Journal of Animal Ecology

Grouping with others can provide enhanced information about resources and threats. A key hypothesis in social evolution proposes that individuals can benefit from social information in environments where it is challenging to meet energetic needs. Here, we test this hypothesis by examining the environmental drivers of conspecific flocking behaviour in a large archive of citizen science observations of two common North American birds, the dark-eyed junco (Junco hyemalis) and black-capped chickadee (Poecile atricapillus). To quantify flocking behaviour, we apply the index of dispersion, D, as a metric of clumpiness in each species spatiotemporal distribution. We show that juncos in winter are nearly always more clustered than a random expectation, whereas chickadees span a range from uniform to socially clustered distributions. In both species, the degree of social clustering strongly increases with abundance. We identify several key environmental variables that explain the extent of conspecific flocking in both species. Flocks are more socially clustered at higher latitudes, higher elevations, closer to midwinter, and at temperatures that are colder than average given the location and time of year. Together, these findings support the hypothesis that sociality is a key strategy for coping with harsh environments. HIGHLIGHTSO_LIGrouping with others can be an important source of information about resources C_LIO_LIWe analyzed how flocking behaviour changes throughout winter in two bird species C_LIO_LIWe used the index of dispersion to quantify social clustering at a broad scale C_LIO_LIIn both species, social clustering increases in response to climate challenges C_LI

Habitat loss and disease outbreak play a major role in the decline of biodiversity. Habitat degradation is often associated with reduced food resources, which can lead to less investment in host immunity and increased infections. However, pathogens use host resources for replication and pathogen traits, such as infecting hosts internally or short generation times, might allow pathogens to rapidly capitalize on host-consumed nutrients. Thus, it is unclear whether increased food consumption by hosts should reduce or amplify pathogen levels. We conducted experiments on Cuban treefrogs (Osteopilus septentrionalis) to test how food availability affects infection levels of Ranavirus and the fungal pathogen Batrachochytrium dendrobatidis (Bd), which are both associated with mass die-offs of amphibians. Given that Ranavirus is an endoparasite with a much shorter generation time than the ectoparasitic Bd, we postulated that Ranavirus might be able to capitalize on host-consumed resources more quickly than Bd. We hypothesized that increased food availability to hosts might reduce Bd infections more than Ranavirus infections. As predicted, augmenting food access decreased Bd infection intensity, but increased Ranavirus infection intensity. Future work should assess whether pathogen traits, such as generation time and endo- versus ectoparasitism, generally affect whether food resources more positively benefit hosts or pathogens.

The gut microbiome (hereafter, GM) varies across individuals of the same species and this pattern has been observed in multiple wild species. Evidence shows that the GM connects to individual health and survival especially in captive species, but more research is needed to understand how the GM connects to host fitness in wild species. We used long-term monitoring data to investigate whether the GM of collared flycatchers Ficedula albicollis associates with annual and lifetime reproductive success (LRS), and survival to the following breeding season. This is the first study that 1) characterized the collared flycatcher GM, and 2) investigated how variation in the GM related to LRS in wild birds. Our results showed that higher GM diversity was associated with a higher annual and lifetime reproductive success in especially male collared flycatchers. We also found that the compositional variation in collared flycatcher GMs was explained by sex, age, and breeding habitat, but not by annual or lifetime reproductive success. Individuals that died before the next breeding season had higher abundances of ASVs belonging to the pathogenic families Enterobacteriaceae and Parachlamydiaceae, and the genera Corynebacteria and Sphingomonas. Our results show that the GM associates with different aspects of host fitness in a wild bird population. More research is needed to evaluate if there is a causal relationship between the GM and individual fitness. These findings also contribute to our understanding of the GMs role in evolution by elucidating the connection between the GM (trait) and reproductive success.

