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91.
Sex differences in mass loss rate and growth efficiency in Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island 总被引:3,自引:0,他引:3
Christophe Guinet Simon D. Goldsworthy Sue Robinson 《Behavioral ecology and sociobiology》1999,46(3):157-163
We investigated the relationship between the mass gained by a pup during a period of maternal attendance (as an index of
milk intake) and the duration of the preceding foraging trip in relation to the mass-specific rate of mass loss during fasting
periods and the growth rate of Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island. We found that (1) serially weighed male pups grew significantly faster than females pups and that
(2) fasting female pups lost mass at a significantly higher rate (2.55% day−1) than male pups (2.12% day−1) of the same mass; (3) during periods of maternal attendance, there were no intersexual differences in the amount of mass
gained by pups of the same size, hence (4) female pups required a higher daily mass gain to grow at the same rate as male
pups. Our results show that intersexual differences in growth rate may be accounted for by intersexual differences in mass-specific
rate of mass loss, because females lost 0.42% more of their total mass per day (i.e. 4.2 g kg−1 day−1) compared with male pups of the same body mass. Despite intersexual differences in growth rates, our results indicate equality
of maternal expenditure between the sexes. Intersexual differences in the rate of mass loss may be due to differences in the
metabolic rate, activity level and/or body composition of male and female pups.
Received: 19 August 1998 / Received in revised form: 19 April 1999 / Accepted: 19 April 1999 相似文献
92.
Assessment of aquatic macroinvertebrates is a critical component of many watershed monitoring programs and passive samplers are often used to collect long-term site data, especially in environments where active sampling is not possible. However, standard passive samplers can be expensive and lost in extreme conditions. We developed a sampler using plastic soda bottles (PSB) filled with river rock and compared its effectiveness with standard Hester-Dendy samplers in both lotic and lentic environments. Abundance, taxa richness, and macroinvertebrate composition showed no significant differences between sampler types in either habitat type. PSB samplers, which can be constructed for less than one dollar each, collected the same number of organisms and represented the same diversity as Hester-Dendy devices that cost around $38 each. In studies where funds are limited, PSB samplers appear to be suitable for passive monitoring. 相似文献
93.
Melissa Emery Thompson Martin N. Muller Richard W. Wrangham 《Behavioral ecology and sociobiology》2014,68(12):1973-1983
Sexual conflict develops when the optimal reproductive strategy for one sex inflicts fitness costs upon the other sex. Among species with intense within-group feeding competition and high costs of reproduction, females are expected to experience reduced foraging efficiency by associating with males, and this may compromise their reproductive ability. Here, we test this hypothesis in chimpanzees, a species with flexible grouping patterns in which female avoidance of large subgroups has been attributed to their relatively high costs of grouping. In an >11-year study of the Kanyawara community of East African chimpanzees (Pan troglodytes schweinfurthii) in the Kibale National Park, Uganda, the availability of sexually receptive females was a key determinant of the number of males in parties. In turn, females experienced significantly lower C-peptide of insulin levels, indicative of reduced energy balance, during periods when they associated with more males. Female associates did not produce the same negative effect. C-peptide levels positively and significantly predicted female ovarian steroid production, indicating that the costs of associating with males can lead to downstream reproductive costs. Therefore, we conclude that Kanyawara chimpanzees exhibit sexual conflict over subgroup formation, with the large groupings that allow males to compete for mating opportunities inflicting energetic and reproductive costs on females. Because association with males is central to female chimpanzees’ anti-infanticide strategy, and males may confer other benefits, we propose that reproductive success in female chimpanzees hinges on a delicate balance between the costs and benefits of associating with male conspecifics. 相似文献
94.
