Search

Animals are increasingly challenged to respond to novel or rapidly changing habitats due to urbanization and/or displacement outside their native range by humans. Behavioral differences, such as increased boldness (i.e., propensity for risk-taking), are often observed in animals persisting in novel environments; however, in many cases, it is unclear how these differences arise (e.g., through developmental plasticity or evolution) or when they arise (i.e., at what age or developmental stage). In the Guttural Toad (Sclerophrys gutturalis), adult urban toads from both native and invasive ranges are bolder than conspecifics in natural habitats. Here, we reared Guttural Toad tadpoles in a common garden experiment, and tested for innate differences in boldness across their development and between individuals whose parents and lineage came from rural-native, urban-native, and urban-invasive localities (i.e., origin populations). Tadpoles did not differ in their boldness or in how their boldness changed over ontogeny based on their origin populations. In general, tadpoles typically became less bold as they aged, irrespective of origin population. Our findings indicate that differences in boldness in free-living adult Guttural Toads are not innate in the tadpole stage and we discuss three possible mechanisms driving phenotypic divergence in adult boldness for the focus of future research: habitat-dependent developmental effects on tadpole behavior, decoupled evolution between the tadpole and adult stage, and/or behavioral flexibility, learning, or acclimatization during the adult stage. Significance statement: To determine if animals can persist in urban areas or become invasive outside their native ranges, it is important to understand how they adapt to life in the city. Our study investigates if differences in boldness that have been found in adult Guttural Toads (Sclerophrys gutturalis) represent heritable differences that can also be found in early life stages by rearing tadpoles from eggs in a common garden experiment. We did not find any differences in boldness among tadpoles from rural-native, urban-native, and urban-invasive origin populations. Our findings suggest that differences in boldness are not innate and/or that boldness is a behavioral trait that is decoupled between the tadpole and the adult stage. [ABSTRACT FROM AUTHOR]

Many biological invasions occur within and between urban areas. If native species adapted to anthropogenically altered habitats are subsequently moved from an urban area in their native range to one within a novel region, then their urban-specialized phenotypes may provide them an advantage via prior adaptation. Here we examine if urban-derived behavioral traits are present within native guttural toad, Sclerophrys gutturalis, populations (Durban, South Africa) and investigate whether these localized phenotypes persisted within their invasive populations in Mauritius and Réunion. In our study, we measured boldness and exploration in populations along the toad's invasion route and found that toads were significantly bolder in urban populations, within both native and invasive ranges. This suggests boldness increased when toads transitioned to urban living in their native range and these heightened levels of boldness were maintained within invaded urban areas. This provides evidence that a bolder phenotype was a prior adaptation that likely increased guttural toad's invasion success. Interestingly, toad boldness returned to pre-urbanization levels within invasive populations that spread into natural areas, replicated on both islands. Exploration, on the other hand, was not increased above pre-urbanization, or pre-invasion, levels for any of the populations, and was lower in toads from Mauritius. Overall, our findings suggest that increased boldness is favored in urban habitats and that urban-derived behavioral traits may provide individuals an advantage when invading new urban landscapes. Significance statement: Species adapting to anthropogenic landscapes have the ability to increase their invasive potential if the altered phenotypes they accrue can provide them advantages once they are transported outside their native range. Our study examined differences in behavioral traits, boldness, and exploration, along the invasion route of guttural toads, Sclerophrys gutturalis, between natural and urban sites from their native origin populations around Durban, South Africa, to their invasive populations in Mauritius and Réunion. We determined that populations were bolder in urban areas in their native range and that this increased boldness persisted in the other anthropogenic habitats within their invasive ranges, but reverted back to natural-native levels within populations that had spread into natural areas on both islands. Our findings support the growing trend that anthropogenically altered landscapes favor bolder individuals, as well as the assertion that urban-derived traits may bolster a species' ability to establish and spread within novel landscapes. [ABSTRACT FROM AUTHOR]

