Novel insight into the genetic diversity of strongylid nematodes infecting South-East and East Asian primates.

With many non-human primates (NHPs) showing continued population decline, there is an ongoing need to better understand their ecology and conservation threats. One such threat is the risk of disease, with various bacterial, viral and parasitic infections previously reported to have damaging consequences for NHP hosts. Strongylid nematodes are one of the most commonly reported parasitic infections in NHPs. Current knowledge of NHP strongylid infections is restricted by their typical occurrence as mixed infections of multiple genera, which are indistinguishable through traditional microscopic approaches. Here, modern metagenomics approaches were applied for insight into the genetic diversity of strongylid infections in South-East and East Asian NHPs. We hypothesized that strongylid nematodes occur in mixed communities of multiple taxa, dominated by Oesophagostomum, matching previous findings using single-specimen genetics. Utilizing the Illumina MiSeq platform, ITS-2 strongylid metabarcoding was applied to 90 samples from various wild NHPs occurring in Malaysian Borneo and Japan. A clear dominance of Oesophagostomum aculeatum was found, with almost all sequences assigned to this species. This study suggests that strongylid communities of Asian NHPs may be less species-rich than those in African NHPs, where multi-genera communities are reported. Such knowledge contributes baseline data, assisting with ongoing monitoring of health threats to NHPs.

Disgust in animals and the application of disease avoidance to wildlife management and conservation.

Disgust is an adaptive system hypothesized to have evolved to reduce the risk of becoming sick. It is associated with behavioural, cognitive and physiological responses tuned to allow animals to avoid and/or get rid of parasites, pathogens and toxins. Little is known about the mechanisms and outcomes of disease avoidance in wild animals. Furthermore, given the escalation of negative human-wildlife interactions, the translation of such knowledge into the design of evolutionarily relevant conservation and wildlife management strategies is becoming urgent. Contemporary methods in animal ecology and related fields, using direct (sensory cues) or indirect (remote sensing technologies and machine learning) means, provide a flexible toolbox for testing and applying disgust at individual and collective levels. In this review/perspective paper, we provide an empirical framework for testing the adaptive function of disgust and its associated disease avoidance behaviours across species, from the least to the most social, in different habitats. We predict various trade-offs to be at play depending on the social system and ecology of the species. We propose five contexts in which disgust-related avoidance behaviours could be applied, including endangered species rehabilitation, invasive species, crop-raiding, urban pests and animal tourism. We highlight some of the perspectives and current challenges of testing disgust in the wild. In particular, we recommend future studies to consider together disease, predation and competition risks. We discuss the ethics associated with disgust experiments in the above contexts. Finally, we promote the creation of a database gathering disease avoidance evidence in animals and its applications.

Le dégoût est un système adaptatif supposé avoir évolué afin de réduire le risque de tomber malade. Il est associé à des réponses comportementales, cognitives et physiologiques adaptées pour permettre aux animaux d'éviter et/ou de se débarrasser des parasites, pathogènes et toxines. On sait peu de choses sur les mécanismes et les conséquences de l'évitement des maladies chez les animaux sauvages. Étant donné l'escalade des interactions négatives entre humains et faune, la traduction de ces connaissances dans la conception de stratégies de conservation et de gestion de la faune - prenant en considération l'évolution des espèces - devient urgente. Les méthodes contemporaines en écologie animale et dans les domaines connexes, utilisant des moyens directs (indices sensoriels) ou indirects (technologies de télédétection et apprentissage automatique), fournissent une boîte à outils flexible pour tester et appliquer le dégoût aux niveaux individuel et collectif. Dans cet article de revue/perspective, nous fournissons un cadre empirique pour tester la fonction adaptative du dégoût et les comportements associés d'évitement des maladies chez différentes espèces - des moins sociales aux plus sociales, et dans différents habitats. Nous prédisons divers compromis en fonction du système social et de l'écologie de l'espèce. Nous proposons cinq contextes dans lesquels les comportements d'évitement liés au dégoût pourraient être appliqués: la réhabilitation d'espèces menacées; les espèces envahissantes; les dommages aux cultures; les nuisibles urbains; et le tourisme animalier. Nous mettons en avant certaines perspectives et défis actuels de l'expérimentation sur le dégoût en milieu naturel. En particulier, nous recommandons la considération de plusieurs risques ensemble: maladie, prédation et compétition. Nous discutons également de l'éthique associée aux expériences sur le dégoût dans les contextes ci-dessus. Enfin, nous promouvons la création d'une base de données rassemblant les stratégies d'évitement des maladies chez les animaux et leurs applications.

