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381.
A Population Viability Analysis for African Elephant (Loxodonta africana): How Big Should Reserves Be? 总被引:1,自引:0,他引:1
We present an age-structured, density-dependent model of elephant population dynamics in a fluctuating environment, drawing primarily upon the life history parameters obtained from studies in semi-arid land at Tsavo National Park, Kenya. Density regulation occurs by changes in the age of first reproduction and calving interval. We model environmental stochasticity with drought events affecting sex- and age-specific survivorships. Results indicate a maximum population growth rate of 3% per year and an equilibrium elephant density of 3.1/mile2 . Analysis of the demographic results and their sensitivity to changes in juvenile survivorship and drought frequencies, supported by genetic considerations, suggests that in semi-arid regions a minimum reserve size of 1000 mile2 is necessary to attain a 99% probability of population persistence for 1000 years. The effect of age-independent culling on population viability is also analyzed. 相似文献
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James A Cunningham J Peter Clinch 《Journal of Environmental Planning and Management》2005,48(3):373-392
Criteria have been developed in general terms for evaluating voluntary approaches. Nevertheless, there still remains limited assessment regarding the performance of environmental voluntary approaches as there is a general dearth of empirical information. In relation to innovation and voluntary approaches there are two main schools of thought, namely, the no innovation scenario and innovation through collective learning. This paper outlines the arguments regarding environmental voluntary approaches and innovation and reports on an empirical study of an Irish packaging voluntary agreement. Its findings would indicate that the no innovation scenario is applicable to the Irish packaging voluntary agreement. 相似文献
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Johannes H. P. Hackstein Peter Langer Jörg Rosenberg 《Environmental monitoring and assessment》1996,42(1-2):39-56
It has been assumed that the feeding habits of animals predispose the composition of the microbial biota living in their intestinal tracts. Here we show that in arthropods and vertebrates the presence of methanogenic bacteria requires a quality of the host that is under phylogenetic rather than dietary constraint: competence for intestinal methanogenic bacteria is a primitive-shared character among reptiles, birds, and mammals, and a shared-derived trait of millipedes, termites, cockroaches and scarab beetles. The presence of methanogenic bacteria seems to be a prerequisite for the evolution of anatomic specializations of the intestinal tract such as hindguts, caeca or rumina, and it is likely that it also has consequences for the reproductive strategies of the animals.Methanogenic animals contribute to atmospheric methane by their breath and faeces. Because the status as either methane-producer or non-producer is shared by most species belonging to a higher taxonomic unit, it is possible to calculate methane emissions that are characteristic for whole taxa. In combination with ecological field data on the biomass it is possible to arive at estimates concerning the global contributions by animals.The demonstration of a genetic basis for the symbiosis between methanogens and animals will allow new approaches for the reduction of methane emission by domestic animals. 相似文献
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Ronald J. Wapner Thomas M. Jenkins Neil Silverman Marion Kaufmann Cheryl Hannau Peter McCue 《黑龙江环境通报》2001,21(4):256-261
The diagnosis of congenital nephrosis is difficult during the antepartum period. The combination of an elevated amniotic fluid alpha-fetoprotein, a negative acetylcholinesterase, and a negative ultrasound examination is highly indicative of congenital nephrosis; however, these findings can also be associated with a normal gestation. This is the first report of pathologic confirmation of congenital nephrosis from an in utero fetal kidney biopsy. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Peter Frederick 《Behavioral ecology and sociobiology》1987,21(4):223-228
Summary I intensively observed the mating behavior of 134 pairs of white ibises for over 15 000 pair hours to examine the responses of males to extrapair copulations (EPC) involving their mates. Females often cooperated completely in apparently fertile EPCs. Male mate-guarding was vigorous and effective. Males did not respond to apparent sperm competition with forced-pair copulation, physical punishment, or abandonment of their mates. I found no negative correlation between degree of female promiscuity and the amount of parental care her mate gave to the entire brood. Males also did not reduce paternal care given to the young most likely to be the result of an EPC. I hypothesize that males are constrained in the behaviors they can use to avoid misplaced paternity in this species. While male mate-guarding reduces the opportunities for female involvement in EPC, the behaviors used by males to protect paternity apparently have not prevented the evolution of female receptiveness during EPC attempts. 相似文献