排序方式: 共有43条查询结果,搜索用时 15 毫秒
11.
P. Neuhaus 《Behavioral ecology and sociobiology》2000,48(1):75-83
I studied reproductive costs in the female Columbian ground squirrel (Spermophilus columbianus) using individually marked animals. I compared weight changes during the active season and over winter, and mortality for
females that did and did not wean young. Females raising young were heavier at emergence in that spring than unsuccessful
ones. Females that did not raise young gained more weight during summer, were heavier than successful females at the time
of entry into hibernation, and were heavier emerging from hibernation the following spring. Over-winter mortality was higher
for females that reared young compared to reproductively unsuccessful females. A food supplementation experiment showed that
energy-rich food can accelerate individuals’ weight gain. Interactions between litter size, birth weight, weight at emergence
from the natal burrow, survival of young to yearling age, and maternal fitness were also studied. Litter sizes were experimentally
manipulated to evaluate how females cope with costs of rearing one additional young. Birth weight of juveniles was positively
correlated with survival to emergence from the natal burrow and with survival to yearling age. Partial litter loss was higher
in experimentally enlarged litters than in either experimentally decreased or control litters. Total litter loss, survival
of adult females or the probability of weaning young the following year were not affected by the litter size manipulation.
Females appear to adjust the size of their litter before birth, and to some extent during lactation, to their ability to wean
young.
Received: 20 January 2000 / Received in revised form: 12 March 2000 / Accepted: 18 March 2000 相似文献
12.
The Journal of Safety Research has partnered with the National Center for Injury Prevention and Control at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, USA, to briefly report on some of the latest findings in the research community. This report is the seventh in a series of CDC articles. 相似文献
13.
Ecological Compensation in Dutch Highway Planning 总被引:13,自引:0,他引:13
The ecological compensation principle was introduced by the Dutch government in 1993. This principle is designed to enhance
the input of nature conservation interests in decision-making on large-scale development projects and to counterbalance the
ecological impacts of such developments when implemented. This article evaluates the application of the Dutch compensation
principle in highway planning. Six current highway projects reveal consistent implementation of this principle, although provincial
policies on compensation and a national method for identifying compensation measures are still under development. As the planning
process has not yet been completed for all the projects, no general conclusions can be drawn on the impact of the compensation
principle on highway decision-making. Nevertheless, several examples show that the principle stimulates project initiators
to develop alternative routes or route sections in order to avoid or reduce ecological impacts and the need for coherent compensation
measures. If the compensation principle is to be properly implemented in the context of highway planning, particular attention
should be paid to the following aspects: (1) sequential assessment of overall project legitimacy and the necessity of intersecting
protected areas and compensation measures, (2) the initiator's attempts to avoid and mitigate ecological impacts in developing
alternative routes prior to compensation for impacts, and (3) the role of uncertain ecological impacts in identifying compensation
measures, especially those concerning habitat isolation. 相似文献
14.
Michelle L. Taylor Nina Wedell David J. Hosken 《Behavioral ecology and sociobiology》2008,62(5):721-728
There is a current debate over the net fitness consequences of sexual selection. Do preferred males increase female fitness or are these males manipulating females for their own benefit? The evidence is mixed. Some studies find that mating with attractive males increases female fitness components, while others show that preferred males decrease measures of female fitness. In this study, we examined some of the fitness consequences of pre-copulatory sexual selection in Drosophila simulans. Virgin females were either paired with one male and given an opportunity for one copulation or were exposed simultaneously to two males. This allowed us to compare female preference (copulation latency) and fitness (longevity, lifetime productivity and rate of offspring production) both with and without the influence of male–male competition. When females had access to a single male, neither female longevity, productivity, nor short-term rate of productivity were associated with female preference, and although females mated more quickly with larger males, male size was also not associated with any female fitness measure. Inclusion of male–male competition showed that female longevity was negatively affected by preference, while productivity and rate of productivity was unaffected. This latter experiment also indicated that females preferred larger males, but again, male size was not associated with female fitness. These results indicate that females may not benefit from mating with preferred males, but they may incur survival costs. 相似文献
15.
This Special Issue provides several different perspectives on the complex issue of packaging waste recycling. It comprises a diverse and rich set of contributions with insights from very different disciplines that range from economics to engineering. All types of “costs and benefits” are addressed in this collection of articles. In addition to the economic and strictly financial impacts of selective collection and sorting of packaging waste, several authors discuss other types of impacts, such as the environmental and social ones. The reader will find articles that address recycling systems as a whole, pieces that focus on specific impacts and detailed discussions of particular material streams or waste management strategies. The Special Issue represents an indispensable resource for academics, policy-makers and practitioners with interests in recycling and packaging waste management. 相似文献
16.
