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Ecological systems per se do not evolve; their constituent species’ populations evolve. The effects of evolution upon the dynamics of predatory systems must, therefore, be sought in the selective forces operating separately upon the predator and prey. Books have been written about little else but evolutionary adaptations for and against predation. Protective morphology, coloration and behavior provide a substantial fraction of the stories with which ecologists regularly amaze one another. Much of the systematic work on predators employs teeth, jaws, raptorial appendages, and other adaptations for pursuit and capture.

Ultrasonics has been investigated as an alternative to biocides such as chlorine for inhibiting the growth of the colonial hydroid, Garveia franciscana in the precondenser intake structures of power plants. This hydroid is a particular problem at power plants that use salt water for cooling because it grows rapidly and forms dense matts that can severely restrict the flow of cooling water. Using free-field ultrasonic radiation, acoustic parameters were sought that would yield the most energy-efficient method of causing tentacle contraction of the hydranths, thus inhibiting feeding and/or growth. At all frequencies tested, the sound intensity threshold that caused tentacle contraction coincided with the sonic degasification threshold.

High voltage, short duration capacitive discharge measurements of human body impedance have been accomplished for different paths through the body. Skin contact impedance and internal body impedance between various locations on the body were examined. Impedance measurement instrumentation capable of measuring impedance once every 0.05 μs was used. Voltages of 100 to 2000 V were applied giving peak currents of 0.2 to 5.0 A. The voltage and current waveforms had time constants ranging from 0.2 to 5.0 μs. These short time constants are consistent with safety requirements, allowing testing with people. However, these impedance measurements can be interpreted as limiting values for shocks of longer, possibly lethal duration. The initial total body impedance between the palm of the hand and the sole of the foot was found to be about 500 to 530 Ω. The internal body impedance for the same current path was found to be about 430 Ω. The internal body impedance between the wrist and the calf was found to be about 50% of the internal body impedance measured between the palm and the sole of the foot.

The fundamental question to which ecologists have addressed themselves since the origin of interest in predation is what functional role predators play in the community. Are predators important to prey populations or are they not? Since these are somewhat vague concerns, the earlier workers sought to pin the topic down by asking more specific questions, the most common of which was: do predators control their prey?

For the sake of convenience we commonly treat populations as though they were homogeneous units, comprised of genetically identical, even-aged organisms having indistinguishable developmental histories. Since such a practice is, with few exceptions, an offense against nature, we ought to devote attention to the effects of relaxing this assumption. The influence of genetic variation upon the predatory process is taken up in Chapter 11. Here I address the effects of variation in age and size in both predator and prey populations.

The major purpose of this book has been to explore what happens when the boundaries of one’s ecological system are expanded from consideration of only a single species to include both a predator and its prey. The lesson I have tried to communicate is that the class of potential population behaviors is so enlarged by such a broadening of perspective that the traditional concepts of single-species dynamics no longer provide a reliable theoretical guide. The question now remaining is what happens when the bounds of the system are drawn even more broadly?

Several decades ago, Solomon (1949) chose to approach the question of predation’s role in population dynamics by partitioning the response of predators to changing prey numbers into a numerical change in predator density and a functional change in the rate of predation per individual predator. In other words, predators can respond to an increase in numbers of prey both by increasing their own numbers and by eating more per predator. In the context of the basic theory used in this book, Equations (2.7) and (2.8), the numerical response is the Equation (2.8), and the functional response is the function f(H). This chapter will discussf(H), the factors that determine its shape, and its implications for population dynamics.

Free-field ultrasonic radiation inhibited the feeding of the macrofouling hydroid Garveia franciscana by causing tentacle contraction at the sonic degasification threshold. Within the frequency range of 250 to 2000 kilohertz, the threshold sound intensity (sonic degasification threshold) that caused tentacle contraction was directly proportional to frequency, with the minimum observed being 0.6 watt per square centimeter at 250 kilohertz. A pulse length of 0.2 second and interpulse period of 102 seconds gave the lowest average power required to produce tentacle contraction at a peak pulse sound intensity of 6.2 watts per square centimeter with a frequency of 250 kilohertz. Twenty-four hour exposures to the sound regime caused destruction of the hydranths and regression of tissue in the stolons.

Plasma currents have been generated by injecting microwaves at the electron cyclotron resonance frequencies to the Continuous Current Tokamak in the absence of any other power input. The radial profiles of plasma current and particle densities show that the current is driven by the radial flow of electrons acted upon by the self‐consistent vertical magnetic fields in a way a dynamo acts. Also the energy spectrum of the current carrying electrons shows that the current is carried by the bulk of the plasma electrons and no superthermal electron contribution was detected.

