The duration of the developmental period represents a fundamental axis of life-history variation, yet broad insights regarding the drivers of this diversity are currently lacking. Here, we test mechanistic and ecological explanations for the evolution of developmental duration using embryological data and information on incubation and fledging for 3096 avian species. Developmental phases associated primarily with growth are the longest and most variable, consistent with a role for allometric constraint in determining the duration of development. In addition, developmental durations retain a strong imprint of deep evolutionary history and body size differences among species explain less variation than previously thought. Finally, we reveal ecological correlates of developmental durations, including variables associated with the relative safety of the developmental environment and pressures of breeding phenology. Overall, our results provide broad-scale insight into the relative importance of mechanistic, ecological and evolutionary constraints in shaping the diversification of this key life-history trait.

Simple SummaryFor a domestic chick, the mother hen is an important role model; chicks learn a great deal from their mother about what to peck, when to rest and how to behave when there is a threat. However, in large farms, natural brooding is not commercially viable and so chicks are hatched in large incubators and reared artificially. Chicks reared without a mother in this way are more fearful and more likely to develop behavioural problems, such as feather pecking. We discuss the important features of maternal care in chickens, the behavioural consequences of deprivation, and the welfare implications on commercial farms. We finish by suggesting ways to simulate natural maternal care to improve commercial chick rearing practice.AbstractIn domestic chickens, the provision of maternal care strongly influences the behavioural development of chicks. Mother hens play an important role in directing their chicks’ behaviour and are able to buffer their chicks’ response to stressors. Chicks imprint upon their mother, who is key in directing the chicks’ behaviour and in allowing them to develop food preferences. Chicks reared by a mother hen are less fearful and show higher levels of behavioural synchronisation than chicks reared artificially. In a commercial setting, more fearful chicks with unsynchronised behaviour are more likely to develop behavioural problems, such as feather pecking. As well as being an inherent welfare problem, fear can also lead to panic responses, smothering, and fractured bones. Despite the beneficial effects of brooding, it is not commercially viable to allow natural brooding on farms and so chicks are hatched in large incubators and reared artificially, without a mother hen. In this review we cover the literature demonstrating the important features of maternal care in domestic chickens, the behavioural consequences of deprivation and the welfare implications on commercial farms. We finish by suggesting ways to use research in natural maternal care to improve commercial chick rearing practice.

Many animals emit calls in the presence of food, but researchers do not always know the function of these calls. Evidence suggests that adult golden lion tamarins (Leontopithecus rosalia) use food-offering calls to teach juveniles which substrate (i.e., microhabitat) to forage on, or in, for food. However, we do not yet know whether juveniles learn from this aspect of the adults’ behavior. Here we examine whether juveniles learn to associate food-offering calls with a foraging substrate, as a step toward assessing whether these calls qualify as teaching behavior. We compared the performance of four wild juvenile golden lion tamarins that were introduced to a novel substrate while exposed to playbacks of food-offering calls (experimental condition) to the performance of three juveniles that were exposed to the novel substrate without the presence of food-offering playbacks (control condition). We varied the location of the novel substrate between trials. We found that food-offering calls had an immediate effect on juveniles’ interactions with the novel substrate, whether they inserted their hands into the substrate and their eating behavior, and a long-term effect on eating behavior at the substrate. The findings imply that juvenile golden lion tamarins can learn through food-offering calls about the availability of food at a substrate, which is consistent with (but does not prove) teaching in golden lion tamarins through stimulus enhancement. Our findings support the hypothesis that teaching might be more likely to evolve in cooperatively breeding species with complex ecological niches.Electronic supplementary materialThe online version of this article (10.1007/s10764-018-0069-z) contains supplementary material, which is available to authorized users.

Scent detection dogs are used in a variety of contexts; however, very few dogs successfully complete their training, and many others are withdrawn from service prematurely due to both detection accuracy issues in the field and wider behavioral issues. This article aims to review our understanding of the factors affecting variation in scent detection dogs' learning of the tasks and performance in the field. For this we deconstructed the scent detection task into its key behavioral elements and examined the literature relating to the factors affecting variation in the dogs' success all across their development. We first consider factors that affect individuality and individual performance, in general, such as temperament, arousal, the handler-dog relationship, training regimes, and the housing and management of scent detections dogs. We then focus on tasks specific to scent detection dogs and critically appraise relevant literature relating to the learning and performance of these tasks by dogs. This includes prenatal and early life exposure and later environment, training regime, and the human-dog relationship, as well as performance limiting factors such as the need to pant in hot environments during work.