Zoe Cook Daniel W. Franks Elva J. H. Robinson 《Behavioral ecology and sociobiology》2014,68(3):509-517
Efficient and robust transportation networks are key to the effectiveness of many natural systems. In polydomous ant colonies, which consist of two or more spatially separated but socially connected nests, resources must be transported between nests. In this study, we analyse the network structure of the inter-nest trails formed by natural polydomous ant colonies. In contrast to previous laboratory studies, the natural colonies in our study do not form minimum spanning tree networks. Instead the networks contain extra connections, suggesting that in natural colonies, robustness may be an important factor in network construction. Spatial analysis shows that nests are randomly distributed within the colony boundary and we find nests are most likely to connect to their nearest neighbours. However, the network structure is not entirely determined by spatial associations. By showing that the networks do not minimise total trail length and are not determined only by spatial associations, the results suggest that the inter-nest networks produced by ant colonies are influenced by previously unconsidered factors. We show that the transportation networks of polydomous ant colonies balance trail costs with the construction of networks that enable efficient transportation of resources. These networks therefore provide excellent examples of effective biological transport networks which may provide insight into the design and management of transportation systems. 相似文献
95.
Factors driving mortality and growth at treeline: a 30-year experiment of 92 000 conifers 总被引:1,自引:0,他引:1
Understanding the interplay between environmental factors contributing to treeline formation and how these factors influence different life stages remains a major research challenge. We used an afforestation experiment including 92 000 trees to investigate the spatial and temporal dynamics of tree mortality and growth at treeline in the Swiss Alps. Seedlings of three high-elevation conifer species (Larix decidua, Pinus mugo ssp. uncinata, and Pinus cembra) were systematically planted along an altitudinal gradient at and above the current treeline (2075 to 2230 m above sea level [a.s.l.]) in 1975 and closely monitored during the following 30 years. We used decision-tree models and generalized additive models to identify patterns in mortality and growth along gradients in elevation, snow duration, wind speed, and solar radiation, and to quantify interactions between the different variables. For all three species, snowmelt date was always the most important environmental factor influencing mortality, and elevation was always the most important factor for growth over the entire period studied. Individuals of all species survived at the highest point of the afforestation for more than 30 years, although mortality was greater above 2160 m a.s.l., 50-100 m above the current treeline. Optimal conditions for height growth differed from those for survival in all three species: early snowmelt (ca. day of year 125-140 [where day 1 is 1 January]) yielded lowest mortality rates, but relatively later snowmelt (ca. day 145-150) yielded highest growth rates. Although snowmelt and elevation were important throughout all life stages of the trees, the importance of radiation decreased over time and that of wind speed increased. Our findings provide experimental evidence that tree survival and height growth require different environmental conditions and that even small changes in the duration of snow cover, in addition to changes in temperature, can strongly impact tree survival and growth patterns at treeline. Further, our results show that the relative importance of different environmental variables for tree seedlings changes during the juvenile phase as they grow taller. 相似文献
96.
Leites LP Robinson AP Rehfeldt GE Marshall JD Crookston NL 《Ecological applications》2012,22(1):154-165
Projected climate change will affect existing forests, as substantial changes are predicted to occur during their life spans. Species that have ample intraspecific genetic differentiation, such as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), are expected to display population-specific growth responses to climate change. Using a mixed-effects modeling approach, we describe three-year height (HT) growth response to changes in climate of interior Douglas-fir populations. We incorporate climate information at the population level, yielding a model that is specific to both species and population. We use data from provenance tests from previous studies that comprised 236 populations from Idaho, Montana, and eastern Washington, USA. The most sensitive indicator of climate was the mean temperature of the coldest month. Population maximum HT and HT growth response to changes in climate were dependent on seed source climate. All populations had optimum HT growth when transferred to climates with warmer winters; those originating in sites with the warmest winters were taller across sites and had highest HT growth at transfer distances closest to zero; those from colder climates were shortest and had optimum HT growth when transferred the farthest. Although this differential response damped the height growth differences among populations, cold-climate populations still achieved their maximum growth at lower temperatures than warm-climate populations. The results highlight the relevance of understanding climate change impacts at the population level, particularly in a species with ample genetic variation among populations. 相似文献
97.
