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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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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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Bugnyar, T.; Kotrschal, K. |
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Title |
Leading a conspecific away from food in ravens ( Corvus corax)? |
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2004 |
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Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
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7 |
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2 |
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69-76 |
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Misleading – Deception – Raven – Social foraging |
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Active misleading of conspecifics has been described as a social strategy mainly for primates. Here we report a raven leading a competitor away from food in a social foraging task. Four individuals had to search and compete for hidden food at color-marked clusters of artificial food caches. At the beginning of the experiment, a subordinate male found and exploited the majority of the food. As a result, the dominant male displaced him from the already opened boxes. The subordinate male then developed a pattern, when the loss of reward to the dominant got high, of moving to unrewarded clusters and opening boxes there. This diversion often led the dominant to approach those unrewarded clusters and the subordinate then had a head start for exploiting the rewarded boxes. Subsequently, however, the dominant male learned not to follow the subordinate to unrewarded clusters and eventually started searching for the reward himself. These interactions between the two males illustrate the ravens' potential for deceptively manipulating conspecifics. We discuss under which circumstances ravens might use this capacity. |
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2080 |
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Kralj-Fiser, S.; Scheiber, I.B.R.; Blejec, A.; Moestl, E.; Kotrschal, K. |
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Individualities in a flock of free-roaming greylag geese: behavioral and physiological consistency over time and across situations |
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2007 |
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Hormones and Behavior |
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Horm Behav |
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51 |
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2 |
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239-248 |
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Animals; Behavior, Animal/*physiology; Corticosterone/metabolism; Feces; Female; Geese/*physiology; Individuality; Male; Personality/*physiology; Population Density; Reproducibility of Results; Seasons; *Social Behavior; Social Environment; Testosterone/*metabolism |
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The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of “temperaments” in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a “low density feeding condition”, (2) a “high density feeding condition”, (3) a “low density post-feeding situation” and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the “low density feeding” and the “high density feeding” conditions. BM levels were very highly consistent over the repeats of handling trials, and the “low density feeding condition” and tended to be consistent over the first two repeats of the “high density feeding condition”. Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, “proximity to the female partner” and “sociability” – the average number of neighboring geese in a close distance while resting – were consistent. We conclude that aggressiveness, “affiliative tendencies” and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese. |
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University of Ljubljana, Biotechnical faculty, Slovenia. simona.kralj@guest.arnes.si |
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0018-506X |
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PMID:17196200 |
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Equine Behaviour @ team @ |
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4189 |
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Range, F.; Bugnyar, T.; Schlogl, C.; Kotrschal, K. |
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Individual and sex differences in learning abilities of ravens |
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2006 |
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Behavioural Processes |
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Behav. Process. |
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73 |
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1 |
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100-106 |
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Animals; Behavior, Animal/*physiology; *Crows; Discrimination Learning/*physiology; Exploratory Behavior/physiology; Female; *Individuality; Male; Sex Factors; Spatial Behavior |
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Behavioral and physiological characteristics of individuals within the same species have been found to be stable across time and contexts. In this study, we investigated individual differences in learning abilities and object and social manipulation to test for consistency within individuals across different tasks. Individual ravens (Corvus corax) were tested in simple color and position discrimination tasks to establish their learning abilities. We found that males were significantly better in the acquisition of the first discrimination task and the object manipulation task, but not in any of the other tasks. Furthermore, faster learners engaged less often in manipulations of conspecifics and exploration of objects to get access to food. No relationship between object and social manipulation and reversal training were found. Our results suggest that individual differences in regard to the acquisition of new tasks may be related to personalities or at least object manipulation in ravens. |
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Konrad Lorenz Research Station, A-4645 Gruenau 11, Austria. friederike.range@univie.ac.at |
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0376-6357 |
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PMID:16675158 |
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Equine Behaviour @ team @ |
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4146 |
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