Scientific disciplines face concerns about replicability and statistical inference, and these concerns are also relevant in animal cognition research. This paper presents a first attempt to assess how researchers make and publish claims about animal physical cognition, and the statistical inferences they use to support them. We surveyed 116 published experiments from 63 papers on physical cognition, covering 43 different species. The most common tasks in our sample were trap-tube tasks (14 papers), other tool use tasks (13 papers), means-end understanding and string-pulling tasks (11 papers), object choice and object permanence tasks (9 papers) and access tasks (5 papers). This sample is not representative of the full scope of physical cognition research; however, it does provide data on the types of statistical design and publication decisions researchers have adopted. Across the 116 experiments, the median sample size was 7. Depending on the definitions we used, we estimated that between 44% and 59% of our sample of papers made positive claims about animals' physical cognitive abilities, between 24% and 46% made inconclusive claims, and between 10% and 17% made negative claims. Several failures of animals to pass physical cognition tasks were reported. Although our measures had low inter-observer reliability, these findings show that negative results can and have been published in the field. However, publication bias is still present, and consistent with this, we observed a drop in the frequency of p-values above .05. This suggests that some non-significant results have not been published. More promisingly, we found that researchers are likely making many correct statistical inferences at the individual-level. The strength of evidence of statistical effects at the group-level was weaker, and its p-value distribution was consistent with some effect sizes being overestimated. Studies such as ours can form part of a wider investigation into statistical reliability in comparative cognition. However, future work should focus on developing the validity and reliability of the measurements they use, and we offer some starting points.

Callitrichidae is a unique primate family not only in terms of the large number of food transfers to infants but also for the prevalence of transfers that are initiated by the adults. It has been hypothesized that, as well as provisioning infants, callitrichid food transfers might function to teach the receiver what food types to eat. If food provisioning has a teaching function, we would expect successful food transfers to be more likely with food types that are novel to the juveniles. We would also expect juveniles to learn about foods from those transfers. We introduced different types of food (some familiar, some novel) to wild groups of golden lion tamarins ( Leontopithecus rosalia ). While novel foods were not more successfully transferred than familiar food in the experiment, transfers were more successful (i.e., the receiver obtained food) when the donor had previous experience with that food. Moreover, we found evidence suggesting that food transfers influenced the future foraging choices of juveniles. Our findings are consistent with the first and third criteria of the functional definition of teaching, which requires that tutors (the adults) modify their behavior in the presence of a naïve individual (a juvenile), and that the naïve individual learns from the modified behavior of the demonstrator. Our findings are also consistent with the provisioning function of food transfer. Social learning seems to play an important role in the development of young tamarins’ foraging preferences. Electronic supplementary material The online version of this article (10.1007/s10329-020-00835-0) contains supplementary material, which is available to authorized users.

Although the evolution of cognitive differences among species has long been of interest in ecology, whether natural selection acts on cognitive processes within populations has only begun to receive similar attention. One of the key challenges is to understand how consistently cognitive traits within any one domain are expressed over time and across different contexts, as this has direct implications for the way in which selection might act on this variation. Animal studies typically measure a cognitive domain using only one task in one context and assume that this captures the likely expression of that domain in different contexts. This use of limited and restricted measures is not surprising because, from an ecologist’s perspective, cognitive tasks are laborious to employ, and if the measure requires learning a particular aspect of the task (e.g., reward type, cue availability, scale of testing), then it is difficult to repeat the task as the learning is context specific. Thus, our knowledge of whether individual differences in cognitive abilities are consistent across contexts is limited, and current evidence suggests that consistency is weak. We tested up to 32 wild great tits (Parus major) to characterize the consistency of two cognitive abilities, each in two different contexts: 1) spatial cognition at two different spatial scales, and 2) behavioral flexibility as performance in a detour reaching task and reversal learning in a spatial task. We found no evidence of a correlation between individuals’ performance in two measures of spatial cognition or two measures of behavioral flexibility. This suggests that cognitive performance is highly plastic and sensitive to differences across tasks, that variants of these well-known tasks may tap into different combinations of both cognitive and non-cognitive mechanisms, or that the tasks simply do not adequately measure each putative cognitive domain. Our results highlight the challenges of developing standardized cognitive assays to explain natural behavior and to understand the selective consequences of that variation.

1. Organisms are constantly under selection to respond effectively to diverse, sometimes rapid, changes in their environment, but not all individuals are equally plastic in their behaviour. Although cognitive processes and personality are expected to influence individual behavioural plasticity, the effects reported are highly inconsistent, which we hypothesise is because ecological context is usually not considered.2. We explored how one type of behavioural plasticity, foraging flexibility, was associated with inhibitory control (assayed using a detour-reaching task) and exploration behaviour in a novel environment (a trait closely linked to the fast-slow personality axis). We investigated how these effects varied across two experimentally manipulated ecological contexts-food value and predation risk.3. In the first phase of the experiment, we trained great tits Parus major to retrieve high value (preferred) food that was hidden in sand so that this became the familiar food source. In the second phase, we offered them the same familiar hidden food at the same time as a new alternative option that was visible on the surface, which was either high or low value, and under either high or low perceived predation risk. Foraging flexibility was defined as the proportion of choices made during 4-min trials that were for the new alternative food source. 4. Our assays captured consistent differences among individuals in foraging flexibility. Inhibitory control was associated with foraging flexibility-birds with high inhibitory control were more flexible when the alternative food was of high value, suggesting they inhibited the urge to select the familiar food and instead selected the new food option. Exploration behaviour also predicted flexibility-fast explorers were more flexible, supporting the information-gathering hypothesis. This | 321