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Levin, L. E. (1996). Passage order through different pathways in groups of schooling fish, and the diversified leadership hypothesis. Behav. Process., 37(1), 1–8.
Abstract: The diversified leadership hypothesis proposes that different individuals within a school of fish act as leaders in different circumstances. This `circumstantial leadership' results from inter-individual behavioral variability and a `cohesion-dispersion' tendency modulated by `failure-success' contingencies. The hypothesis predicts that when offered different pathways to escape the restriction of their swimming space, individuals within a group of fish will show 1. (a) consistent passage orders in each pathway, but2. (b) different passage orders in different pathways. Using an avoidance paddle and three different groups of fish (Aphyocharax erithrurus) the results confirmed prediction 1. (a) while prediction2. (b) was verified only in one group.
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Packer, C., & Heinsohn, R. (1996). Response:Lioness leadership. Science, 271(5253), 1215–1216.
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Gary C. Jahn, & Craig Packer, R. H. (1996). Lioness leadership. Science, 271(5253), 1216–1219.
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Brunner, D., Kacelnik, A., & Gibbon, J. (1996). Memory for inter-reinforcement interval variability and patch departure decisions in the starling,Sturnus vulgaris. Anim. Behav., 51(5), 1025–1045.
Abstract: An experiment with starlings was conducted to investigate the effect of variability in inter-reinforcement intervals on foraging decisions. The experimental design simulated an environment in which food was distributed in patches. Patches contained zero to four food items which could be collected by pecking at a key. All patches ended with sudden depletion. The time elapsed since the last reinforcement was the only way to detect the depletion of the patch. Once a patch was depleted, a new patch could be reached by completion of a travel requirement of 20 flights between two perches. Key pecks within a patch and the time of the last response in a patch (giving-in time) were recorded. The level of variability in the inter-reinforcement intervals was varied between different conditions. An increase in inter-reinforcement interval variability resulted in a flattening of response rate functions and giving-in time distributions, and in more asymmetry of the response functions, but not of the giving-in time distributions. Two theoretical models of decision making are presented, which differ in the assumptions about memory constraints. In one case, all inter-reinforcement intervals are remembered but in the other, only the intervals with extreme values are remembered. Both models accommodate response rates as a function of trial time, but only the second is compatible with the observed departure decision. Our results are compatible with net rate maximization.
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Fragaszy, D., & Visalberghi, E. (1996). Primates “primacy” reconsidered. In C. Heyes, & B. G. Galef (Eds.), Social learning in animals: the roots of culture (pp. 65–84). Academic Press, Inc.
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Tebbich, S., Taborsky, M., & Winkler, H. (1996). Social manipulation causes cooperation in keas.52(1), 1–10.
Abstract: Abstract. This study assessed whether keas,Nestor notabilis, are able to cooperate in an instrumental task. Seven birds of a captive group were tested in group situations and in dyads. At least two individuals had to manipulate an apparatus to obtain food but only one participant was rewarded. One bird had to push down a lever to enable another one to collect food from a box. The distribution of the two different roles was clearly dependent on hierarchy. The higher ranking individual always obtained the reward and each bird changed its role according to dominance status. Owing to the non-linear hierarchy in the group, each bird participating in cooperative interactions had at least one submissive partner. Therefore, in group situations the reward was distributed symmetrically and cooperation was persistent. In dyadic test situations, three individual keas aggressively manipulated their respective subordinate partners to open the apparatus. Their dominance status enabled them to force cooperation.
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Barnes, J. I., & Jager, J. L. V. de. (1996). Economic and financial incentives for wildlife use on private land in Namibia and the implications for policy. S. Afr. J. Wildl. Res, 26(2), 37–46.
Abstract: Abstract
Aggregate estimates for wildlife populations and species diversity on private land in Namibia were made for 1972 and 1992, using questionnaire surveys. Numbers of species and biomass appear to have increased by some 80 percent, or three percent per annum over the period. The number of game species recorded increased by 44 percent. Cost – benefit analysis models were developed and used to analyse economic and financial efficiency of land use involving wildlife on private land. Financial profitability was generally low with both livestock – game production for consumptive use and wildlife production for non-consumptive use. However these activities appear to be economically efficient, and result in a positive contribution to National Income. The results suggest that there are financial incentives for private landholders to group together and form large scale conservancies. The latter benefit from economies of scale which make them more financially profitable and robust, and also more economically efficient, than ranches. Wildlife production for non-consumptive wildlife viewing was found to yield greater economic net value added per unit of land than livestock – wildlife production for consumptive use. This was particularly the case at the larger conservancy scale of operation. Aggregate estimates, in 1994 prices, of the annual net value added to National Income from wildlife use on private land are N$ 30.6 million in 1972 and N$ 56 million in 1992. The economic value of wildlife use as a proportion of the economic value of all private land rangeland uses appears to have risen from five percent to eleven percent over the twenty year period. Current policy to promote the development of wildlife conservancies appears to be economically sound, particularly where these are aimed at eventual conversion to wildlife-based tourism uses. _________________________ |
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Kaseda, Y., & K. Nozawa, K. (1996). Father-daughter matings and its avoidance in Misaki feral horses. Anim Sci Tech, 67(11), 996–1002.
