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The cognition of ‘nuisance’ species
Abstract
We discuss the importance of considering animal cognition in conflict mitigation.
Recent work in animal cognition has focused on how animals respond to new or changing environments. Although many species are currently in decline, other species are thriving in human-altered habitats by taking advantage of new resources and opportunities associated with anthropogenic disturbance. Yet, as a result, these same species are often in conflict with humans and treated as a nuisance. Therefore, cognitive abilities such as innovation and behavioural flexibility may, paradoxically, lead to the demise of especially adaptive individuals. Here we review what is known about the cognition of ‘nuisance’ species and ‘problem’ individuals to shed light on the struggles of coexistence with humans along disturbed landscapes. We take an in-depth look at several cognitive abilities that are hypothesized to be of critical importance for species that are successfully utilizing human-altered environments, including neophilia, boldness, categorization, innovation, memory, learning, social learning and behavioural flexibility, and examine evidence that these cognitive abilities may also bring animals into conflict with humans. We also highlight some examples of species that may be using cognitive mechanisms to change their behaviour to avoid conflict with humans. We then discuss the role of animal cognition in current mitigation strategies that have been developed to address human–wildlife conflict. Additionally, we consider the role that human behaviour and perception of animals might play in either worsening or lessening conflict with wildlife. Finally, we propose some directions for future research and suggest that empirical investigation of ‘nuisance’ animal cognition could reveal the cognitive mechanisms underlying adaptation to anthropogenic change as well as help mitigate human–wildlife conflict.
... Therefore, some sensory stimuli can be applied to interventions for multiple animal groups, such as the toriline to deter seabirds and reflecting ribbon for farmland birds, flashing lights to deter terrestrial carnivores in ranches and illuminators to reduce the fishery-marine fauna interactions and loud sound to deter farmland birds and cetaceans, though the devices used in these interventions are ostensibly different. In (Barrett et al., 2019;Blackwell et al., 2016). ...
... More evidence not only benefits the implementation of existing interventions but also may help to design new ones (Blackwell et al., 2016;Elmer et al., 2021;Garvey et al., 2020). Although a specific type of stimuli might be more effective than the others within or across animal groups (Barrett et al., 2019;Blackwell et al., 2016;Garvey et al., 2020), we did not find obvious differences either across or within animal groups. This result is in part because the specific stimuli varied greatly in a broad stimulus category. ...
Evidence‐based interventions designed to reduce wildlife‐caused losses are essential for human–wildlife coexistence. The lack of systematic summarization of research effort and evidence makes it challenging for researchers, managers and policymakers to prioritize interventions for evaluation and implementation.
Here, we compiled experimental case studies of nonlethal technical interventions designed to reduce the losses of crops, livestock and fishery catches caused by terrestrial carnivores, elephants, farmland birds and marine fauna worldwide. Then, we summarized the research effort and the performance of interventions by their sensory stimuli and target animals.
We found that: (i) 54 of 88 interventions included in this study had statistically effective evidence, where only 39% (21/54) were evaluated with more than three experiments; (ii) physical‐, sound‐, chemical‐ and light (or visual) ‐based interventions were the most in numbers and their performance varied greatly; (iii) farmland birds, seabirds and cetaceans were the most studied animal groups while there are only a few experiments for elephants; and (iv) the interventions for marine fauna generally had no impact on the target catch of fisheries.
Syntheses and applications: Our results indicated that collective effort is needed to further evaluate interventions using various sensory stimuli and launch incentive programs to motivate the implementation of interventions, particularly related to marine fauna conservation. Our synthesis could be helpful for stakeholders to tackle the negative human‐wildlife interactions outlined as Target 4 of the Kunming–Montreal Global Biodiversity Framework.
... Animal species with socially learned behaviours involved in negative HWI can be resilient to mitigation solutions, owing to their cognitive and social capacities to overcome methods typically used in such solutions (e.g. habituation) [72]. This is the case in elephants, where it is critical to adopt approaches that include the identification of demographic and personality traits of the concerned elephant populations, the hormonal status of the perpetrators (i.e. ...