AimElucidating the mechanisms shaping parasite diversity patterns is critical because parasites encompass about 40% of known species, and are crucial for ecosystem structure and function. In free-living species, diversity patterns in the Anthropocene are shaped by niche-breadth because specialists (narrow niche-breadth taxa) are more sensitive to environmental disturbance compared to generalists (broad niche-breadth taxa). Like free-living species, parasites too can be categorized as specialists or generalists according to their niche-breadth (i.e., diversity of hosts they can infect). However, unlike free-living species, the effects of niche-breadth on parasite diversity patterns remain unclear. Here, we used haemosporidian parasites as a model system to identify factors affecting parasite diversity patterns, and test if these patterns differ between specialist (Haemoproteus) and generalist (Plasmodium) parasites. LocationSouthern India TaxonHaemoproteus spp. and Plasmodium spp. (Haemosporida) MethodsBlood samples from wild birds were screened using molecular tools to identify haemosporidian parasite lineages. Statistical analyses, including random forest models and generalized dissimilarity models, were utilized to evaluate how environmental and host factors drive spatial patterns of parasite and {beta} diversity. ResultsOur results reveal that phylogenetic diversity is primarily shaped by host-related variables in the specialist parasites, but by numerous host- and environment-related factors in the generalists. In keeping with ecological theory, the specialist parasites showed higher diversity and lower evenness compared to the generalists. Additionally, while {beta} diversity of the specialist parasites was primarily driven by spatial differences in richness (e.g., taxon nestedness) rather than replacement (e.g., taxon turnover), the opposite pattern was found in the generalist. Main conclusionThe differential patterns and drivers of diversity in specialist vs. generalist parasites demonstrates why specialists parasites are good indicators of ecosystem health and elucidates the mechanism by which anthropogenic disturbance increases the risk of emerging infectious diseases which are primarily caused by generalist parasites.

Much ecological research focuses on phenomena where a given variable can affect another either directly or indirectly through the effect of one or more intervening variables. While various methods to quantify the magnitude of these effects are available, they can be difficult to interpret in a meaningful way, especially for indirect effects. Studies thus often quantity direct effects and infer indirect ones more or less formally. We propose a method for visualizing indirect effects by means of plotting model predictions of an outcome in the presence of both exposure and mediator variables. We demonstrate the method through simulations and apply them to a real-world example involving Tree Swallows (Tachycineta bicolor) and their obligatory hematophagous ectoparasites, Protocalliphora bird blowflies (Diptera: Calliphoridae). Our procedure, which can be seamlessly integrated into an analysts workflow using commonplace software, should prove instrumental to disentangle and interpret relationships among variables involved in ecological mechanisms.

Understanding where and when pathogens occur in the environment has implications for reservoir population health and infection risk. In reservoir hosts, infection status and pathogen shedding are affected by processes interacting across different scales: from landscape features affecting host location and transmission to within-host processes affecting host immunity and infectiousness. While uncommonly done, simultaneously incorporating processes across multiple scales may improve pathogen shedding predictions. In Australia, the black flying fox (Pteropus alecto) is a natural host for the zoonotic Hendra virus, which is hypothesized to cause latent infections in bats. Re-activation and virus shedding may be triggered by poor host condition, leading to virus excretion through urine. Here, we developed a statistical modeling approach that combined data at multiple spatial and temporal scales to capture ecological and biological processes potentially affecting virus shedding. We parameterized these models using existing datasets and compared model performance to under-roost virus shedding data from 2011-2014 in 23 roosts across a 1200-km transect. Our approach enabled comparisons among multiple model structures to determine which variables at which scales are most influential for accurate predictions of virus shedding in space and time. We identified environmental predictors and temporal lags of these features that were important for determining where reservoirs are located and multiple independent proxies for reservoir condition. The best-performing multi-scale model delineated periods of low and high virus prevalence, reflecting observed shedding patterns from pooled under-roost samples. Incorporating regional indicators of food scarcity enhanced model accuracy while incorporating other stress indicators at local scales confounded this signal. This multiscale modeling approach enabled the combination of processes from different ecological scales and identified environmental variables influencing Hendra virus shedding, highlighting how integrating data across scales may improve risk forecasts for other pathogen systems.

