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Bugnyar, T.; Kotrschal, K. |
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Title |
Movement coordination and signalling in ravens (Corvus corax): an experimental field study |
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Journal Article |
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Year |
2001 |
Publication |
Acta ethologica |
Abbreviated Journal |
Acta. Ethol. |
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3 |
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2 |
Pages |
101-109 |
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Keywords |
Ravens – Corvus corax – Foraging – Coordination – Communication |
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Abstract |
Vagrant non-breeding ravens frequently attract conspecifics to rich ephemeral food sources. There, grouping may allow them to overcome the defence of territorial breeders. Here, we focus on ravens making use of regular food supplies in a game park, where they divert food from the provision of park animals. We investigated if ravens foraging in the Cumberland game park (Grünau, Austria) are attentive towards one another when they experience some unpredictability in food provisioning. We confronted a group of 30-50 ravens with two different treatments. Ten minutes ahead of the feeding of either wolves or wild boars we showed buckets containing pieces of meat to the ravens flying overhead. In the reliable cue treatment (RCT), the meat was placed next to one of the two enclosures, whereas in the unreliable cue treatment (UCT), the buckets were placed simultaneously in front of both enclosures though only in one of the enclosures were the animals fed 10 min later. Thus, during RCT but not during UCT, ravens could predict where food would become available. Only during UCT, ravens moved in large groups between the two feeding sites. Many ravens moving at the same time in the same direction may indicate some co-ordination in space and time, which is most likely achieved by social attraction among individuals. Furthermore, the number of ravens approaching and leaving, respectively, a feeding site cross-correlated with a temporary increase in the rate of a food-associated call, the yell. This suggests that in addition to watching each other, calling may have contributed to group formation. Possible benefits of group formation during food inspection are discussed. |
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2081 |
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Author |
Bugnyar, T.; Kotrschal, K. |
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Title |
Observational learning and the raiding of food caches in ravens, Corvus corax: is it `tactical' deception? |
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Journal Article |
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Year |
2002 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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64 |
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2 |
Pages |
185-195 |
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Abstract |
Group-foraging ravens scatter-hoard when they are competing for food and, to some extent, also raid the caches made by others. We investigated the effects of observational spatial memory on individual caching and raiding tactics. With captive ravens, we found visual observation was essential for locating and raiding the caches of conspecifics. Both captive and free-ranging ravens, food cachers as well as potential cache raiders, responded to each other's presence. Cachers withdrew from conspecifics and most often placed their caches behind structures, obstructing the view of potential observers. Raiders watched inconspicuously and kept at a distance to cachers close to their cache sites. In response to the presence of potential raiders or because of their initial movements towards caches, the cachers frequently interrupted caching, changed cache sites, or recovered their food items. These results suggest that ravens, regardless of whether they act as cachers or raiders, are capable of withholding information about their intentions and, hence, manipulate the other bird's attention either to prevent or to achieve social-learning opportunities. Such interactions may qualify as `tactical' deception and may have created a considerable pressure selecting for social cognition in ravens. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. |
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Equine Behaviour @ team @ |
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2904 |
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Bugnyar, T.; Heinrich, B. |
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Pilfering ravens, Corvus corax, adjust their behaviour to social context and identity of competitors |
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2006 |
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Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
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9 |
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4 |
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369-376 |
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Adaptation, Psychological; Animals; *Behavior, Animal; *Competitive Behavior; Crows/*physiology; *Deception; Feeding Behavior; Female; Male; Social Behavior; *Social Environment |
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Like other corvids, food-storing ravens protect their caches from being pilfered by conspecifics by means of aggression and by re-caching. In the wild and in captivity, potential pilferers rarely approach caches until the storers have left the cache vicinity. When storers are experimentally prevented from leaving, pilferers first search at places other than the cache sites. These behaviours raise the possibility that ravens are capable of withholding intentions and providing false information to avoid provoking the storers' aggression for cache protection. Alternatively, birds may refrain from pilfering to avoid conflicts with dominants. Here we examined whether ravens adjust their pilfer tactics according to social context and type of competitors. We allowed birds that had witnessed a conspecific making caches to pilfer those caches either in private, together with the storer, or together with a conspecific bystander that had not created the caches (non-storer) but had seen them being made. Compared to in-private trials, ravens delayed approaching the caches only in the presence of storers. Furthermore, they quickly engaged in searching away from the caches when together with dominant storers but directly approached the caches when together with dominant non-storers. These findings demonstrate that ravens selectively alter their pilfer behaviour with those individuals that are likely to defend the caches (storers) and support the interpretation that they are deceptively manipulating the others' behaviour. |
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Department of Biology, University of Vermont, Burlington, VT 05405, USA. thomas.bugnyar@univie.ac.at |