Urban wildlife faces a novel set of challenges resulting in selective pressure that can lead to population-level changes. We studied Australian water dragons (Intellagama lesueurii) from urban and natural populations to test if urban populations differed in body size, shape, and performance capacity. If urban-derived morphology has arisen through selection, we predicted distinct morphological differences between wild dragons from urban and natural areas in both adult and hatchling life-stages. Urban hatchlings were morphologically distinct (shorter body lengths and longer limbs) from natural populations, while urban adult males continued this trend but only for body size (shorter body lengths). We then experimentally reared hatchlings originating from urban and natural populations within urban- and natural-style enclosures (2 × 2 factorial design) for a year to determine if differences in morphology and performance capacity (sprint speed, endurance, and clinging ability) were related to either the individual's origin population or developmental environment. Yearlings reared in urban-style enclosures, irrespective of population origin, had smaller body sizes compared to those from natural-style enclosures, suggesting developmental environment was affecting their morphology. Despite this difference in body size, yearling dragon performance capacity was not significantly different between treatments. Overall, this study provides evidence of a complex relationship driving urban-divergent morphology – whereby urban dragons emerge as smaller hatchlings with longer limbs (innate traits) and are then further influenced by the urban environments that they develop in (phenotypic plasticity); however, and potentially owing to behavioral, ecological, and demographical differences, these changes appear to be sex-specific. [ABSTRACT FROM AUTHOR]

The adaptive nature of invasive species facilitates their survival in conditions that differ markedly from their native range. Behavioral changes in invasive populations are poorly explored but offer a wide potential when combined with physiological traits. For amphibians invading xeric habitats, finding water is important to function optimally and avoid dehydration. The water-finding hypothesis postulates that survival can be enhanced through the increased behavioral ability to find water. We tested the water-finding hypothesis in guttural toads (Sclerophrys gutturalis) from their native range and an invasive population. Additionally, we tested if artificially elevated corticosterone levels, which increase during dehydration, affect behavioral traits linked to water balance. In a labyrinth experiment, we observed the toads' ability to find water in different hydration states (100%, 90%, and 80%). We found that individuals from the invasive population took longer to engage in water-searching behavior and spent more time close to the water source after finding it. Toads from the invasive population were also more active, and at 90% hydration, their attempts to find water increased. Moreover, artificially increasing corticosterone in fully hydrated invasive toads increased water-finding success. Our experiments demonstrated that invasive toads show water-conservation behaviors that can optimize water balance and might facilitate survival in an invaded xeric environment. Additionally, we suggest a link between elevated corticosterone levels and water-finding success. Our results lend support to the importance of behavior in successful invasions and the modulation of water-finding behavior by corticosterone. Significant statement: Invasion success is associated with behavioral and physiological adaptations of invasive species. For anuran species invading xeric habitats, the ability to find water is an important behavioral trait. Using a labyrinth experiment and toads (Sclerophrys gutturalis) dehydrated at different levels, we observed that individuals invading a hydric challenging habitat showed advantageous water-conservation behaviors (e.g., taking longer to engage in water-searching behavior and spent more time close to the water source after finding it) compared to toads from the native range. Transdermal treatment with corticosterone, a hormone that increases its plasma concentrations under dehydration, increased success of finding water in 100% hydrated animals. Our results indicate that, compared to the native population, invasive toads display water-conservation behaviors that might improve survival rates in a novel xeric environment and that experimental corticosterone elevation modulates this water-finding behavior. [ABSTRACT FROM AUTHOR]

Pollinating insects are vital to the survival of many primary producers in terrestrial ecosystems, as up to 80-85 % of the world's flowering plants require pollinators for reproduction. Over the last few decades however, numerous pollinating insect populations have declined substantially. The causes of these declines are multifaceted and synergistic, and include pesticides, herbicides, monoculture, urbanization, disease, parasites, and climate change. Here, we present evidence for a generally understudied yet potentially significant source of pollinator mortality, collisions with vehicles. Negative impacts from roads have been observed for the majority of vertebrate groups but studies of the effects on invertebrates have remained largely absent from the scientific literature. We documented road mortality of pollinating insects along a 2 km stretch of highway in Ontario, Canada and used our findings to extrapolate expected levels of road mortality across a number of landscape scales. Our extrapolations demonstrate the potential for loss of hundreds of thousands (on our studied highway) to hundreds of billions (generalised across North America) of Lepidopterans, Hymenopterans and pollinating Dipterans each summer. Our projections of such high levels of annual road mortality highlight the need for research to assess whether the mortality levels observed are contributing to the substantial declines of pollinating insects occurring on a global scale, thus putting the ecological functioning of natural areas and agricultural productivity in jeopardy. [ABSTRACT FROM AUTHOR]

