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Author Parker, G.A.; Rubenstein, D.I.
Title Role assessment, reserve strategy, and acquisition of information in asymmetric animal conflicts Type Journal Article
Year (up) 1981 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 29 Issue 1 Pages 221-240
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Abstract It was formerly argued that alternative evolutionarily stable strategies (ESSs) are possible for animal contests characterized by some asymmetry that can be perceived with perfect accuracy. Where roles A and B refer to the asymmetry between opponents, ESSs are: [`]fight when A, retreat when B', and vice versa. Either can be an ESS, but only if the [`]reserve strategy' (=what an animal does when it fights) is sufficiently damaging. We examine the [`]war of attrition' (winner = opponent that persists longer). In a population at either ESS, reserve strategy is never normally shown; it is therefore subject to drift unless the selective action of rare individuals which break the convention is considered. These could arise either by mutation or by mistakes in role assessment. When mutations and mistakes simply specify that occasionally an animal fights when it [`]should' retreat, selection adjusts reserve strategy to a level where only one ESS (the [`]commonsense' ESS) is possible, if the asymmetry is relevant to payoff. Thus for asymmetries in fighting ability or resource value, the individual with the lower score will retreat. However, we are particularly concerned with cases where both payoff-relevant aspects (fighting ability and resource value) are asymmetric. If opponents sustain contest costs at rates KA and KB, and their resource values are VA and VB, an [`]optimal assessor' strategy defined by the interaction between the two asymmetries, is a unique ESS. It obeys the rule [`]fight on estimating role A, where VA/KA>VB/KB; retreat in B'. If mistakes can occur in both roles, but are very rate, the ESS is not fundamentally altered though there will be infinitesimal tendencies for persisting in role B. Selection to improve assessment abilities intensifies as abilities improve, but is weak if roles A and B are rather similar. Over a range of similarity between roles, an [`]owner wins' convention may be adopted if ownership correlates positively with role A and an individual cannot tell when it would otherwise pay him to break the convention. We also examine a contest in which information about roles can be acquired only during a contest itself, and at a cost. Much depends on the rate at which information is acquired relative to the rate at which costs are expended, and on whether contests normally escalate in intensity, remain at the same level, or de-escalate. Selection favours short contests when costs are high relative to resource value, where the outcome of a round contains much information about fighting ability, and where the actual disparity in fighting ability is large.
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ISSN 0003-3472 ISBN Medium
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Notes Approved no
Call Number Equine Behaviour @ team @ Serial 5325
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Author Rubenstein, D. I.,
Title Ecology and sociality in horses and zebras Type Book Chapter
Year (up) 1986 Publication Ecological Aspects of Social Evolution Abbreviated Journal Ecological Aspects of Social Evolution
Volume Issue Pages 282-302
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Publisher Princeton University Press Place of Publication Princeton, NJ. Editor Rubenstein, D. I. ; Wrangham, R. W.
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Notes from Professor Hans Klingels Equine Reference List Approved no
Call Number Serial 1526
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Author Rubenstein, D.I
Title Life history and social organization in arid adapted ungulates Type Journal Article
Year (up) 1989 Publication Journal of Arid Environments Abbreviated Journal J. Arid. Environ.
Volume 17 Issue Pages 145-156
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Notes from Professor Hans Klingels Equine Reference List Approved yes
Call Number Serial 1527
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Author Rubenstein, D.I.; Hohmann, M.E
Title Parasites and Social Behavior of Island Feral Horses Type Journal Article
Year (up) 1989 Publication Oikos Abbreviated Journal Oikos
Volume 3 Issue Pages 312-320
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Abstract The horses of Shackelford Banks, North Carolina, USA, are heavily parasitized by intestinal worms and harassed by dipterans, and although both types influence behavior only internal parasites affect bodily condition and the structuring of horse society. Thirteen species of internal parasites were identified, but only 4 of 13 groups contain them all and even within groups differences among individuals are large. Among individuals ova emissions vary ranging from 50 to 76,875 eggs per gram. The most important environmental factors influencing egg production are season and a group's location on the island, presumably because of salinity and soil differences and their effects on ova survival. Of the social and life history factors, age, and group size, but neither reproductive state nor dominance status are important. The fitness consequences of internal parasitism may be large since the number emitted is negatively correlated with next year's bodily condition. Biting fly burdens are also affected by a variety of environmental factors. In general, horses are covered with more flies on sunny days, when winds are moderately brisk, when occupying dunes, and around mid-day. In contrast to endoparasites, fly burden is affected by reproductive condition and dominance status and tends to decrease as groups increase in size. Since groups do not grow very large, nor do females attempt to bring groups together, the negative effects of endoparasites appear to overide those associated with ectoparasites. Consequently, endoparasites appear to exert a stronger influence on social structure, even though ectoparasites seem to play a stronger role in shaping details of behavior.