The Costs of Meeting the Environmental Objectives for the Baltic Sea: A Review of the Literature 总被引:1,自引:0,他引:1
Katarina Elofsson 《Ambio》2010,39(1):49-58
The environmental targets of the recently agreed Baltic Sea Action Plan (BSAP) targets are likely associated with a considerable
cost, which motivates a search for low-cost policies. The following review shows there is a substantial literature on cost-efficient
nutrient reduction strategies, including suggestions regarding low-cost abatement, but actual policies at international and
national scale tend to be considerably more expensive due to lack of instruments that ensure a cost-efficient allocation of
abatement across countries and sectors. Economic research on the costs of reducing hazardous substances and oil spill damages
in the Baltic Sea is not available, but lessons from the international literature suggest that resources could be used more
efficiently if appropriate analysis is undertaken. Common to these pollution problems is the need to ensure that all countries
in the region are provided with positive incentives to implement international agreements. 相似文献
17.
Female seaweed flies, Coelopa frigida, have the potential to benefit from mating more than once. Single matings result in low fertility so females may benefit directly from multiple copulations by sperm replenishment. A chromosomal inversion associated with larval fitness, with heterokaryotypic larvae having higher viability than homokaryotypes, means that polyandrous homokaryotypic females have a higher probability of producing genetically fit offspring than monandrous homokaryotypic females. We allowed females to mate only once, repeatedly four times to the same male, or polyandrously four times to four different males. Multiply mated and polyandrous females laid more eggs and produced more offspring than singly mated and monandrous females, respectively. Polyandrous females laid more eggs, had higher egg-to-adult survival rates and produced more offspring than repeatedly mated females. Fertility rates did not differ between treatments. The observed fitness patterns therefore resulted from increased oviposition through multiple mating per se, and a further increase in oviposition coupled with higher egg-to-adult offspring survival benefits to polyandry. Daily monitoring of individual females over their entire life spans showed that multiple copulations induced early oviposition, with polyandrous females ovipositing earlier than repeatedly mated females. Singly mated and polyandrous females incurred a longevity cost independent of egg production, whereas repeatedly mated females did not. This suggests that repeatedly mating with the same male may counteract a general cost of mating. Longevity, however, was not correlated with overall female fitness. Our data are discussed in the overall context of the seaweed fly mating system.Communicated by G. Wilkinson 相似文献
18.
Adaptive management (AM) is the process of implementing land management activities in incremental steps and evaluating whether desired outcomes are being achieved at each step. If conditions deviate substantially from predictions, management activities are adjusted to achieve the desired outcomes. Thus, AM is a kind of monitoring, an activity that land management agencies have done poorly for the most part, at least with respect to ground-based monitoring. Will they do better in the future? We doubt it unless costs, personnel, and future commitment are seriously addressed. Because ecosystem responses to management impacts can ripple into the distant future, monitoring programs that address only the near future (e.g., 10–20 years), are probably unreliable for making statements about resource conditions in the distant future. We give examples of this. Feedback loops between ecosystem response and adjustment of management actions are often broken, and therefore AM again fails. Successful ground-based monitoring must address these and other points that agencies commonly ignore. As part of the solution, publics distrustful of agency activities should be included in any monitoring program. 相似文献
19.
Anja Widdig Wolf Jürgen Streich Peter Nürnberg Peter J. P. Croucher Fred B. Bercovitch Michael Krawczak 《Behavioral ecology and sociobiology》2006,61(2):205-214
When agonistic interventions are nepotistic, individuals are expected to side more often with kin but less often against kin in comparison with non-kin. As yet, however, few mammal studies have been in a position to test the validity of this assertion with respect to paternal relatedness. We therefore used molecular genetic kinship testing to assess whether adult female rhesus macaques (Macaca mulatta) from the free-ranging colony of Cayo Santiago (Puerto Rico) bias their interventions in ongoing dyadic aggressive interactions towards maternal and paternal half-sisters compared with unrelated females. It turned out that females supported maternal half-sisters significantly more often than paternal half-sisters or non-kin regardless of the costs associated with such interventions. Similarly, females targeted maternal half-sisters significantly less often than non-kin when this was associated with high costs. Unrelated females provided significantly higher mean rates of both high- and low-cost support to each other than did paternal half-sisters. However, females targeted paternal half-sisters significantly less often than non-kin when targeting was at low cost, suggesting that females refrain from intervening against paternal half-sisters. Our data confirm the general view that coalition formation in female mammals is a function of both the level of maternal relatedness and of the costs of intervention. The patterns of coalition formation among paternal kin were found to be more complex, and may also differ across species, but clear evidence for paternal kin discrimination was observed in female rhesus as predicted by kin selection theory. 相似文献
20.
Several surveys have investigated the nature of farming under urban fringe conditions but none, until now, have involved the continuous monitoring of criminal and civil law incidents over a period of time. This paper describes the results of such a survey on urban fringe farms between Tyneside and Sunderland in North‐East England. The analysis outlines the nature of offences which occurred, the type of offender, the time incurred by and cost of the incident to the farmer. The cost of the offences should determine how many resources are devoted to remedying the problem, e.g. in modifying local plans. 相似文献