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Heyes, C. M. (1995). Imitation and flattery: a reply to Byrne & Tomasello. Anim. Behav., 50(5), 1421–1424.
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Ellis, L. (1995). Dominance and reproductive success among nonhuman animals: A cross-species comparison. Ethol. a. Sociob., 16(4), 257–333.
Abstract: This paper updates and extends Dewsbury's (1982) review of the literature on dominance and reproductive success (RS). The findings from approximately 700 studies are included, over two thirds of which were unavailable to Dewsbury. In order to give a highly condensed and yet meaningful overview, the main findings are represented in four tables, one for male nonprimates, one for female nonprimates, one for male primates, and one for female primates. In the tables for males, findings are analyzed in terms of six different indicators of RS, and in the tables for females, in terms of eight RS indicators. Outside the primate order, evidence largely supported the hypothesis that high-ranking males enjoy greater RS than do subordinate males. For females, studies are more evenly divided between those supporting the hypothesis that high rank and RS are positively correlated and those indicating no significant rank-RS relationship. This may reflect both the lower saliency of hierarchical relationships among females, as well as the lower variability in RS among females, relative to males. Among primates, a complex picture has emerged, especially in the case of males. Much of the complexity appears due to the importance of age and seniority in affecting dominance rank. Also, in some primate species, female preferences for sex partners seem to have little to do with the male's dominance rank, at least at the time mating takes place. Nevertheless, the majority of studies suggest that high- to middle-ranking males have at least a slight lifetime reproductive advantage over the lowest ranking males.
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Fournier, F., & Festa-Bianchet, M. (1995). Social dominance in adult female mountain goats. Anim. Behav., 49(6), 1449–1459.
Abstract: The social behaviour of adult female mountain goats, Oreamnos americanus, was studied for 2 years in an unhunted population in west-central Alberta, Canada. Compared with other female ungulates, mountain goat females interacted aggressively much more frequently and their dominance ranks were less stable in time and less age-related. Goats were organized in a non-linear but non-random dominance hierarchy, with many reversals in rank. The best morphological predictor of dominance rank was horn length one year and body mass in the following year. Age was a weaker predictor of dominance status than what has been reported for other female ungulates. The ranks of individual goats changed between years and dominance rank one year was not a good predictor of rank the following year. These results suggest that linearity may only be possible when a contested resource can be defended. Dominant female goats did not forage more efficiently than subordinate goats, and dominant status did not affect the amount of time devoted to alert behaviour.
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Clutton-Brock, T. H., & Parker, G. A. (1995). Sexual coercion in animal societies. Anim. Behav., 49(5), 1345–1365.
Abstract: In a wide range of animal species, males coerce females to mate with them, either by physically forcing them to mate, by harassing them until they mate or by punishing persistent refusal to mate. The first section of this paper argues that the possibility of forced copulation can generate arms races between males and females that may have substantial costs to both sexes. In the second section, it is suggested that sexual harassment commonly represents a `war of attrition' between the sexes; existing game theory models that may apply to sexual conflict over mating decisions are reviewed. The third section develops a simple prospective model for the evolution of intimidation by punishment in situations where males can raise the probability that females will accept their advances in future by punishing them for refusal to mate. Where the benefits of sexual coercion to males are high, all three male strategies may develop to a point where they have substantial costs to females. In the final section, evidence that female behaviour is adapted to minimizing these costs is reviewed.
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PITRA, C. H., STREICH, W. J., REINSCH, A., & FICKEL, J. (1995). Die Population des Somali-Wildesels (Equus africanus somalicus Sclater) in menschlicher Obhut: Demographische und genetische Aspekte. Zool. Garten., N.F. 65(4), 245–257.
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Bateson, M., & Kacelnik, A. (1995). Accuracy of memory for amount in the foraging starling,Sturnus vulgaris. Anim. Behav., 50(2), 431–443.
