Temporal repeatability of behaviour in a lizard: implications for behavioural syndrome studies

It is well established that, across taxa, individuals within populations exhibit consistent differences in their behaviour across time and/or contexts. Further, the functional coupling of traits may result in the formation of a behavioural syndrome. Despite extensive evidence on the existence of consistent among-individual differences in behaviour and behavioural syndromes in the animal realm, these findings are predominately based upon short-term assessments, leading to questions regarding their stability over longer periods. Understanding if these estimates are temporally stable would allow predictions of individual behaviour to be made using short-term repeated measures. Here, we used 57 adult male delicate skinks (Lampropholis delicata) to evaluate the stability of behavioural variation observed both among (animal personality and behavioural plasticity) and within individuals (behavioural predictability), as well as behavioural syndromes, across short (four weeks) and long (five months) timeframes. To do so, we repeatedly assayed activity, exploration, and boldness five times per each individual. Overall, our study revealed complex patterns of behavioural variation and trait (co)variation over time. Activity was always repeatable across time intervals, whereas behavioural differences among individuals in exploration and boldness were not consistent. Yet a behavioural syndrome between activity and exploration was detected at both shorter and longer temporal scales, suggesting that syndrome structure in these traits does not vary as a function of time. Our findings indicate that, at least for some traits (e.g. activity) and studies, short-term measures may be adequate in serving as a proxy for long-term variation in individual behaviour, and to reveal the existence of behavioural syndromes at the population level

Predicting the impacts of chemical pollutants on animal groups

Wildlife are exposed to an increasing number and diversity of chemical pollutants.Chemical pollutants can elicit a range of sublethal effects on individual organisms, but research on how these contaminants affect social interactions and animal groups is severely lacking.It is imperative that perspectives from behavioural ecology and ecotoxicology are integrated, to increase our understanding of how contaminant effects on individuals might cascade to group-level processes.We present a conceptual framework for researchers and practitioners to guide the study of how chemical pollutants might affect the emergence, organisation, and function of animal social groups.Chemical pollution is among the fastest-growing agents of global change. Synthetic chemicals with diverse modes-of-action are being detected in the tissues of wildlife and pervade entire food webs. Although such pollutants can elicit a range of sublethal effects on individual organisms, research on how chemical pollutants affect animal groups is severely lacking. Here we synthesise research from two related, but largely segregated fields – ecotoxicology and behavioural ecology – to examine pathways by which chemical contaminants could disrupt processes that govern the emergence, self-organisation, and collective function of animal groups. Our review provides a roadmap for prioritising the study of chemical pollutants within the context of sociality and highlights important methodological advancements for future research

Social context mediates the expression of a personality trait in a gregarious lizard

The social environment is a key factor that influences behavioural traits across a wide array of species. Yet, when investigating individual differences in behaviour, studies tend to measure animals in isolation from other conspecifics-even in social species. Surprisingly, whether behavioural traits measured in isolation are predictive of individual-level behaviour when in social groups is still poorly understood. Here, we repeatedly measured risk-taking behaviour (i.e. boldness; 741 total trials) in both the presence and absence of conspecifics in a social lizard, the delicate skink (Lampropholis delicata). Further, we manipulated food availability during group trials to test whether the effect of the social environment on risk-taking behaviour was mediated by competition over resources. Using 105 lizards collected from three independent populations, we found that individual risk-taking behaviour was repeatable when measured in either social isolation or within groups both with and without food resources available. However, lizards that were bolder during individual trials were not also bolder when in groups, regardless of resource availability. This was largely driven by individual differences in social behavioural plasticity, whereby individual skinks responded differently to the presence of conspecifics. Together, this resulted in a rank order change of individual behavioural types across the social conditions. Our results highlight the importance of the social environment in mediating animal personality traits across varying levels of resource availability. Further, these findings suggest that behavioural traits when measured in isolation, may not reflect individual variation in behaviour when measured in more ecologically realistic social groups

Biological invasions as a selective filter driving behavioral divergence

Biological invasions are a multi-stage process (i.e., transport, introduction, establishment, spread), with each stage potentially acting as a selective filter on traits associated with invasion success. Behavior (e.g., exploration, activity, boldness) plays a key role in facilitating species introductions, but whether invasion acts as a selective filter on such traits is not well known. Here we capitalize on the well-characterized introduction of an invasive lizard (Lampropholis delicata) across three independent lineages throughout the Pacific, and show that invasion shifted behavioral trait means and reduced among-individual variation-two key predictions of the selective filter hypothesis. Moreover, lizards from all three invasive ranges were also more behaviorally plastic (i.e., greater within-individual variation) than their native range counterparts. We provide support for the importance of selective filtering of behavioral traits in a widespread invasion. Given that invasive species are a leading driver of global biodiversity loss, understanding how invasion selects for specific behaviors is critical for improving predictions of the effects of alien species on invaded communities.Invasive species are a leading driver of global biodiversity loss. Here, the authors show that the process of invasion itself can promote behavioral changes important to the success of widespread invaders, with implications for understanding the effects of alien species on invaded communities

