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Anderson, J. R., Kuwahata, H., & Fujita, K. (2007). Gaze alternation during “pointing” by squirrel monkeys (Saimiri sciureus)? Anim. Cogn., 10(2), 267–271.
Abstract: Gaze alternation (GA) is considered a hallmark of pointing in human infants, a sign of intentionality underlying the gesture. GA has occasionally been observed in great apes, and reported only anecdotally in a few monkeys. Three squirrel monkeys that had previously learned to reach toward out-of-reach food in the presence of a human partner were videotaped while the latter visually attended to the food, a distractor object, or the ceiling. Frame-by-frame video analysis revealed that, especially when reaching toward the food, the monkeys rapidly and repeatedly switched between looking at the partner's face and the food. This type of GA suggests that the monkeys were communicating with the partner. However, the monkeys' behavior was not influenced by changes in the partner's focus of attention.
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McComb, K., & Clutton-Brock, T. (1994). Is mate choice copying or aggregation responsible for skewed distributions of females on leks? Proc Biol Sci, 255(1342), 13–19.
Abstract: In several lek-breeding populations of birds and mammals, females arriving on leks tend to join males that already have females in their territories. This might occur either because females have an evolved preference for mating with males that are attractive to other females, or because they join groups of other females to obtain greater safety from predation or dangerous harassment by males. We have previously used controlled experiments to show that oestrous fallow deer females join males with established harems because they are attracted to female groups rather than to the males themselves. Here we demonstrate that the preference for males with females over males without females is specific to oestrous females and weak or absent in anoestrous ones, and that it is not associated with a preference for mating with males that have previously been seen to mate with other females. Furthermore, oestrous females given the choice between males that do not already have females with them show no significant preference for antlered over deantlered males or for older males over younger ones. We conclude that female attraction to other females on the lek is likely to be an adaptation to avoiding harassment in mixed-sex herds. In this situation, a male's ability to maintain the cohesion of his harem may be the principal cause of variation in mating success between males.
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Ratcliffe, J. M., Fenton, M. B., & Shettleworth, S. J. (2006). Behavioral flexibility positively correlated with relative brain volume in predatory bats. Brain Behav Evol, 67(3), 165–176.
Abstract: We investigated the potential relationships between foraging strategies and relative brain and brain region volumes in predatory (animal-eating) echolocating bats. The species we considered represent the ancestral state for the order and approximately 70% of living bat species. The two dominant foraging strategies used by echolocating predatory bats are substrate-gleaning (taking prey from surfaces) and aerial hawking (taking airborne prey). We used species-specific behavioral, morphological, and ecological data to classify each of 59 predatory species as one of the following: (1) ground gleaning, (2) behaviorally flexible (i.e., known to both glean and hawk prey), (3) clutter tolerant aerial hawking, or (4) open-space aerial hawking. In analyses using both species level data and phylogenetically independent contrasts, relative brain size was larger in behaviorally flexible species. Further, relative neocortex volume was significantly reduced in bats that aerially hawk prey primarily in open spaces. Conversely, our foraging behavior index did not account for variability in hippocampus and inferior colliculus volume and we discuss these results in the context of past research.
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Villani, M., Cairoli, F., Kindahl, H., Galeati, G., Faustini, M., Carluccio, A., et al. (2006). Effects of mating on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF2alpha in stallions. Reprod Domest Anim, 41(6), 544–548.
Abstract: Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the jugular vein with heparinized tubes, 20 and 10 min before oestrous mare exposure, at exposure and 10, 20, 30 min after dismounting. Testosterone concentrations showed a sharp rise 10 min after mating (p < 0.001), reached a plateau, and then showed a further increase 30 min after mating (p < 0.001). Cortisol concentrations increased 10 min after mating (p < 0.001) and remained at high levels in the subsequent samples taken. A peak of oestrone sulphate was observed 10 min after mating (p < 0.001). 15-Ketodihydro-PGF(2alpha) concentrations decreased rapidly at the moment of the exposure of the stallions to an oestrous mare (p < 0.05), returned to pre-mating concentrations and then decreased again 30 min after mating (p < 0.05).
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Hedberg, Y., Dalin, A. - M., Ohagen, P., Holm, K. R., & Kindahl, H. (2005). Effect of oestrous-cycle stage on the response of mares in a novel object test and isolation test. Reprod Domest Anim, 40(5), 480–488.
Abstract: In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioural and two heart rate variables were measured for the novel object test and two heart rate variables for the isolation test. Oestrous-cycle stage and whether a mare was classified as a 'problem' mare did not affect the mare's response. However, test order, i.e. the cycle stage a mare was tested in first, affected its reaction. This effect could partly be explained by significant differences between test occasions 1 and 2 in three behavioural variables and one heart rate variable (p < 0.05) in the novel object test. The mares explored the novel object more and had a higher mean heart rate in the first test. Exploring the novel object more could largely be attributed to those mares tested in dioestrus first, perhaps indicating that the mares in oestrus were less receptive to the novel object. The reason for the differences between test occasions could be an effect of learning or habituation.
