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Author Smith, J.E.; Van Horn, R.C.; Powning, K.S.; Cole, A.R.; Graham, K.E.; Memenis, S.K.; Holekamp, K.E.
Title Evolutionary forces favoring intragroup coalitions among spotted hyenas and other animals Type Journal Article
Year 2010 Publication Behavioral Ecology Abbreviated Journal Behav. Ecol.
Volume 21 Issue (up) 2 Pages 284-303
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Abstract Coalitionary support in agonistic interactions represents cooperation because intervening in a fight is potentially costly to the donor of support but benefits the recipient. Here, we first review the characteristics of, and evolutionary forces favoring, intragroup coalitions in 49 species and find that patterns of intragroup coalition formation are remarkably similar between primates and nonprimates. We then test hypotheses suggesting kin selection, reciprocal altruism, and direct benefits as adaptive explanations for coalitionary interventions among adult female spotted hyenas (Crocuta crocuta) belonging to a large social group in Kenya. As predicted by kin selection theory, females supported close kin most often, and the density (connectedness) of cooperation networks increased with genetic relatedness. Nevertheless, kinship failed to protect females from coalitionary attacks. We found no evidence of enduring alliances based on reciprocal support among unrelated adult females. Instead, donors generally minimized costs to themselves, intervening most often during low-intensity fights and when feeding opportunities were unavailable. Females also gained direct benefits from directing coalitionary attacks toward subordinates. Finally, females monitored the number of dominant bystanders in the “audience” at fights and modified their level of cooperation based on this knowledge. Overall, hyenas made flexible decisions regarding whether or not to intervene in fights, modifying their tendency to cooperate based on multiple types of information about their immediate social and ecological environments. Taken together, these findings indicate that the combined evolutionary forces of kin selection and direct benefits derived from reinforcing the status quo drive coalitionary interventions among adult female spotted hyenas.
Address agonistic support, audience effect, cooperation network, direct benefits, kin selection * reciprocal altruism * review
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Notes 10.1093/beheco/arp181 Approved no
Call Number Equine Behaviour @ team @ Serial 5285
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Author Mirabet, V.; Fréon, P.; Lett, C.
Title Factors affecting information transfer from knowledgeable to naive individuals in groups Type Journal Article
Year 2008 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 63 Issue (up) 2 Pages 159-171-171
Keywords Biomedical and Life Sciences
Abstract There is evidence that individuals in animal groups benefit from the presence of knowledgeable group members in different ways. Experiments and computer simulations have shown that a few individuals within a group can lead others, for a precise task and at a specific moment. As a group travels, different individuals possessing a particular knowledge may act as temporary leaders, so that the group will, as a whole, follow their behaviour. In this paper, we use a model to study different factors influencing group response to temporary leadership. The model is based on four individual behaviours. Three of those, attraction, repulsion, and alignment, are shared by all individuals. The last one, attraction toward the source of a stimulus, concerns only a fraction of the group members. We explore the influence of group size, proportion of stimulated individuals, number of influential neighbours, and intensity of the attraction to the source of the stimulus, on the proportion of the group reaching this source. Special attention is given to the simulation of large group size, close to those observed in nature. Groups of 100, 400 and 900 individuals are currently simulated, and up to 8,000 in one experiment. We show that more stimulated individuals and a larger group size both induce the arrival of a larger fraction of the group. The number of influential neighbours and the intensity of the stimulus have a non-linear influence on the proportion of the group arrival, displaying first a positive relationship and then, above a given threshold, a negative one. We conclude that an intermediate level of group cohesion provides optimal transfer information from knowledgeable to naive individuals.
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Publisher Springer Berlin / Heidelberg Place of Publication Editor
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ISSN 0340-5443 ISBN Medium
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Notes Approved no
Call Number Equine Behaviour @ team @ Serial 5295
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Author Dugatkin, L.A.
Title Bystander effects and the structure of dominance hierarchies Type Journal Article
Year 2001 Publication Behavioral Ecology Abbreviated Journal Behav. Ecol.
Volume 12 Issue (up) 3 Pages 348-352
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Abstract Prior modeling work has found that pure winner and loser effects (i.e., changing the estimation of your own fighting ability as a function of direct prior experience) can have important consequences for hierarchy formation. Here these models are extended to incorporate “bystander effects.” When bystander effects are in operation, observers (i.e., bystanders) of aggressive interactions change their assessment of the protagonists' fighting abilities (depending on who wins and who loses). Computer simulations demonstrate that when bystander winner effects alone are at play, groups have a clear omega (bottom-ranking individual), while the relative position of other group members remains difficult to determine. When only bystander loser effects are in operation, wins and losses are randomly distributed throughout a group (i.e., no discernible hierarchy). When pure and bystander winner effects are jointly in place, a linear hierarchy, in which all positions (i.e., {alpha} to {delta} when N = 4) are clearly defined, emerges. Joint pure and bystander loser effects produce the same result. In principle one could test the predictions from the models developed here in a straightforward comparative study. Hopefully, the results of this model will spur on such studies in the future.
