Heat stress inhibits cognitive performance in wild Western Australian magpies, Cracticus tibicen dorsalis

Early life adversity has sex-dependent effects on survival across the lifespan in rhesus macaques

Exposure to early life adversity is linked to detrimental fitness outcomes across taxa. Owing to the challenges of collecting longitudinal data, direct evidence for long-term fitness effects of early life adversity from long-lived species remains relatively scarce. Here, we test the effects of early life adversity on male and female longevity in a free-ranging population of rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico. We leveraged six decades of data to quantify the relative importance of 10 forms of early life adversity for 6599 macaques. Individuals that experienced more early life adversity died earlier than those that experienced less adversity. Mortality risk was highest during early life, defined as birth to 4 years old, but heightened mortality risk was also present in macaques that survived to adulthood. Females and males were affected differently by some forms of adversity, and these differences might be driven by varying energetic demands and dispersal patterns. Our results show that the fitness consequences of early life adversity are not uniform across individuals but vary as a function of the type of adversity, timing and social context, and thus contribute to our limited but growing understanding of the evolution of early life sensitivities.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Experimental playback of urban noise does not affect cognitive performance in captive Australian magpies

Exposure of wildlife to anthropogenic noise is associated with disruptive effects. Research on this topic has focused on behavioural and physiological responses of animals to noise, with little work investigating links to cognitive function. Neurological processes that maintain cognitive performance can be impacted by stress and sleep disturbances. While sleep loss impairs cognitive performance in Australian magpies, it is unclear whether urban noise, which disrupts sleep, can impact cognition as well. To fill this gap, we explored how environmentally relevant urban noise affected the performance of wild-caught, city-living Australian magpies (Gymnorhina tibicen tyrannica) on a cognitive task battery including associative and reversal learning, inhibitory control, and spatial memory. Birds were housed and tested in a laboratory environment; sample sizes varied across tasks (n=7-9 birds). Tests were conducted over 4 weeks, during which all magpies were exposed to both an urban noise playback and a quiet control. Birds were presented with the entire test battery twice: following exposure to, and in the absence of, an anthropogenic noise playback; however, tests were always performed without noise (playback muted during testing). Magpies performed similarly in both treatments on all four tasks. We also found that prior experience with the associative learning task had a strong effect on performance, with birds performing better on their second round of trials. Like previous findings on Australian magpies tested on the same tasks in the wild under noisy conditions, we could not find any disruptive effects on cognitive performance in a controlled experimental laboratory setting.

Investigating the relationship between physical cognitive tasks and a social cognitive task in a wild bird

Despite considerable research into the structure of cognition in non-human animal species, there is still much debate as to whether animal cognition is organised as a series of discrete domains or an overarching general cognitive factor. In humans, the existence of general intelligence is widely accepted, but less work has been undertaken in animal psychometrics to address this question. The relatively few studies on non-primate animal species that do investigate the structure of cognition rarely include tasks assessing social cognition and focus instead on physical cognitive tasks. In this study, we tested 36 wild Western Australian magpies (Gymnorhina tibicen dorsalis) on a battery of three physical (associative learning, spatial memory, and numerical assessment) and one social (observational spatial memory) cognitive task, to investigate if cognition in this species fits a general cognitive factor model, or instead one of separate physical and social cognitive domains. A principal component analysis (PCA) identified two principal components with eigenvalues exceeding 1; a first component onto which all three physical tasks loaded strongly and positively, and a second component onto which only the social task (observational spatial memory) loaded strongly and positively. These findings provide tentative evidence for separate physical and social cognitive domains in this species, and highlight the importance of including tasks assessing both social and physical cognition in cognitive test batteries.

Call combination production is linked to the social environment in Western Australian magpies (Gymnorhina tibicen dorsalis)

It has recently become clear that some language-specific traits previously thought to be unique to humans (such as the capacity to combine sounds) are widespread in the animal kingdom. Despite the increase in studies documenting the presence of call combinations in non-human animals, factors promoting this vocal trait are unclear. One leading hypothesis proposes that communicative complexity co-evolved with social complexity owing to the need to transmit a diversity of information to a wider range of social partners. The Western Australian magpie (Gymnorhina tibicen dorsalis) provides a unique model to investigate this proposed link because it is a group-living, vocal learning species that is capable of multi-level combinatoriality (independently produced calls contain vocal segments and comprise combinations). Here, we compare variations in the production of call combinations across magpie groups ranging in size from 2 to 11 birds. We found that callers in larger groups give call combinations: (i) in greater diversity and (ii) more frequently than callers in smaller groups. Significantly, these observations support the hypothesis that combinatorial complexity may be related to social complexity in an open-ended vocal learner, providing an important step in understanding the role that sociality may have played in the development of vocal combinatorial complexity. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.

