. The most commonly reported parasite was Calodium hepaticum. Prevalence and risk factors of helminth infection in urban rats varied greatly between studies. Observed pathological findings in the rat host were generally minor, except for C. hepaticum. Several rat helminths can parasitize humans and are therefore of public health significance. The lack of references to identification keys and the rare use of molecular tools for species confirmation represent the main limitation of these studies. Knowledge gap on this topic and the needs for future research are discussed.

Outcomes, Mortality Causes, and Pathological Findings in European Hedgehogs (Erinaceus europeus, Linnaeus 1758): A Seventeen Year Retrospective Analysis in the North of Portugal

Simple Summary

The Western European hedgehog Erinaceus europaeus (Linnaeus, 1758) is one of the most common mammals in urban areas. We collected data over 17 years (2002–2019) regarding outcomes and causes of mortality on this species from two of the main wildlife rehabilitation centers in the north of Portugal. A total of 740 animals were admitted; the majority were juveniles, with the highest admission rate occurring during summer (36.8%). The main cause of admission was debilitation (30.7%). Of the total number of individuals admitted to these centers, 66.6% were released successfully. The main cause of death was trauma of unknown origin (32.7%).

Abstract

This study aimed to analyze the admission causes, outcomes, primary causes of death, and main lesions observed in the post mortem examinations of Western European hedgehogs, Erinaceus europaeus (Linnaeus, 1758), in the north of Portugal. The data were obtained by consulting the records from the two main wildlife rehabilitation centers located in the north of Portugal (Wildlife Rehabilitation Centre of Parque Biologico de Gaia and the Wildlife Rehabilitation Centre of the University of Trás-os-Montes and Alto Douro). Over 17 years (2002–2019) a total of 740 animals were admitted. Most of the animals were juveniles, with the highest number of admissions occurring during summer (36.8%) and spring (33.2%). The main reasons for admission were debilitation (30.7%) and random finds (28.4%). Of the total number of individuals admitted to these centers, 66.6% were successfully released back into the wild. The most relevant causes of death were trauma of unknown origin (32.7%), nontrauma causes of unknown origin (26.6%), and nutritional disorders (20.2%). The main lesions observed were related to trauma, including skeletal and skin lesions (fractures, hemorrhages, wounds) and organ damage, particularly to the lungs and liver. The hedgehog is a highly resilient and adaptable animal. The urban environment has many benefits for hedgehogs, yet the presence of humans can be harmful. In the future, the public needs to become even more involved in the activities of the wildlife centres, which will make a positive difference for these populations.

Physiological stress does not increase with urbanization in European blackbirds: Evidence from hormonal, immunological and cellular indicators

Urbanization changes the landscape structure and ecological processes of natural habitats. While urban areas expose animal communities to novel challenges, they may also provide more stable environments in which environmental fluctuations are buffered. Species´ ecology and physiology may determine their capacity to cope with the city life. However, the physiological mechanisms underlying organismal responses to urbanization, and whether different physiological systems are equally affected by urban environments remain poorly understood. This severely limits our capacity to predict the impact of anthropogenic habitats on wild populations. In this study, we measured indicators of physiological stress at the endocrine, immune and cellular level (feather corticosterone levels, heterophil to lymphocyte ratio, and heat-shock proteins) in urban and non-urban European blackbirds (Turdus merula) across 10 European populations. Among the three variables, we found consistent differences in feather corticosterone, which was higher in non-urban habitats. This effect seems to be dependent on sex, being greater in males. In contrast, we found no significant differences between urban and non-urban habitats in the two other physiological indicators. The discrepancy between these different measurements of physiological stress highlights the importance of including multiple physiological variables to understand the impact of urbanization on species' physiology. Overall, our findings suggest that adult European blackbirds living in urban and non-urban habitats do not differ in terms of physiological stress at an organismal level. Furthermore, we found large differences among populations on the strength and direction of the urbanization effect, which illustrates the relevance of spatial replication when investigating urban-induced physiological responses.

Local- and landscape-scale variables shape insect diversity in an urban biodiversity hot spot

Local community structure is shaped by processes acting at local and landscape scales. The relative importance of drivers operating across different spatial scales is difficult to test without observations across regional or latitudinal gradients. Cities exhibit strong but predictable environmental gradients overlaying a mosaic of highly variable but repeated habitat types within a constrained area. Thus, cities present a unique opportunity to explore how both local and landscape factors influence local biotic communities. We used insect communities to examine the interactions among local environmental variables (such as temperature and relative humidity), local habitat characteristics (such as plant community composition), and broad-scale patterns of urbanization (including biophysical, human-built, and socioeconomic variables) on local insect abundance, species richness, and species composition in Los Angeles, a hot, dry, near-desert city. After accounting for seasonal trends, insect species richness and abundance were highest in drier and hotter sites, but the magnitude of local environmental effects varied with the degree of urbanization. In contrast, insect species composition was best predicted by broad-scale urbanization trends, with the more native communities occurring in less urbanized sites and more cosmopolitan insects occurring in highly urbanized sites. However, insect species richness and abundance were >30% higher and insect composition was similar across sites that hosted either native or drought-tolerant plants, regardless of the degree of urbanization. These results demonstrate that urban insect biodiversity is a product of interacting mechanisms working at both local and landscape scales. However, local-scale changes to urban habitats, such as cultivating plants that are adapted to the natural environment nearest the city, can positively impact urban biodiversity regardless of location.