Pharmaceutical pollution disrupts the behaviour and predator–prey interactions of two widespread aquatic insects

Pharmaceutical pollution represents a rapidly growing threat to ecosystems worldwide. Drugs are now commonly detected in the tissues of wildlife and have the potential to alter the natural expression of behavior, though relatively little is known about how pharmaceuticals impact predator-prey interactions. We conducted parallel laboratory experiments using larval odonates (dragonfly and damselfly nymphs) to investigate the effects of exposure to two pharmaceuticals, cetirizine and citalopram, and their mixture on the outcomes of predator-prey interactions. We found that exposure to both compounds elevated dragonfly activity and impacted their predation success and efficiency in complex ways. While exposure to citalopram reduced predation efficiency, exposure to cetirizine showed varied effects, with predation success being enhanced in some contexts but impaired in others. Our findings underscore the importance of evaluating pharmaceutical effects under multiple contexts and indicate that these compounds can affect predator-prey outcomes at sublethal concentrations

Frontiers in quantifying wildlife behavioural responses to chemical pollution

Animal behaviour is remarkably sensitive to disruption by chemical pollution, with widespread implications for ecological and evolutionary processes in contaminated wildlife populations. However, conventional approaches applied to study the impacts of chemical pollutants on wildlife behaviour seldom address the complexity of natural environments in which contamination occurs. The aim of this review is to guide the rapidly developing field of behavioural ecotoxicology towards increased environmental realism, ecological complexity, and mechanistic understanding. We identify research areas in ecology that to date have been largely overlooked within behavioural ecotoxicology but which promise to yield valuable insights, including within- and among-individual variation, social networks and collective behaviour, and multi-stressor interactions. Further, we feature methodological and technological innovations that enable the collection of data on pollutant-induced behavioural changes at an unprecedented resolution and scale in the laboratory and the field. In an era of rapid environmental change, there is an urgent need to advance our understanding of the real-world impacts of chemical pollution on wildlife behaviour. This review therefore provides a roadmap of the major outstanding questions in behavioural ecotoxicology and highlights the need for increased cross-talk with other disciplines in order to find the answers

Personality, spatiotemporal ecological variation, and resident/explorer movement syndromes in the sleepy lizard

