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241.
Patterns of courtship behavior and ejaculate characteristics in male red-winged blackbirds 总被引:1,自引:0,他引:1
David F. Westneat Lisa A. McGraw Jennifer M. Fraterrigo Tim R. Birkhead F. Fletcher 《Behavioral ecology and sociobiology》1998,43(3):161-171
Sperm competition in birds is likely to have important effects on the behavior and physiology of reproduction in both sexes.
For males, such competition should select for large sperm reserves and behavioral adjustment of copulation when reserves are
low. We investigated both these possibilities in free-living red-winged blackbirds (Agelaius phoeniceus), a highly polygynous species with apparently strong sperm competition. We found that the recent copulatory behavior of males
did not affect the propensity to copulate with a model female. Ejaculates collected from individual males at 1-h intervals
showed no evidence of sperm depletion, yet repeated ejaculates collected less than 10 min apart did. Male ejaculate size was
significantly larger if it was the first one of the day (i.e., after an overnight rest). The average ejaculate size was 12.5
(±12.5 SD) million sperm. Males captured during the breeding season had an average of 111.7 (±52.8) million sperm stored in
their seminal glomera. Because males average a peak copulation rate of six per female per day, in one day a male might utilize
all the sperm in his seminal glomera if more than two females on his territory are fertilizable. We hypothesize that polygyny
and sperm competition in this species have combined to select for rapid replenishment of the seminal glomera throughout the
day, in contrast to other species that have been studied. Testis size and sperm reserves of male red-winged blackbirds are
intermediate between monogamous species and species with intense sperm competition. Several possible explanations for this
are discussed.
Received: 21 October 1997 / Accepted after revision: 15 February 1998 相似文献
242.
针对白马雪山国家级自然保护区与周边社区村民在环保观念、管理模式、资源利用以及补偿措施等方面的矛盾冲突,对其产生的原因进行了分析,并从社区经济发展、社区村民传统生活习惯约束、社区管理机构完善和少数民族传统文化有效利用等方面提出了主要的缓解冲突的措施和方法。 相似文献
243.
针对生物燃油生产过程中热载体复合加热装置中集气箱结构与热交换管的支撑问题可能带来的不安全因素,将创新设计方法学——TRIZ(发明问题解决理论)应用于加热装置的安全设计中,按照TRIZ解决问题的系统化方法,通过技术矛盾分析和创新原理应用解决存在的技术冲突,能有效地消除设备存在的不安全因素。在设备的安全设计中应用TRIZ理论,与传统方法相比能降低解决问题的难度,提高解决问题的效率,增强设备的安全可靠性,是一种值得推广的经济实用的创新方法。 相似文献
244.
《Journal of Environmental Policy & Planning》2012,14(2):169-184
This paper shows how prevailing economic development paradigms over the last five decades have favoured an urban-based model of economic development at the expense of environmental considerations in developing countries. How the disjuncture between these competing agendas has been experienced in Egypt forms the focus of the paper. Tension between environmental and development/urbanization policies reflects their political encoding aimed at maintaining regime stability. The state has attempted to mediate between the domestic interests of an urban-based elite and the urban poor, international donor dominance of Egypt's economic and urban development strategies, and the country's limited institutional capacity to manage its developmental aspirations. In a policy configuration that buttresses macro-economic policy with urban development priorities, the unfettered role of market processes has produced vast but unregulated urban expansion with, now, increasingly severe environmental consequences. Despite attempts to reconcile the two agendas in the last decade, the paper concludes that the main issues endemic to the public policy domain in Egypt, and in many developing countries, remain: poor line ministry coordination, weak enforcement of environment law, resistance to participation, limited implementation capacity, conflicts between sectoral and cross-sectoral policy formulation, and dependency on external donors. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
245.
Wild geese foraging on farmland cause increasing conflicts with agricultural interests, calling for a strategic approach to mitigation. In central Norway, conflicts between farmers and spring-staging pink-footed geese feeding on pastures have escalated. To alleviate the conflict, a scheme by which farmers are subsidized to allow geese to forage undisturbed was introduced. To guide allocation of subsidies, an ecological-based ranking of fields at a regional level was recommended and applied. Here we evaluate the scheme. On average, 40 % of subsidized fields were in the top 5 % of the ranking, and 80 % were within the top 20 %. Goose grazing pressure on subsidized pastures was 13 times higher compared to a stratified random selection of non-subsidized pastures, capturing 67 % of the pasture feeding geese despite that subsidized fields only comprised 13 % of the grassland area. Close dialogue between scientists and managers is regarded as a key to the success of the scheme. 相似文献
246.
Changing household responses to drought in Tharaka, Kenya: vulnerability, persistence and challenge 总被引:2,自引:0,他引:2
Drought is a recurring challenge to the livelihoods of those living in Tharaka District, Kenya, situated in the semi-arid zone to the east of Mount Kenya, from the lowest slopes of the mountain to the banks of the Tana River. This part of Kenya has been marginal to the economic and political life of Kenya from the colonial period until the present day. A study of more than 30 years of change in how people in Tharaka cope with drought reveals resilience in the face of major macro-level transformations, which include privatisation of landownership, population growth, political decentralisation, increased conflict over natural resources, different market conditions, and environmental shifts. However, the study also shows troubling signs of increased use of drought responses that are incompatible with long-term agrarian livelihoods. Government policy needs to address the challenge of drought under these new macro conditions if sustainable human development is to be achieved. 相似文献
247.