Emma Nelson Christy L. Hoffman Melissa S. Gerald Susanne Shultz 《Behavioral ecology and sociobiology》2010,64(6):1001-1009
Female rhesus macaques exhibit matrilineal dominance structures, and high dominance rank confers fitness benefits across a
lifetime and across generations. Rank effects are “inherited” through social processes that are well understood; however,
biological mechanisms that might impact these processes are not well known. Recently, it has been shown that prenatal androgens
appear to be implicated in supporting dominance rank hierarchies in some mammals. In humans, interindividual differences in
the second (index) to fourth (ring) digit ratio (2D:4D) have been linked indirectly to variation in prenatal androgens, with
low 2D:4D in both sexes associated with higher inferred prenatal androgen effects. 2D:4D has also been related to dominant
social behavior and has been shown to co-vary with social systems across nonhuman primate species. Here, we investigate how
2D:4D co-varies with socially inherited dominance rank in female rhesus macaques. Low 2D:4D was associated with higher-ranking
females, while higher 2D:4D was associated with lower-ranking females. Similar relationships were also shown between ranked
families within matrilines. This is the first study to show such a relationship between 2D:4D and dominance rank in a nonhuman
primate and suggests that prenatal androgen effects could be involved in the maintenance of dominance rank in female cercopithecine
primates. 相似文献
98.
Investigations into the nature of mate choice suggest that variation in female mate preferences is often context dependent,
varying in response to genetic and environmental influences on female condition as well as to external environmental stimuli.
Determining whether variation in female mate preference is adaptive requires understanding the variables involved that produce
this variation and how they interact. Comparative, multivariate studies of wild-caught adult females can be used as initial
assessments of variation in female mate preferences, providing valuable insights into the parameters that influence female
preferences under natural conditions. We examined variation in female preferences for the pigment pattern vertical bars across
five populations of the swordtail, Xiphophorus cortezi. The populations we examined are genetically differentiated and varied in the frequency of males and females with bars. We
also considered a variable indicative of within-individual variation (size, as influenced by age) and a variable that varies
across individuals (genotype for vertical bars: barred or barless). Using Akaike information criterion, all candidate models
explaining variation in strength of preference included female bar state, female size, and population. We suggest that a combination
of genetic (bar state) and environmental (female size) conditions influenced how they responded to experience with both male
phenotypes in X. cortezi. Future studies should examine the possibility that barred and barless females respond differently over an environmental
gradient. 相似文献
99.
Melissa Jacobs Jacobus Pienaar 《International journal of occupational safety and ergonomics》2013,19(2):152-161
The primary objective of this study was to investigate the relationship of work stress, consisting of role stressors and job insecurity, with safety compliance at work. A secondary objective was to test for the possible moderating effect of individual employees’ coping behaviour between experienced work stress and job insecurity, and their safety compliance. A cross-sectional survey design was used (n?=?771). An electronic survey, with a biographical questionnaire and scales on role conflict, role ambiguity, role overload, job insecurity, coping and safety compliance at work, was administered. The results indicated that specific aspects of work stress, notably role conflict, role ambiguity and quantitative job insecurity, and of coping, namely an avoidance style and changing the situation, were important in understanding safety compliance. A moderating effect of avoidance coping was also found. 相似文献
100.
A bacterium classified as Achromobacter xylosoxidans strain IR08 by phenotypic typing coupled with 16S rRNA gene analysis was isolated from a soil contaminated with electrical transformer ?uid for over sixty years using Aroclor 1221 as an enrichment substrate. The substrate utilization profiles revealed that IR08 could grow on all three monochlorobiphenyls (CBs), 2,4'- and 4,4'-dichlorobiphenyl as well as 2-chlorobenzoate (2-CBA), 3-CBA, 4-CBA, and 2,3-dichlorobenzoate. Unusually, growth was poorly sustaine... 相似文献