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繁殖是动物权衡不同自然选择压力和自身生理限制的结果。蝙蝠的繁殖受气候(温度、光周期和降雨量)和食物资源等非生物因素影响。本文通过野外调查犬蝠食物资源、设网捕捉和标志重捕的方法研究西双版纳地区降雨、食物资源可获得程度对犬蝠分娩时机的影响。研究发现,随着3 - 8 月降雨量逐渐增加(19.82 -41.13 kg/ m2 ),犬蝠取食的植物种类呈明显的增加趋势(4 - 9 种)。幼蝠捕捉量与植物资源可获得程度呈显著正相关关系(r = 0. 94,P = 0.01)。西双版纳犬蝠虽然具有一年两次动情和分娩的能力,但是绝大多数个体一年只分娩一次,且集中于3 -5 月。犬蝠分娩时机的选择使得幼蝠飞行学习和捕食时间与食物资源可获得程度高峰期相吻合,有利于提高幼体的生存适合度。 相似文献
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Following the traditions of ethnographic analysis, an account is given here of Best Value, the United Kingdom government's inspection of the services provided by municipalities and other local units of administration. My analysis is based largely upon the categories and terms used by the inspectorate itself. It is argued that in each of the main areas of inspection the results appear to contradict the intentions set out for the inspection. This appears to be the result of processes of abstraction which arise during the inspection. Such abstraction was located in the rise of jargon and bureaucracy as a result of the sheer scale of this audit, in the externalization of critical factors during market testing, in the emphasis on the representation of consulting over the results of consultation, and through the privileging of quantitative over qualitative information. Finally, the phrase 'owning the process' is analysed to show how the central ethos of serving the public is negated by these same forces. All these forms of abstraction are shown to occur despite, rather than because of, the intentions of the inspectorate. In the conclusion, they are analysed as contradictions which arise as a result of forces that are described by a theory of Virtualism. 相似文献
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