Chapter 7 dealt in part with a class of predator-prey systems in which spatial structure provided a degree of stability, as a consequence of relatively limited movements by a voracious predator. The dispersal of prey from untouched populations to empty habitats counteracted the unhesitating devastation by a predator of its local prey base. But this result must apply only to those spatially-structured systems in which the dispersal abilities of the protagonist species are delicately balanced. Too mobile a predator and the prey lose their necessary sanctuaries; too mobile a prey and the spatial structure evaporates as the predator loses any reason for abandoning an area.

Etude menee dans des pâturages des hauts-plateaux de la Nouvelle-Angleterre, Nouvelle-Galles du Sud (Australie). Il existe chez Macropus giganteus et Macropus robustus robustus dont l'aire de repartition se chevauche largement des differences dans le choix de l'habitat, selon que l'animal se repose ou qu'il pâture. La repartition des deux especes a differe egalement en fonction de la qualite et de la composition du pâturage

The report provides a practical up-to-date guide that enables the practicing engineer to select and size common anchor types, including direct- embedment anchors, deadweight anchors, drag-embedment anchors, and pile anchors. For each anchor type, the report includes site survey recommendations, a brief description of various anchors within each anchor category, methods for determining anchor performance, and, in certain cases, suggestions for improving poor anchor behavior. Sources for additional information are suggested where the treatment of a broad topic is necessarily limited.

Southern grasshopper mice (Onychomys torridus) were allowed to junt buried mealworms in a laboratory arena. The prey were arranged in two patterns, one aggregated and one relatively dispersed. Mice captured more prey from the dispersed treatment in the 2 h experiment, a result that can be attributed to both the greater ease of finding the first prey and a more efficient style of search for dispersed prey.

ABSTRACT A propellant-actuated direct embedment anchor is being developed to moor deep ocean surface and subsurface structures. The anchor is designed to have a long-term holding capacity of 20,000 lb. and function in sea floors ranging from very soft sediments to hard rock (basalt) in water depths from 100 ft to 20,000 ft. Anchor flukes were designed for sediments and rock. The sediment fluke uses a new quick keying design to maximize efficiency. A launching system utilizing existing ammunition components was developed that was capable of providing the energy necessary to propel the flukes to the required penetration depths. The anchor has been fabricated and tested on land and in water at 110 ft. The anchors functioned properly during the water firings; short-term capacities in silt using reduced propellant charges were about 45,000 lb. Continued testing under a variety of conditions is planned. INTRODUCTION Deep ocean anchorage has long been a neglected area of development. Anchoring requirements for sophisticated structures, weather buoys, surface and subsurface instrument arrays, and any number of other constructions must be satisfied by conventional drag or deadweight anchors, anchors ill-suited to the demands imposed on them in the deep ocean. To help alleviate this problem, the Naval Facilities Engineering Command is sponsoring a program being conducted by the Naval Civil Engineering Laboratory to develop practical direct embedment anchors that are both reliable and efficient for use in mooring deep ocean surface or subsurface structures. Operational requirements for the anchor are that it be functional in water depths to 20,000 ft, have a long-term holding capacity of 20,000 Ib and develop this capacity in sea floors from soft clay to hard rock. To date, a propellant-actuated anchor has been designed, fabricated and tested on land and in water at 110 ft. During its first in water tests, the anchor functioned properly and held short-term loads of about 45,000 Ib in silt, using reduced propellant charges. Also, the anchor demonstrated that it could be safely and quickly assembled and deployed at sea. BACKGROUND Present deep-water installation techniques require continuous at-sea operation through a long time period. Therefore, the installation process is vulnerable to inclement weather. It would be advantageous if improved hardware and procedures were available to ease and speed installation. The solution to this problem, however, encompasses a broad spectrum of considerations. Anchor designs, special appurtenances, connective gear, and special operational techniques are among the more critical areas that need improvement. The single most important consideration is the anchor design because improved anchors can alleviate problems in the other areas. Based upon the operational requirements established in the program objectives, the state-of-the-art and the available time frame, it appeared that this critical mooring problem could be most easily solved through development of a propellant-actuated direct embedment anchor.