我国道路交通事故特征分析与对策研究 总被引:6,自引:16,他引:6
针对我国道路交通安全形势日益严峻的现状,在分析我国城市道路交通安全特点的基础上,从交通事故的发生机理出发,分析研究了道路交通事故的宏观规律。从安全系统工程的角度,提出通过制定科学合理的城市道路交通安全管理规划和建立健全城市交通事故紧急救援系统、加强交通参与者的交通安全意识、综合协调道路—交通流—管理者之间的关系,以消除道路交通系统中人的不安全行为和物的不安全状态。明确指出当前乃至今后交通安全的发展方向和趋势,规划长远、决策当前,彻底改变目前交通安全工作的事后处理状态,做到防患于未然。对提高交通安全宏观管理整体水平具有一定的借鉴作用和应用价值。 相似文献
248.
Studies evaluating human–wildlife interactions (HWIs) in a conservation context often include psychometric scales to measure attitudes and tolerance toward wildlife. However, data quality is at risk when such scales are used without appropriate validation or reliability testing, potentially leading to erroneous interpretation or application of findings. We used 2 online databases (ProQuest Psych Info and Web of Science) to identify published HWI studies that included attitude and tolerance. We analyzed these studies to determine the methods used to measure attitudes or tolerance toward predators and other wildlife; determine the proportion of these methods applying psychometric scales; and evaluate the rigor with which the scales were used by examining whether the psychometric properties of validity and reliability were reported. From 2007 to 2017, 114 published studies were identified. Ninety-four (82%) used questionnaires and many of these (53 [56%]) utilized a psychometric scale. Most scales (39 [74%]) had at least 1 test of reliability reported, but reliance on a single test was notable, contrary to recommended practice. Fewer studies (35 [66%]) reported a test of validity, but this was primarily restricted to structural validity rather than more comprehensive testing. Encouragingly, HWI investigators increasingly utilized the necessary psychometric tools for designing and analyzing questionnaire data, but failure to assess the validity or reliability of psychometric scales used in over one-third of published HWI attitude research warrants attention. We advocate incorporation of more robust application of psychometric scales to advance understanding of stakeholder attitudes as they relate to HWI. 相似文献
249.
Feral cats are abundant in many parts of the world and a source of conservation conflict. Our goal was to clarify the beliefs and desires held by stakeholders regarding feral cat abundance and management. We measured people's desired abundance of feral cats in the Hawaiian Islands and identified an order of preference for 7 feral cat management techniques. In 2011 we disseminated a survey to 5407 Hawaii residents. Approximately 46% of preidentified stakeholders and 20% of random residents responded to the survey (1510 surveys returned). Results from the potential for conflict index revealed a high level of consensus (86.9% of respondents) that feral cat abundance should be decreased. The 3 most common explanatory variables for respondents’ stated desires were enjoyment from seeing feral cats (84%), intrinsic value of feral cats (12%), and threat to native fauna (73%). The frequency with which respondents saw cats and change in the perceived abundance of cats also affected respondent's desired abundance of cats; 41.3% of respondents stated that they saw feral cats daily and 44.7% stated that the cat population had increased in recent years. Other potential environmental impacts of feral cats had little affect on desired abundance. The majority of respondents (78%) supported removing feral cats from the natural environment permanently. Consensus convergence models with data from 1388 respondents who completed the relevant questions showed live capture and lethal injection was the most preferred technique and trap‐neuter‐release was the least preferred technique for managing feral cats. However, the acceptability of each technique varied among stakeholders. Our results suggest that the majority of Hawaii's residents would like to see effective management that reduces the abundance of feral or free‐roaming cats. Deseos y Preferencias de Manejo de las Partes Interesadas con Respecto a los Gatos Ferales en las Islas Hawaianas. 相似文献
250.
Simone Tenan Aaron Iemma Natalia Bragalanti Paolo Pedrini Marta De Barba Ettore Randi Claudio Groff Meritxell Genovart 《Conservation biology》2016,30(6):1307-1319
The conservation of wildlife requires management based on quantitative evidence, and especially for large carnivores, unraveling cause‐specific mortalities and understanding their impact on population dynamics is crucial. Acquiring this knowledge is challenging because it is difficult to obtain robust long‐term data sets on endangered populations and, usually, data are collected through diverse sampling strategies. Integrated population models (IPMs) offer a way to integrate data generated through different processes. However, IPMs are female‐based models that cannot account for mate availability, and this feature limits their applicability to monogamous species only. We extended classical IPMs to a two‐sex framework that allows investigation of population dynamics and quantification of cause‐specific mortality rates in nonmonogamous species. We illustrated our approach by simultaneously modeling different types of data from a reintroduced, unhunted brown bear (Ursus arctos) population living in an area with a dense human population. In a population mainly driven by adult survival, we estimated that on average 11% of cubs and 61% of adults died from human‐related causes. Although the population is currently not at risk, adult survival and thus population dynamics are driven by anthropogenic mortality. Given the recent increase of human‐bear conflicts in the area, removal of individuals for management purposes and through poaching may increase, reversing the positive population growth rate. Our approach can be generalized to other species affected by cause‐specific mortality and will be useful to inform conservation decisions for other nonmonogamous species, such as most large carnivores, for which data are scarce and diverse and thus data integration is highly desirable. 相似文献