Abstract: Father-daughter matings and its avoidance mechanism were analysed on the basis of data which gained from behavioural observations and paternity tests in Misaki feral horses from 1979 to 1994. Twelve stallions and their 51 daughters had 176 breeding seasons, but they lived in the different home range in 82 breeding seasons. About half of 1- to 3-year-old mares emigrated from natal area to the other and grew up there. Therefore, emigrations of young mares may result reduction of contacts and avoidance of inbreeding with their fathers. The stallions and their daughters lived in the same area in 94 breeding seasons, but there were no cases that daughters which left their natal harem groups before sexual maturity formed again stable consort relations with their natal harem stallions. It is possible that separation of young mares from their natal groups before sexual maturity may result avoidance of formation of consort relation with their fathers. Two father-daughter matings were observed in 124 paternity tests. These two daughters were born in the other harem groups than their father's and left their natal groups before maturity. After maturity, one of them formed a stable consort relation with her father and the other remained together with her father for 2 months in the breeding season. Both of them had not experience to have lived with their fathers before maturity. The persent result supports the hypothesis in wild and semi-wild horses that inbreedings between fathers and daughters may be avioded by the experience to have lived together before sexual maturity.
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Kaseda, Y., & Khalil, A. M. (1996). Harem size and reproductive success of stallions in Misaki feral horses. Appl. Anim. Behav. Sci., 47(3-4), 163–173.
Abstract: Over a 16-year period (1979-1994), long-term investigations were carried out on 14 Misaki feral stallions to analyze changes in harem size and the reproductive success. Harem size changed with the age of the stallions. Most stallions formed harem groups with four to five mares at the age of 4-6 and then the number of mares increased rapidly to the maximum at the age of 6-9 years. Thereafter, harem size decreased gradually to a minimum with advancing age. The harem size of 60 stable harem groups ranged from 1 to 9, and the average varied from a minimum mean of 1.8 in 1988 to a maximum mean of 5.3 in 1982. Mean harem size increased as adult sex ratio increased and a significant and positive correlation was found between them. One hundred and ninety-eight sire-foal pairs were determined by a paternity test with blood types and consort relations between stallions and mares during the study period. Out of 99 foals which were born in the stable harem groups, the true sires of 84 foals (85%) were the harem stallions in which the foals were born but the remaining 15 foals (15%) were sired by other harem stallions. Two out of three stallions which were studied throughout their lifetime produced 24 and 25 foals in 10 and 11 years of their reproductive lifespan, respectively. Another one produced only five foals in 6 years. The number of foals sired by the harem stallions was less than two over harem size 7 and some of the foals born in the harem were sired by other harem stallions. These results suggest that if a particular stallion monopolizes too many mares, he could not sire so many offspring because he could not always prevent his rival stallions from mating with his mares in wild or feral circumstances.
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Monard, A. - M., & Duncan, P. (1996). Consequences of natal dispersal in female horses. Anim. Behav., 52(3), 565–579.
Abstract: Social, genetic and reproductive consequences of natal dispersal were investigated in female horses,Equus caballus, living in a herd with a natural social structure. Dispersal did not as a rule reduce the level of competition the young mares faced: they did not selectively join groups with fewer resident females than the groups they left, and they did not attain higher ranks; there was also no tendency for females to disperse to groups with the fewest resident females, and they suffered more aggression from the mares in their new groups than in their natal groups. These results therefore do not support the hypothesis that a function of natal dispersal is to reduce intra-sexual competition. The young mares nevertheless dispersed non-randomly, generally joining harems with one stallion and at least two subadult females; and they preferred to move to groups with familiar females but no familiar males. As a result, most were closely related to some females of their new groups, but distantly related or unrelated to the male(s). Since after dispersal the young mares bred only with a male of their new groups, inbreeding coefficients of most (85%) of their offspring were lower than from matings between half siblings. These results are consistent with the hypothesis that a function of natal dispersal is to avoid close inbreeding. Dispersal did not appear to involve reproductive costs: the young mares suffered no delay in age at first reproduction, and the survival rates of their first foals tended to be higher if the females had emigrated, although not significantly so.
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