The behaviour of both humans and wildlife is central to the conservation of biodiversity because conservation requires human actions at multiple scales. In species with evidence of socially learned behaviour and culture, the juxtaposition of human and animal culture increases the complexity of human–wildlife interactions and their investigation but also offers opportunities to mitigate negative interactions. In this paper, we consider the language used to analyse human–animal interactions and we review the effect of culture and socially learned behaviours on those interactions. We investigate how knowledge of culture and theory from behavioural studies can be used to negotiate the complex interactions between humans and wildlife, providing specific examples of how culture can be mined for developing policies regarding negative interactions. We highlight that interactions between animal and human culture are central to the conservation of wildlife, and that such human–wildlife interactions are a key target for studies of biodiversity conservation. Integrating culture and social learning into conservation research offers scope to leverage knowledge gaps, misconceptions and concerns into conservation actions that are targeted, relevant and meaningful.
This article is part of the theme issue ‘Animal culture: conservation in a changing world’.
... This then leads to reduced opportunities for social learning and subsequent loss of culture in a process coined the fragility of traditions. Yet, human activities can drive a diverse range of ecologically important behavioural responses in non-human animals [25,26], including promoting innovation through the provision of new opportunities [22,27,28]. Additionally, species that have responded to human impact by increasing in population size or density may be experiencing increasing opportunities for social learning [29]. ...
There is increasing evidence that habitat decline via fragmentation or species loss can lead to loss of cultural diversity, complexity or richness in non-human animals. For example, a reduction in local bird species richness leads lyrebirds to sing fewer complex songs, while great apes living in fragmented landscapes have smaller cultural repertoires. However, the link between animal culture and local ecology remains understudied, and the potentially complex interactions between ongoing ecological change and animal culture are poorly understood. Here, we review the current state of knowledge on how ecology influences animal culture, focusing on vocal communication and foraging behaviour. We identify key factors affecting cultural patterning, including direct effects (e.g. environmental variability) and indirect effects (e.g. connectivity). We then review the emerging evidence for the effects of environmental change on culture, identifying three major threatening processes: habitat fragmentation, habitat degradation and urbanization. Finally, we develop a predictive framework for the effect of these threatening processes on animal culture and highlight how the loss of cultural diversity and complexity can lead to fitness costs with conservation implications.
This article is part of the theme issue ‘Animal culture: conservation in a changing world’.
... All behavioural responses and explorative actions were retrospectively coded from video recordings using software INTERACT (Mangold, version 9.7, Arnstorf, Germany). We recorded the following three measurements to quantify an animal's motivation to explore the novel items: latency to touch (routinely used as a measurement of neophobia/neophilia; Barrett et al., 2019;Benson-Amram et al., 2014;Greenberg & Mettke-Hofmann, 2001;Greggor et al., 2015) from when the animal crossed over the hula hoop ring, frequency of exploration events (number of times a monkey sniffed, touched, lifted, licked, poked, manipulated or chew on an item within the hula hoop ring) and exploration duration (the total time a monkey spent interacting/manipulating an item within the hula hoop ring). ...
Consistent individual differences in animals' reactions to novel objects and foods serve as a proximate measure of personality in many subfields of biology and psychology. However, these responses may be subject to contextual influences such as the nature of the novel stimuli and the social context during the tests. To help gain some more clarity as to whether this widely used method provides a robust measure of personality, here, we focus on the exploration axis of personality. How animals explore novel objects has important implications for how they innovate, learn from and interact in the environment. We therefore evaluate the robustness of exploration tendency within and across contexts as well as time by testing common marmosets, Callithrix jacchus, with a 'test battery' of 12 novel stimuli from 2 categories (food and objects) in both individual and social contexts. Furthermore, we compare the stability of individual exploration tendency over a period of 2 years in two similar novelty exploration tests. We find that marmosets' reactions measured in terms of latency to touch items, number of exploration events and proportion of exploration time are predominantly explained by the stimulus category and the social context. We do not find strong support for consistent individual differences. Moreover, we observe no correlation between responses in the novelty exploration tests conducted 2 years apart. Our results show that social context and stimulus type can lead to differences in exploration tendency and thereby emphasize the importance of considering these variables, when using novel stimulus paradigms, which apply to a broad range of scientific disciplines such as animal cognition, behavioural ecology and comparative psychology.
