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1.
An increasing number of marine mammal studies on physiology, behaviour and ecology rely on data, which have been collected from back-mounted devices, such as bio-logging tags and satellite transmitters. However, external devices may influence an animal’s hydrodynamics, behaviour and energy expenditure and, therefore, can impede the individual animal. To investigate the influence of external devices on seals, the water flow along a grey seal was simulated using computational fluid dynamics calculations. The simulations revealed several changes in forces and moments and thus balance, due to this device. The investigated satellite transmitter creates an average 12% increase of the drag coefficient. Additionally, there are significant relative transmitter-induced increases in pitching moment (32%) and lift (240%). The simulations also showed that the transmitter generates areas of decreased wall shear stress on the seal’s back. The results of this study demonstrate that external devices can change the hydrodynamics of the seal, which is expected to alter the seal’s physiology and behaviour and its use of the ecosystem. Long-term attachment may have adverse effects on the animal’s welfare. It is important to take these effects into consideration when studying tagged seals; otherwise, the value of the data obtained will be poor. Therefore, interpretations and extrapolations regarding ‘natural behaviour’ of animals in their ‘natural environment’ should only be made with great caution.  相似文献   

2.
The simplest approach to quantifying animal behavior begins by identifying a list of discrete behaviors and observing the animal’s behavior at regular intervals for a specified period of time. The behavioral distribution (the fraction of observations corresponding to each behavior) is then determined. This is an incomplete characterization of behavior, and in some instances, mild injury is not reflected by statistically significant changes in the distribution even though a human observer can confidently and correctly assert that the animal is not behaving normally. In these circumstances, an examination of the sequential structure of the animal’s behavior may, however, show significant alteration. This contribution describes procedures derived from symbolic dynamics for quantifying the sequential structure of animal behavior. Normalization procedures for complexity estimates are presented, and the limitations of complexity measures are discussed.  相似文献   

3.
In the first part of this paper, we showed how life-cycle impact assessment can be described as an exercise in decision analysis. We developed a structure for how to decide on the relative importance of different environmental stressors. In this second part, we offer criteria for the grouping of stressors into impact categories and for the development of impact indicators. Facts to be included in a characterization method should be selected according to their relevance and combined following established scientific models. Facts should be included only if they are informative, that is, if sufficient and sufficiently certain information is available for all stressors that should be evaluated by this method. Abstract, constructed indicators at the ‘midpoint level’ are better suited to compare similar impacts than indicators reflecting ‘observable environmental endpoints’ if there is a large uncertainty about the effects on observable endpoints. We argue that midpoint modeling should be retained. The additional evidence introduced by endpoint methods should be used to support ‘judgments about facts’ needed to evaluate the importance of different impact categories (or means objectives) in the means-ends objectives network.  相似文献   

4.
Animals receive benefits from social behavior. As part of a group, individuals spend less time having to be vigilant. This phenomenon, called the “group size effect,” is considered the most dominant factor in an animal’s demonstrated level of vigilance. However, in addition to group size, many other social and environmental factors also influence the degree of vigilance, including the season of the year and the sex of the individual. In our study, we examined the vigilant behavior of goitered gazelles in the Xinjiang Province in western China to test whether and how seasons, the yearly breeding cycle, and group size affect vigilance. According to our results, we found that seasonal factors were not a substantial influence on a gazelle’s level of vigilance, while group size had a tangible effect. In comparison, the yearly breeding cycle (a natural phenomenon) was the most powerful factor: it significantly changed the degree of vigilance in females during birthing and males during rut. Anthropogenic factors (unnatural phenomena) were also potential causes of increased vigilance in both sexes during winter.  相似文献   

5.
Sewall Wright first encountered the complex systems characteristic of gene combinations while a graduate student at Harvard’s Bussey Institute from 1912 to 1915. In Mendelian breeding experiments, Wright observed a hierarchical dependence of the organism’s phenotype on dynamic networks of genetic interaction and organization. An animal’s physical traits, and thus its autonomy from surrounding environmental constraints, depended greatly on how genes behaved in certain combinations. Wright recognized that while genes are the material determinants of the animal phenotype, operating with great regularity, the special nature of genetic systems contributes to the animal phenotype a degree of spontaneity and novelty, creating unpredictable trait variations by virtue of gene interactions. As a result of his experimentation, as well as his keen interest in the philosophical literature of his day, Wright was inspired to see genetic systems as conscious, living organisms in their own right. Moreover, he decided that since genetic systems maintain ordered stability and cause unpredictable novelty in their organic wholes (the animal phenotype), it would be necessary for biologists to integrate techniques for studying causally ordered phenomena (experimental method) and chance phenomena (correlation method). From 1914 to 1921 Wright developed his “method of path coefficient” (or “path analysis”), a new procedure drawing from both laboratory experimentation and statistical correlation in order to analyze the relative influence of specific genetic interactions on phenotype variation. In this paper I aim to show how Wright’s philosophy for understanding complex genetic systems (panpsychic organicism) logically motivated his 1914–1921 design of path analysis.  相似文献   