Aggressive interactions influence cognitive performance in Western Australian magpies

Extensive research has investigated the relationship between the social environment and cognition, suggesting that social complexity may drive cognitive evolution and development. However, evidence for this relationship remains equivocal. Group size is often used as a measure of social complexity, but this may not capture intraspecific variation in social interactions. Social network analysis can provide insight into the cognitively demanding challenges associated with group living at the individual level. Here, we use social networks to investigate whether the cognitive performance of wild Western Australian magpies (Gymnorhina tibicen dorsalis) is related to group size and individual social connectedness. We quantified social connectedness using four interaction types: proximity, affiliative, agonistic and vocal. Consistent with previous research on this species, individuals in larger groups performed better on an associative learning task. However, social network position was also related to cognitive performance. Individuals receiving aggressive interactions performed better, while those involved in aggressive interactions with more group members performed worse. Overall, this suggests that cognitive performance is related to specific types of social interaction. The findings from this study highlight the value of considering fine-grained metrics of sociality that capture the challenges associated with social life when testing the relationship between the social environment and cognition.

The evolution of social play in songbirds, parrots and cockatoos - emotional or highly complex cognitive behaviour or both?

Social play has been described in many animals. However, much of this social behaviour among birds, particularly in adults, is still relatively unexplored in terms of the environmental, psychological, and social dynamics of play. This paper provides an overview of what we know about adult social play in birds and addresses areas in which subtleties and distinctions, such as in play initiation and social organisation and its relationship to expressions of play, are considered in detail. The paper considers emotional, social, innovative, and cognitive aspects of play, then the environmental conditions and affiliative bonds, suggesting a surprisingly complex framework of criteria awaiting further research. Adult social play has so far been studied in only a small number of avian species, exclusively in those with a particularly large brain relative to body size without necessarily addressing brain functions and lateralization. When lateralization of brain function is considered, it can further illuminate a possibly significant relevance of play behaviour to the evolution of cognition, to management of emotions, and the development of sociality.

Heritability of cognitive performance in wild Western Australian magpies

Individual differences in cognitive performance can have genetic, social and environmental components. Most research on the heritability of cognitive traits comes from humans or captive non-human animals, while less attention has been given to wild populations. Western Australian magpies (Gymnorhina tibicen dorsalis, hereafter magpies) show phenotypic variation in cognitive performance, which affects reproductive success. Despite high levels of individual repeatability, we do not know whether cognitive performance is heritable in this species. Here, we quantify the broad-sense heritability of associative learning ability in a wild population of Western Australian magpies. Specifically, we explore whether offspring associative learning performance is predicted by maternal associative learning performance or by the social environment (group size) when tested at three time points during the first year of life. We found little evidence that offspring associative learning performance is heritable, with an estimated broad-sense heritability of just -0.046 ± 0.084 (confidence interval: -0.234/0.140). However, complementing previous findings, we find that at 300 days post-fledging, individuals raised in larger groups passed the test in fewer trials compared with individuals from small groups. Our results highlight the pivotal influence of the social environment on cognitive development.

High temperatures during early development reduce adult cognitive performance and reproductive success in a wild animal population

Global warming is rapidly changing the phenology, distribution, behaviour and demography of wild animal populations. Recent studies in wild animals have shown that high temperatures can induce short-term cognitive impairment, and captive studies have demonstrated that heat exposure during early development can lead to long-term cognitive impairment. Given that cognition underpins behavioural flexibility and can be directly linked to fitness, understanding how high temperatures during early life might impact adult cognitive performance in wild animals is a critical next step to predict wildlife responses to climate change. Here, we investigated the relationship between temperatures experienced during development, adult cognitive performance, and reproductive success in wild southern pied babblers (Turdoides bicolor). We found that higher mean daily maximum temperatures during nestling development led to long-term cognitive impairment in associative learning performance, but not reversal learning performance. Additionally, a higher number of hot days (exceeding 35.5 °C, temperature threshold at which foraging efficiency and offspring provisioning decline) during post-fledging care led to reduced reproductive success in adulthood. We did not find evidence that low reproductive success was linked to impaired associative learning performance: associative learning performance was not related to reproductive success. In contrast, reversal learning performance was negatively related to reproductive success in breeding adults. This suggests that reproduction can carry a cost in terms of reduced performance in cognitively demanding tasks, confirming previous evidence in this species. Taken together, these findings indicate that naturally occurring high temperatures during early development have long-term negative effects on cognition and reproductive success in wild animals. Compounding effects of high temperatures on current nestling mortality and on the long-term cognitive and reproductive performance of survivors are highly concerning given ongoing global warming.

Australian magpies

Robin D. Johnsson and colleagues introduce Australian magpies, which are not actually magpies.

Cognition mediates response to anthropogenic noise in wild Western Australian magpies (Gmynorhina tibicen dorsalis)

Anthropogenic noise is a pollutant of growing concern, with wide-ranging effects on taxa across ecosystems. Until recently, studies investigating the effects of anthropogenic noise on animals focused primarily on population-level consequences, rather than individual-level impacts. Individual variation in response to anthropogenic noise may result from extrinsic or intrinsic factors. One such intrinsic factor, cognitive performance, varies between individuals and is hypothesised to aid behavioural response to novel stressors. Here, we combine cognitive testing, behavioural focals and playback experiments to investigate how anthropogenic noise affects the behaviour and anti-predator response of Western Australian magpies (Gymnorhina tibicen dorsalis), and to determine whether this response is linked to cognitive performance. We found a significant population-level effect of anthropogenic noise on the foraging effort, foraging efficiency, vigilance, vocalisation rate and anti-predator response of magpies, with birds decreasing their foraging, vocalisation behaviours and anti-predator response, and increasing vigilance when loud anthropogenic noise was present. We also found that individuals varied in their response to playbacks depending on their cognitive performance, with individuals that performed better in an associative learning task maintaining their anti-predator response when an alarm call was played in anthropogenic noise. Our results add to the growing body of literature documenting the adverse effects of anthropogenic noise on wildlife and provide the first evidence for an association between individual cognitive performance and behavioural responses to anthropogenic noise.