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Notes Approved no
Call Number Equine Behaviour @ team @ Serial 2360
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Author Ginsberg, J. R; Rubenstein, D. I.
Title Sperm competiton and variation in zebra mating behaviour Type Journal Article
Year (up) 1990 Publication Behavioral Ecology and Sociobiology Abbreviated Journal Behav. Ecol. Sociobiol.
Volume 26 Issue 6 Pages 427-434
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Abstract Data are presented on the breeding behavior of two zebra species to test whether intra- and interspecific variation in male reproductive behavior and physiology are correlated with differences in female promiscuity. In one species, plains zebra (Equus burchelli) females live in closed membership single male groups and mate monandrously. In the other species, the Grevy's zebra (E. grevyi) females live in groups whose membership is much more temporary. Typically, associations with individual males are brief and mating is polyandrous. However, some females – those having just given birth – reside with one male for long periods, mating monandrously. These differences in female mating behavior generate variability in the potential for sperm competition. We show that behavioral differences in male investment in reproductive activities correlate with the potential for sperm competition. When mating with promiscuous mares, Grevy's zebra stallions made a greater investment in reproductive behavior (calling, mounting, ejaculations) than did stallions of either species when mating with monandrous females. The evolution of large testes size in the Grevy's zebra, when compared to the congeneric plains zebra, horse, and mountain zebra, allows for this increased investment.
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Notes from Professor Hans Klingels Equine Reference List Approved yes
Call Number Serial 1113
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Author Rubenstein, D. I.; Hack, M. A.
Title Horse signals: The sounds and scents of fury Type Journal Article
Year (up) 1992 Publication Evolutionary Ecology Abbreviated Journal Evol. Ecol.
Volume 6 Issue 3 Pages 254-260
Keywords ommunication – combat – fighting ability – individual identity – signals – information – assessment – displays
Abstract During contests animals typically exchange information about fighting ability. Among feral horses these signals involve olfactory or acoustical elements and each type can effectively terminate contests before physical contact becomes necessary. Dung transplant experiments show that for stallions, irrespective of rank, olfactory signals such as dung sniffing encode information about familiarity suggesting that such signals can be used as signatures. As such they can provide indirect information about fighting ability as long as opponents associate identity with past performance. Play-back experiments, however, show that vocalizations, such as squeals, directly provide information about status regardless of stallion familiarity. Sonographs reveal that squeals of dominants are longer than those of subordinates and that only those of dominants have at their onset high-frequency components.
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Notes Approved no
Call Number refbase @ user @ Serial 506
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Author Rubenstein, D. I.
Title The ecology of female social behaviour in horses, zebras and asses Type Book Chapter
Year (up) 1994 Publication Animal Societies Abbreviated Journal Animal Societies
Volume Issue Pages 13-28
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Publisher Kyoto University Press Place of Publication Editor Jarman, P.J.;, Rositter, A.
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ISSN ISBN 4-87698-014-4 Medium
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Notes Approved yes
Call Number Serial 1528
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Author Gueron, S.; Levin, S.A.; Rubenstein, D.I.
Title The Dynamics of Herds: From Individuals to Aggregations Type Journal Article
Year (up) 1996 Publication Journal of Theoretical Biology Abbreviated Journal J. Theor. Biol.
Volume 182 Issue 1 Pages 85-98
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Abstract The dynamic behavior of small herds is investigated by means of simulations of two-dimensional discrete-stochastic models. An individual-based approach is used to relate collective behavior to individual decisions. In our model, the motion of an individual in a herd is assumed to be the combined result of both density-independent and density-dependent decisions, in the latter case based on the influence of surrounding neighbors; assumed decision rules are hierarchical, balancing short range repulsion against long-range attraction. The probability of fragmentation of the model herd depends on parameter values. We explore the variety and characteristics of spatial patterns that develop during migration, for herds that are homogeneous and heterogeneous regarding intrinsic walking speeds. Group integrity can be maintained even in mixed populations, but fragmentation results for these more easily than for a homogeneous herd. Observations of natural populations suggest that animals move away from individuals that intrude too closely into their environment, but are attracted to individuals at a distance. Between these extremes, there appears to be a neutral zone, within which other individuals engender no response. We explore the importance of this neutral zone, and offer evolutionary interpretations. In particular, the neutral zone, if not too large, permits the individual to remain in contact with the herd, while reducing the frequency with which acceleration or deceleration must be undertaken. This offers obvious energetic benefits.