... Animals adapt their behavior in response to human disturbance in their environment (Frid and Dill 2002). Behavioral plasticity increases the adaptability of wildlife living in areas of human disturbance (Barrett, Stanton, and Benson-Amram 2018). For example, urban wildlife that becomes accustomed to human disturbance through learning may exhibit increased boldness or tolerance over time (Lowry, Lill, and Wong 2013). ...
Herons (Ardeidae), an important group in wetland ecosystems, have a particularly strong relationship with humans. However, their predation on farmed fish and shrimp in aquafarms can lead to economic losses for local fish farmers. Consequently, notable conflicts arise between fish farmers and herons. Fish farmers adopt various measures to deter herons from “stealing” their fish; however, there is limited research on the behavioral responses of herons under such pressures of human disturbance. Flight initiation distance (FID) is an important manifestation of avian anti‐predation behavior and serves as an indicator of birds' tolerance to human disturbance. This study investigated the potential variations in tolerance to human disturbance between the little egret (Egretta garzetta) and the Chinese pond heron (Ardeola bacchus) in “stealing” environments (aquafarm environments) and non‐aquafarm environments in Hainan and Guangdong Provinces, south China, using FID as an indicator. Herons in aquafarm environments were less tolerant (having longer FIDs) to human disturbance compared to herons in non‐aquafarm environments. The main cause of this phenomenon could be the harsh deterrents used by humans to prevent herons from “stealing” fish. These deterrents increase the predation risk for herons when “stealing” in aquafarms, causing them to exhibit less tolerance to human disturbance. Our study increases understanding of the behavioral response patterns of herons in human–wildlife conflicts and provides valuable insights for more scientific and rational management and protection of Ardeidae species.
The aim of this study was to investigate the ability of barn swallows (Hirundo rustica) to recognize humans. A field study was conducted in Caoyang Village, Zhanjiang City, Guangdong Province, South China. We assessed the responses of female barn swallows to the recognition of different types of human individuals by measuring their flight initiation distance (FID) when they incubated eggs in the nests. Our results demonstrated that barn swallows can identify the householder where their nest is located, displaying lower FID when the householder approaches, compared to an unfamiliar experimenter. Furthermore, there was no significant difference in FID between swallows reacting to householders who were rarely at home versus those who were frequently present, suggesting that barn swallows may possess the capability to recognize and retain memory of individual humans over time. Our findings provide evidence that barn swallows exhibit remarkable cognitive abilities. The long-standing symbiotic relationship between barn swallows and humans provides a unique model for studying the adaptation of species to environments with close human interactions. Research on their behavior and survival strategies can offer insights into the influence of symbiotic relationships on species adaptability and evolution.