The social environment has diverse consequences for individuals welfare, health, reproductive success, and survival. This environment consists of different kinds of dyadic bonds that exist at different levels; in many social species, smaller social units come together in larger groups, creating multilevel societies. In great tits (Parus major), individuals have four major types of dyadic bonds: pair mates, breeding neighbours, flockmates, and spatial associates, all of which have been previously linked to fitness outcomes. Here, we show that these different types of dyadic bonds are differentially linked with subsequent reproductive success metrics in this wild population and that considering spatial effects provides further insights into these relationships. We provide evidence that more social individuals had a higher number of fledglings, and individuals with more spatial associates had smaller clutch sizes. We also show individuals with stronger bonds with their pair mate had earlier lay dates. Our study highlights the importance of considering different types of dyadic relationships when investigating the relationship between wellbeing and sociality, and the need for future work aimed at experimentally testing these relationships, particularly in spatially structured populations.

Environmental factors, such as elevated temperature, can have varying effects on hosts and their parasites, which can have consequences for disease outcomes. The individual direct effects of temperature must be disentangled to determine the net-effect in host-parasite relationships, yet few studies have determined the net-effects in a multi-host system. To address this gap, we experimentally manipulated temperature and parasite presence in the nests of two host species infested by parasitic blowflies (Protocalliphora sialia). We conducted a factorial experiment by increasing temperature (or not) and removing all parasites (or not) in the nests of eastern bluebirds (Sialia sialis) and tree swallows (Tachycineta bicolor). We then measured nestling morphometrics, blood loss, and survival and quantified parasite abundance. We predicted that if temperature had a direct effect on parasite fitness, then elevated temperature would cause similar directional effects on parasite abundance across host species. If temperature had a direct effect on hosts, and therefore an indirect effect on the parasite, parasite abundance would differ across host species. Heated swallow nests had fewer parasites compared to non-heated nests. In contrast, heated bluebird nests had more parasites compared to non-heated nests. The results of our study demonstrate that elevated temperature can have differential effects on host species, which can impact infestation susceptibility. Furthermore, changing climates could have complex net-effects on parasite fitness and host health across multi-host-parasite interactions.

Age-dependent survival is central to understanding population dynamics and life-history evolution. We analysed carcass weight and age-at-harvest data from 6022 red foxes (Vulpes vulpes) collected across Sweden between 1967 and 1971 to evaluate latitudinal effects on body mass and age-dependent survival. Carcass weights decreased from south to north in both adults and sub-adults, contrary to Bergmann's rule, with southern foxes weighing approximately 1.27 times more than northern foxes. The latitudinal weight gradient exceeded the sex difference in both age classes, and no sex x region interaction was detected. The decrease in weight with latitude is consistent with reduced prey availability and harsher winter conditions in the north, which limit growth and body size during development. Using a Bayesian age-at-harvest model with region-specific population growth rates (lambda), we estimated age-dependent survival probabilities for four latitudinal regions and both sexes. Despite the strong latitudinal gradient in weight, survival did not show a corresponding pattern - regional differences were uncertain, with all credible intervals spanning zero. Regional population growth rates were consistent with slight decline in the north and near-stability in the south-central region, which suggests that body condition and population dynamics are coupled at the regional scale despite no survival gradient. The decoupling of body condition and survival across regions suggests that mortality patterns are similar across the latitudinal gradient. We discuss these patterns in terms of latitudinal productivity gradients, prey availability, and life-history trade-offs in a widely distributed carnivore.