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ISSN 0022-5193 ISBN Medium
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Notes Approved no
Call Number Equine Behaviour @ team @ Serial 5253
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Author Fischhoff, I.R.; Sundaresan, S.R.; Cordingley, J.; Larkin, H.M.; Sellier, M.-J.; Rubenstein, D.I.
Title Social relationships and reproductive state influence leadership roles in movements of plains zebra, Equus burchellii Type Journal Article
Year (up) 2007 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 73 Issue 5 Pages 825-831
Keywords collective movements; drinking; equid; Equus burchellii; foraging; group dynamics; motivation; plains zebra; reproductive status; social relationships
Abstract In animal groups, collective movements emerge from individual interactions. Biologists seek to identify how characteristics of actors in these groups, and their relationships, influence the decision-making process. We distinguished two basic factors determining leadership in group choices: identity and state. We hypothesized that identity is more important to leadership in groups with stable relationships, which permit the development of habitual roles. In groups with fluid membership, particular individuals or subgroups are less likely to emerge as consistent leaders. Instead, we predicted that movement initiation in unstable groups depends on individual state at the time of the decision. We characterized how identity and reproductive state influenced leadership patterns in the movements of plains zebra. As in many other mammals, lactation in this species significantly alters water and energy needs. We investigated leadership in tightly knit harems and loosely bonded herds of multiple harems. Harem females tended to have habitual roles in the initiation of harem movement. In herds, however, we found no consistent leaders among harems. At both levels of social organization, lactation was a key determinant of leadership. In harems, lactating females were more likely to initiate movement than nonlactating females. In turn, harems containing lactating females were more likely to lead herd movements. Thus, we conclude that social relationships and reproductive state together shape the interactions that produce group behaviours. One benefit to lactating females of leading herd movements is preferential access to scarce water. Thus, leadership roles in group decisions may have fitness consequences.
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Notes Approved no
Call Number Equine Behaviour @ team @ room B 3.092 Serial 1825
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Author Sundaresan, S.R.; Fischhoff, I.R.; Dushoff, J.; Rubenstein, D.I.
Title Network metrics reveal differences in social organization between two fission-fusion species, Grevy's zebra and onager Type Journal Article
Year (up) 2007 Publication Oecologia Abbreviated Journal Oecologia
Volume 151 Issue 1 Pages 140-149
Keywords Analysis of Variance; Animals; Behavior, Animal/*physiology; *Environment; Equidae/*physiology; Female; India; Kenya; Male; *Models, Theoretical; *Social Behavior; *Social Environment
Abstract For species in which group membership frequently changes, it has been a challenge to characterize variation in individual interactions and social structure. Quantifying this variation is necessary to test hypotheses about ecological determinants of social patterns and to make predictions about how group dynamics affect the development of cooperative relationships and transmission processes. Network models have recently become popular for analyzing individual contacts within a population context. We use network metrics to compare populations of Grevy's zebra (Equus grevyi) and onagers (Equus hemionus khur). These closely related equids, previously described as having the same social system, inhabit environments differing in the distribution of food, water, and predators. Grevy's zebra and onagers are one example of many sets of coarsely similar fission-fusion species and populations, observed elsewhere in other ungulates, primates, and cetaceans. Our analysis of the population association networks reveals contrasts consistent with their distinctive environments. Grevy's zebra individuals are more selective in their association choices. Grevy's zebra form stable cliques, while onager associations are more fluid. We find evidence that females associate assortatively by reproductive state in Grevy's zebra but not in onagers. The current approach demonstrates the utility of network metrics for identifying fine-grained variation among individuals and populations in association patterns. From our analysis, we can make testable predictions about behavioral mechanisms underlying social structure and its effects on transmission processes.
Address Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA. ssundare@princeton.edu
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Language English Summary Language Original Title
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Series Volume Series Issue Edition
ISSN 0029-8549 ISBN Medium
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Notes PMID:16964497 Approved no
Call Number Serial 1863
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