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1.
Robert M. Gibson 《Behavioral ecology and sociobiology》1996,39(1):55-59
Previous studies of female choice in sage grouse Centrocercus urophasianus have implicated both the acoustic quality and repetition rate of the stereotyped strut display as putative cues for female
choice. Stages in the choice process at which specific components of male courtship display influence female decisions were
investigated using field observations of female pre-mating behavior. Females visited a subset of territorial males and then
actively chose one of these as a mate. The order in which males were visited suggested that females searched until an acceptable
mate was found, rather than employing a “best-of-n” tactic. Numbers of females visiting a male were related to differences
in an acoustical component of display (inter-pop interval) whereas the probability that a visiting female mated was related
to display rate (Table 3), indicating that initial attraction and active choice are influenced by different components of
display. In addition, inter-pop interval and display rate tended to covary inversely (Fig. 1), suggesting that attraction
and active choice may impose conflicting selection pressures on display performance.
Received: 11 November 1995/Accepted after revision: 16 March 1996 相似文献
2.
D. M. Shuker E. M. Sykes L. E. Browning L. W. Beukeboom S. A. West 《Behavioral ecology and sociobiology》2006,59(6):829-835
Sex allocation is an important reproductive decision for parents. However, it is often assumed that females have substantial
control over sex allocation decisions, and this is particularly true in haplodiploid insects, in which females apparently
determine sex by deciding whether to fertilise an egg (and produce a diploid daughter) or not (and produce a haploid son).
Mechanisms by which males may influence sex allocation are not so straightforward, and their potential influence on sex ratios
has been somewhat neglected. Here, we test whether males influence offspring sex ratios in the parasitoid wasp Nasonia vitripennis. We show that some of the variation in observed sex ratios can be attributed to males when comparing the affect of male strain
on sex ratio. We did not find among-male variation in sex ratio with a less powerful experiment using males from only one
strain or an effect of male mating environment. Our data suggest that males can influence female sex ratios and contribute
to the variation around the sex ratios optimal for females. However, the influence is not large, suggesting that females have
more influence on sex allocation than do males. We conclude by considering whether male influences on sex ratio represent
differences in male reproductive competence or deliberate attempts by males to increase their fitness by influencing daughter
production. 相似文献
3.
Problems and constraints in Philippine municipal fisheries: The case of San Miguel Bay,Camarines Sur
The Philippine fisheries accounted for 3.7% of the gross national product at current prices. The sector employed about 990,872
persons. Of the divisions comprising the industry, municipal fisheries continued to contribute the largest share of fish production.
However, the sector is beset with problems, many of which are best examplified by the case of San Miguel Bay (SMB). This paper
presents the problems and constraints confronting SMB, a common property resource. This bay's open access condition has led
to various problems, such as declining fishery resources, depressed socioeconomic conditions, illegal fishing, increasing
population, and conflict among resource users. A poor marketing system, low level of fishing technology, fishermen's noncompliance
and authorities' lax enforcement of rules and regulations, as well as lack of alternative sources of income further characterize
the condition in SMB. Establishment of fishing rights, improvement of the marketing system, provision of alternative sources
of income, and improvement of fishing technology were some of the solutions suggested. One major constraint, however, is financial,
Comanagement complemented with other management tools has been proposed in addressing the problems in SMB. 相似文献
4.
Britton NR 《Disasters》1984,8(2):124-137
An analysis of organizations involved in response to disaster within Australia is offered. The location of these key organizations within the existing institutional framework, and a discussion of the functions of each, together with the relationships between them is provided. Particular emphasis is placed on the location and role of the State and Territory Emergency Service organizations (S/TES's) within this organizational network. The paper suggests there are a number of constraints that operate upon the S/TES's which prejudice both the effectiveness of this organizational type and that of the entire organizational network. These constraints are analyzed in terms of power and influence variables. The outcome of this discussion is the development of a taxonomy of Australia's counter-disaster organizations that is based on: (1) the ability of individual organizations within the network to determine the role which it will perform; and (2) the potential of the organization to influence the direction of the network. 相似文献
5.
Brigitte Cambon de Lavalette Charles Tijus Sbastien Poitrenaud Christine Leproux Jacques Bergeron Jean-Paul Thouez 《Safety Science》2009,47(9):1248-1253
Among road users, pedestrians are those whose continued trajectory is the less constrained by the environment and by the regulation rules. Consequently, the choice of where, when and how to cross roads are more or less conforming with the awaited behavior. Proceeding with an experimental approach, from observations of pedestrian crossings to the modeling of the decision-making process, a categorization of both environments and of pedestrian behavior is proposed. 相似文献
6.