Gut microbial communities regulate host physiology and health of humans and laboratory animals. The functional significance of these collective bacterial genomes (i.e. the microbiome) to the adaptive potential of wildlife hosts is still unknown. Studies demonstrating convincing examples of microbial flexibility to environmental change so far lack the experimental approaches to demonstrate the effect on host physiology. Invasive species provide natural experiments to tease apart these host-microbe relationships. However, no studies have investigated how microbial symbionts might mediate responses of invasive hosts physiology to environmental change. In this study, we examine whether invasive gut microbiomes have significantly diverged in their ability to respond to novel environmental change (i.e. a dietary challenge) compared to native gut microbiomes by performing reciprocal faecal microbial transplant (FMT) experiments in native and invasive guttural toad (Sclerophrys gutturalis) populations. Subsequently, we determine how the microbiome regulates host physiological changes in response to a dietary challenge. We show that invasive gut microbiomes exhibit higher microbial compositional and predicted functional flexibility to novel dietary change, compared to native gut microbiomes. This increased microbial flexibility is coupled with significant flexibility in energy harvesting. Furthermore, our results indicate that overall invasive gut microbiomes significantly upregulate energy harvesting and physiological performance of hosts, compared to native microbiomes. Our study is the first identifying gut microbiota as the sole factor contributing to the adaptive physiology of a vertebrate using a unique study design. These findings provide novel insights into the key role of gut microbial symbionts in increasing the invasive potential of its vertebrate host.

O_LIEvents such as anthropogenic activities and periodic tree masting can alter resource provisioning in the environment, directly affecting animals, and potentially impacting the spread of infectious diseases in wildlife. The effect of these supplemental resources on infectious diseases can manifest through different pathways, affecting host susceptibility, transmission and host demography. C_LIO_LITo date however, empirical research has tended to examine these different pathways in isolation, for example by quantifying the effects of provisioning on host behaviour in the wild or changes in immune responses in controlled laboratory studies. Further, while theory has investigated the interactions between these pathways, thus far this work has focussed on a narrow subset of pathogen types, typically directly-transmitted microparasites. Given the diverse ways that provisioning can affect host susceptibility, contact patterns or host demography, we may expect the epidemiological consequences of provisioning to depend on key aspects of parasite life-history, such as the duration of infection and transmission mode. C_LIO_LIWe developed a suite of generic epidemiological models to compare how resource provisioning alters responses for different parasites that vary in their biology (micro- and macro-parasite), transmission mode (direct, environmental, and vector transmitted) and duration of infection (acute, latent, and chronic). Next, we parameterised these different parasite types using data from the diverse parasite community of wild wood mice as a case study. C_LIO_LIWe show there are common epidemiological responses to host resource provisioning across all parasite types examined. In particular, the response to provisioning could be driven in opposite directions, depending on which host pathways (contact rate, susceptibility or host demography) are most altered by the addition of resources to the environment. Broadly, these responses were qualitatively consistent across all parasite types, emphasising the importance of identifying general trade-offs between provisioning-altered parameters. C_LIO_LIDespite the qualitative consistency in responses to provisioning across parasite types, we found notable quantitative differences between parasites, suggesting specific epidemiological outcomes could strongly depend on parasite type, infection duration and permanency of recovery, and whether the parasite is directly, environmentally, or vector transmitted. These analyses therefore highlight the importance of knowing key specific aspects of host-parasite biology, such as host contact behaviours, parasite interactions with the host immune system, and how resource availability shapes host demographics, in order to understand and predict epidemiological responses to provisioning for any specific host-parasite system. C_LI

O_LIPhenological shifts are a major ecological consequence of climate change, yet studies often focus on single life stages meaning that the potential for carryover effects between life stages remains poorly understood. Failing to account for these effects may lead to inaccurate estimates of phenological shifts, with consequences for predicted synchrony among interacting species. This is especially relevant for temperate systems where climate warming is occurring unevenly across the year. C_LIO_LIHere, we investigated how temperature experienced the previous autumn and winter (during the pupal and egg stage) influences spring phenology in the winter moth (Operophtera brumata), a herbivorous insect with distinct life stages. Using 50 years of local climate data to create five experimental temperature regimes, we first quantified phenotypic plasticity in the duration and temporal variability of pupal and egg development. We then examined how timing of adult moth emergence affects timing of offspring hatching. C_LIO_LIWe found divergent effects of temperature on different life stages; pupal development time was shortest at intermediate temperatures while egg development time decreased linearly with increasing temperature. Furthermore, phenological shifts due to the conditions experienced by the mother were carried over to influence the phenology of her offspring. While this carryover effect was partially compensated during subsequent stages, compensation decreased under warming conditions. C_LIO_LIThese results refine our understanding of the sensitivity of the annual cycle of winter moth phenology to variation in temperature with potential implications for population dynamics and interspecific interactions. Overall, our findings highlight the need to consider the impacts of warming across multiple life stages so that carryover effects can be properly accounted for. Doing so will improve predictions of phenological shifts under future climates. C_LI