6.
In an invasive species, selection for increased rates of dispersal at the expanding range front may favor the evolution of reduced investment into any trait that does not contribute to more rapid dispersal. Thus, populations at the invasion front may exhibit reduced investment into the immune system. To test this prediction, cane toads (Rhinella marina) from parents collected from populations across the toads’ invasion history in tropical Australia were raised in a standard environment. When their immune systems were challenged by injection of bacterial lipopolysaccharide, the toads’ metabolic rates rose by up to 40%. The magnitude of elevation in metabolic rate was lower in toads derived from the invasion front than in those from long-established populations. Our results support the hypothesis that an animal’s investment in immune defenses can be modified by selective forces that arise in the course of a biological invasion.  相似文献   

7.
A well preserved subadult rhino mandible from Mosbach 2 can be attributed toStephanorhinus hundsheimensis based on a metrical and morphological analysis. A comparison to tooth eruption of livingDiceros bicornis suggests an individual age for the animal of about 7 years at death. The described mandible shows a significant tooth anomaly: two teeth occupy the p3 position on each side of the mandible. Comparisons with three younger juvenileStephanorhinus hundsheimensis from Mosbach 2 show the sequence of tooth eruption for the species and allow us to determine that the anomalous teeth are not persistent milk teeth but are supernumerary teeth, which are morphologically intermediate between normal p2 and p3. The animal’s occlusion was compromised to some degree by the anomaly, and the functional disadvantage may have been critical during a harsh period.   相似文献   

8.
Declines in bird populations are an important issue facing conservationists. Although studies have documented bird declines in a variety of lowland habitats, montane habitats are generally under represented in these investigations. Nevertheless, montane habitats are vulnerable because of their restricted geographic distribution as well as their exposure to environmental stressors such as atmospheric deposition and climate change. We surveyed birds at 768 points on 42 transects in montane spruce-fir forests the White Mountains of New Hampshire from 1993–2003. We detected 17,479 individuals of 73 species during this period, of which 10 were abundant enough for analyses. Of these 10 species, three exhibited significant population declines during the survey period: Yellow-bellied Flycatcher (Empidonax flaviventris), Bicknell’s Thrush (Catharus bicknelli) and Magnolia Warbler (Dendroica magnolia). Two of these species (Yellow-bellied Flycatcher and Bicknell’s Thrush) are considered ecological indicator species for montane spruce-fir forest. Declines in these species are an indication that recent concern on the part of conservationists about montane spruce-fir forest and the birds that inhabit them are justified. Our observation that these trends were not reflected in the National Breeding Bird Survey (BBS) analyses, and that one high priority species, the Bicknell’s Thrush, did not occur on BBS routes in New Hampshire during the survey period, argues for the importance of continued efforts to monitor these habitats.  相似文献   

9.
Weakly electric fish orient at night by employing active electrolocation. South American and African species emit electric signals and perceive the consequences of these emissions with epidermal electroreceptors. Objects are detected by analyzing the electric images which they project onto the animal’s electroreceptive skin surface. Electric images depend on size, distance, shape, and material of objects and on the morphology of the electric organ and the fish’s body. It is proposed that the mormyrid Gnathonemus petersii possesses two electroreceptive “foveae” at its Schnauzenorgan and its nasal region, both of which resemble the visual fovea in the retina of many animals in design, function, and behavioral use. Behavioral experiments have shown that G. petersii can determine the resistive and capacitive components of an object’s complex impedance in order to identify prey items during foraging. In addition, fish can measure the distance and three-dimensional shape of objects. In order to determine object properties during active electrolocation, the fish have to determine at least four parameters of the local signal within an object’s electric image: peak amplitude, maximal slope, image width, and waveform distortions. A crucial parameter is the object distance, which is essential for unambiguous evaluation of object properties.  相似文献   