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Notes 10.1093/beheco/12.3.348 Approved no
Call Number refbase @ user @ Serial 441
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Author Dugatkin, L.A.; Earley, R.L.
Title Group fusion: the impact of winner, loser, and bystander effects on hierarchy formation in large groups Type Journal Article
Year 2003 Publication Behavioral Ecology Abbreviated Journal Behav. Ecol.
Volume 14 Issue (up) 3 Pages 367-373
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Abstract We present the results of a series of computer simulations that examined the impact of winner, loser, and bystander effects on hierarchy formation in fused groups. These effects and their implications for hierarchy structure and aggressive interactions were first examined in small four-member groups. Subsequent to this, the two small groups were fused into a single larger group. Further interactions took place in this fused group, generating a new hierarchy. Our models demonstrate clearly that winner, loser, and bystander effects strongly influence both the structure and types of interactions that emerge from the fusion of smaller groups. Four conditions produced results in which the same general patterns were uncovered in pre- and postfusion groups: (1) winner effects alone, (2) bystander loser effects alone, (3) winner and bystander winner effects operating simultaneously, and (4) all four effects in play simultaneously. Outside this parameter space, hierarchy structure and the nature of aggressive interactions differed in pre- and postfusion groups. When only loser effects were in play, one of the two clear alphas from the prefused groups dropped in rank in the eight-member fused group. When bystander winner effects were in play, it was difficult to rank any of the eight individuals in the fused group, and players interacted almost exclusively with those that were not in their original four-member group. When loser and bystander loser effects operated simultaneously, two top-ranking individuals emerged in the fused groups, but the relative rank of the other players was difficult to assign.
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Notes 10.1093/beheco/14.3.367 Approved no
Call Number refbase @ user @ Serial 519
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Author Kirkpatrick, J.F.; Turner, J.W.
Title Changes in herd stallions among feral horse bands and the absence of forced copulation and induced abortion Type Journal Article
Year 1991 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 29 Issue (up) 3 Pages 217-219
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Abstract Forced copulation and induced abortion were investigated in a herd of feral horses inhabiting a coastal barrier island. Eight mares were diagnosed pregnant in August and October 1989 by means of urinary and fecal steroid metabolites, prior to documented changes in herd stallions. These mares were observed for harassment and forced copulation by the new stallions and for the presence of foals during the spring and summer of 1990. No incidents of harassment or attempts at forced copulation were witnessed and seven of the eight mares produced foals in 1990. These data indicate that forced copulation and induced abortion are not common events among all feral horse herds and suggest reinvestigation of this hypothesized phenomenon.
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Call Number Equine Behaviour @ team @ Serial 2327
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Author Wanker, R.; Apcin, J.; Jennerjahn, B.; Waibel, B.
Title Discrimination of different social companions in spectacled parrotlets ( Forpus conspicillatus ): evidence for individual vocal recognition Type Journal Article
Year 1998 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 43 Issue (up) 3 Pages 197-202
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Abstract Abstract: Individual recognition is generally assumed to be a prerequisite for establishing and maintaining a complex social system. Indeed, there is good evidence that highly social species have complex systems of vocal communication with individual recognition by acoustic cues. In this study, we provide experimental evidence that vocal class and individual recognition is present in a non-passerine bird, the spectacled parrotlet (Forpus conspicillatus). Spectacled parrotlets live in a complex system of social relationships. Soon after fledging, the young establish close sibling relationships which are important for successful socialization, pairing and reproduction. In a series of playback experiments we tested if spectacled parrotlets use contact calls for vocal recognition. The results showed that spectacled parrotlets discriminate between the contact calls of different social categories. Adult birds preferred to respond to the contact calls of their mates. Subadult individuals recognized the contact calls of their siblings. During the period of pair bond formation, the affiliative contacts to the siblings decrease, but the parrotlets continue to respond to the calls of their siblings. This is the first evidence that vocal sibling recognition might outlast the period of strong sibling interaction and extends into the period of pair bond formation. In cases of mate loss or divorce, the acoustic contact to their siblings might facilitate the re-establishment of close sibling relationships.
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Call Number Equine Behaviour @ team @ Serial 4571
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Author Krause, J.; Bumann, D.; Todt, D.
