California scrub-jays reduce visual cues available to potential pilferers by matching food colour to caching substrate

This is the final version. Available from the Royal Society via the DOI in this record. Some animals hide food to consume later; however, these caches are susceptible to theft by conspecifics and heterospecifics. Caching animals can use protective strategies to minimize sensory cues available to potential pilferers, such as caching in shaded areas and in quiet substrate. Background matching (where object patterning matches the visual background) is commonly seen in prey animals to reduce conspicuousness, and caching animals may also use this tactic to hide caches, for example, by hiding coloured food in a similar coloured substrate. We tested whether California scrubjays (Aphelocoma californica) camouflage their food in this way by offering them caching substrates that either matched or did not match the colour of food available for caching. We also determined whether this caching behaviour was sensitive to social context by allowing the birds to cache when a conspecific potential pilferer could be both heard and seen (acoustic and visual cues present), or unseen (acoustic cues only). When caching events could be both heard and seen by a potential pilferer, birds cached randomly in matching and non-matching substrates. However, they preferentially hid food in the substrate that matched the food colour when only acoustic cues were present. This is a novel cache protection strategy that also appears to be sensitive to social context. We conclude that studies of cache protection strategies should consider the perceptual capabilities of the cacher and potential pilferers.European Union’s Seventh Framework Programm

Rook, But Not Jackdaw, Post-Conflict Third-Party Affiliation Reduces Aggression for Aggressors

Post-conflict (PC) affiliation refers to positive social interactions that occur after fights. Although this behavior has been widely studied, its functions are rarely tested. We examine a potential function of PC third-party affiliation (affiliation between former opponents and bystanders) in rooks and jackdaws by investigating the hypothesis that conflicts lead to further aggression and that PC third-party affiliation increases to reduce such aggression. The results show that PC affiliation reduces PC aggression for rook aggressors who were less likely to receive aggression after conflicts when they were affiliating with another vs. when they were alone. The opposite result was found for victims of both species who received more aggression after conflicts, and this aggression was not reduced by the act of affiliating. Finally, for jackdaw aggressors, the amount of aggression received after conflicts was not influenced by whether the individual was affiliating or alone, indicating that PC third-party affiliation may serve a function that we did not examine. These findings highlight the importance of investigating functional differences in PC affiliative behavior according to the role played in the conflict.We are grateful for financial support from the Gates Cambridge Scholar-ship and Murray Edwards College (CJL), and the BBSRC, the Royal Society, and the University of Cambridge (NSC).This is the author accepted manuscript. The final version is available from Wiley via https://doi.org/10.1111/eth.12078IN

Neophobia is not only avoidance: Improving neophobia tests by combining cognition and ecology

Psychologists and behavioural ecologists use neophobia tests to measure behaviours ranging from anxiety to predatory wariness. Psychologists typically focus on underlying cognitive mechanisms at the expense of ecological validity, while behavioural ecologists generally examine adaptive function but ignore cognition. However, neophobia is an ecologically relevant fear behaviour that arises through a cognitive assessment of novel stimuli. Both fields have accrued conflicting results using various testing protocols, making it unclear what neophobia tests measure and what correlations between neophobia and other traits mean. Developing cognitively and ecologically informed tests allows neophobia to be empirically evaluated where appropriate and controlled for where it interferes with other behavioural measures. We offer guidelines for designing tests and stress the need for interdisciplinary dialogue to better explore neophobia's proximate causes and ecological consequences.We would like to thank Alecia Carter for helpful discussion and comments on the manuscript and to thank two anonymous reviewers and the editor, Dr. Hofmann, for their thoughtful and insightful feedback. A.L.G. received generous support from the Gates-Cambridge Trust; A.T. is funded by a BBSRC David Phillips Fellowship (BB/H021817/1).This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.cobeha.2015.10.00

New Caledonian crows infer the weight of objects from observing their movements in a breeze

