Rutberg, A. T., & Greenberg, S. A. (1990). Dominance, aggression frequencies and modes of aggressive competition in feral pony mares. Anim. Behav., 40(2), 322–331.
Abstract: Feral pony mares, Equus caballus, at Assateague Island, Maryland, formed linear dominance hierarchies within bands. Generally, older mares dominated younger mares, and larger mares dominated smaller mares. Large mares initiated aggression more often than small mares when age was controlled for but, surprisingly, older mares initiated aggression less often than younger mares when size was controlled for. Thus, mares peak in aggressiveness fairly soon after achieving full size and then, while maintaining or improving their rank in the domainance hierarchy, progressively reduce their involvement in aggression as they grow older, Involvement in aggression per mare increased as number of mares in the group increased; this effect was independent of nearest-mare distances. Frequency of involvement in aggression did not differ between mares that had changed bands within the year and mares whose band association had continued for a year or more. Aggression was directed more frequently than expected at subordinate mares who were nursing, and also occurred more frequently than expected at water holes. The proportion of aggressive encounters during grazing closely matched the total proportion of time spent grazing. Subordinate mares with foals received aggression more often than subordinate mares without foals. The high frequency of aggression associated with foals and nursing suggests that interference with reproduction of subordiantes is an important mode of competition between mares. Such interference may be common in animals that feed on dispersed resources and live in small, cohesive groups.
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Janson, C. H. (1990). Social correlates of individual spatial choice in foraging groups of brown capuchin monkeys, Cebus apella. Anim. Behav., 40(5), 910–921.
Abstract: Individuals in a foraging group of wild bronwn capuchin monkeys choose different spatial positions relative to the rest of the group. Markov analysis of sequencess of individual spatial positions demonstrated significant differnces between individuals, which coul be categorized a posteriori into four homogenous subgroups. An individual's spatial position was related primarily to the amount of aggression it received from the group's dominant male, but also varied with its sex. Spatial choice varied with changes in an individual's social status, but did not vary consistently with seasonal differences in food availability. These results support the hypothesis that individuals compete for preferred spatial positions within a foraging group.
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Janson, C. H. (1990). Ecological consequences of individual spatial choice in foraging groups of brown capuchin monkeys, Cebus apella. Anim. Behav., 40(5), 922–934.
Abstract: Individuals in a foraging group of brown capuchin monkeys choose different spatial positions relative to the rest of the group. An individual's choice of spatial positiion affects its foraging success and perceived predation risk (as measured by vigilance behaviour). The two most dominant group members preferred to forage where their expected forwaging success was greatest. Juveniles chose to forage where their perceived predation risk was least, not where they would achieve the highest foraging success. The positions used by non-dominant adults neither maximized foraging success nor minimized predation risk. It is likely that subordinate adults accept spatial positions with suboptimal ecological consequences to avoid the costs of frequent confrontations with the dominant members of the group over foraging sites in poreferred positions.
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Becker, C. D., & Ginsberg, J. R. (1990). Mother-infant behaviour of wild Grevy's zebra: adaptations for survival in semidesert East Africa. Anim. Behav., 40(6), 1111–1118.
Abstract: Mother-infant interactions and patterns of foal behaviour in the Grevy's zebra, Equus grevyi, differe from those reported for other equids. Grevy's zebra foals exhibit longer intervals between suckling bouts, do not drink water until they are 3 months old, and reach independence from the mare sooner than other equids. Furthermore, Grevy's zebra foals advance their acquisition of adult feeding behaviour. A 6-week-old Grevy's zebra foal spends as much time feeding as a 5-month-old wild horse foal. From the time their foals are born until the foals reach an age of 3 months, females form small groups (three females and their foals). These groups are never found further than 2·0 km from surface water and are usually associated with a territorial male. Unlike other equids, the foals of which always follow their mares, when female Grevy's zebra go to drink, they leave their foals in “kindergartens”, which are guarded by a single adult animal, usually a territorial male. It is proposed that many of these differences in behaviour and rates of juvenile development are the result of adaptation to an arid environment. Water requirements during early lactation appear to influence strongly the social behaviour of the Grevy's zebra and should also be a strong influence on the mother-infant behaviour of other arid-living ungulates.
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Feh, C.,. (1990). Long-term paternity data in relation to different aspects of rank for Camargue stallions, Equus caballus. Anim. Behav., 40(5), 995–996.