Humans are altering natural environments at unprecedented rates. Ecological generalism is one of the strongest predictors of survival in light of these changes which, in animals, may be shaped by bold and innovative behaviours. Species with greater habitat generalism are proposed to behave more boldly (e.g., touching and ingesting novel food). Species with greater dietary generalism are proposed to behave more innovatively (e.g., novel problem-solving to access food). Support for both hypotheses exists but remains largely restricted to broad comparisons between generalists and specialists. Further comparative data are needed to understand the extent to which these behavioural patterns might shape more nuanced ecological variation between species, such as species with finer-scale niche differences. We compared bold and innovative behaviour in two wild sympatric generalists, the Northern raccoon ( Procyon lotor ) and Virginia opossum ( Didelphis virginiana ), using a pull-string task with strings and wires attached to vertical cups containing high-value food. Although both species are broadly classified as generalists, raccoons show relatively greater habitat and dietary flexibility than opossums. Because they live sympatrically, it offers a unique opportunity to test – at the same time and locations – whether these finer-scale niche differences are reflective of differences in their bold and innovative behaviour. We predicted that raccoons would display bolder behaviour (in terms of touching our novel task) and more innovative behaviour (in terms of solving it). We found that both species were equally likely to acknowledge and touch the task, but raccoons were more likely to display innovation to access the food. Raccoons’ propensity for using innovation to solve novel foraging challenges may contribute to their greater ecological flexibility compared to opossums. More broadly, our findings may help explain differences in how each species adapts to environmental changes.
Highlights
Bold and innovative behaviour may help some species adapt to environmental changes
We administered a novel pull-string task to wild raccoons and opossums
Raccoons displayed more innovative, not bolder, behaviour than opossums
Both species are generalists, but raccoons are more flexible than opossums
Differences in innovation may shape their finer-scale niche differences
We evaluated whether the inclusion of elephant cognition in an education program resulted in changes in attitudes towards elephants and elephant conservation and the effect of rurality, gender, and age on attitudinal change. The study group was comprised of villagers living in and around Bannerghatta National Park. We found that adolescents had more favourable attitudes towards Asian elephants than adults, and participants in urban areas had more favourable attitudes than those in rural areas. No gender differences were observed. Overall, using elephant cognition as an educational tool did not result in more favourable attitudes towards elephants and elephant conservation.
This scholarly book magnifies reflections from young scientists in South Africa, Africa and beyond around the COVID-19 pandemic. With contributions by upcoming scientists, this scholarly book provides a synopsis of socio-ecological-economic views on the impact of COVID-19. Through its chapters, the book takes a multi-disciplinary approach to reflecting on what it was like to be a scientist during the COVID-19 pandemic. By doing so, each chapter re-imagines science from the viewpoint of its discipline, offering insights from the perspective of young scientists that could benefit other scholars, academics and policymakers.
Herring gulls (Larus argentatus) are ubiquitous at our coasts and seaside resorts, a fact acknowledged by the catch-all name 'seagull' that is used interchangeably for these and other gull species. However, despite this long-standing association with coastal habitats, gull behaviour regularly incites anger amongst seaside residents and visitors. Whilst gulls can cause harm to humans through their daily activities, humans also cause harm right back. This short article, drawing on data from interviews with participants in an animal welfare education project and media coverage of gull stories, explores some of the tensions between gulls and people that can lead to acts of cruelty towards these birds. It considers both how conflict is created and fostered, and the ways in which some of the apparent vitriol humans feel towards gulls might be dissipated. HUMANS VERSUS HERRING GULLS The natural history of the gull indicates that these birds lead long and complex lives (Pierotti and Good, 1994). However, interview data and newspaper analysis reveals that their food choices and eating habits are amongst the factors impacting most significantly on our opinions and attitudes towards them. Many gull species exhibit plastic feeding behaviours, learning and adapting to the resources available, and some count interspecific kleptoparasitism amongst their skills. This can be a successful foraging strategy and demonstrates the gull's mastery of their habitat and their application of brain-power to