10.
Although robust sex differences are abundant in men and women’s mating psychology, there is a considerable degree of overlap between the two as well. In an effort to understand where and when this overlap exists, the current study provides an exploration of within-sex variation in women’s mate preferences. We hypothesized that women’s intelligence, given an environment where women can use that intelligence to attain educational and career opportunities, would be: (1) positively related to their willingness to engage in short-term sexual relationships, (2) negatively related to their desire for qualities in a partner that indicated wealth and status, and (3) negatively related to their endorsement of traditional gender roles in romantic relationships. These predictions were supported. Results suggest that intelligence may be one important individual difference influencing women’s mate preferences.  相似文献   

11.
Sagers CL  Goggin FL 《Oecologia》2007,151(3):464-472
The isotopic enrichment between an animal and its diet can vary among and within living systems, but the sources of variation are not yet fully understood. Some studies have found that diet quality or an animal’s nutritional status can influence the degree of trophic enrichment, while others have dismissed nutrition as a contributing factor. We evaluated the effects of nutrient and water availability on carbon and nitrogen isotopic enrichment in a specialized plant–herbivore system. Aphids are largely sedentary and rely exclusively on nitrogen-poor phloem sap of their host for nutrition. We grew potato aphids [Macrosiphum euphorbiae (Aphididae)] on an accepted host, pumpkin [Cucurbita pepo L. (Cucurbitaceae)], in a glasshouse environment. Twelve pumpkin plants growing under high- and low-watering regimes were inoculated at 4 weeks of age with aphids. During the course of the experiment we collected leaves, phloem sap, aphids and honeydew (i.e., aphid exudates). We found no trophic enrichment between aphids and their phloem sap diet, but significant carbon enrichment of honeydew relative to aphids (2.5‰) and phloem sap (2.1‰). Honeydew was also enriched in nitrogen compared to the phloem sap (1.2‰). Watering treatment had a substantial impact on trophic enrichment. Correlations among tissues, an indication of uniform trophic enrichment among samples, were significant only for the carbon isotopic composition, and then only for plants and aphids grown in the low-water treatment. Diet quality also influenced the degree of isotopic enrichment; trophic enrichment for both carbon and nitrogen isotopic composition increased as diet quality (C/N) declined. We conclude that the degree of trophic enrichment is variable due, in part, to diet quality, but that the scale of variation is small.  相似文献   

12.
We hypothesize that black women experience accelerated biological aging in response to repeated or prolonged adaptation to subjective and objective stressors. Drawing on stress physiology and ethnographic, social science, and public health literature, we lay out the rationale for this hypothesis. We also perform a first population-based test of its plausibility, focusing on telomere length, a biomeasure of aging that may be shortened by stressors. Analyzing data from the Study of Women’s Health Across the Nation (SWAN), we estimate that at ages 49–55, black women are 7.5 years biologically “older” than white women. Indicators of perceived stress and poverty account for 27% of this difference. Data limitations preclude assessing objective stressors and also result in imprecise estimates, limiting our ability to draw firm inferences. Further investigation of black-white differences in telomere length using large-population-based samples of broad age range and with detailed measures of environmental stressors is merited.  相似文献   

13.
Acclimation is possibly the most important criterion deciding an animal’s ability to survive change. Species with poor abilities to acclimate to small environmental change are likely to be the most vulnerable in future warming scenarios. Two separate assemblages of Ophionotus victoriae were slowly acclimated from 0°C to either +2 or +3°C and then held at these higher temperatures over a prolonged timescale. None of the animals were able to acclimate; with failure occurring from day 19 at +3°C and day 24 at +2°C, indicating that this species is very sensitive to small long-term seawater temperature increases. These data indicate that O. victoriae has probably the poorest ability to acclimate to elevated temperatures of any species studied to date. Given previous data showing some Antarctic fish can acclimate to +4°C, the predicted effects of increased seawater temperatures on the Antarctic food web and ecology must be assessed at the individual species level and interpreted with care.  相似文献   