Maternal and offspring behavior in free-ranging Japanese and moor macaques: A comparative approach.

Female primates represent the most important social partner for their developing offspring. However, mothers may strongly differ in the way they relate to their offspring (e.g., in terms of two different dimensions: protectiveness and rejection). In this study, we aimed to assess how dominance style predicts (i) changes in maternal behavior through offspring development, and (ii) the link between maternal behavior and offspring behavior. We conducted behavioral observations on 34 free-ranging immatures of two species of macaques with different dominance styles: less tolerant Japanese macaques (JM; Macaca fuscata) and more tolerant moor macaques (MM; Macaca maura). Our results showed that maternal behavior differed between JM and MM: maternal proximity and grooming decreased through offspring development more quickly in MM than in JM, whereas maternal rejection and aggression, which were generally more frequent in JM, decreased with offspring age similarly in both species. In contrast, maternal restraint of offspring decreased similarly with offspring age in both species. Furthermore, dominance style was differentially associated with the link between maternal and offspring behavior: in MM only, maternal grooming predicted an increase of the probability that offspring interacted with partners other than their mothers and engaged in solitary play, whereas maternal rejection predicted a decrease in the occurrence of solitary play. Overall, these results suggest interspecific variation in maternal behavior during offspring's first years of life, and point to the possibility that these differences may have an important role in shaping their behavioral development.

Host genetics and pathogen species modulate infection-induced changes in social aggregation behaviour.

Identifying how infection modifies host behaviours that determine social contact networks is important for understanding heterogeneity in infectious disease dynamics. Here, we investigate whether group social behaviour is modified during bacterial infection in fruit flies (Drosophila melanogaster) according to pathogen species, infectious dose, host genetic background and sex. In one experiment, we find that systemic infection with four different bacterial species results in a reduction in the mean pairwise distance within infected female flies, and that the extent of this change depends on pathogen species. However, susceptible flies did not show any evidence of avoidance in the presence of infected flies. In a separate experiment, we observed genetic- and sex-based variation in social aggregation within infected, same-sex groups, with infected female flies aggregating more closely than infected males. In general, our results confirm that bacterial infection induces changes in fruit fly behaviour across a range of pathogen species, but also highlight that these effects vary between fly genetic backgrounds and can be sex-specific. We discuss possible explanations for sex differences in social aggregation and their consequences for individual variation in pathogen transmission.

Evaluation of anaesthetic and cardiorespiratory effects after intramuscular administration of alfaxalone alone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets (Callithrix jacchus).

BACKGROUND: Anaesthesia is often required in common marmosets undergoing various procedures. The aim of this study was to evaluate anaesthetic and cardiopulmonary effects of alfaxalone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets. METHODS: The following treatments were repeatedly administered to seven female common marmosets: Treatment A, alfaxalone (12 mg kg-1 ) alone; treatment AK, alfaxalone (1 mg animal-1 ) plus ketamine (2.5 mg animal-1 ); treatment AMB, alfaxalone (4 mg kg-1 ), medetomidine (50 µg kg-1 ) plus butorphanol (0.3 mg kg-1 ); and treatment AMB-Ati, AMB with atipamezole at 45 minutes. RESULTS AND CONCLUSIONS: Marmosets became laterally recumbent and unresponsive for approximately 30 minutes in A and AK and for approximately 60 minutes in AMB. The animals showed rapid recovery following atipamezole injection in AMB-Ati. The decrease in heart rate and SpO2 was significantly greater in AMB compared to A and AK. Oxygen supplementation, anaesthetic monitors and atipamezole should be available especially when AMB is administered.

Play behavior in immature moor macaques (Macaca maura) and Japanese macaques (Macaca fuscata).

