Isabel Damas-Moreira

Urbanisation is a key driver of global environmental change and presents animals with novel stressors and challenges. It can fundamentally influence social behaviour and has the potential to reshape within‐ and between‐species social interactions. Given the role of social behaviour in reproductive fitness and survival, understanding how social interactions change in response to urban conditions is crucial in addressing individual‐, population‐, and species‐level responses to urbanisation, as well as the consequential ecological impacts. Here, we conducted the first systematic review addressing the impact of urbanisation on social systems and interspecific interactions. We synthesise the outcomes of the 227 studies from our literature search, organised across three key topics: ( i ) effects of urban stressors on social behaviour ( N = 170), ( ii ) social system responses to urban environments ( N = 75), and ( iii ) the impact of urbanisation on interspecific interactions ( N = 12). Our review revealed that urbanisation is having a substantial impact on multiple facets of social behaviour, with 92% of studies finding a significant impact. We also identified several biases and gaps in the current literature. For example, 62% of all studies were conducted on birds, and 85% of studies testing urban stressors focused on anthropogenic noise. Given the diversity of animal social systems, there is obvious variation in social responses to urban conditions. However, we offer predictions for how social systems might change as urban environments continue to expand rapidly and suggest guidelines for future research to enhance generalisations across taxa. Our review brings together multiple areas of research, provides timely insights and outlines a framework for a unified and proactive approach to addressing social responses to urbanisation. This represents an essential foundation for anticipating species' responses to urban expansion and guiding effective conservation efforts.

Cities are expanding globally, exposing animals to novel ecological conditions that can alter the frequency and nature of their social interactions. Urban habitat features, such as built infrastructure and patchy resource distributions, can constrain movement and promote aggregation, potentially increasing encounters among conspecifics and introducing unique social challenges. Understanding how urbanization affects social behaviour is therefore crucial. However, these effects remain poorly understood, and studies on solitary or non-gregarious species are particularly scarce. Here, we investigate how urbanization influences social behaviour in the common wall lizard ( Podarcis muralis ), a territorial species and successful urban dweller. We constructed social networks using proximity-based association data from urban and non-urban lizard populations. Urban lizards had more social connections, stronger associations and were observed in more associations overall. These differences were not explained by variation in population density. We propose that spatial constraints and resource heterogeneity in urban habitats may enhance social tolerance. Our results reveal that urbanization can reshape social behaviour even in less gregarious species and suggest that shifts in social strategies may facilitate persistence in urban landscapes.

Interspecific associations can provide various benefits, including reducing predation risk, sharing information, or acquiring food. Studying these associations is key to understanding the drivers and mechanisms underlying non‐kin cooperation. Here, we present the first evidence of single individuals of ocelot (Leopardus pardalis) and common opossum (Didelphis marsupialis) associating and moving together in the rainforest. This association, unknown until now, was captured in four independent events, through camera‐trap videos and photographs taken across different times and locations, suggesting a consistent pattern among different individuals. Additionally, we experimentally show that opossums are significantly more attracted to ocelot scent cues, on which they often rub their bodies, compared to control and puma scents. Both the ocelot and the common opossum are nocturnal, solitary species that share territories and can overlap diets; yet, ocelots can also prey on opossums. This puzzling association might emerge because both species could benefit from each other's presence, potentially improving foraging efficiency or safety. Such a newly discovered association offers insight into the complex dynamics of interspecific associations in tropical ecosystems. Future research investigating its prevalence and benefits will deepen our understanding of the ecological and evolutionary conditions driving this behaviour.

Animals need to recognize different individuals, both con- and heterospecifics, to make appropriate decisions. In the wild, responses to familiar individuals may vary depending on the context, which can be beneficial. However, differing responses towards human experimenters can influence experimental outcomes. Such effects might be particularly overlooked in reptiles which are frequently viewed as cognitively less advanced. We tested Tokay geckos’ (Gekko gecko) ability to distinguish between familiar and unfamiliar handlers in two situations: in a novel situation (exerting physical constraint) and a routine situation (feeding from forceps as during regular husbandry). Geckos showed sex-specific differences towards familiar and unfamiliar handlers in a routine situation, but not in a novel situation, in which they showed individual repeatability. Our results further advance our understanding of reptile cognition revealing important insights into context specific responses in relation to handler identity with implications for experimental animal studies that are rarely considered.

Human-induced rapid environmental change is intensifying globally. Urbanization, a major form of human-induced rapid environmental change, alters ecosystems and exposes wildlife to urban stressors, including altered ambient temperatures and resource shifts. These alterations can impose selective pressures on wildlife, influencing behavior, physiology, and morphology. Alterations in resource availability and quality, and ambient temperature may be especially important for ectotherms, which depend on environmental conditions for regulating body temperature and activity. To date, little research has examined the physiological changes of ectotherms that are associated with urban life. In this study, we measured standard metabolic rate (SMR; N = 38) and recorded body mass and size in common wall lizards ( Podarcis muralis ) from an urban (N = 123) and a semi-natural habitat (N = 125) in Croatia. Our results show that urban lizards exhibit a lower SMR, reduced body mass, and shorter snout-vent length than their semi-natural counterparts. Despite these differences, body condition, assessed via the scaled mass index, did not vary between the two habitat types, potentially reflecting adaptive responses to urbanization-related environmental pressures. These findings suggest adaptive strategies of reptiles in urban environments and highlight the importance of studying both physiological and morphological traits to better understand the effects of urbanization on wildlife.