14.
Muscular hydrostats, such as tongues, trunks or tentacles, have fewer constraints on their degrees of freedom than musculoskeletal systems, so changes in a structure’s shape may alter the positions and lengths of other components (i.e., induce mechanical reconfiguration). We studied mechanical reconfiguration during rejection and swallowing in the marine mollusk Aplysia californica. During rejection, inedible material is pushed out of an animal’s buccal cavity. The grasper (radula/odontophore) closes on inedible material, and then a posterior muscle, I2, pushes the grasper toward the jaws (protracts it). After the material is released, an anterior muscle complex (the I1/I3/jaw complex) pushes the grasper toward the esophagus (retracts it). During swallowing, the grasper is protracted open, and then retracts closed, pulling in food. Grasper closure changes its shape. Magnetic resonance images show that grasper closure lengthens I2. A kinetic model quantified the changes in the ability of I2 and I1/I3 to exert force as grasper shape changed. Grasper closure increases I2’s ability to protract during rejection, and increases I1/I3’s ability to retract during swallowing. Motor neurons controlling radular closure may therefore affect the behavioral outputs of I2’s and I1/I3’s motor neurons. Thus, motor neurons may modulate the outputs of other motor neurons through mechanical reconfiguration.Valerie A. Novakovic and Gregory P. Sutton contributed equally to the paper.  相似文献   

15.
By expanding on issues raised by D’Eath (1998), I address in this article three aspects of vision that are difficult to reproduce in the video- and computer-generated images used in experiments, in which images of conspecifics or of predators are replayed to animals. The lack of depth cues derived from binocular stereopsis, from accommodation, and from motion parallax may be one of the reasons why animals do not respond to video displays in the same way as they do to real conspecifics or to predators. Part of the problem is the difficulty of reproducing the closed-loop nature of natural vision in video playback experiments. Every movement an animal makes has consequences for the pattern of stimulation on its retina and this ”optic flow” in turn carries information about both the animal’s own movement and about the three-dimensional structure of the environment. A further critical issue is the behavioural context that often determines what animals attend to but that may be difficult to induce or reproduce in an experimental setting. I illustrate this point by describing some visual behaviours in fiddler crabs, in which social and spatial context define which part of the visual field a crab attends to and which visual information is used to guide behaviour. I finally mention some aspects of natural illumination that may influence how animals perceive an object or a scene: shadows, specular reflections, and polarisation reflections. Received: 23 November 1999 / Received in revised form: 9 February 2000 / Accepted: 10 February 2000  相似文献   

16.
Background  Small and medium sized enterprises in developed regions, as well as larger ‘Southern’ firms are more exposed to risk in regards to allocation decisions. This includes expenditures on fixed assets, R&D and environmental management, as well as the choice of suitable markets for the product or service at hand. For either type of firm, the consequences of not selecting, or timing, suitable markets can lead to bankruptcy. Objectives  This paper examines means for SMEs to expand internationally given the current fiscal climate, and rapid advances in certain enabling technologies. The goal is to identify a set of criteria which smaller firms can use to globalize which reduce risk and increase access to capital. Methods  Case studies are presented of a European Start-Up as well as a century-old Latin American firm, both in the water-treatment sector. The similarities in the risk-reward profiles are used to identify some key strategic guidelines for enterprises wishing to be, selectively, multinational. Results and Discussion  Selective multinationality is an immediate plan for international expansion which identifies the most appropriate markets, independent of their proximity to the firm’s production base or headquarters. At the base of selective multinationality, is the goal to impose the firm’s product in regions of high growth, high selling price and low risk of price dumping. Therefore, this requires theto resist the temptation to expand to markets based on merely geographical proximity. The globalization strategy should be established, along with environmental management, from the outset of the creation of the firm. It will be shown, herein, to be a key driver in the valuation of High Tech industrial SMEs, in particular those with high risk-high reward tradeoffs. Selective multinationality can best be implemented if the firm in question has a technology which addresses unmet needs in niche markets, where there is an expanding customer base focusing on client relationships and cost effectiveness, and where the multinationals enter from outside the sector via resellers. It will be demonstrated to be effective for startups from developed regions, as well as SMEs from developing/emerging countries, to both of whom the consequences of sub-optimal resource allocation can risk the future of the firm itself. Therefore, SMEs can, with appropriate planning and the integration of marketing and environmental strategies, become, selectively, global firms, with better credit access and sales growth, concomitant with lower risks. The High Tech industrial SME will succeed better if, from the outset, they behave like the organization they want to become, with globalization a key element of strategy, from the business plan foreword. Two case studies are presented, one documenting the water sector and die other the cost savings possible by integrating environmental management into die firm’s strategy.  相似文献   

