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Schuck-Paim, C.; Kacelnik, A. |
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Rationality in risk-sensitive foraging choices by starlings |
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2002 |
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Animal Behaviour. |
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Anim. Behav. |
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64 |
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6 |
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869-879 |
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Normative models of choice usually predict preferences between alternatives by computing their value according to some criterion, then identifying the alternative with greatest value. An important consequence of this procedure is captured in the economic concept of rationality, defined through a number of principles that are necessary for the existence of an ordinal scale of value upon which organisms base their choices. Violations of these principles, such as some recently reported breaches of transitivity and regularity in birds and honeybees, have strong implications for the understanding of decision mechanisms in humans and nonhumans alike. We investigated rationality in risky choice using European starlings, Sturnus vulgaris. Birds had to choose between two or three food sources, each associated with a different variance in delay to reward. In three experiments, starlings were strongly risk prone, showing regular and consistent preferences in binary and trinary choices. Preferences also satisfied weak and strong stochastic transitivity. Our results extend the generality of previous research in risk-sensitive foraging to situations where more than two alternatives are present and suggest that violations of rationality in risk-sensitive choices may be expressed only under restricted sets of conditions. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. |
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Bugnyar, T.; Kotrschal, K. |
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Observational learning and the raiding of food caches in ravens, Corvus corax: is it `tactical' deception? |
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2002 |
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Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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64 |
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2 |
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185-195 |
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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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Hauser MD; Pearson H; Seelig D |
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Ontogeny of tool use in cottontop tamarins, Saguinus oedipus: innate recognition of functionally relevant features |
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2002 |
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Animal Behaviour. |
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Anim. Behav. |
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64 |
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299 |
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Equine Behaviour @ team @ |
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3066 |
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Hauser MD; Santos LR; Spaepen GM; Pearson HE |
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Problem solving, inhibition and domain-specific experience: experiments on cotton-top tamarins, Saguinus oedipus |
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2002 |
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Animal Behaviour. |
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Anim. Behav. |
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64 |
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387 |
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Equine Behaviour @ team @ |
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3067 |
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Dingemanse, N.J.; Both, C.; Drent, P.J.; van Oers, K.; van Noordwijk, A.J. |
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Repeatability and heritability of exploratory behaviour in great tits from the wild |
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2002 |
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Animal Behaviour |
Abbreviated Journal |
Anim. Behav. |
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64 |
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6 |
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929-938 |
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We investigated whether individual great tits, Parus major, vary consistently in their exploratory behaviour in a novel environment and measured the repeatability and heritability of this trait. Wild birds were caught in their natural habitat, tested in the laboratory in an open field test on the following morning, then released at the capture site. We measured individual consistency of exploratory behaviour for recaptured individuals (repeatability) and estimated the heritability with parent-offspring regressions and sibling analyses. Measures of exploratory behaviour of individuals at repeated captures were consistent in both sexes and study areas (repeatabilities ranged from 0.27 to 0.48). Exploration scores did not differ between the sexes, and were unrelated to age, condition at fledging or condition during measurement. Heritability estimates were 0.22-0.41 (parent-offspring regressions) and 0.37-0.40 (sibling analyses). We conclude that (1) consistent individual variation in open field behaviour exists in individuals from the wild, and (2) this behavioural variation is heritable. This is one of the first studies showing heritable variation in a behavioural trait in animals from the wild, and poses the question of how this variation is maintained under natural conditions. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved. |
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0003-3472 |
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Equine Behaviour @ team @ |
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5389 |
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Gazzola, A.; Avanzinelli, E.; Mauri, L.; Scandura, M.; Apollonio, M. |
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Temporal changes of howling in south European wolf packs |
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2002 |
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Ital J Zool |
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69 |
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Equine Behaviour @ team @ Gazzola2002 |
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6495 |
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BROUCEK,J.; UHRINCAT,M.; ARAVE,C. W.; FRIEND,T. H.; MIHINA,S.; KISAC,P.; HANUS, A. |
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Title |
Effects of Rearing Methods of Heifers during Milk Replacement Period |
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Journal Article |
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2002 |
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Czech Journal of Animal Science |
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Czech J. Anim. Sci |
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71 |
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4 |
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509-516 |
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Heifers, behaviour, maze, feeding, housing |