High temperatures are associated with reduced cognitive performance in wild southern pied babblers

Global temperatures are increasing rapidly. While considerable research is accumulating regarding the lethal and sublethal effects of heat on wildlife, its potential impact on animal cognition has received limited attention. Here, we tested wild southern pied babblers (Turdoides bicolor) on three cognitive tasks (associative learning, reversal learning and inhibitory control) under naturally occurring heat stress and non-heat stress conditions. We determined whether cognitive performance was explained by temperature, heat dissipation behaviours, individual and social attributes, or proxies of motivation. We found that temperature, but not heat dissipation behaviours, predicted variation in associative learning performance. Individuals required on average twice as many trials to learn an association when the maximum temperature during testing exceeded 38°C compared with moderate temperatures. Higher temperatures during testing were also associated with reduced inhibitory control performance, but only in females. By contrast, we found no temperature-related decline in performance in the reversal learning task, albeit individuals reached learning criterion in only 14 reversal learning tests. Our findings provide novel evidence of temperature-mediated cognitive impairment in a wild animal and indicate that its occurrence depends on the cognitive trait examined and individual sex.

Early life adversity has sex-dependent effects on survival across the lifespan in rhesus macaques

Exposure to adversity during early life is linked to lasting detrimental effects on evolutionary fitness across many taxa. However, due to the challenges of collecting longitudinal data, especially in species where one sex disperses, direct evidence from long-lived species remains relatively scarce. Here we test the effects of early life adversity on male and female longevity in a free-ranging population of rhesus macaques (Macaca mulatta) at Cayo Santiago, Puerto Rico. We leveraged six decades of data to quantify the relative importance of ten forms of early life adversity for 6,599 macaques (3,230 male, 3,369 female), with a smaller sample size (N=299) for one form of adversity (maternal social isolation) which required high-resolution behavioral data. We found that individuals who experienced more early life adversity died earlier than those who experienced less adversity. Mortality risk was highest during early life, defined as birth to four years old, suggesting acute survival effects of adversity, but heightened mortality risk was also present in macaques who survived to adulthood. Females and males were affected differently by some forms of adversity, and these differences might be driven by varying energetic demands, female philopatry, and male dispersal. By leveraging data on thousands of macaques collected over decades, our results show that the fitness consequences of early life adversity are not uniform across individuals but vary as a function of the type of adversity, timing, and social context, and thus contribute to our limited but growing understanding of the evolution of early life sensitivities in long-lived species.

Does trappability and self-selection influence cognitive performance?

Recent research has highlighted how trappability and self-selection-the processes by which individuals with particular traits may be more likely to be caught or to participate in experiments-may be sources of bias in studies of animal behaviour and cognition. It is crucial to determine whether such biases exist, and if they do, what effect they have on results. In this study, we investigated if trappability (quantified through 'ringing status'-whether or not a bird had been trapped for ringing) and self-selection are sources of bias in a series of associative learning experiments spanning 5 years in the Western Australian magpie (Gymnorhina tibicen dorsalis). We found no evidence of self-selection, with no biases in task participation associated with sex, age, group size or ringing status. In addition, we found that there was no effect of trappability on cognitive performance. These findings give us confidence in the results generated in the animal cognition literature and add to a growing body of literature seeking to determine potential sources of bias in studies of animal behaviour, and how they influence the generalizability and reproducibility of findings.

Long-term repeatability of cognitive performance

Measures of cognitive performance, derived from psychometric tasks, have yielded important insights into the factors governing cognitive variation. However, concerns remain over the robustness of these measures, which may be susceptible to non-cognitive factors such as motivation and persistence. Efforts to quantify short-term repeatability of cognitive performance have gone some way to address this, but crucially the long-term repeatability of cognitive performance has been largely overlooked. Quantifying the long-term repeatability of cognitive performance provides the opportunity to determine the stability of cognitive phenotypes and the potential for selection to act on them. To this end, we quantified long-term repeatability of cognitive performance in wild Australian magpies over a three-year period. Cognitive performance was repeatable in two out of four cognitive tasks-associative learning and reversal-learning performance was repeatable, but spatial memory and inhibitory control performance, although trending toward significance, was not. Measures of general cognitive performance, obtained from principal components analyses carried out on each cognitive test battery, were highly repeatable. Together, these findings provide evidence that at least some cognitive phenotypes are stable, which in turn has important implications for our understanding of cognitive evolution.