Play is widespread across mammalian taxa, but species strongly vary in the ways they play. In less despotic primate species (i.e., with less steep dominance hierarchies, less severe conflicts, and more reconciliation), play has been described as being more frequent, cooperative, and freely expressed. To study the link between social play and dominance style, we compared play behavior in free-ranging infants, juveniles and subadults of more despotic Japanese macaques (Macaca fuscata, N = 24) and less despotic moor macaques (Macaca maura, N = 17). We found interspecific differences in play behavior that corresponded with the contrasting dominance styles of the study species, largely confirming our predictions. In particular, moor macaques spent a larger proportion of time in solitary and social play than Japanese macaques, while Japanese macaques spent a larger proportion of time in grooming interactions. In moor macaques, play sessions included more players, a larger variety of play behaviors, greater play face rates, a greater proportion of time in contact play, and a higher rate of reciprocal play-biting than in Japanese macaques. Aggressive escalations were not common, but more frequent in Japanese macaques. Finally, a higher frequency of play faces during play sessions predicted the occurrence of more reciprocal play-bites, but not the proportion of time spent in contact play behaviors. Additional studies on other groups and species will allow a better understanding of the link between dominance style and social play.

Hematological and blood chemistry values in captive Japanese macaques (Macaca fuscata fuscata).

BACKGROUND: Biological information about captive Japanese macaques, including hematology and blood chemistry, is still lacking despite the fact that ethological and ecological data have accumulated during decades of field research. METHODS: Hematological (511 examinations of 280 Japanese macaques) and blood chemistry data (between 33 and 284 examinations from between 29 and 257 individual macaques) in clinically healthy, simian retrovirus-free Japanese macaques tested between 2009 and 2013 were reviewed. RESULTS AND CONCLUSIONS: Specific hematological and blood chemistry data for Japanese macaques without clinical signs of disease were provided in this study. Averages presented can be used as hematological parameters for Japanese macaques. Some differences between Japanese macaques and other closely related macaque species were found. Some parameters varied according to macaque age and sex, as well as regional origin. The data in this study will provide useful clinical indices for Japanese macaques in captive and similar conditions.

Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins (Pygoscelis adeliae).

The Southern Ocean is currently experiencing major environmental changes, including in sea-ice cover. Such changes strongly influence ecosystem structure and functioning and affect the survival and reproduction of predators such as seabirds. These effects are likely mediated by reduced availability of food resources. As such, seabirds are reliable eco-indicators of environmental conditions in the Antarctic region. Here, based on 9 years of sea-ice data, we found that the breeding success of Adélie penguins (Pygoscelis adeliae) reaches a peak at intermediate sea-ice cover (ca. 20%). We further examined the effects of sea-ice conditions on the foraging activity of penguins, measured at multiple scales from individual dives to foraging trips. Analysis of temporal organisation of dives, including fractal and bout analyses, revealed an increasingly consistent behaviour during years with extensive sea-ice cover. The relationship between several dive parameters and sea-ice cover in the foraging area appears to be quadratic. In years of low and high sea-ice cover, individuals adjusted their diving effort by generally diving deeper, more frequently and by resting at the surface between dives for shorter periods of time than in years with intermediate sea-ice cover. Our study therefore suggests that sea-ice cover is likely to affect the reproductive performance of Adélie penguins through its effects on foraging behaviour, as breeding success and most diving parameters share a common optimum. Some years, however, deviated from this general trend, suggesting that other factors (e.g. precipitation during the breeding season) might sometimes become preponderant over the sea-ice effects on breeding and foraging performance. Our study highlights the value of monitoring fitness parameters and individual behaviour concomitantly over the long-term to better characterize optimal environmental conditions and potential resilience of wildlife. Such an approach is crucial if we want to anticipate the effects of environmental change on Antarctic penguin populations.

Modeling infection transmission in primate networks to predict centrality-based risk.

Social structure can theoretically regulate disease risk by mediating exposure to pathogens via social proximity and contact. Investigating the role of central individuals within a network may help predict infectious agent transmission as well as implement disease control strategies, but little is known about such dynamics in real primate networks. We combined social network analysis and a modeling approach to better understand transmission of a theoretical infectious agent in wild Japanese macaques, highly social animals which form extended but highly differentiated social networks. We collected focal data from adult females living on the islands of Koshima and Yakushima, Japan. Individual identities as well as grooming networks were included in a Markov graph-based simulation. In this model, the probability that an individual will transmit an infectious agent depends on the strength of its relationships with other group members. Similarly, its probability of being infected depends on its relationships with already infected group members. We correlated: (i) the percentage of subjects infected during a latency-constrained epidemic; (ii) the mean latency to complete transmission; (iii) the probability that an individual is infected first among all group members; and (iv) each individual's mean rank in the chain of transmission with different individual network centralities (eigenvector, strength, betweenness). Our results support the hypothesis that more central individuals transmit infections in a shorter amount of time and to more subjects but also become infected more quickly than less central individuals. However, we also observed that the spread of infectious agents on the Yakushima network did not always differ from expectations of spread on random networks. Generalizations about the importance of observed social networks in pathogen flow should thus be made with caution, since individual characteristics in some real world networks appear less relevant than they are in others in predicting disease spread. Am. J. Primatol. 78:767-779, 2016. © 2016 Wiley Periodicals, Inc.

