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141.
Variations in the birth sex ratio and neonatal mortality in a natural herd of horses 总被引:3,自引:0,他引:3
Anne-Marie Monard Patrick Duncan Hervé Fritz Claudia Feh 《Behavioral ecology and sociobiology》1997,41(4):243-249
Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many
cases have been linked to resource availability. Most of these biases in offspring sex ratios concern polygynous species with
pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies,
such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of
horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality
rates in nutritionally poor years than in good ones, whereas “year quality” had no effect on the mortality of female offspring;
year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental
conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following
year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There
was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The
mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As
there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary
to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were
more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth
interval between their two subsequent offspring.
Received: 28 December 1996 / Accepted after revision: 27 July 1997 相似文献
142.
George M. Leigh William S. Hearn Kenneth H. Pollock 《Environmental and Ecological Statistics》2006,13(1):89-108
Instantaneous natural mortality rates and a nonparametric hunting mortality function are estimated from a multiple-year tagging
experiment with arbitrary, time-dependent fishing or hunting mortality. Our theory allows animals to be tagged over a range
of times in each year, and to take time to mix into the population. Animals are recovered by hunting or fishing, and death
events from natural causes occur but are not observed. We combine a long-standing approach based on yearly totals, described
by Brownie et al. (1985, Statistical Inference from Band Recovery Data: A Handbook, Second edition, United States Fish and Wildlife Service, Washington, Resource Publication, 156), with an exact-time-of-recovery
approach originated by Hearn, Sandland and Hampton (1987, Journal du Conseil International pour l’Exploration de la Mer, 43, 107–117), who modeled times at liberty without regard to time of tagging. Our model allows for exact times of release
and recovery, incomplete reporting of recoveries, and potential tag shedding. We apply our methods to data on the heavily
exploited southern bluefin tuna (Thunnus maccoyii). 相似文献
143.
Effects of Road Fencing on Population Persistence 总被引:6,自引:0,他引:6
Abstract: Roads affect animal populations in three adverse ways. They act as barriers to movement, enhance mortality due to collisions with vehicles, and reduce the amount and quality of habitat. Putting fences along roads removes the problem of road mortality but increases the barrier effect. We studied this trade-off through a stochastic, spatially explicit, individual-based model of population dynamics. We investigated the conditions under which fences reduce the impact of roads on population persistence. Our results showed that a fence may or may not reduce the effect of the road on population persistence, depending on the degree of road avoidance by the animal and the probability that an animal that enters the road is killed by a vehicle. Our model predicted a lower value of traffic mortality below which a fence was always harmful and an upper value of traffic mortality above which a fence was always beneficial. Between these two values the suitability of fences depended on the degree of road avoidance. Fences were more likely to be beneficial the lower the degree of road avoidance and the higher the probability of an animal being killed on the road. We recommend the use of fences when traffic is so high that animals almost never succeed in their attempts to cross the road or the population of the species of concern is declining and high traffic mortality is known to contribute to the decline. We discourage the use of fences when population size is stable or increasing or if the animals need access to resources on both sides of the road, unless fences are used in combination with wildlife crossing structures. In many cases, the use of fences may be beneficial as an interim measure until more permanent measures are implemented. 相似文献
144.
Previous studies have found that mean-residential-radon (Rn) levels for U.S. counties are negatively associated with age-adjusted county rates of lung-cancer mortality (LCM), after adjustments for potentially confounding factors. Those results may be due to (a) confounding unaddressable by any county-level (ecological) study design, or (b) county-level factors such as Rn/smoking or age/radon correlations or exposure misclassifications from the use of disparate data sources. Possibilities (b) were addressed by comparing age-specific LCM rates for white women in 2821 U.S. counties who died in 1950–54 at age 40+ (11% of whom ever smoked), or at age 60+ (% of whom ever smoked), to county Rn levels newly estimated from U.S. Rn, climatic and geological-survey data. Significant negative LCM v Rn trends were found for both age groups, after adjusting for age and subsets of 21 county-level socioeconomic, climatic and other factors. Negative trends were largest for counties with 100 Bq m–3 Rn (p 0.00087; 420 analyses). Adjusted relative risk (RRadj) for LCM was significantly elevated (1 < [95% conf. limits on RRadj] 1.46) in 43 of 210 analyses comparing LCM rates in counties with > 150 Bq m–3
v 65–100 Bq m–3 Rn, most involving adjustment for climate- and education-related factors likely to have influenced exposure to indoor air contaminants such as Rn and cigarette smoke. Though inconclusive due to potential ecological-fallacy-related confounding that could not be controlled, results from this ecological study are most consistent with a U-shaped dose-response relationship between 1950–54 LCM risk and U.S. residential radon in white women who predominantly never smoked. 相似文献
145.