Vertebrate gut microbiome has significant effects on host development, health, and fitness. Multiple external factors contribute to gut microbiome variation, and the role of ambient temperature has gained increasing attention. Yet, temperature effects are often tested in extremes and in captive systems. We experimentally studied the effect of subtle temperature decreases during post-natal development on gut microbiome diversity and composition in wild pied flycatchers (Ficedula hypoleuca). We also performed partial cross-fostering to study the relative contribution of genetic and rearing environment on microbiome. Nest-box cold treatment did not influence gut microbiome diversity or composition, which may be due to the small temperature change, ontogenetic stage, or other factors, such as diet, causing large variation in the data. Rearing environment explained more of the variation in gut microbiome than genetic background, but the variance explained was relatively small. Future studies need to further address the drivers of the large intraspecific variation in microbiome in natural populations.

Bat populations experience inter-annual variation in demographic rates in response to environmental conditions. This variation has the potential to impact population sizes and structures, in addition to population-level processes such as disease spread. To establish the influence of variation in demography on these processes, we develop a spatial, individual based model of a serotine bat (Eptesicus serotinus) population, within which we introduce a synthetic lyssavirus-like disease. Model results show that increasing demographic variation, particularly in survival rates, may drive substantial population decline in bat populations. Increasing environmental fluctuations driven by climate change may therefore be problematic for population persistence. The likelihood of disease persistence was also reduced by increasing variation. These findings highlight the limitations of only considering mean demographic rates for prediction of population size change and disease dynamics from models.

Host life-history traits can influence host-vector encounter rates, and so differentially determine the exposure risk of bird species. This modulation of host-virus encounters dynamics is especially important when facing "generalist" arboviruses like West Nile virus (WNV) and Saint Louis Encephalitis virus (SLEV). Using prevalence data collected by our laboratory since 2004, we tested several hypothesis that included birds ecological and life-history traits to determine which traits were better predictors of birds exposure risk to these arboviruses. By means of information-theoretic procedures and generalized mixed linear models, we observed that body mass was an important trait when predicting birds exposure risk to WNV and SLEV and migratory status significantly influenced birds exposure risk only to WNV. Our study highlights important traits to consider when studying the transmission system of these arboviruses, being useful to focus resources when characterizing viral transmission networks and discuss the repercussions of these traits over birds immune function throughout the pace of life syndrome and trade-offs theory.

Animal personality and parasite infections are key forces shaping the ecology and evolution of natural populations. Personality traits--such as activity, exploration, and boldness--shape how individuals interact with their environment and conspecifics, influencing both their exposure and susceptibility to parasite infection. In turn, parasites can impact host fitness and energy allocation, and may modify host behaviour either through manipulations to enhance transmission or as consequences of energetic trade-offs associated with mounting an immune response. Despite growing interest in the interplay between behaviour and infection, the overall directionality and consistency of personality-parasite relationships remain unclear. This relationship is further modulated by ecological and biological factors, such as parasite type (e.g. micro-, ecto-, or endoparasites) and host type (e.g. intermediate versus definitive), which can influence both infection risk and the nature of behavioural responses. To disentangle these effects, we performed a meta-analysis of 226 effect sizes across 80 studies, assessing (i) the impact of experimental infections on host personality traits, and (ii) the correlation between personality and infection status in observational studies of wild populations--while accounting for variation in parasite groups and host roles. In experimental studies, infected hosts exhibited significantly reduced levels of activity and exploration, while effects on boldness and aggressiveness were non-significant. These findings suggest that infection imposes energetic costs that suppress behaviours requiring sustained effort, such as movement and exploration. Conversely, observational studies showed a positive association between activity-exploration and infection probability, likely reflecting greater exposure of more active individuals to parasites via increased interaction with conspecifics or contaminated environments. Meta-regression analyses further revealed that parasite type and host role modulate personality-infection dynamics. In experimental studies, microparasites were associated with reduced boldness and activity-exploration, while endoparasites led to reduced activity- exploration--particularly in intermediate hosts. Notably, hosts showed significant behavioural suppression in experimental contexts, but not in observational studies, potentially indicating that behaviourally tolerant individuals are favoured in natural environments where personality traits relate directly to fitness. Together, these findings underscore the importance of ecological context and study design in interpreting personality-parasite associations. Experimental infections tend to reveal the physiological costs of infection, while observational studies highlight behavioural traits that modulate infection risk. By integrating data across host types, parasite groups, and methodological approaches, our meta-analysis provides a more comprehensive understanding of how personality and infection interact. These insights contribute to a broader effort to link behavioural ecology with disease ecology, clarifying how individual variation in behaviour shapes--and is shaped by--host-parasite dynamics.