Urban environments are novel landscapes that markedly alter animal behavior. Divergence in behavior in response to urbanization may provide advantages in navigation, exploiting resources, and surviving under a novel suite of selective pressures. Relatively few studies, however, have identified population-level behavioral changes in response to urbanization that are not confounded by rearing environment and prior experience (e.g., an urban upbringing). To address this, we used the Australian water dragon (Intellagama lesueurii) to test whether populations under varying levels of urbanization (urban, semi-natural, and natural populations) differ in their innate behavioral traits; acquired either heritably or due to population-specific maternal effects. Eggs were collected from wild mothers and hatched in the lab. Hatchlings were then reared in the lab under standardized conditions (a common-garden experiment). We then assayed individual behavioral traits (boldness, exploration, and neophilia) five times across their first year of development. We compared behavioral traits, as well as their expression (repeatability), between urban, semi-natural, and natural populations. Neophilia and explorative behavior was similar among all populations. However, dragons from semi-natural populations were significantly bolder than those from natural populations. Urban dragons were also bolder than dragons from natural populations, although this trend was not significant because of high variance in boldness. Dragons from semi-natural and urban populations had similar boldness scores, suggesting a potentially biologically relevant difference in boldness between them and natural populations. We also saw some differences in the consistency of the expression of behavior. Boldness in individuals from urban environments was also the only repeatable trait. Overall, our study suggests that boldness is an innate, urban-derived divergent behavioral trait that likely contributes to the success of these lizards in anthropogenically altered environments. Significance statement: Lizards from human-modified areas are innately bolder than ones from natural habitats. To determine this, we raised lizards from eggs collected from urban, semi-natural, and natural populations in a standardized environment, removing the effects of prior experience and developmental environment, and examined their behavioral traits over time. The difference we found in boldness was related to their origin population, rather than being shaped through experience, suggesting this trait may be heritable and is being selected for in anthropogenic landscapes. Our study addresses an important gap in studies of urban behavioral ecology by examining behavioral differences among replicated, differently urbanized, sites after experimentally accounting for both rearing environment and prior experience. [ABSTRACT FROM AUTHOR]

Abstract: Innate antipredator responses are integral for survival in many species, particularly those which lack parental care. Antipredator responses include both active (fight or flight) and passive behaviours (immobility). As the success of antipredator responses directly relates to survival and fitness, investigating the drivers that explain variance in these traits is key to understanding how predation shapes the instinctive behaviour of animals. We quantified innate antipredator behaviour of hatchling Australian water dragons (Intellagama lesueurii) immediately after hatching using a model snake to simulate a series of attacks, and scored their behaviour using a fight or flight index. Then we explored which factors were related to dragon antipredator behaviour, such as habitat disturbance, origin population, morphology, and parental genetic effects and phenotype (clutch effects). We developed multiple hypotheses and used model selection to determine which factors drive variation in hatchling antipredator behaviour. Clutch effects explained a significant proportion of variation in innate antipredator responses, suggesting a heritable component. We also found an effect of body size on innate antipredator behaviour: larger hatchlings were more prone to flight behaviour (e.g. short-distance runs and long-distance sprinting), while smaller individuals were more prone to standing their ground and being aggressive (e.g. throat puffing, mouth gaping, biting). Clutch effects also explained a significant proportion of the variance in dragon body size. Our study provides evidence that the innate antipredator responses of water dragons are heritable in origin (directly through clutch effects, and indirectly through body size) and not associated with particular populations or habitat types. We suggest future research examine the survival implications of these responses.Significance statement: The action an animal takes in response to a predator is a life or death decision, and can be required immediately after birth. These innate antipredator behaviours may be genetically linked, and enable individuals to emerge into their environment with the necessary behaviour to promote survival. We examined what factors drive hatchling lizards to exhibit different innate antipredator behaviour. Our study found that body size affected their innate behaviour: larger hatchlings were more prone to flee and smaller hatchlings were more likely to fight. Interestingly, parental genetics and phenotype (clutch effects) also significantly explained the variation in innate antipredator behaviour, which supports the hypothesis that these behaviours are heritable. Understanding what drives variation is a cornerstone of evolutionary biology, and our findings raise questions about how selection acts on antipredator behaviour and the degree to which they are plastic. [ABSTRACT FROM AUTHOR]