Records |
Author |
Viscido, S.V.; Miller, M.; Wethey, D.S. |
Title |
The response of a selfish herd to an attack from outside the group perimeter |
Type |
Journal Article |
Year |
2001 |
Publication |
Journal of theoretical biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
208 |
Issue |
3 |
Pages |
315-328 |
Keywords |
Animals; *Behavior, Animal; *Computer Simulation; Models, Biological; *Movement; Predatory Behavior |
Abstract |
According to the selfish herd hypothesis, animals can decrease predation risk by moving toward one another if the predator can appear anywhere and will attack the nearest target. Previous studies have shown that aggregations can form using simple movement rules designed to decrease each animal's Domain of Danger. However, if the predator attacks from outside the group's perimeter, these simple movement rules might not lead to aggregation. To test whether simple selfish movement rules would decrease predation risk for those situations when the predator attacks from outside the flock perimeter, we constructed a computer model that allowed flocks of 75 simulated fiddler crabs to react to one another, and to a predator attacking from 7 m away. We attacked simulated crab flocks with predators of different sizes and attack speeds, and computed relative predation risk after 120 time steps. Final trajectories showed flight toward the center of the flock, but curving away from the predator. Path curvature depended on the predator's size and approach speed. The average crab experienced a greater decrease in predation risk when the predator was small or slow moving. Regardless of the predator's size and speed, however, predation risk always decreased as long as crabs took their flock-mates into account. We conclude that, even when flight away from an external predator occurs, the selfish avoidance of danger can lead to aggregation. |
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Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, U.S.A. viscido@u.washington.edu |
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0022-5193 |
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PMID:11207093 |
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refbase @ user @ |
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555 |
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Author |
Fishman, M.A. |
Title |
Predator Inspection: Closer Approach as a Way to Improve Assessment of Potential Threats |
Type |
Journal Article |
Year |
1999 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
196 |
Issue |
2 |
Pages |
225-235 |
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Abstract |
When detecting a predator, some prey animals respond in a counterintuitive fashion by approaching, rather than fleeing, that potential threat of extinction. This seemingly paradoxical behaviour, known aspredator inspection, has been reported for a wide variety of taxa--and therefore can be assumed to be adaptive. However, the view of predator inspection as a paradoxical behaviour rests on two implicit assumptions: (a) initial predator detecting is unambiguous, with no uncertainty in discriminating between hunting and non hunting members of predator species, or members of predator species and unrelated phenomena; (b) the costs of flight are negligible relative to the risk of predation. Upon reflection assumption (a) is not really tenable. Whereas assumption (b) is not consistent with experimental evidence [Godin & Crossman (1994)Behav. Ecol. Sociobiol.34,359-366]. Given that predator detection is ambiguous and the costs of flight are not negligible, a prey individual may benefit by a closer approach to the source of the alarming signals, thus improving its assessment of the situation--despite the increased risk of predation. In this paper, the above statement is given rigor by reformulating the problem in game theoretical terms. The results indicate that a prey will minimize its costs by performing predator inspection whenever its degree of certainty regarding predator identification and/or assessment of its intentions is less than a threshold, which is determined by the model's parameters. |
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523 |
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Author |
Gueron, S.; Levin, S.A.; Rubenstein, D.I. |
Title |
The Dynamics of Herds: From Individuals to Aggregations |
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Journal Article |
Year |
1996 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
182 |
Issue |
1 |
Pages |
85-98 |
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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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0022-5193 |
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Equine Behaviour @ team @ |
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5253 |
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Author |
Dugatkin, L.A.; Hoglund, J. |
Title |
Delayed breeding and the evolution of mate copying in lekking species |
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Journal Article |
Year |
1995 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
174 |
Issue |
3 |
Pages |
261-267 |
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Abstract |
Recent experimental evidence indicates that females may copy the mate choice of others. Here, we present a model for the evolution of mate copying strategies in lekking species. In the model, all females (copiers and non-copiers) assess male quality, but a copier's assessment of a male's quality increases after males have mated with other females. The model demonstrates that mate copying is favored when breeding late in the season has a relatively high cost. We hope that our results will spur empirical work quantifying the time constraints associated with breeding, thus allowing more direct tests of the model's predictions. |
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refbase @ user @ |
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482 |