Title Relationship between the position preference and nutritional state of individuals in schools of juvenile roach (Rutilus rutilus) Type Journal Article
Year 1992 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 30 Issue (up) 3 Pages 177-180
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Abstract Position preferences of well-fed and food-deprived juvenile roach were investigated in schools of 2 and 4 fish in the laboratory. Food-deprived fish appeared significantly more often in the front position than their well-fed conspecifics. For fish at the same hunger level, individuals at the front of the school had the highest feeding rate. These results represent the first evidence for a relationship between the nutritional state of individual fish and their positions in a school and suggest a functional advantage of the preference.
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Call Number Equine Behaviour @ team @ Serial 5140
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Author Mesterton-Gibbons, M.; Dugatkin, L.A.
Title Toward a theory of dominance hierarchies: effects of assessment, group size, and variation in fighting ability Type Journal Article
Year 1995 Publication Behavioral Ecology Abbreviated Journal Behav. Ecol.
Volume 6 Issue (up) 4 Pages 416-423
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Abstract We introduce assessment to the analysis of dominance hierarchies by exploring the effect of an evolutionarily stable fighting rule when there is variation in resource holding potential (RHP) and RHP is not a perfectly reliable predictor of the outcome of a fight. With assessment, the probability of a linear hierarchy decreases with group size but can remain appreciable for groups of up to seven or eight individuals, whereas it decreases virtually to zero if there is no assessment. The probability of a hierarchy that correlates perfectly with RHP is low unless group size is small.
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Notes 10.1093/beheco/6.4.416 Approved no
Call Number refbase @ user @ Serial 447
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Author Cant, M.A.; Field, J.
Title Helping effort in a dominance hierarchy Type Journal Article
Year 2005 Publication Behavioral Ecology Abbreviated Journal Behav. Ecol.
Volume 16 Issue (up) 4 Pages 708-715
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Abstract In many cooperatively breeding species, group members form a dominance hierarchy or queue to inherit the position of breeder. Models aimed at understanding individual variation in helping behavior, however, rarely take into account the effect of dominance rank on expected future reproductive success and thus the potential direct fitness costs of helping. Here we develop a kin-selection model of helping behavior in multimember groups in which only the highest ranking individual breeds. Each group member can invest in the dominant's offspring at a cost to its own survivorship. The model predicts that lower ranked subordinates, who have a smaller probability of inheriting the group, should work harder than higher ranked subordinates. This prediction holds regardless of whether the intrinsic mortality rate of subordinates increases or decreases with rank. The prediction does not necessarily hold, however, where the costs of helping are higher for lower ranked individuals: a situation that may be common in vertebrates. The model makes two further testable predictions: that the helping effort of an individual of given rank should be lower in larger groups, and the reproductive success of dominants should be greater where group members are more closely related. Empirical evidence for these predictions is discussed. We argue that the effects of rank on stable helping effort may explain why attempts to correlate individual helping effort with relatedness in cooperatively breeding species have met with limited success.
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Notes 10.1093/beheco/ari051 Approved no
Call Number refbase @ user @ Serial 760
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Author Cameron, E.Z.; Linklater, W.L.; Stafford, K.J.; Minot, E.O.
Title Aging and improving reproductive success in horses: declining residual reproductive value or just older and wiser? Type Journal Article
Year 2000 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 47 Issue (up) 4 Pages 243-249
Keywords Maternal investment – Equidae – Equus caballus
Abstract In many mammalian species, female success in raising offspring improves as they age. The residual reproductive value hypothesis predicts that each individual offspring will be more valuable to the mother as she ages because there is less conflict between the current and potential future offspring. Therefore, as mothers age, their investment into individual offspring should increase. Empirical evidence for an influence of declining residual reproductive value on maternal investment is unconvincing. Older mothers may not invest more, but may be more successful due to greater experience, allowing them to target their investment more appropriately (targeted reproductive effort hypothesis). Most studies do not preclude either hypothesis. Mare age significantly influenced maternal investment in feral horses living on the North Island of New Zealand. Older mares, that were more successful at raising foals, were more protective for the first 20 days of life, but less diligent thereafter. Total maternal input by older mothers did not seem to be any greater, but was better targeted at the most critical period for foal survival and a similar pattern was observed in mares that had lost a foal in the previous year. In addition, older mothers were more likely to foal in consecutive years, supporting the hypothesis that they are investing less than younger mares in individual offspring. Therefore, older mothers seem to become more successful by targeting their investment better due to experience, not by investing more in their offspring.
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Notes Approved no
Call Number Serial 2019
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