problem-solving (Morand-Ferron et al., 2007). However, these survival-enhancing behaviours can cause gulls to come into conflict with humans. Diners take umbrage at having their chips, doughnuts and ice creams 'stolen' from them, as evidenced by the story of the unsuspecting Mrs Dack, relieved of her doughnut by a passing gull on Brighton seafront (Linning, 2014). Her husband commented 'If there's one thing Mrs Dack doesn't like its having her doughnuts pinched.' Gulls also appear to have developed a taste for more than just doughnuts. Newspapers eagerly report them swooping to snatch small dogs (Mullin, 2015), false teeth (Bexhill-on-Sea Observer, 2013), crisps (Barnes, 2016), and most popular of all, any food from Greggs (Edwards, 2016). Despite the sometimes humorous portrayals in such articles, the underlying pattern is that of the media systematically depicting gulls in a negative light. Content analysis of newspapers featuring gull stories showed that descriptions of gulls and gull behaviour is predominantly negative, with 'victims' of gull attacks being variously described as having been mugged, intimidated, terrorised, stalked relentlessly, and more. Gulls are pigeon-holed as masters of intimidation, winged raiders, and greedy, swaggering, cunning beasts. Newspaper headlines such as 'Call for action over Kirkcaldy Seagull Menace' (Fife Today, 2012) or 'Seagull Terror: Lock up your babies' (Perry, 2015) further promote the viewpoint that gulls are a problem and thus require a solution. And it is not just the media that frames gulls as menaces to society; their reputation is consolidated in our popular culture from an early age. Stories such as The Lighthouse Keeper's Lunch (Armatige, 2007) depict gulls as thieving varmints that have to be outwitted at all costs. And the upshot of all this negativity − seemingly derived from just one of their natural behaviours, and the human inability to share − is the casting of the gull as a 'problem' animal, which in turn can lead to an uprising of humans against gulls. It is within this landscape of people versus 'problem animals' that we find individuals taking matters into their own hands. Across England and Wales there are hundreds of wildlife rehabilitation centres, caring for thousands of sick and injured wild animals each year. Data from the four RSPCA wildlife centres alone shows that nationally they admit an average of 30 shot gulls each year, alongside gulls that have been deliberately poisoned, stoned, kicked or fished. Such acts of purposeful cruelty appear to indicate that some people are happy to respond to the 'call for action' newspapers espouse. And even those that do not commit acts of cruelty may try to tackle the perceived problem in a range of creative ways. One interviewee commented 'If a gull ate my chips I wouldn't finish them. I would feed them the rest. I'm playing the long game and giving gulls diabetes.' In short, gulls seem to be unpopular, unwanted, and perceived as out-of-place in our modern landscapes. And yet herring gulls are listed as species with a red status in conservation terms, whilst lesser black-backed gulls (Larus fuscus) and great black-backed gulls (Larus marinus) have amber status (RSPB, 2017). Gull populations in the UK have suffered declines, so it appears that from a conservation perspective alone we should be caring for these species, even before we consider their individual welfare as sentient creatures. But if we then argue that it is necessary to try
Innovative problem solving, repeated innovation, learning, and inhibitory control are cognitive abilities commonly regarded as important components of behaviorally flexible species. Animals exhibiting these cognitive abilities may be more likely to adapt to the unique demands of living in novel and rapidly changing environments, such as urbanized landscapes. Raccoons (Procyon lotor) are an abundant, generalist species frequently found in urban habitats, and are capable of innovative problem solving, which makes them an ideal species to assess their behavioral flexibility. We gave 20 captive raccoons a multi-access puzzle box to investigate which behavioral and cognitive mechanisms enable the generation of innovative and flexible behaviors in this species. Over two-thirds of raccoons tested were not only capable of innovative problem solving, but displayed repeated innovation by solving more than one solution on the multi-access puzzle box and demonstrated that they learned multiple solutions to a novel problem. Although we found no relationship between our measure of inhibitory control and a raccoon’s ability to exhibit repeated innovations, we did find a positive relationship between the diversity of behaviors that an individual exhibited when interacting with the problem and the number of solution types that they solved. We identified other predictors of problem-solving performance, including neophobia and persistence. Finally, we examine the implications of our results in the context of the cognitive-buffer hypothesis and consider whether the widespread success of an adaptive generalist carnivore could be due in part to having these cognitive and behavioral traits.