Individual variation in movement is profoundly important for fitness and offers key insights into the spatial and temporal dynamics of populations and communities. Nonetheless, individual variation in fine-scale movement behaviours are rarely examined even though animal tracking devices offer the long-term, high-resolution, repeatable data in natural conditions that are ideal for studying this variation. Furthermore, of the few studies that consider individual variation in movement, even fewer also consider the internal traits and environmental factors that drive movement behaviour which are necessary for contextualising individual differences in movement patterns. In this study, we GPS-tracked a free-ranging population of sleepy lizards, Tiliqua rugosa, each Austral spring over five years to examine consistent among-individual variation in movement patterns, as well as how these differences were mediated by key internal and ecological factors. We found that individuals consistently differed in a suite of weekly movement traits, and that these traits strongly covaried among-individuals, forming movement syndromes. Lizards fell on a primary movement continuum, from 'residents' that spent extended periods of time residing within smaller core areas of their home range, to 'explorers' that moved greater distances and explored vaster areas of the environment. Importantly, we also found that these consistent differences in lizard movement were related to two ecologically important animal personality traits (boldness and aggression), their sex, key features of the environment (including food availability, and a key water resource), habitat type, and seasonal variation (cool/moist vs hot/drier) in environmental conditions. Broadly, these movement specialisations likely reflect variation in life-history tactics including foraging and mating tactics that ultimately underlie key differences in space use. Such information can be used to connect phenotypic population structure to key ecological and evolutionary processes, for example social networks and disease-transmission pathways, further highlighting the value of examining individual variation in movement behaviour.Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: DEB-1456730Funding provided by: Australian Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000923Award Number: DP0877384Funding provided by: Australian Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000923Award Number: DP130100145The following description is from Michelangeli et al. (2021) but modified for brevity. Note that citations have been removed, but can be found in Michelangeli et al. (2021) Study system The sleepy lizard is a common skink species to South Australia. They are large-bodied (adults are 400 – 950g, snout-vent-length 25 – 35 cm), long-lived (up to ~48 years) and slow-moving. They have been found to maintain relatively stable and consistent home ranges (HR) over multiple years (our tracking covering up to 8 years; mean 95% HR area in hectres [95% CI]; females: 3.53 [3.07, 4.01] and males: 4.91 [4.42, 5.43]). We studied a population within a ~1.2km2 field site near Bundey Bore Station (33.888240 S, 139.310718 E). Our field site has semi-arid Mediterranean climate and is primarily chenopod shrubland dominated by bluebush (Maireana sedifolia) and some black oak (Casuarina cristata). Various annual plants, including the lizards'preferred food item, the invasive Ward's weed, Carrichtera annua , tend to grow around and under these shrubs. The field site has a seasonal dam that retains water and soil moisture for longer than other parts of the area. Lizards at this field site are primarily active from September (early spring) to December (early summer). The beginning of the lizard's activity period is characterised by moderate temperatures and higher relative abundance of food and water. Early spring is also the breeding season in which lizards form monogamous pairs for up to 10 weeks before they mate. During this time males perform more scent-marking and competition is higher, potentially leading to sex differences in movement behaviour early in the season. On the other hand, the late season is hotter and drier, and food and water resources become increasingly scarce and patchier in distribution. GPS data collection Sleepy lizards were GPS tracked during their activity season between 2013-2017. The GPS data was filtered to remove all errors and points that were outside a lizards primary activity period (between 06:00 and 20:00). The data was also thinned to follow a 20 min resolution. Using the wrangled GPS data, we calculated six movement metrics - daily distance travelled, max daily displacement, straightness index, residence time, home range size and home range use ratio. These metrics are commonly used to represent a range of possible movement and spatial patterns that we predicted might vary among lizards. To enable comparison between all metrics, we averaged the daily scale metrics within weeks. To eliminate correlation between the number of weekly GPS points and corresponding movement metric value, we only included weeks in our analysis with at least 120 GPS locations (which represents ~ 3.5 days of GPS data). we obtained GPS data from 128 lizards and a total of 569341 GPS fixes (after sub-sampling that data to 20 min intervals). From these data, we obtained on average 17 ± 11.6 (mean ± SD; range 2 – 45) weekly replicates for each movement metric over an average of 2.35 ± 1.4 (range 1-5) years per lizard. Each weekly replicate contained on average 189.64 ± 30.00 GPS points Measurement of lizard internal traits In addition to the movement data, we also collected data on each lizards size every 2 weeks. Between 2015-2017 seasons, lizard aggression and boldness behaviour was also assayed 2-3 times per year, with each trials occuring at least 2 weeks apart. . To assess a lizard's boldness, we measured a lizard's response to a preferred food item (a piece of banana) in the presence of a potential threat (a looming observer). A lizard's boldness was ranked based on their response, from quickly approaching the food item and the observer (high boldness rank), to showing very little response (intermediate boldness), to quickly fleeing from the observer into refuge (shy). Boldness was ranked on a 1-10 scale in 2015 and on a 1-7 scale in 2016-2017, but higher ranks always referred to bolder animals and thus ranks were standardized within year (by subtracting the mean and dividing by the standard deviation). To assess a lizard's aggression, we ranked a lizard's response to a simulated capture attempt by an observer which involved the observer's hand coming to within ~10 cm of the lizard's head. Responses were ranked on a scale of 1-11, from fleeing the observer into refuge (passive = 1) to attempting to bite the observer (high aggression = 11). Both aggression and boldness have shown to be repeatable over an 8-year period (r ± SE = 0.43 ± 0.05 and r = 0.27 ± 0.04, respectively), and are only weakly positively correlated suggesting independence between the traits (correlation coefficient ± 95% CI = 0.15 [-0.07, 0.39]). In the present study, we used the average personality score for each individual within each year in our analysis Measurment of environmental variables From the movement trajectories within each year, we calculated an individual's mean weekly distance from the dam (DamDist) and the number of unique visits to the dam (i.e. DamVisits). A unique visit to the dam involved a lizard entering and then leaving a 15m radius around the dam. The dam is the only reliable water resource at our field site, and lizards are often observed in this area, but we also know that approximately only about 50% of our study population access the dam within a given year. We also calculated a lizard 95% weekly HR overlap with 'forested' habitat (ForestHR). Forested areas tend to contain denser vegetation and refuge for lizards and may be preferred by lizards seeking shelter. Forested habitats were defined by drawing polygons around forested regions based on satellite images from Google Earth. During 2015 -2017, we also conducted habitat surveys of food quality in 123 quadrats distributed in a grid over the field site. Within each quadrat, we surveyed a 40m radius around a central point, and ranked the availability of moist food (i.e. primarily Ward's weed) on a 1-5 scale. Since lizard HRs could include multiple quadrats, we averaged the quadrat food scores within a lizard's 95% HR, weighted by the usage of that quadrat (relative to usage of all quadrats within the focal lizard's 95% HR), within each week, (FoodQualityHR)