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Hausberger, M., Bruderer, C., Le Scolan, N., & Pierre, J. - S. (2004). Interplay between environmental and genetic factors in temperament/personality traits in horses (Equus caballus). J Comp Psychol, 118(4), 434–446.
Abstract: The aim of the present study was to broach the question of the relative influence of different genetic and environmental factors on different temperament/personality traits of horses (Equus caballus). The researchers submitted 702 horses to standardized experimental tests and investigated 9 factors, either genetic or environmental. Genetic factors, such as sire or breed, seemed to influence more neophobic reactions, whereas environmental factors, such as the type of work, seemed to play a more dominant role in reactions to social separation or learning abilities. Additive effects were evident, showing how environmental factors may modulate behavioral traits. This study constitutes a first step toward understanding the relative weights of genetic factors and how the environment may intervene in determining individual behavioral characteristics.
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Kaiser, L., Heleski, C. R., Siegford, J., & Smith, K. A. (2006). Stress-related behaviors among horses used in a therapeutic riding program. J Am Vet Med Assoc, 228(1), 39–45.
Abstract: OBJECTIVE: To determine whether therapeutic riding resulted in higher levels of stress or frustration for horses than did recreational riding and whether therapeutic riding with at-risk individuals was more stressful for the horses than was therapeutic riding with individuals with physical or emotional handicaps. DESIGN: Observational study. ANIMALS: 14 horses in a therapeutic riding program. PROCEDURE: An ethogram of equine behaviors was created, and horses were observed while ridden by 5 groups of riders (recreational riders, physically handicapped riders, psychologically handicapped riders, at risk children, and special education children). Number of stress-related behaviors (ears pinned back, head raised, head turned, head tossed, head shaken, head down, and defecation) was compared among groups. RESULTS: No significant differences in mean number of stress-related behaviors were found when horses were ridden by recreational riders, physically handicapped riders, psychologically handicapped riders, or special education children. However, mean number of stress-related behaviors was significantly higher when horses were ridden by the at-risk children. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that for horses in a therapeutic riding program, being ridden by physically or psychologically handicapped individuals is no more stressful for the horses than is being ridden in the same setting by recreational riders. However, at-risk children caused more stress to the horses, suggesting that the time horses are ridden by at-risk children should be limited both daily and weekly.
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King, A. J., Douglas, C. M. S., Huchard, E., Isaac, N. J. B., & Cowlishaw, G. (2008). Dominance and affiliation mediate despotism in a social primate. Curr Biol, 18(23), 1833–1838.
Abstract: Group-living animals routinely have to reach a consensus decision and choose between mutually exclusive actions in order to coordinate their activities and benefit from sociality. Theoretical models predict “democratic” rather than “despotic” decisions to be widespread in social vertebrates, because they result in lower “consensus costs”-the costs of an individual foregoing its optimal action to comply with the decision-for the group as a whole. Yet, quantification of consensus costs is entirely lacking, and empirical observations provide strong support for the occurrence of both democratic and despotic decisions in nature. We conducted a foraging experiment on a wild social primate (chacma baboons, Papio ursinus) in order to gain new insights into despotic group decision making. The results show that group foraging decisions were consistently led by the individual who acquired the greatest benefits from those decisions, namely the dominant male. Subordinate group members followed the leader despite considerable consensus costs. Follower behavior was mediated by social ties to the leader, and where these ties were weaker, group fission was more likely to occur. Our findings highlight the importance of leader incentives and social relationships in group decision-making processes and the emergence of despotism.
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Minero, M., Canali, E., Ferrante, V., Verga, M., & Odberg, F. O. (1999). Heart rate and behavioural responses of crib-biting horses to two acute stressors. Vet. Rec., 145(15), 430–433.
Abstract: The heart rate and behaviour of 14 adult saddle horses, eight crib-biters and six normal controls, were investigated. Initially, the relationship between crib-biting and heart rate was investigated while the horses were undisturbed. The horses were tested when restrained with a lip twitch, and assessed when they were exposed suddenly to the rapid inflation of a balloon. The heart rate of the crib-biters during crib-biting was lower than during other behaviours. The crib-biters had a higher overall mean heart rate (P<0.05) suggesting that they may have had a higher basal sympathetic activity. After the application of the twitch, all the horses had a transient increase in heart rate which returned to basal values more rapidly in the crib-biters. The crib-biters were less reactive to the lip twitch, five of the six investigated remaining calm, and after the release of the twitch, they spent more time nibbling (P<0.05) than the control horses. The crib-biters reacted more strongly to the inflation of the balloon (three of the six reacted), and after it had been inflated they spent more time walking in the box.
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Range, F., Bugnyar, T., Schlogl, C., & Kotrschal, K. (2006). Individual and sex differences in learning abilities of ravens. Behav. Process., 73(1), 100–106.
Abstract: 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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