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Rutberg, A. T. (1990). Inter-group transfer in assateague pony mares. Anim. Behav., 40(5), 945–952.
Abstract: Between-previous termgroup transfernext term of adult female previous termponies,next term Equus caballus, was investigated for three consecutive summers on previous Assateaguenext Island, Maryland, U.S.A. Both the previous terminternext term-band movements of individual previous termmares and the marenext term turnover rates of one-male “harem” bands were examined. Long-term previous termtransfersnext term occurred at rates ranging from 0·06 to 0·18 per previous termmarenext term per month. previous termMaresnext term with foals transferred more frequently than previous termmaresnext term without foals, but neither female age, pregnancy, nearest-neighbour distances nor dominance rank affected the likelihood of transferring. Band turnover rates were uncorrelated with the average frequency of previous termmare-marenext term aggression within the band, but new previous termmaresnext term entering a band suffered a transient rise in aggression received. Thus, female aggression did not encourage, and may have discouraged, previous terminternext term-band previous termtransfers.next term Older stallions and stallions who had held bands for 2 years or more had significantly larger and more stable bands. Fewer previous termmarenext term turnovers were seen in bands whose stallions tended to face their previous termmares,next term showed a relatively high proportion of time feeding, and showed a relatively low proportion of time involved in aggression with other stallions, although at marginal levels of significance for all three variables. Thus, variability in stallion attributes, and possibly behaviour, probably plays the strongest role in determining previous termmare transfernext term patterns at previous termAssateague.next term
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Cuthill, I., & Kacelnik, A. (1990). Central place foraging: a reappraisal of the `loading effect'. Anim. Behav., 40(6), 1087–1101.
Abstract: Animals that provision a central place usually bring back larger loads when foraging far from home. This positive correlation between average load size and distance is typically explained as rate-maximizing behaviour in the face of a trade-off between travel costs and a decelerating rate of prey gain in food patches (the `loading effect'). By using feeders to provide wild parent starlings, Sturnus vulgaris, with constant rates of prey loading, a positive load-distance correlation was shown to exist in the absence of a loading effect (experiment I). However, in a laboratory simulation where no load was transported (experiment II). the average number of prey eaten in patch visits by self-feeding starlings was invariant with travel distance, so the explanation of the load-distance correlation in experiment I must lie in featues peculiar to central place foraging. Bottlenecks in ingestion by chicks and interruption by visual detection of nest disturbance (experiment III) were rejected as causes of the correlation. Risks of dropping prey in flight appeared low, but the risk of kleptoparasitism received weak support. The travel-load size correlation may be an adaptive response to load transport costs, as return travel times increased with the load size being carried (experiment IV).
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Reboreda, J. C., & Kacelnik, A. (1990). On cooperation, tit-for-tat and mirros. Anim. Behav., 40(6), 1188–1189.
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Cuthill, I. C., Kacelnik, A., Krebs, J. R., Haccou, P., & Iwasa, Y. (1990). Starlings exploiting patches: the effect of recent experience on foraging decisions. Anim. Behav., 40(4), 625–640.
Abstract: Laboratory and field experiments have shown that, as predicted by the marginal value model, starlings, Sturnus vulgaris, stay longer in a food patch when the average travel time between patches is long. A laboratory analogue of a patchy environment was used to investigate how starlings respond to rapidly fluctuating changes in travel time in order to find out the length of experience over which information is integrated. When there was a progressive increase in the amount of work required to obtain successive food items in a patch (experiment 1), birds consistently took more prey after long than after short travel times; travel experience before the most recent had no effect on the number of prey taken. Such behaviour does not maximize the rate of energy intake in this environment. The possibility that this is the result of a simple constraint on crop capacity is rejected as, when successive prey were equally easy to obtain up until a stepwise depletion of the patch (experiment 2), birds took equal numbers of prey per visit after long and short travel times: the rate-maximizing behaviour. A series of models are developed to suggest the possible constraints on optimal behaviour that affect starlings in the type of environment mimicked by experiment 1.
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Kacelnik, A. (1990). R.C. Bolies and M.D. Beecher, Editors, Evolution and Learning, Lawrence Erlbaum, Hillsdale, New Jersey (1988), p. x. Anim. Behav., 40(3), 602–603.
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