Urbanization occurs at a global scale, imposing dramatic and abrupt environmental changes that lead to biodiversity loss. Yet, some animal species can handle these changes, and thrive in such artificial environments. One possible explanation is that urban individuals are equipped with better cognitive abilities, but most studies have focused on birds and mammals and yielded varied results. Reptiles have received much less attention, despite some lizard species being common city dwellers. The Italian wall lizard, Podarcis siculus, and the common wall lizard, Podarcis muralis, are two successful lizards in anthropogenic habitats that thrive in urban locations. To test for differences in a cognitive skill between urban and semi-natural environments, we investigated inhibitory control through a detour task in syntopic populations of the two species, across 249 lizards that were tested in partially artificial field settings. Sophisticated inhibitory control is considered essential for higher degrees of cognitive flexibility and other higher-level cognitive abilities. In this task, we confronted lizards with a transparent barrier, separating them from a desired shelter area that they could only reach by controlling their impulse to go straight and instead detour the barrier. We found no differences between lizards in urban and semi-natural environments, nor between species, but females overall performed better than males. Moreover, 48% of the lizards in our study did not perform a correct trial in any of the 5 trials, hinting at the difficulty of the task for these species. This study is among the first to address lizard cognition, through their inhibitory control, as a potential explanation for success in cities and highlights one should be careful with assuming that urban animals generally have enhanced cognitive performance, as it might be taxa, task, or condition dependent.

Island biogeography theories predict that characteristics such as island size, age, and isolation interplay in host-parasite dynamics. In this study, we analyzed haemogregarines of the Aegean wall lizard, Podarcis erhardii, to investigate how island characteristics relate to parasite prevalence and intensity. A previous assessment of 19 Greek island populations suggested that isolation time and host population density were key predictors of haemogregarines. Here, by combining microscopy and genetic techniques, we extend this previous study to four additional islands: Syros, Folegandros, Santorini and Nea Kameni. We also recorded the prevalence of ticks and mites, definitive hosts for these parasites. The genetically identified haemogregarines are part of a clade with parasites from other lizard species, including some considered as Karyolysus, but others assigned to Hepatozoon. The prevalence of these parasites differed significantly between islands, while their intensity did not. The presence of ticks was associated with endoparasite prevalence, and males were more frequently infected by haemogregarines than females. Combining our data with that of the previous study, we found no significant impact of the island age and area on parasite prevalence. We also confirmed the presence of the unrelated parasite genus Schellackia through microscopy and DNA sequencing, which is the first record of this genus in this host species. Our results further highlight the complexity of host-parasite systems.

Assessment of parasites and their pathogenicity is essential for studying the ecology of populations and understanding their dynamics. In this study, we investigate the prevalence and intensity of infection of haemogregarines (phylum Apicomplexa) in two sympatric lizard species, Podarcis vaucheri and Scelarcis perspicillata , across three localities in Morocco, and their effect on host immune response. We used the Phytohaemagglutinin (PHA) skin testing technique to relate the level of immune response with parasite infection. Prevalence and intensity levels were estimated with microscopy, and 18S rRNA gene sequences were used to confirm parasite identity. All parasites belong to the haemogregarine lineage found in other North African reptiles. There were differences in prevalence between localities and sexes. Overall, infected lizards were larger than uninfected ones, although we did not detect differences in parasitaemia across species, sex or locality. The swelling response was not related to the presence or number of haemogregarines, or to host body size, body condition, sex or species. We found no evidence of impact for these parasites on the circulating blood cells or the hosts’ immune system, but more data is needed to assess the potential impact of mixed infections, and the possibility of cryptic parasite species.

Invasive species can carry parasites to introduced locations, which may be key to understand the success or failure of species establishment and the invasive potential of introduced species. We compared the prevalence and infection levels of haemogregarine blood parasites between two sympatric congeneric species in Lisbon, Portugal: the invasive Italian wall lizard (Podarcis siculus) and the native green Iberian wall lizard (Podarcis virescens). The two species had significant differences in their infection levels: while P. virescens had high prevalence of infection (69.0%), only one individual of P. siculus was infected (3.7%), and while P. virescens exhibited an average intensity of 1.36%, the infected P. siculus individual had an infection rate of only 0.04%. Genetic analyses of 18S rRNA identified two different haemogregarine haplotypes in P. virescens. Due to the low levels of infection, we were not able to amplify parasite DNA from the infected P. siculus individual, although it was morphologically similar to those found in P. virescens. Since other studies also reported low levels of parasites in P. siculus, we hypothesize that this general lack of parasites could be one of the factors contributing to its competitive advantage over native lizard species and introduction success.