Humans use a variety of cues to infer an object’s weight, including how easily objects can be moved. For example, if we observe an object being blown down the street by the wind, we can infer that it is light. Here, we tested whether New Caledonian crows make this type of inference. After training that only one type of object (either light: 6 birds, or heavy: 6 birds) was rewarded when dropped into a food dispenser, birds observed pairs of novel objects (one light, one heavy) suspended from strings in front of an electric fan. The fan was either on – creating a breeze which buffeted the light, but not the heavy, object – or off, leaving both objects stationary. In subsequent test trials, birds could drop one, or both, of the novel objects into the food dispenser. Despite having no opportunity to handle these objects prior to test, birds touched the correct object (light or heavy) first in 73% of experimental trials, and were at chance in control trials. Our results suggest that birds used pre-existing knowledge about the behaviour exhibited by differently weighted objects in the wind to infer their weight, using this information to guide their choices.ER

New Caledonian crows use mental representations to solve metatool problems

One of the mysteries of animal problem solving is the extent to which animals mentally represent problems in their minds. Humans can imagine both the solution to a problem and the stages along the way [1–3], such as when we plan one or two moves ahead in chess. The extent to which other animals can do the same is far less clear [5-26]. Here, we presented New Caledonian crows with a series of metatool problems where each stage was out-of-sight of the others and the crows had to avoid either a distractor apparatus containing a non-functional tool or a non-functional apparatus containing a functional tool. Crows were able to mentally represent the sub-goals and goals of metatool problems: crows kept in mind the location and identities of out-of-sight tools and apparatuses while planning and performing a sequence of tool behaviours. This provides the first conclusive evidence that birds can plan several moves ahead while using tools.ER

Eurasian jays do not copy the choices of conspecifics, but they do show evidence of stimulus enhancement

Corvids (birds in the crow family) are hypothesised to have a general cognitive tool-kit because they show a wide range of transferrable skills across social, physical and temporal tasks, despite differences in socioecology. However, it is unknown whether relatively asocial corvids differ from social corvids in their use of social information in the context of copying the choices of others, because only one such test has been conducted in a relatively asocial corvid. We investigated whether relatively asocial Eurasian jays ($\textit{Garrulus glandarius}$) use social information (i.e., information made available by others). Previous studies have indicated that jays attend to social context in their caching and mate provisioning behaviour; however, it is unknown whether jays copy the choices of others. We tested the jays in two different tasks varying in difficulty, where social corvid species have demonstrated social information use in both tasks. Firstly, an object-dropping task was conducted requiring objects to be dropped down a tube to release a food reward from a collapsible platform, which corvids can learn through explicit training. Only one rook and one New Caledonian crow have learned the task using social information from a demonstrator. Secondly, we tested the birds on a simple colour discrimination task, which should be easy to solve, because it has been shown that corvids can make colour discriminations. Using the same colour discrimination task in a previous study, all common ravens and carrion crows copied the demonstrator. After observing a conspecific demonstrator, none of the jays solved the object-dropping task, though all jays were subsequently able to learn to solve the task in a non-social situation through explicit training, and jays chose the demonstrated colour at chance levels. Our results suggest that social and relatively asocial corvids differ in social information use, indicating that relatively asocial species may have secondarily lost this ability due to lack of selection pressure from an asocial environment.RM and NSC received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC Grant Agreement No. 3399933, awarded to NSC. CJL was funded by the Leverhulme Trust and Isaac Newton Trust with a Leverhulme Early Career Fellowship

Prospective object search in dogs: mixed evidence for knowledge of What and Where

We investigated whether two dogs that had been specially trained to retrieve objects by their names were able to integrate information about the identity (What) as well as the location (Where) of those objects so that they could plan their search accordingly. In a first study, two sets of objects were placed in two separate rooms and subjects were asked to retrieve the objects, one after the other. Both dogs remembered the identity of the objects as they reliably retrieved the correct objects. One of the dogs was also able to integrate information about the object’s location as he chose the correct location in which the object had been placed. Further investigation of the second dog’s behavior revealed that she followed a more stereotyped search strategy. Despite this variation in performance, this study provides evidence for the memory of What and Where in a domestic dog and shows the prospective use of such information in a search task