Abstract: Attempts to include psychological constraints in models of foraging behaviour differ in their assumptions concerning the accuracy of estimation of environmental parameters. Psychologists model estimation error as increasing linearly with the magnitude of a stimulus (Weber's Law), whereas behavioural ecologists either ignore error or assume it to be independent of stimulus magnitude. Studies on the estimation of time intervals have confirmed Weber's Law, but there are few data on the accuracy of estimation of amounts of food. Since the currency of most foraging models is the amount of food acquired per unit of time spent foraging, information on estimation of amount is required. Here, a titration method was used in which starlings chose between two cues. One colour signalled a standard food reward, and the other a reward that adjusted in magnitude according to the birds' choices: it increased when the standard was preferred and decreased when the adjusting option was preferred. There were two standards of 3 and 9 units of food, each of which was delivered at two rates to control for possible effects of rate of reinforcement on discrimination. The observed value of the adjusting option oscillated around a mean value slightly larger than that of the standard. The amplitude and period of these oscillations were larger when the standard was larger, independent of the rate of reinforcement. Also, molecular analysis showed that the probability of choosing the currently larger alternative increased as the relative difference between the adjusting option and standard increased. These results are consistent with Weber's Law applying to starlings' memories for amounts of food.
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Templeton, J. J., & Giraldeau, L. - A. (1995). Public information cues affect the scrounging decisions of starlings.49(6), 1617–1626.
Abstract: The foraging decisions that individuals make within groups should depend on the information available to them. An aviary experiment was conducted to examine whether a starling's, Sturnus vulgaris, decisions either to approach and feed from (scrounge) or to avoid the patches exploited by a partner bird are influenced by the information the partner provides. Both the type of information a subject could recognize and the point at which this information became available during the partner's exploitation of a patch were manipulaed. Information concerning the quality of a patch was available in the form of a concealed colour cue and from the behaviour of the partner bird. The foraging environment was manipulated such that colour cues were either present or absent, and provided either correct or incorrect information concerning the presence of food. When cues corresponded with past foraging experience, test subjects responded selectively and profitably to the patch exploitations of the partner; they scrounged from a higher proportion of profitable patches than control birds, which lacked the ability to recognize colour cues. Test subjects also arrived more quickly at profitable patches that the partner bird discovered than did control birds; and consequently, were able to obtain more food at each food patch scrounged. Finally, test subjects avoided scrounging when the partner discovered empty patches and thus saved foraging time. Responding selectively to public information, therefore, allows an individual to compete more effectively for resources within a foraging group.
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Swaddle, J. P., & Witter, M. S. (1995). Chest Plumage, Dominance and Fluctuating Asymmetry in Female Starlings. Proc. Roy. Soc. Lond. B Biol. Sci., 260(1358), 219–223.
Abstract: It has been proposed that levels of fluctuating asymmetry (FA) may be used in establishing and maintaining dominance hierarchies, as asymmetry reflects aspects of individual quality. However, previous manipulations of FA have failed to reveal that the level or outcome of agonistic intra-sexual interactions are affected by levels of FA. In female European starlings (Sturnus vulgaris), correlational data suggest that FA of the speckled chest plumage may be related to dominance status. These data are confounded, however, by total number of spots on the chest and the proportion of the chest that is white, both of which positively covary with chest asymmetry. Thus, we deconfounded the effects of these plumage traits on dominance by experimentally manipulating the number of spots and spot number asymmetry in a factorial design. The results indicated that dominance is influenced by the number of spots on the chest, but not by spot asymmetry. Birds with spottier chests were dominant over birds with experimentally decreased spot number. We suggest that female starlings' chests are exposed to extensive abrasion throughout the breeding season and so are susceptible to damage asymmetries that may mask the `true' fluctuating asymmetry of the trait. This may devalue the use of chest asymmetry as a quality indicator. Spottier chests may be costly to maintain, in part because of increased susceptibility to abrasion, and so may be a better indicator of quality than asymmetry.
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Ben-Shahar, R. (1995). Habitat classification in relation to movements and densities of ungulates in a semi-arid savanna. Afr. J. Ecol., 33, 50–63.