Cities are rapidly expanding, and wildlife may experience different selection pressures in urban environments when compared to natural habitats. Phenotypic differences between urban and natural populations may occur because of the altered urban environment. Behavior, the activity of the hypothalamic-pituitary-adrenal (HPA) axis and body condition can be expected to differ between urban and natural habitats. We used the eastern chipmunk (Tamias striatus) to test for differences in behavior assayed from an open field test, hair and fecal cortisol concentrations, and body condition (size-corrected body mass), predicting that urban chipmunks would exhibit more exploratory behavior, higher cortisol concentrations, and higher body condition, than their counterparts from natural habitats. We sampled eastern chipmunks in 2 urban areas paired with natural habitats and subjected adult chipmunks to an open field test, collected hair and fecal samples for the determination of cortisol concentrations, and measured body size and body mass to estimate body condition. Eastern chipmunks in urban habitats had significantly different behavior, tending toward reduced locomotion and grooming, and greater latency, than their counterparts from natural habitats. Urban chipmunks also had lower fecal cortisol concentrations than those from natural habitats, and female chipmunks were in better body condition when captured in urban habitats. These results suggest that urban habitats may be relatively benign for urban chipmunks, perhaps because of reduced need for exploration and the availability of anthropogenic food subsidies associated with urban environments.
Using social information can benefit individuals in many ways. Responding to alarm signals can, for instance, maximize survival under predation risk. However, foraging individuals should consider the reliability of such risk-based information to balance antipredator behavior and resource acquisition. Receiver decisions could depend on personality effects, as individual variation in risk-taking tendencies (i.e., boldness) could not only affect receiver perception of the signaled threat but also signaler reliability. Recent theoretical models support the possibility of coevolution between personality and communication strategies. Using a playback experiment, we show that wild eastern chipmunks (Tamias striatus) respond to alarm calls according to their own boldness level (measured as consistent individual differences in basal vigilance) and that they increase their vigilance response to bolder callers potentially considered as more reliable. Further, receivers respond to the callers' boldness regardless of their own boldness and independently of their familiarity level with callers, therefore decoding this information from vocalizations. Such effects of individual behavioral variation on the perception and interpretation of social information could apply to signals used in a variety of ecological contexts. ©The Author(s) 2017. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
A range of species exploit anthropogenic food resources in behaviour known as 'raiding'. Such behavioural flexibility is considered a central component of a species' ability to cope with human-induced environmental changes. Here, we study the behavioural processes by which raiding male chacma baboons (Papio ursinus) exploit the opportunities and mitigate the risks presented by raiding in the suburbs of Cape Town, South Africa. Ecological sampling and interviews conducted with 'rangers' (employed to manage the baboons' space use) revealed that baboons are at risk of being herded out of urban spaces that contain high-energy anthropogenic food sources. Baboon-attached motion/GPS tracking collars showed that raiding male baboons spent almost all of their time at the urban edge, engaging in short, high-activity forays into the urban space. Moreover, activity levels were increased where the likelihood of deterrence by rangers was greater. Overall, these raiding baboons display a time-activity balance that is drastically altered in comparison to individuals living in more remote regions. We suggest our methods can be used to obtain precise estimates of management impact for this and other species in conflict with people.
One of the most important human social skills is the ability to recognize faces. Humans recognize familiar faces easily, and can learn to identify unfamiliar faces from repeatedly presented images. Sheep are social animals that can recognize other sheep as well as familiar humans. Little is known, however, about their holistic face-processing abilities. In this study, we trained eight sheep (Ovis aries) to recognize the faces of four celebrities from photographic portraits displayed on computer screens. After training, the sheep chose the ‘learned-familiar’ faces rather than the unfamiliar faces significantly above chance. We then tested whether the sheep could recognize the four celebrity faces if they were presented in different perspectives. This ability has previously been shown only in humans. Sheep successfully recognized the four celebrity faces from tilted images. Interestingly, there was a drop in performance with the tilted images (from 79.22±7.5% to 66.5±4.1%) of a magnitude similar to that seen when humans perform this task. Finally, we asked whether sheep could recognize a very familiar handler from photographs. Sheep identified the handler in 71.8±2.3% of the trials without pretraining. Together these data show that sheep have advanced face-recognition abilities, comparable with those of humans and non-human primates.
