Object caching in corvids: incidence and significance

Socio-ecological correlates of neophobia in corvids

Behavioral responses to novelty, including fear and subsequent avoidance of novel stimuli, i.e., neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species; however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and novel food conditions relative to the baseline. Four of seven socio-ecological factors influenced object neophobia: (1) use of urban habitat (versus not), (2) territorial pair versus family group sociality, (3) large versus small maximum flock size, and (4) moderate versus specialized caching (whereas range, hunting live animals, and genus did not), while only maximum flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e., consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioral trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group. VIDEO ABSTRACT.

Tools and food on heat lamps: pyrocognitive sparks in New Caledonian crows?

Fire has substantially altered the course of human evolution. Cooking kindled brain expansion through improved energy and time budgets. However, little is known about the origins of fire use and its cognitive underpinnings (pyrocognition). Debates on how hominins innovated cooking focus on archaeological findings, but should also be informed by the response of animals towards heat sources. Here, we report six observations on two captive New Caledonian crows (Corvus moneduloides) contacting heat lamps with tools or placing raw food on them. The tools became singed or melted and the food had browned (and was removed). These results suggest that New Caledonian crows can use tools to investigate hot objects, which extends earlier findings that they use tools to examine potential hazards (pericular tool use), and place food on a heat source as play or exploration. Further research on animals will provide novel insights into the pyrocognitive origins of early humans.

Beyond the Chicken: Alternative Avian Models for Developmental Physiological Research

Biomedical research focusing on physiological, morphological, behavioral, and other aspects of development has long depended upon the chicken (Gallus gallus domesticus) as a key animal model that is presumed to be typical of birds and generally applicable to mammals. Yet, the modern chicken in its many forms is the result of artificial selection more intense than almost any other domesticated animal. A consequence of great variation in genotype and phenotype is that some breeds have inherent aberrant physiological and morphological traits that may show up relatively early in development (e.g., hypertension, hyperglycemia, and limb defects in the broiler chickens). While such traits can be useful as models of specific diseases, this high degree of specialization can color general experimental results and affect their translational value. Against this background, in this review we first consider the characteristics that make an animal model attractive for developmental research (e.g., accessibility, ease of rearing, size, fecundity, development rates, genetic variation, etc.). We then explore opportunities presented by the embryo to adult continuum of alternative bird models, including quail, ratites, songbirds, birds of prey, and corvids. We conclude by indicating that expanding developmental studies beyond the chicken model to include additional avian groups will both validate the chicken model as well as potentially identify even more suitable avian models for answering questions applicable to both basic biology and the human condition.

Carrion Crows and Azure-Winged Magpies Show No Prosocial Tendencies When Tested in a Token Transfer Paradigm

To study the evolution of humans' cooperative nature, researchers have recently sought comparisons with other species. Studies investigating corvids, for example, showed that carrion crows and azure-winged magpies delivered food to group members when tested in naturalistic or simple experimental paradigms. Here, we investigated whether we could replicate these positive findings when testing the same two species in a token transfer paradigm. After training the birds to exchange tokens with an experimenter for food rewards, we tested whether they would also transfer tokens to other birds, when they did not have the opportunity to exchange the tokens themselves. To control for the effects of motivation, and of social or stimulus enhancement, we tested each individual in three additional control conditions. We witnessed very few attempts and/or successful token transfers, and those few instances did not occur more frequently in the test condition than in the controls, which would suggest that the birds lack prosocial tendencies. Alternatively, we propose that this absence of prosociality may stem from the artificial nature and cognitive complexity of the token transfer task. Consequently, our findings highlight the strong impact of methodology on animals' capability to exhibit prosocial tendencies and stress the importance of comparing multiple experimental paradigms.

Individual and social factors affecting the ability of American crows to solve and master a string pulling task

Crows and other birds in the family Corvidae regularly share information to learn the identity and whereabouts of dangerous predators, but can they use social learning to solve a novel task for a food reward? Here we examined the factors affecting the ability of 27 wild-caught American crows to solve a common string-pulling task in a laboratory setting. We split crows into two groups; one group was given the task after repeatedly observing a conspecific model the solution, the other solved in the absence of conspecific models. We recorded the crows' estimated age, sex, size, body condition, level of nervousness, and brain volume using DICOM images from a CT scan. Although none of these variables were statistically significant, crows without a conspecific model and large brain volumes consistently mastered the task in the minimum number of days, whereas those with conspecific models and smaller brain volumes required varying and sometimes a substantial number of days to master the task. We found indirect evidence that body condition might also be important for motivating crows to solve the task. Crows with conspecific models were no more likely to initially solve the task than those working the puzzle without social information, but those that mastered the task usually copied the method most frequently demonstrated by their knowledgeable neighbors. These findings suggest that brain volume and possibly body condition may be factors in learning new tasks, and that crows can use social learning to refine their ability to obtain a novel food source, although they must initially learn to access it themselves.

A novel tool-use mode in animals: New Caledonian crows insert tools to transport objects

New Caledonian crows (Corvus moneduloides) rely heavily on a range of tools to extract prey. They manufacture novel tools, save tools for later use, and have morphological features that facilitate tool use. We report six observations, in two individuals, of a novel tool-use mode not previously reported in non-human animals. Insert-and-transport tool use involves inserting a stick into an object and then moving away, thereby transporting both object and tool. All transported objects were non-food objects. One subject used a stick to transport an object that was too large to be handled by beak, which suggests the tool facilitated object control. The function in the other cases is unclear but seems to be an expression of play or exploration. Further studies should investigate whether it is adaptive in the wild and to what extent crows can flexibly apply the behaviour in experimental settings when purposive transportation of objects is advantageous.

Spontaneous object recognition: a promising approach to the comparative study of memory

Spontaneous recognition of a novel object is a popular measure of exploratory behavior, perception and recognition memory in rodent models. Because of its relative simplicity and speed of testing, the variety of stimuli that can be used, and its ecological validity across species, it is also an attractive task for comparative research. To date, variants of this test have been used with vertebrate and invertebrate species, but the methods have seldom been sufficiently standardized to allow cross-species comparison. Here, we review the methods necessary for the study of novel object recognition in mammalian and non-mammalian models, as well as the results of these experiments. Critical to the use of this test is an understanding of the organism's initial response to a novel object, the modulation of exploration by context, and species differences in object perception and exploratory behaviors. We argue that with appropriate consideration of species differences in perception, object affordances, and natural exploratory behaviors, the spontaneous object recognition test can be a valid and versatile tool for translational research with non-mammalian models.

'The thieving magpie'? No evidence for attraction to shiny objects

It is widely accepted in European culture that magpies (Pica pica) are unconditionally attracted to shiny objects and routinely steal small trinkets such as jewellery, almost as a compulsion. Despite the long history of this folklore, published accounts of magpies collecting shiny objects are rare and empirical evidence for the behaviour is lacking. The latter is surprising considering that an attraction to bright objects is well documented in some bird species. The present study aims to clarify whether magpies show greater attraction to shiny objects than non-shiny objects when presented at the same time. We did not find evidence of an unconditional attraction to shiny objects in either captive or free-living birds. Instead, all objects elicited responses indicating neophobia in free-living birds. We suggest that humans notice when magpies occasionally pick up shiny objects because they believe the birds find them attractive, while it goes unnoticed when magpies interact with less eye-catching items. The folklore may therefore result from observation bias and cultural inflation of orally transmitted episodic events.