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English |
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1435-9448 |
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PMID:16909235 |
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Equine Behaviour @ team @ |
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2449 |
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Bugnyar, T.; Stöwe, M.; Heinrich, B. |
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Title |
Ravens, Corvus corax, follow gaze direction of humans around obstacles |
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Journal Article |
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Year |
2004 |
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Proceedings of the Royal Society B: Biological Sciences |
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Proc. Roy. Soc. Lond. B Biol. Sci. |
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271 |
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1546 |
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1331-1336 |
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The ability to follow gaze (i.e. head and eye direction) has recently been shown for social mammals, particularly primates. In most studies, individuals could use gaze direction as a behavioural cue without understanding that the view of others may be different from their own. Here, we show that hand–raised ravens not only visually co–orient with the look–ups of a human experimenter but also reposition themselves to follow the experimenter's gaze around a visual barrier. Birds were capable of visual co–orientation already as fledglings but consistently tracked gaze direction behind obstacles not before six months of age. These results raise the possibility that sub–adult and adult ravens can project a line of sight for the other person into the distance. To what extent ravens may attribute mental significance to the visual behaviour of others is discussed. |
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10.1098/rspb.2004.2738 |
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Equine Behaviour @ team @ |
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5009 |
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Author |
Bílá, K.; Beránková, J.; Veselý, P.; Bugnyar, T.; Schwab, C. |
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Title |
Responses of urban crows to con- and hetero-specific alarm calls in predator and non-predator zoo enclosures |
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Journal Article |
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2017 |
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Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
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20 |
Issue |
1 |
Pages |
43-51 |
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Urban animals and birds in particular are able to cope with diverse novel threats in a city environment such as avoiding novel, unfamiliar predators. Predator avoidance often includes alarm signals that can be used also by hetero-specifics, which is mainly the case in mixed-species flocks. It can also occur when species do not form flocks but co-occur together. In this study we tested whether urban crows use alarm calls of conspecifics and hetero-specifics (jackdaws, Corvus monedula) differently in a predator and a non-predator context with partly novel and unfamiliar zoo animal species. Birds were tested at the Tiergarten Schönbrunn in the city of Vienna by playing back con- and hetero-specific alarm calls and control stimuli (great tit song and no stimuli) at predator (wolf, polar bear) and non-predator (eland antelope and cranes, peccaries) enclosures. We recorded responses of crows as the percentage of birds flying away after hearing the playback (out of those present before the playback) and as the number of vocalizations given by the present birds. A significantly higher percentage of crows flew away after hearing either con- or hetero-specific alarm calls, but it did not significantly differ between the predator and the non-predator context. Crows treated jackdaw calls just as crow calls, indicating that they make proper use of hetero-specific alarm calls. Responding similarly in both contexts may suggest that the crows were uncertain about the threat a particular zoo animal represents and were generally cautious. In the predator context, however, a high percentage of crows also flew away upon hearing the great tit control song which suggests that they may still evaluate those species which occasionally killed crows as more dangerous and respond to any conspicuous sound. |
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1435-9456 |
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Equine Behaviour @ team @ Bílá2017 |
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6159 |
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Range, F.; Horn, L.; Bugnyar, T.; Gajdon, G.; Huber, L. |
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Title |
Social attention in keas, dogs, and human children |
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Journal Article |
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Year |
2009 |
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Animal Cognition |
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Anim. Cogn. |
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12 |
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1 |
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181-192 |
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Abstract: Understanding animals" abilities to cooperate with and learn from each other has been an active field of research in recent years. One important basis for all types of social interactions is the disposition of animals to pay attention to each other-a factor often neglected in discussions and experiments. Since attention differs between species as well as between individuals, it is likely to influence the amount and type of information different species and/or observers may extract from conspecifics in any given situation. Here, we carried out a standardized comparative study on attention towards a model demonstrating food-related behavior in keas, dogs and children. In a series of experimental sessions, individuals watched different conspecific models while searching, manipulating and feeding. Visual access to the demonstration was provided by two observation holes, which allowed us to determine exactly how often and for how long observers watched the model. We found profound differences in the factors that influence attention within as well as between the tested species. This study suggests that attention should be incorporated as an important variable when testing species in social situations. |
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Equine Behaviour @ team @ |
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4713 |
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