7.
Sook Yan Choy Krishna Murthy Nagendra Pras Ta Yeong Wu Mavinakere Eshwaraiah Raghunandan Ramakrishnan Nagasundara Ramanan 《环境科学学报(英文版)》2014,26(11):2178-2189
Rapid industrial developments coupled with surging population growth have complicated issues dealing with water scarcity as the quest for clean and sanitized water intensifies globally. Existing flesh water supplies could be contaminated with organic, inorganic and biological matters that have potential harm to the society. Turbidity in general is a measure of water cloudiness induced by such colloidal and suspended matters and is also one of the major criteria in raw water monitoring to meet the stipulated water quality guidelines. Turbidity reduction is often accomplished using chemical coagulants such as alum. The use of alum is widely associated with potential development of health issues and generation of voluminous sludge. Natural coagulants that are available in abundance can certainly be considered in addressing the drawbacks associated with the use of chemical coagulants. Twenty one types of plant-based natural coagulants categorized as fruit waste and others are identified and presented collectively with their research summary in this review. The barriers and prospects of commercialization of natural coagulants in near future are also discussed. 相似文献
8.
Iniobong Aniefiok Akpabio 《Environment, Development and Sustainability》2009,11(2):307-317
The study attempted to document beneficiaries’ perceptions on the contributions of Women NGOs (WNGOs) to the socio-economic
empowerment of rural women in Akwa Ibom State, Nigeria. The specific objectives of the study included: an assessment of WNGOs
contributions to improvements’ in beneficiaries’ socio-economic activities and constraints affecting beneficiaries’ participation
in WNGOs activities. An attempt was also made to determine the existence of a significant relationship between the pre and
post-participation income of WNGOs beneficiaries. A sample size of 240 respondents from 48 Local Women Groups (LWGs), which
are affiliated to three active WNGOs in four states of the Niger Delta were utilized for the study. Findings revealed that
WNGOs cater for a broad spectrum of rural women. WNGOs were revealed to affect beneficiaries’ socio-economic statuses through
increased income generation, health awareness and acquisition of food processing skills. Constraints affecting beneficiaries’
participation in WNGOs activities include: inadequate credit facilities, and poor utilization of credit advances, resulting
in poor loan repayment levels. A direct relationship was also revealed to exist between increased beneficiary exposures to
WNGOs credit facilities and increased beneficiary income. It is believed that WNGOs are capable of more effective inputs into
human and community development activities. Recommendations are proffered in this respect.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
9.
ABSTRACT: Proper planning of water resource management programs is the essential ingredient for effective decision-making. Increasing demands on our finite water resources make it more vital that programs get off the shelf and are acted upon. There is a gap between our intentions for and OUI results from the planning process. We should examine our failures, identify causes, and learn from them. One of the primary causes is failure to identify the potentials of the implementing agencies early in the planning process. These agencies constitute a hierarchy of governmental units at national, state, regional and local levels. Each of these levels has its own interests, point of view, capabilities and constraints. A plan which is technically and functionally sound can fail as a program if these conflicting interests are not accounted for. The implementation mechanisms must be identified as an initial phase of the planning process. All levels of the governmental hierarchy must be involved throughout the planning process. The successful plan must also provide for suitable assignment of responsibilities which are accepted by the executing agency and monitored for satisfactory fulfillment. Consistency and continuity of the advocate agency are further essential elements to the success of the plan. Experience in water resource management planning has shown that these strategies will produce programs which are accepted, implemented and accomplish the goals and objectives of the planning process. 相似文献
10.
David C. Krakauer 《Behavioral ecology and sociobiology》1995,36(6):421-429
Aggregation is a well documented behaviour in a number of animal groups. The confusion effect is one mechanism thought to mitigate the success of predators feeding on gregarious prey and hence favour aggregation. An artificial neural network model of prey targeting is developed to explore the advantages prey species might derive through a tendency to group. The network illustrates how an abstract model of the computational mechanisms mediating the perception of prey position is able to show a degradation in performance as group size increases. The relationship between group size and predator confusion has a characteristic decreasing decelerating shape. Prey oddity is shown to reduce the impact of the confusion effect, thereby allowing predators to target prey more accurately. Hence shoaling behaviour is most profitable to the prey when prey phenotypes are visually indistinguishable to a predator. Futhermore it is shown that prey oddity is relatively more costly in large groups than in small groups and the implications for assortative schooling are discussed. Both the model and the results are intended to make the general point that cognitive constraints will limit the information that a nervous system can process at a number of different levels of neural organization. 相似文献