Abstract: Habitat types were classified in a semi-arid nature reserve in South Africa in order to assess the spatial requirements of resident ungulates, namely zebra, wildebeest and impala. Multivariate analyses showed patterns of soil factors and plant species associations that corresponded with variations of local geological formations and the abundance of plants. The response of ungulates to habitats of different degrees of complexity in terms of soils and plant species associations was examined on the basis of annual occurrence. New habitat types were described through merging or subdividing the existing classification. New habitat categories which corresponded with high occurrences of ungulates provided better indications of the resource requirements for large herbivores. Wildebeest were restricted in their habitat requirements and were characterized by high seasonal densities in bottom lands, particularly during the late wet period. There was a considerable overlap in the preference of habitat types between wildebeest and zebra although zebra were aggregated during longer periods within the dolerite formation. Impala had a consistent annual preference for the granite formation where seepage lines and bottom lands were inhabited seasonally by large herd concentrations.
Résumé On a classifié les types d'habitat dans une réserve naturelle semiaride d'Afrique du Sud, dans le but d'évaluer les exigences spatiales des ongulés qui y vivent, c'est à dire les zèbres, les gnous et les impalas. Des analyses multivariées ont révélé des schémas pour les facteurs du sol et pour les associations d'espèces végétales qui correspondent aux variations des formations géologiques locales et à l'abon-dance des plantes. On a examiné la réponse des ongulés à des habitats de complexité différente en termes de sols et d'associations d'espéces végétales, d'après leur présence annuelle. On a décrit de nouveaux types d'habitats en fusionnant ou en subdivisant la classification existante. Les nouvelles catégories d'habitats qui correspondaient à des présences abondantes d'ongulés ont fourni de meilleures indications sur les ressources exigées par les grands herbivores. Les gnous se limitaient aux endroits qui répondaient a leurs exigences et se caractérisaient par de hautes densités saisonnières dans les régions basses, spécialement pendant la dernière saison des pluies. Il y avait un recouvrement considérable des types d'habitats préferés par les gnous et les zébres, encore que les zébres se rassemblent plus longtemps dans la formation doléritique. Les impalas marquent une préférence annuelle constante pour la formation granitique où les sources et les terres basses sont occupées de façon saisonnière par des hardes très concentrées. |
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Saltz, D., & Rubenstein D.I. (1995). Population Dynamics of a Reintroduced Asiatic Wild Ass (Equus Hemionus) Herd. Ecol Appl, 5(2), 327–335.
Abstract: Reintroduction is the release of animals into an area where they were extirpated or have significantly declined. Little is known about the factors that determine the success of failure of ungulate reintroduction. We studied the dynamics of a reintroduced Asiatic wild ass (Equus hemionus) population for 10 yr (1983-1993) following the first successful release into the wild. A total of 14 adult females and 14 adult males were released into a nature reserve in the Negev Desert of southern Israel. Over this 10-yr span the female population has grown to only 16 adults. Reproductive success of reintroduced females was low in the first 5 yr following release (0.0-0.8 foals@?female^-^1@?yr^-^1), but increased to 0.5-1.0 foals@?female^-^1@?yr^-^1 in the last 5 yr. Reproductive success of wild-born females @>3 yr old was higher than that of reintroduced females of similar ages, and ranged from 0.5-1.0 foals@?female@?^-^1yr^-^1. Our study and data from the E. hemionus studbook suggest that young nonprimiparous females produced primarily males, while primiparous and old females produced primarily females. We attribute the low reproductive success following reintroduction to the stress caused by capture, transport, and release procedures; we consider the age-dependent progeny sex ratio within the framework of Trivers and Willard's (1973) maternal allocation hypothesis. We conclude that the slow growth of the female population was due to: (a) low reproductive success of females in the early years following reintroduction, and (b) a male-skewed progeny sex ratio among prime-aged reintroduced females. A simple stochastic Leslie matrix model suggests that high survival and improved reproductive success of reintroduced females at later stages of the study, and the reproductive success of wild-born females, make the population relatively unsusceptible to extinction from random demographic processes. In-depth knowledge of the dynamics of reintroduced populations is vital for the correct assessment of their viability. We offer suggestions for increasing the efficacy of future wild ass reintroductions.
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