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Marinier, S.L.; Alexander, A.J. |
Title |
Coprophagy as an avenue for foals of the domestic horse to learn food preferences from their dams |
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Journal Article |
Year |
1995 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
173 |
Issue |
2 |
Pages |
121-124 |
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Observation of foal development shows that the appearance of adult-type motor grazing behaviour, selection of grass vs. non-grass and the avoidance of poisonous plants occur concurrently between the ages of 4 and 6 weeks. Suckling behaviour and close association of foal with dam change with time but show no particular coincidence with grazing behavioural changes. Coprophagy of the foal on maternal faeces does, however, correspond chronologically with the foal learning to graze selectively. This correspondence suggests that, as well as other uses, in domestic horses coprophagy may function to imprint on the foal the food-selective values of its dam. |
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Equine Behaviour @ team @ |
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3626 |
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Author |
Thierry, B. |
Title |
Feedback loop between kinship and dominance: the macaque model |
Type |
Journal Article |
Year |
1990 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
145 |
Issue |
4 |
Pages |
511-522 |
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Abstract |
There is growing evidence that macaque social systems represent sets of coadapted traits in which strength of hierarchies and degree of nepotism covary. A framework is developed to explain the link between dominance and kinship phenomena, assuming that power brought by alliances among non-kin is allometrically related to those involving relatives. This can account for the type of social relationships observed in “despotic” systems vs. “egalitarian” ones. When social bonds are mostly founded on kinship, lineages are closed and social power generated by coalitions among relatives may reach high levels; social power frequently outweighs the fighting abilities of single individuals, and asymmetry of dominance between group members may be marked. When lineages are more open, social bonds and alliances are less kin-biased, social relationships are more equal, and as the influence of coalitions is less important, the individual retains a certain degree of freedom in relation to the power of kin-networks. Acknowledging that the balance between individual and social power is not set at the same level across different species can explain a number of variations in rules of rank inheritance and relative dominance of males and females among macaques. The framework illustrates how epigenetic processes may shape complex features of primate social systems, and offers opportunities for testing. |
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refbase @ user @ |
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867 |
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Author |
Hemelrijk C K |
Title |
A matrix partial correlation test used in investigations of reciprocity and other social interaction patterns at group level |
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Journal Article |
Year |
1990 |
Publication |
Journal of theoretical biology |
Abbreviated Journal |
J. Theor. Biol. |
Volume |
143 |
Issue |
3 |
Pages |
405-420 |
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Reciprocity and other social interaction patterns can be studied at two levels, within pairs (i.e. dyadic level) and among pairs (i.e. at group level). In this paper advantages of the latter approach are emphasized. However, an analysis at group level implies the correlation of interaction matrices and because such data are statistically dependent, the significance of a correlation has to be calculated in a special way |
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Equine Behaviour @ team @ |
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5050 |
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Author |
Seyfarth, R.M. |
Title |
A model of social grooming among adult female monkeys |
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Journal Article |
Year |
1977 |
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Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
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65 |
Issue |
4 |
Pages |
671-698 |
Keywords |
Animals; Behavior, Animal; Female; *Grooming; Haplorhini/*physiology; *Models, Biological; Reproduction; Social Dominance; Time Factors |
Abstract |
Grooming networks among adult female monkeys exhibit two similar features across a number of different species. High-ranking animals receive more grooming than others, and the majority of grooming occurs between females of adjacent rank. A theoretical model which duplicates these features is presented, and the properties of the model are used to explain the possible causation and function of female grooming behaviour. The model illustrates how relatively simple principles governing the behaviour of individuals may be used to explain more complex aspects of the social structure of non-human primate groups. |
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0022-5193 |
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PMID:406485 |
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Equine Behaviour @ team @ |
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5259 |
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Author |
Bernstein, I. S. |
Title |
Dominance, aggression and reproduction in primate societies |
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Journal Article |
Year |
1976 |
Publication |
Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
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60 |
Issue |
2 |
Pages |
459-472 |