利用江西省大量岩石类型和食管癌死亡调查资料,对食管癌死亡率与人群生存区岩石类型的相关性进行了研究。结果表明,江西省食管癌死亡率与岩石类型密切相关。食管癌死亡率与变质岩、碳酸盐岩、第四系松散岩、红色碎屑岩呈正相关,与岩浆岩呈负相关,与碎屑岩相关不显著。 相似文献
146.
In order to assess the applicability of an earthworm bioassayas a technique for monitoring the soil flushing process, short-term and long-term toxicity tests were conducted on remediatedsoil using various pore volumes of surfactant solution. Resultsobtained on short-term toxicity testing indicated that biomassincreased as the soil flushing proceeded, and on diesel-contaminated soils this testing showed that the effect of dieselis lethal and that 25 pore volumes of soil surfactant were notsufficient to abrogate the toxic effect of diesel. These short-term tests also showed strong sublethal relationships between the development of biomass, and the concentrations of toxic chemicals in the soil. Although relationships between contaminants and the various bioassay parameters examined werenot significant in long-term testing, an increase in the numberof juveniles was observed over time, which may have been a consequence of a reduction in toxicity associated with the flushing process. 相似文献
147.
148.
Carola Borries 《Behavioral ecology and sociobiology》1997,41(3):139-150
In the seasonally breeding langur (Presbytis entellus) population of Ramnagar, South Nepal, where multimale groups prevail, 25 attacks on 11 infants (including one actual killing)
by seven adult males were witnessed in five groups by six observers between 1990 and 1996. Circumstantial evidence also indicates
three additional attempts at infanticide and in seven additional cases infanticide was presumed or likely. Infanticide presumably
accounted for 30.8–62.5% of infant mortality in the first 2 years of life. Most attackers (91.4%) were residents of the infants'
group and had immigrated after the infants had been born (75.0%) or conceived (25.0%). Thus, they were not related to the
victims. The interbirth interval was shortened if an infant died either prior to September of its 1st year of life (mean = 1.2
years), or its 2nd year (mean = 2.0) and even its 3rd year (mean = 2.4). All attackers remained in the group at least until
the next mating season; high-ranking males maintained their dominance rank and lower-ranking males rose in rank. Since rank
and mating success were correlated and rank and reproductive success might be correlated, all attackers had a good chance
of siring the next infant of the victims' mothers and could thus have benefited by their action. Infanticide seems to be a
male reproductive strategy at Ramnagar. Infanticide has never before been reported among seasonally breeding langurs living
at such low densities. This is also the first detailed report of infanticide as a male reproductive strategy in a seasonally
breeding primate population.
Received: 19 December 1996 / Accepted after revision: 7 June 1997 相似文献
149.
Air pollution leads to serious negative impacts on health. Thephysical evidence is compelling. An attempt has been made inthis paper to establish dose-response relationship of AmbientAir Quality Index and human health, based on time spent by anindividual in different microenvironments during one day.Economic valuation of morbidity and mortality has been attemptedthrough lost salary approach. The results show that theavoidance cost is 29% of the total health damage cost. 相似文献
150.
Sheikh Imran Uddin Ahmed 《环境质量管理》2019,29(2):51-55
This study reports the probability of increased mortality of people within the political border of Bangladesh due to the emission of fine particulate matter with diameters of 2.5 microns or less (PM2.5) from the Matarbari coal power plant (MCPP). A Gaussian plume dispersion model has been used for this estimation. The PM2.5 emission rate data are unavailable as the construction of MCPP is still in its initial stage; therefore, the anticipated PM2.5 emission rate has been estimated based on data from a number of coal‐fired power plants in India and China. To make this study more meaningful, two different emission rates have been considered representing the best‐case and worst‐case scenarios. In both cases, the intake fraction has been found to be 0.12×10?2, and the value of relative risk varies between 1.134 and 1.374, respectively. Finally, it is estimated that approximately 11.5 million people inside Bangladesh will be exposed to the PM2.5 emission from MCPP, and between 7,667 and 17,675 people will experience premature death every year. 相似文献