Hygienic tendencies correlate with low geohelminth infection in free-ranging macaques.

Parasites are ubiquitous in nature and can be costly to animal fitness, so hosts have evolved behavioural counter-strategies to mitigate infection risk. We investigated feeding-related infection-avoidance strategies in Japanese macaques via field-experimentation and observation. We first examined risk sensitivity during foraging tasks involving faecally contaminated or debris-covered food items, and then investigated individual tendencies to manipulate food items during natural foraging bouts. We concurrently monitored geohelminth infection in all subjects. We ran a principal component analysis on the observational/experimental data to generate a hygienic index across individuals and found that hygienic tendencies towards faeces avoidance and food manipulation correlated negatively with geohelminth infection. Females scored higher in hygienic tendencies than males, which might contribute to the common vertebrate pattern of male-biased infection. The behavioural tendencies observed may reflect a general form of hygiene, providing a mechanism of behavioural immunity against parasites with implications for the evolution and diversification of health maintenance strategies in humans.

The role of social attraction and social avoidance in shaping modular networks.

How interactions between individuals contribute to the emergence of complex societies is a major question in behavioural ecology. Nonetheless, little remains known about the type of immediate social structure (i.e. social network) that emerges from relationships that maximize beneficial interactions (e.g. social attraction towards informed individuals) and minimize costly relationships (e.g. social avoidance of infected group mates). We developed an agent-based model where individuals vary in the degree to which individuals signal benefits versus costs to others and, on this basis, choose with whom to interact depending on simple rules of social attraction (e.g. access to the highest benefits) and social avoidance (e.g. avoiding the highest costs). Our main findings demonstrate that the accumulation of individual decisions to avoid interactions with highly costly individuals, but that are to some extent homogeneously beneficial, leads to more modular networks. On the contrary, individuals favouring interactions with highly beneficial individuals, but that are to some extent homogeneously costly, lead to less modular networks. Interestingly, statistical models also indicate that when individuals have multiple potentially beneficial partners to interact with, and no interaction cost exists, this also leads to more modular networks. Yet, the degree of modularity is contingent upon the variability in benefit levels held by individuals. We discuss the emergence of modularity in the systems and their consequences for understanding social trade-offs.

When population growth intensifies intergroup competition, female colobus monkeys free-ride less.

Intergroup aggression often results in the production of public goods, such as a safe and stable social environment and a home range containing the resources required to survive and reproduce. We investigate temporal variation in intergroup aggression in a growing population of colobus monkeys (Colobus vellerosus) to ask a novel question: "Who stepped-up to produce these public goods when doing so became more difficult?". Both whole-group encounters and male incursions occurred more frequently as the population grew. Males and females were both more likely to participate in whole-group encounters when monopolizable food resources were available, indicating both sexes engaged in food defence. However, only females increasingly did so as the population grew, suggesting that it was females who increasingly produced the public good of home range defence as intergroup competition intensified. Females were also more active in male incursions at high population densities, suggesting they increasingly produced the public good of a safe and stable social environment. This is not to say that males were chronic free-riders when it came to maintaining public goods. Males consistently participated in the majority of intergroup interactions throughout the study period, indicating they may have lacked the capacity to invest more time and effort.

Exposure, but not timing of exposure, to a sulfonylurea herbicide alters larval development and behaviour in an amphibian species.

