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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Kroodsma, D. E., & Miller, E. H. (Eds.). (1996). Ecology and evolution of acoustic communication in birds. Ithaca: Cornell University Press.
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Heyes, C., & Galef, B. G. (Eds.). (1996). Social learning in animals: the roots of culture. San Diego, CA: Academic Press, Inc.
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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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Feh, C., Enchbold, S., & Munchtuya, B. (1996). Preliminary assessment of the Gurvan Saikhan National Conservation Park's potential for Gobi khulan (Equus hemionus luteus). GTZ, .
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