O_LIHow early-life exploration shapes the adult annual cycle routines of migratory animals remains challenging to study, especially in long-lived species. Delayed recruitment often observed in long-lived migratory birds suggests that the first breeding attempt may be constrained by a protracted learning process in which individuals develop their annual itinerary, which may involve extensive exploration of the winter and breeding sites, potentially causing inexperienced young to wander beyond traditional population areas. C_LIO_LIUsing greater flamingo Phoenicopterus roseus GPS tracking data from 83 individuals tagged as nestlings in the Mediterranean, we analyzed ontogenetic changes in mobility and space use for up to 8 years of age. We segmented autumn-winter and spring-summer tracks (n = 223 device-bird-year combinations) into staging events (n = 1914). We then computed seasonal staging metrics and analysed how they changed with age. We map the traditional congregation sites of flamingos to investigate age-related changes in space use between males and females. C_LIO_LIFlamingos were more exploratory during their early years, gradually transitioning to a more sedentary lifestyle as they grew older. With each additional year of age, the number of staging events decreased by 16%, while the average duration of staging events increased by 8 days. C_LIO_LIBirds remained faithful to the non-breeding staging sites where they spent most of their time during the first year of life. Over time, they returned progressively closer to their natal sites, even after years of exploration at non-traditional locations. Breeding was rare (8%) and occurred at a relatively late age ([≥]5 years), highlighting an extended exploratory phase, a pattern observed in other long-lived species. C_LIO_LIOlder birds were more likely to use traditional sites and spent more time at these sites, particularly after age 5. Our study reveals the individual exploration process underlying natal and non-breeding dispersal patterns previously laid bare by ring-resighting studies and shows that flamingos retain long-term memory of sites learned in early life. C_LI

O_LIDemographic processes in populations are inherently heterogeneous across both space and time. Many ecological models explicitly account for temporal heterogeneity in the demographic rates that govern these processes, but assume spatial homogeneity. Ignoring spatial heterogeneity can bias inference, limit predictive performance, and obscure key spatial structure in demographic rates. Integrated population models (IPMs) offer a powerful framework to estimate spatio-temporal demographic rates by combining diverse ecological data sources collected from multiple sampling locations. However, to accomplish this, IPMs face significant statistical and computational hurdles, including misalignment between different data sources and the need to efficiently account for residual spatial autocorrelation. C_LIO_LIWe present a novel Bayesian spatially explicit integrated population model (sIPM) which integrates population count and capture-recapture data from multiple sampling locations to estimate and predict continuous spatio-temporal demographic rates, such as survival, recruitment and population growth rate, across large geographic domains. This framework employs a joint likelihood approach with change of support to flexibly accommodate spatial and spatio-temporal data misalignment, and incorporates a nearest-neighbor Gaussian process to efficiently model residual spatial autocorrelation and generate spatial predictions. C_LIO_LIWe assess the performance of our sIPM through an extensive simulation study. Results show that our approach provides unbiased and precise estimates and predictions of spatio-temporal demographic rates, even in the presence of significant data misalignment and residual spatial autocorrelation. We demonstrate the utility of our method by analyzing data on Gray Catbirds (Dumetella carolinensis) from the North American Breeding Bird Survey and the Monitoring Avian Productivity and Survivorship program across the eastern coast of the United States from 2004-2014. This analysis results in maps of apparent survival, recruitment and population growth rate, thereby revealing important spatio-temporal variations in demographic rates that would have been obscured by traditional, spatially homogeneous IPMs. C_LIO_LIOur sIPM offers a robust and computationally efficient method for studying spatio-temporal variation in demographic processes across large areas, even in the presence of data misalignment and residual spatial autocorrelation. Ultimately, this framework, applicable to many ecological monitoring programs, facilitates the development of spatially targeted strategies necessary for effective conservation and management. C_LI