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Dominance relationships in primate societies are generally inferred by analyses of agonistic interactions. This aspect of social organization is so striking in macaque and baboon societies that many theoreticians have postulated selective mechanisms operating on the genetic attributes which contribute to high dominance rank. Alpha males were hypothesized to increase their genetic fitness by successfully competing with other males for access to ovulating females. Evidence relevant to these speculations has been mixed. Whereas some investigators found alpha males had near exclusive sexual access to females, others failed to confirm preferential access to ovulating females. Indeed, considerable variability in competition for females existed not only among species, but also among troops of the same species living in different habitats. Further, partner selection was not an exclusive male prerogative; females proved to express active preferences for particular males as sexual partners, and these preferences were not related to high male aggressivity. Alpha males, however, were noted to maintain their positions through social skills as members of a central core or alliance, and high rank was related primarily to seniority. Moreover, alpha males responded actively to challenges to the troop and were judged to contribute significantly to the survival of infants. It was therefore hypothesized that increased genetic fitness related to the increased survival of immature animals in the troop, most of which would already be the offspring of senior (and hence alpha) males. Selection would then be for the social skills leading to successful alliances in troop defense. Such skills might also relate to female partner preferences thus increasing the reproductive effectiveness of alpha males at any point in their careers, including years prior to and following their assumption of alpha rank. |
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0022-5193 |
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Equine Behaviour @ team @ |
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5441 |
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Author |
Parker, G.A. |
Title |
Assessment strategy and the evolution of fighting behaviour |
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Journal Article |
Year |
1974 |
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Journal of Theoretical Biology |
Abbreviated Journal |
J. Theor. Biol. |
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47 |
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1 |
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223-243 |
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The view is examined that the adaptive value of conventional aspects of fighting behaviour is for assessment of relative RHP (resource holding power) of the combatants. Outcomes of aggressive disputes should be decided by each individual's fitness budget available for expenditure during a fight (determined by the fitness difference between adoption of alternative strategies, escalation or withdrawal without escalation) and on the rate of expenditure of the fitness budget if escalation occurs (determined by the RHPs of the combatants). Thus response thresholds for alternative strategies (“assessments”) will be determined by natural selection on a basis of which opponent is likely to expend its fitness budget first, should escalation occur. This “loser” should retreat (before escalation) and the winner should stay in possession of the resource. Many aggressive decisions depend on whether one is a resource holder, or an attacker. Assuming the RHP of the combatants to be equal, there are many instances of fitness pay-off imbalances between holder and attacker which should weight the dispute outcome in favour of one or other opponent by allowing it a greater expendable fitness budget. Usually the weighting favours the holder; the attacker therefore needs a correspondingly higher RHP before it may be expected to win. This is not invariably the case, and much observed data fits the predictions of this sort of model. If assessments are perfect and budget expenditure rates exactly predictable, then there would never seem to be any case for escalation. Escalation can be explained in terms of injury inflictions (expenditures) occurring as discrete events; i.e. as “bouts” won or lost during fighting. Assessment can give only a probabilistic prediction of the outcome of a bout. A simple model is developed to investigate escalation situations. Each combatant assesses relative RHP; this correlates with an absolute probability of winning the next bout (cabs). The stake played for is infliction of loss of RHP and is determined by the fitness budgets of the opponents. (Each individual plays for the withdrawal of its opponent.) This defines a critical probability of winning (ccrit) for each combatant, above which escalation is the favourable strategy (cabs > ccrit) and below which withdrawal is favourable (cabs < ccrit). Escalation should occur only where cabs-ccrit is positive for both combatants. This model gives predictions compatible with the observations, indicating that RHP loss alone can be adequate to explain withdrawal: escalation behaviour. Withdrawal tendency will be increased by low searching costs. Escalations should be restricted to closely matched RHP opponents if RHP disparity is the major imbalance. Outside the “escalation range” of a given individual, the higher RHP individual wins and the lower one loses (i.e. it should withdraw after conventional display). RHP disparity and holder: attacker imbalance should both interact to shape the observed pattern, though their relative importances will depend on species and situation. In some instances selection may favour immediate withdrawal from an occupied territory even without assessment of RHP. |
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Equine Behaviour @ team @ |
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