Environmental contamination is one of the major causes of biodiversity loss. Wetlands are particularly susceptible to contamination and species inhabiting these habitats are subjected to pollutants during sensitive phases of their development. In this study, tadpoles of a widespread amphibian, the spined toad (Bufo spinosus), were exposed to environmental concentrations of nicosulfuron (0 µg/L; 0.15 ± 0.05 µg/L and 0.83 ± 0.04 µg/L), a sulfonylurea herbicide, during different phases of development. Tadpoles were exposed during embryonic (12.98 ± 0.90 days) or larval development (93.74± 0.85 days), or throughout both phases, and we quantified development duration, morphological traits and behavioural features as responses to exposure. Developing tadpoles exposed to nicosulfuron were larger, but with smaller body, and had shorter but wider tail muscles. They were also more active and swam faster than control tadpoles and showed diverging patterns of behavioural complexity. We showed that higher concentrations had greater effects on individuals than lower concentrations, but the timing of nicosulfuron exposure did not influence the metrics studied: Exposure to nicosulfuron triggered similar effects irrespective of the developmental stages at which exposure occurred. These results further indicate that transient exposure (e.g., during embryonic development) can induce long-lasting effects throughout larval development to metamorphosis. Our study confirms that contaminants at environmental concentrations can have strong consequences on non-target organisms. Our results emphasize the need for regulation agencies and policy makers to consider sublethal concentrations of sulfonulyrea herbicides, such as nicosulfuron, as a minimum threshold in their recommendations.

Linking parasitism to network centrality and the impact of sampling bias in its interpretation.

Group living is beneficial for individuals, but also comes with costs. One such cost is the increased possibility of pathogen transmission because increased numbers or frequencies of social contacts are often associated with increased parasite abundance or diversity. The social structure of a group or population is paramount to patterns of infection and transmission. Yet, for various reasons, studies investigating the links between sociality and parasitism in animals, especially in primates, have only accounted for parts of the group (e.g., only adults), which is likely to impact the interpretation of results. Here, we investigated the relationship between social network centrality and an estimate of gastrointestinal helminth infection intensity in a whole group of Japanese macaques (Macaca fuscata). We then tested the impact of omitting parts of the group on this relationship. We aimed to test: (1) whether social network centrality -in terms of the number of partners (degree), frequency of interactions (strength), and level of social integration (eigenvector) -was linked to parasite infection intensity (estimated by eggs per gram of faeces, EPG); and, (2) to what extent excluding portions of individuals within the group might influence the observed relationship. We conducted social network analysis on data collected from one group of Japanese macaques over three months on Koshima Island, Japan. We then ran a series of knock-out simulations. General linear mixed models showed that, at the whole-group level, network centrality was positively associated with geohelminth infection intensity. However, in partial networks with only adult females, only juveniles, or random subsets of the group, the strength of this relationship - albeit still generally positive - lost statistical significance. Furthermore, knock-out simulations where individuals were removed but network metrics were retained from the original whole-group network showed that these changes are partly a power issue and partly an effect of sampling the incomplete network. Our study indicates that sampling bias can thus hamper our ability to detect real network effects involving social interaction and parasitism. In addition to supporting earlier results linking geohelminth infection to Japanese macaque social networks, this work introduces important methodological considerations for research into the dynamics of social transmission, with implications for infectious disease epidemiology, population management, and health interventions.

Japanese Macaques' (Macaca fuscata) sensitivity to human gaze and visual perspective in contexts of threat, cooperation, and competition.

Gaze sensitivity allows us to interpret the visual perspective of others, inferring their intentions and attentional states. In order to clarify the evolutionary history of this ability, we assessed the response of free-ranging Japanese macaques (Macaca fuscata) to human gaze in three contexts: threat (Experiment 1), cooperation (Experiment 2), and competition (Experiment 3). Subjects interpreted the direct gaze of an approaching human as a sign of threat, showing a greater flight initiation distance and more threats towards the human in this condition than when the human gazed in another direction. Subjects also adapted their behavior to the attentional cues of a human who gave them food, by for example moving into his visual field. However, the macaques did not seem to take the visual perspective of a human competing with them over food, as they failed to first retrieve the food that was not visible to the human (i.e., located behind an opaque barrier). Our results support the idea that Japanese macaques can respond to a human's gaze flexibly depending on the context. Moreover, they highlight the importance of studying animal behavior across different species and contexts to better understand the selective pressures that might have led to its evolution.

Parasite community structure in sympatric Bornean primates.