17.
Evolutionary change results from selection acting on genetic variation. For migration to be successful, many different aspects of an animal’s physiology and behaviour need to function in a co-coordinated way. Changes in one migratory trait are therefore likely to be accompanied by changes in other migratory and life-history traits. At present, we have some knowledge of the pressures that operate at the various stages of migration, but we know very little about the extent of genetic variation in various aspects of the migratory syndrome. As a consequence, our ability to predict which species is capable of what kind of evolutionary change, and at which rate, is limited. Here, we review how our evolutionary understanding of migration may benefit from taking a quantitative-genetic approach and present a framework for studying the causes of phenotypic variation. We review past research, that has mainly studied single migratory traits in captive birds, and discuss how this work could be extended to study genetic variation in the wild and to account for genetic correlations and correlated selection. In the future, reaction-norm approaches may become very important, as they allow the study of genetic and environmental effects on phenotypic expression within a single framework, as well as of their interactions. We advocate making more use of repeated measurements on single individuals to study the causes of among-individual variation in the wild, as they are easier to obtain than data on relatives and can provide valuable information for identifying and selecting traits. This approach will be particularly informative if it involves systematic testing of individuals under different environmental conditions. We propose extending this research agenda by using optimality models to predict levels of variation and covariation among traits and constraints. This may help us to select traits in which we might expect genetic variation, and to identify the most informative environmental axes. We also recommend an expansion of the passerine model, as this model does not apply to birds, like geese, where cultural transmission of spatio-temporal information is an important determinant of migration patterns and their variation.  相似文献   

18.
We analyzed the environmental determinants of the regional distribution of Bonelli’s eagle (Aquila fasciata) in Spain (ca. 500,000 km2), taking into account its frequency of occurrence on UTM blocks of 50 × 50 km. We found that the distribution pattern of Bonelli’s eagle was a highly predictable phenomenon based on climate, vegetation and interspecific relationships. The proportion of sunny, anticyclonic days, per year (i.e., high levels of solar radiation) was the main environmental predictor explaining the distribution and abundance pattern of the Bonelli’s eagle. Sparse plant formations (mainly shrublands) had also a positive effect, while altitude, agricultural land and deciduous forests had a negative influence. The relative abundance of one of its main preys, the Red Partridge (Alectoris rufa), favored the probability of occurrence of Bonelli’s eagle, but only in the less sunny areas located in the north of Spain. The relative abundance of its main competitor, the Golden eagle (Aquila chrysaetos), was slightly but positively correlated with both the distribution and the abundance of the Bonelli’s eagle in the Spanish portion of the Iberian Peninsula, probably due to similarities in their habitat preferences. Finally, we did not find further regional effects of the variables describing the degree of human pressure (density of roads, urban cover, and length of power lines).  相似文献   

19.
Our objective was to determine whether an animal’s decisions to cross inhospitable open space are influenced by the visual characteristics of targets it can see across the space. We studied jumping spiders (Salticidae) in the genus Phidippus. We considered the effect of target size (short vs. tall) and distance (close vs. distant) in no-choice experiments. How often spiders approached close targets, regardless of target size, was not significantly different from how often they approached tall, distant targets, but they approached close targets of either size significantly more often than short, distant targets. When presented simultaneously with short, close and tall, distant targets the spiders’ choices did not differ significantly from random. We also tested for the effects of the contrast of targets with their background and found that the spiders crossed open space to reach green, but not white, targets, regardless of background. Finally, spiders were more likely to approach a green grass-like target rather than a target composed of geometric shapes. We conclude that target size, distance and appearance all influence the spiders’ willingness to cross open space.  相似文献   

20.
Garnering support from local people is critical for maintaining ecologically viable and functional protected areas. However, empirical data illustrating local people’s awareness of the importance of nature’s services is limited; hence possibly impeding effective ecosystem (environmental)-services based conservation efforts. Using data from five protected forests in four developing Southeast Asian countries, we provide evidence that local people living near parks value a wide range of environmental services, including cultural, provisioning, and regulating services, provided by the forests. Local people with longer residency valued environmental services more. Educated as well as poor people valued forest ecosystem services more. Conservation education has some influence on people’s environmental awareness. For conservation endeavors to be successful, large-scale transmigration programs should be avoided and local people must be provided with alternative sustenance opportunities and basic education in addition to environmental outreach to reduce their reliance on protected forests and to enhance conservation support.  相似文献   

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