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Fifty-eight Holstein heifer calves were assigned to one out of three treatment groups after having nursed by their mothers for the first week: BN) individual hutch, bucket with nipple n=25; DF)loose housing pen, machine milk feeder, n=16; NC) loose housing pen, nursing cow, n=17. After weaning at 8 weeks, all calves were kept in group pens. At 15 weeks of age, the behaviour in the 6-unit maze (16.4 – 4.5 m) was determined. On the first observation day, the calves were tested five times (the first one for training); on the second day there were four runs. The calves had to solve two tasks. In task A, the passage was open on the left side, and on the right side (task B) on the next day. We were testing the following hypothesis: the speed of traversing the maze is affected by the rearing system. The slowest were NC calves. On the first day (task A), the average time to traverse the maze among treatments DF (43.9 s), BN (53 s) and NC (111.3 s) was different (F = 8.26*, P = 0.0007). On the second day (task B), the averages were: BN 77.1 s, DF 83.8 s and DC 166.6 s (F=8.17*, P = 0.0008). The results indicate that the feeding method and housing used to rear calves may have a significant impact on their maze behaviour. |
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Equine Behaviour @ team @ |
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4323 |
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Davies Morel, M.C.G.; Newcombe, J.R.; Holland, S.J. |
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Factors affecting gestation length in the Thoroughbred mare |
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2002 |
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Animal Reproduction Science |
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74 |
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3-4 |
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175-185 |
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Gestation length; Mare age; Foals; Month of year; Ovulation-mating interval |
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In order to assist in the accurate prediction of the timing of parturition in the mare true gestation length, along with the potential effect of a number of factors, was investigated. Data from 433 Thoroughbred foal pregnancies were used. Sequential ultrasonic scanning allowed the true gestation length (fertilisation-parturition) to be ascertained, as apposed to previous work, which used the mating-parturition interval. An average gestation length of 344.1+/-0.49 days was evident. Colt foal pregnancies were significantly (P<0.001) longer (346.2+/-0.72) than fillies (342.4+/-0.65). Month of birth had a significant effect on gestation length in all foals (P<0.001). With foals born in January having the shortest gestation lengths and those born in April the longest. Mare age, year of birth, stallion age, stud farm and the interval between ovulation and mating had no significant effect. It is concluded that (i) the gestation length range (315-388 days), all resulting in viable foals is noteworthy and of clinical importance when considering the classification of dysmaturity in foals, (ii) mares carrying colt foals due to be born in the middle of the breeding season (April) are likely to have the longer gestation lengths. |
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Equine Behaviour @ team @ |
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3638 |
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Christensen, J.W.; Ladewig, J.; Sondergaard, E.; Malmkvist, J. |
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Effects of individual versus group stabling on social behaviour in domestic stallions |
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2002 |
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Applied Animal Behaviour Science |
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Appl. Anim. Behav. Sci. |
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75 |
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3 |
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233-248 |
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Horse; Individual stabling; Group stabling; Social behaviour |
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Domestic horses (Equus caballus) are typically kept in individual housing systems, in which they are deprived of physical contact. In order to study the effects of social restrictions on behaviour in young horses, nineteen 2-year-old stallions were housed either singly (n=7), or in groups of three (n=12) for 9 months. Subsequently, the stallions were released into two separate 2 ha enclosures according to treatment, and recordings were made on social interactions and nearest neighbours during a 6-week-period, 28 h per week. Previously group stabled stallions frequently had a former group mate as their nearest neighbour (P=0.001), whereas previously singly stabled stallions did not associate more with their former box neighbours, to whom physical contact was limited by bars during the previous treatment. The nearest neighbour was more frequently recorded to be within one horselength of singly stabled than of group stabled stallions (P=0.005). More aggressive behaviour was recorded in the group of previously singly stabled stallions, i.e. bite threats (P=0.032), whereas group stabled stallions tended to make more use of subtle agonistic interactions (displacements, submissive behaviour). Singly stabled stallions also responded to the 9 months of social deprivation by significantly increasing the level of social grooming (P<0.001) and play behaviour (P<0.001), when subsequently interacting freely with other horses. The increased occurrence may relate to a build-up of motivation (a rebound effect), as well as to external factors, such as playful pasture companions and the increased space allowance of the pasture. It is concluded that 2-year-old domestic stallions are sensitive to social deprivation and that stabling has long-term effects, lasting 6 weeks at least, on the social behaviour in stallions. |
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Equine Behaviour @ team @ |
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2257 |
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Visser, E.K.; van Reenen, C.G.; van der Werf, J.T.N.; Schilder, M.B.H.; Knaap, J.H.; Barneveld, A.; Blokhuis, H.J. |
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Heart rate and heart rate variability during a novel object test and a handling test in young horses |
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2002 |
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Physiology & Behavior |
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Physiol. Behav. |
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76 |
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2 |
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289-296 |
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Heart rate; Heart rate variability; Consistency; Behavioral tests; Temperament; Emotionality; Horses |
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Forty-one Dutch Warmblood immature horses were used in a study to quantify temperamental traits on the basis of heart rate (HR) and heart rate variability (HRV) measures. Half of the horses received additional training from the age of 5 months onwards; the other half did not. Horses were tested at 9, 10, 21 and 22 months of age in a novel object and a handling test. During the tests, mean HR and two heart variability indices, e.g. standard deviation of beat-to-beat intervals (SDRR) and root mean square of successive beat-to-beat differences (rMSSD), were calculated and expressed as response values to baseline measures. In both tests, horses showed at all ages a significant increase in mean HR and decrease in HRV measures, which suggests a marked shift of the balance of the autonomic nervous system towards a sympathetic dominance. In the novel object test, this shift was more pronounced in horses that had not been trained. Furthermore, statistical analysis showed that the increase in mean HR could not be entirely explained by the physical activity. The additional increase in HR, the nonmotor HR, was more pronounced in the untrained horses compared to the trained. Hence, it is suggested that this nonmotor HR might be due to the level of emotionality. HR variables showed consistency between years, as well as within the second year. These tests bring about a HR response in horses, part of which may indicate a higher level of emotionality; and horses show individual consistency of these HR variables over ages. Therefore, it is concluded that mean HR and HRV measures used with these tests quantify certain aspects of a horse's temperament. |
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