Sleep is a highly complex and conserved biological process that affects several body functions and behaviors. Recent evidence suggests that there is a reciprocal interaction between sleep and immunity. For instance, fragmented sleep can increase the probability of parasitic infections and reduce the ability of infected hosts to fight infections. It is also known, particularly in humans and other mammals, that viral and bacterial infections alter the sleep patterns of infected individuals. However, the effects of macro-parasitic infections on sleep remain largely unknown. In this study, we investigated whether macro-parasite infections could alter the sleep of their hosts. We experimentally infected three-spined sticklebacks (Gasterosteus aculeatus) with the tapeworm Schistocephalus solidus and used a hidden Markov model to characterize sleep-associated behaviors in the sticklebacks. At an early time-point, 1-4 days after parasite exposure, infected fish showed no difference in sleep compared with non-exposed fish, whereas fish that were exposed but could fend off the infection slept less during the daytime. At a later time-point, 29-32 days after exposure, infected fish slept more than uninfected fish, while exposed-but-not-infected fish slept less than non-exposed fish. Using RNA-seq of brain tissue, we identified several immune- and sleep-associated genes that potentially underlie the observed behavioral changes. These results provide the first insight into the complex association between macro-parasite infection, immunity, and sleep in fish and may thus contribute to a better understanding of the reciprocal interaction between sleep and immunity.

1. Integrated step-selection analyses (ISSAs) are frequently used to study habitat selection using animal movement data. Methods for incorporating random effects in ISSAs have been developed, making it possible to quantify variability among animals in their space-use patterns. Although it is possible to model variability in both habitat selection and movement parameters, applications to date have focused on the former despite the widely acknowledged and important role that movement plays in determining ecological processes from the individual to ecosystem level. One potential explanation for this omission is the absence of readily-available software or examples demonstrating methods for estimating movement parameters in ISSAs with random effects. 2. We demonstrated methods for characterizing among-individual variability in both movement and habitat-selection parameters using a simulated data set and by fitting two models to an acoustic telemetry data set containing locations of 35 red snapper (Lutjanus campechanus). Movement kernels were assumed to depend on either the type of benthic reef habitat in which the fish was located (model 1) or the distance between the fishs current location and nearest edge habitat (model 2). In both models, we also quantified habitat selection for different benthic habitat classes and distance to edge habitat, and we allowed for individual variability in movement and habitat-selection parameters using random effects. 3. The simulation example highlights the benefits of a mixed effects specification, namely we can increase precision when estimating individual-specific movement parameters by borrowing information across like individuals. In our applied example, we found substantial among-individual variability in both habitat selection and movement parameters. Nonetheless, most red snapper selected for hardbottom habitat and for locations nearer to edge habitat. They also moved less when in hardbottom habitat. Turn angles were frequently near {+/-}{pi}, but were more dispersed when fish were far away from edge habitat. 4. We provide code templates and functions for quantifying variability in movement and habitat-selection parameters when implementing ISSAs with random effects. In doing so, we hope to encourage ecologists conducting ISSAs to take full advantage of their ability to model among-individual variability in both habitat-selection and movement patterns.