Parasites are important components of ecosystems, influencing trophic networks, competitive interactions and biodiversity patterns. Nonetheless, we are not nearly close to disentangling their complex roles in natural systems. Southeast Asia falls within global areas targeted as most likely to source parasites with zoonotic potential, where high rates of land conversion and fragmentation have altered the circulation of wildlife species and their parasites, potentially resulting in altered host-parasite systems. Although the overall biodiversity in the region predicts equally high, or even higher, parasite diversity, we know surprisingly little about wild primate parasites, even though this constitutes the first step towards a more comprehensive understanding of parasite transmission processes. Here, we characterise the gastrointestinal helminth parasite assemblages of a community of Bornean primates living along the Kinabatangan floodplain in Sabah (Malaysian Borneo), including two species endemic to the island. Through parasitological analyses, and by using several measures of parasite infection as proxies for parasite diversity and distribution, we show that (i) most parasite taxonomic groups are not limited to a single host, suggesting a greater flexibility for habitat disturbance, (ii) parasite infracommunities of nocturnal primates differ from their diurnal counterparts, reflecting both phylogenetic and ecological constraints, and (iii) soil-transmitted helminths such as whipworm, threadworm and nodule worm are widespread across the primate community. This study also provides new parasite records for southern pig-tailed macaques (Macaca nemestrina), silvered langurs (Trachypithecus cristatus) and Western tarsiers (Cephalopachus bancanus) in the wild, while adding to the limited records for the other primate species in the community. Given the information gap regarding primate-parasite associations in the region, the information presented here should prove relevant for future studies of parasite biodiversity and infectious disease ecology in Asia and elsewhere.

Dominance style predicts differences in food retrieval strategies.

In several species, rank predicts access to food, and subordinates may need specific behavioural strategies to get a share of resources. This may be especially important in despotic species, where resources are strongly biased in favour of dominants and subordinates may more strongly rely on specific tactics to maximize food intake. Here, we compared three macaque species with an experimental set-up reproducing feeding competition contest. Following our predictions, more tolerant species mostly retrieved food in the presence of others and were less dependent on specific tactics. Contrarily, subordinates in more despotic species more likely collected food (1) when dominants could not see food or (2) were attacking others, (3) while "dissimulating", or (4) "storing food". Our study reveals that dominance styles reliably predict the probability of using specific food retrieval tactics and provides important insights on the social conditions that might have led to the emergence of tactical deception.

Stemming the Flow: Information, Infection, and Social Evolution.

Social information and socially transmitted pathogens are governed by social structure, and also shape social interactions. However, information and infection are rarely investigated as interactive factors driving social evolution. We propose exactly such an integrative framework, drawing attention to mechanisms of social phenotypic plasticity for information spread and pathogen control.

Divergent strategies in faeces avoidance between two cercopithecoid primates.

Parasites constitute a major selective pressure which has shaped animal behaviour through evolutionary time. One adaption to parasites consists of recognizing and avoiding substrates or cues that indicate their presence. Among substrates harbouring infectious agents, faeces are known to elicit avoidance behaviour in numerous animal species. However, the function and mechanisms of faeces avoidance in non-human primates has been largely overlooked by scientists. In this study, we used an experimental approach to investigate whether aversion to faeces in a foraging context is mediated by visual and olfactory cues in two cercopithecoid primates: mandrills (Mandrillus sphinx) and long-tailed macaques (Macaca fascicularis). Visual and olfactory cues of faeces elicited lower food consumption rates in mandrills and higher food manipulation rates in long-tailed macaques. Both results support the infection-avoidance hypothesis and confirm similar tendencies observed in other primate species. More studies are now needed to investigate the divergence of avoidance strategies observed in non-human primates regarding food contamination.

Oceanic thermal structure mediates dive sequences in a foraging seabird.

Changes in marine ecosystems are easier to detect in upper-level predators, like seabirds, which integrate trophic interactions throughout the food web.Here, we examined whether diving parameters and complexity in the temporal organization of diving behavior of little penguins (Eudyptula minor) are influenced by sea surface temperature (SST), water stratification, and wind speed-three oceanographic features influencing prey abundance and distribution in the water column.Using fractal time series analysis, we found that foraging complexity, expressed as the degree of long-range correlations or memory in the dive series, was associated with SST and water stratification throughout the breeding season, but not with wind speed. Little penguins foraging in warmer/more-stratified waters exhibited greater determinism (memory) in foraging sequences, likely as a response to prey aggregations near the thermocline. They also showed higher foraging efficiency, performed more dives and dove to shallower depths than those foraging in colder/less-stratified waters.Reductions in the long-term memory of dive sequences, or in other words increases in behavioral stochasticity, may suggest different strategies concerning the exploration-exploitation trade-off under contrasting environmental conditions.