The Living Elephants is the authoritative resource for information on both Asian and African elephants. From the ancient origins of the proboscideans to the present-day crisis of the living elephants, this volume synthesizes the behavior, ecology and conservation of elephants, while covering also the history of human interactions with elephants, all within the theoretical framework of evolutionary biology. The book begins with a survey of the 60-million year evolutionary history of the proboscideans emphasizing the role of climate and vegetation change in giving rise to a bewildering array of species, but also discussing the possible role of humans in the late Pleistocene extinction of mastodonts and mammoths. The latest information on the molecular genetics of African and Asian elephants and its taxonomic implications are then presented. The rise of the elephant culture in Asia, and its early demise in Africa are traced along with an original interpretation of this unique animal-human relationship. The book then moves on to the social life of elephants as it relates to reproductive strategies of males and females, development of behavior in young, communication, ranging patterns, and societal organization. The foraging strategies of elephants, their impact on the vegetation and landscape are then discussed. The dynamics of elephant populations in relation to hunting for ivory and their population viability are described with the aid of mathematical models. A detailed account of elephant-human interactions includes a treatment of crop depredation by elephants in relation to their natural ecology, manslaughter by elephants, habitat manipulation by humans, and a history of the ivory trade and poaching in the two continents. The ecological information is brought together in the final chapter to formulate a set of pragmatic recommendations for the long-term conservation of elephants. The broadest treatment of the subject yet undertaken, by one of the leading workers in the field, Raman Sukumar, the book promises to bring the understanding of elephants to a new level. It should be of interest not only to biologists but also a broader audience including field ecologists, wildlife administrators, historians, conservationists and all those interested in elephants and their future.
This chapter relies on recent data to address the old question of why some animals have large brains relative to body size even though such brains incur substantial costs in terms of delayed maturation and high maintenance. It reviews recent studies providing support for the cognitive-buffer hypothesis, which states that a relatively large brain is associated with an enhanced ability to handle novel situations and hence with increased probability of survival in novel or altered environments. The cognitive-buffer hypothesis is the most general explanation for the benefits of the evolution and development of large brains, proposing that a major advantage of a large brain is to produce behavioral responses that protect the animal from the vagaries of the environment. The buffer function of the brain has the potential to generate “autocatalytic” and positive-feedback processes that, although still not well understood, could accelerate brain evolution.
Behavioural flexibility has been argued to be an evolutionarily favourable trait that helps invasive species to establish themselves in non-native environments. Few studies, however, have compared the level of flexibility (whether considered as an outcome or as a process) in mammalian invaders and related native species. Here, we tested whether flexibility differs between groups of free-ranging invasive eastern grey squirrels, Sciurus carolinensis, and native Eurasian red squirrels, Sciurus vulgaris, in the U.K., using an easy and a difficult food extraction task. All individuals of both species showed flexibility, at the outcome level, in solving the easy task and solution time was comparable between species across a series of successes. A higher proportion of grey squirrels than red squirrels solved the difficult task. However, for those squirrels that did solve the task, solving efficiency was comparable between species on their first success, and a few red squirrels outperformed the grey squirrels in subsequent successes. Between- species analysis showed that instantaneous flexibility, flexibility at the process level that was measured as the rate of switching between tactics after a failed attempt, was higher in red squirrels than in grey squirrels. Within-species analysis also revealed that red squirrel problem solvers showed higher flexibility at the process level than their nonsolver counterparts. Nonsolvers also failed to make ‘pro- ductive’ switches (switching from ineffective to effective tactics). Together, the results suggest that problem-solving ability overlaps in the two species, but is less variable, and on average higher, in grey squirrels than in red squirrels. The superior behavioural flexibility of the grey squirrels, shown here by success at problem solving, may have facilitated their invasion success, but it may also have resulted from selective pressures during the invasion process.