Background Influenza is rarely confirmed with laboratory testing and accurate assessment of the overall burden of influenza is difficult. We used statistical modelling methods to generate updated, granular estimates of the number/rate of influenza-attributable hospitalisations and deaths in the United Kingdom. Such data are needed on a continuing basis to inform on cost-benefit analyses of treatment interventions, including vaccination. Methods Weekly age specific data on hospital admissions (1997–2009) and on deaths (1997–2009) were obtained from national databases. Virology reports (1996–2009) of influenza and respiratory syncytial virus detections were provided by Public Health England. We used an expanded set of ICD-codes to estimate the burden of illness attributable to influenza which we refer to as ‘respiratory disease broadly defined’. These codes were chosen to optimise the balance between sensitivity and specificity. A multiple linear regression model controlled for respiratory syncytial virus circulation, with stratification by age and the presence of comorbid risk status (conditions associated with severe influenza outcomes). Results In the United Kingdom there were 28,516 hospitalisations and 7163 deaths estimated to be attributable to influenza respiratory disease in a mean season, with marked variability between seasons. The highest incidence rates of influenza-attributable hospitalisations and deaths were observed in adults aged 75+ years (252/100,000 and 131/100,000 population, respectively). Influenza B hospitalisations were highest among 5–17 year olds (12/100,000 population). Of all estimated influenza respiratory deaths in 75+ year olds, 50 % occurred out of hospital, and 25 % in 50–64 year olds. Rates of hospitalisations and death due to influenza-attributable respiratory disease were increased in adults identified as at-risk. Conclusions Our study points to a substantial but highly variable seasonal influenza burden in all age groups, particularly affecting 75+ year olds. Effective influenza prevention or early intervention with anti-viral treatment in this age group may substantially impact the disease burden and associated healthcare costs. The high burden of influenza B hospitalisation among 5–17 year olds supports current United Kingdom vaccine policy to extend quadrivalent seasonal influenza vaccination to this age group. Trial registration ClinicalTrial.gov, NCT01520935 Electronic supplementary material The online version of this article (doi:10.1186/s12889-016-3128-4) contains supplementary material, which is available to authorized users.

We describe broadly applicable principles for the conservation of wild living resources and mechanisms for their implementation. These principles were engendered from three starting points. First, a set of principles for the conservation of wild living resources (Holt and Talbot 1978) required reexamination and updating. Second, those principles lacked mechanisms for implementation and consequently were not as effective as they might have been. Third, all conservation problems have scientific, economic, and social aspects, and although the mix may vary from problem to problem, all three aspects must be included in problem solving. We illustrate the derivation of, and amplify the meaning of, the principles, and discuss mechanisms for their implementation. The principles are: Principle I. Maintenance of healthy populations of wild living resources in perpetuity is inconsistent with unlimited growth of human consumption of and demand for those resources. Principle II. The goal of conservation should be to se...

A comparison of the dynamics of pairs of adjacent moose (Alces alces) populations, one lightly harvested by controlled hunts and the other heavily harvested by open hunts, was conducted in 3 areas in southwestern Quebec. Computer simulations were used to evaluate effects of different hunting regimes on populations, and to generate management predictions. The model assumed that predation was the major mortality factor in the absence of hunting, and that natural mortality was density dependent. The model gave acceptable predictions. Results revealed that density was inversely related to hunting pressure. Field data suggested that unbalanced sex ratios diminished productivity; when this relationship was included in simulations, it appeared to predict observed differences. To optimize moose harvest in southwestern Quebec, we recommend retaining at least 40% males among adults, increasing calf cropping, and limiting hunting to the level of maximum sustained yield. J. WILDL. MANAGE. 45(3):598-611 Computer models for simulating responses of wildlife populations to harvest schemes are being used with increasing frequency. Workers seldom lack ingenuity for simulating population mechanisms; a major limitation, however, arises in applying existing data to calibrate and test these mechanisms. Without a basic understanding of population responses, quantitative predictions having the accuracy required by managers cannot be made. The study reported here, involving 2 levels of hunting pressure on moose, appears to demonstrate that simulated relationships based on data can provide a reasonable basis for management predictions. Moose management in North America has been strongly influenced by the concepts of net and gross productivity (Pimlott 1959), but these do not account for variations in density or nonhunting mortality as functions of hunting impact (Caughley 1974). Caughley (1976) preented a model for ungulates that was based on optimum yield, as was the more general model of Clark (1976); we have applied this approach to moose. In Quebec, the number of moose hunters increased from 43,000 to 98,000 between 1964 and 1977, while the legal take remained relatively stable at 8,000 moose, resulting in declining hunter success (Bouchard and Gauthier 1978). It was essential to determine whether the decline was due to a declining moose population, an inability of new hunters to find suitable hunting sites, or increasing wariness of moose. We designed a study to document effects of different hunting pressures on moose populations, and constructed models to incorporate field data for predicting an optimum-yield management strategy. We thank D. St.-Hilaire, who was in charge of the aerial surveys for most of the project, and J. Boivin, L. Breton, G. Michaud, D. Pare, R. Pariseau, and M. Poulin, who participated in the surveys. We appreciate the skill of pilots B. BenI Present address: Department of Zoology, Clemson University, Clemson, SC 29631. 598 J. Wildl. Manage. 45(3):1981 This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 05:39:53 UTC All use subject to http://about.jstor.org/terms MOOSE HARVEST IN QUEBEC* Crete et al. 599 bridge, P. Langlois, J.-G. Lejeune, F. Lemieux, Z. Lemieux, C. Richard, and B. Samson and mechanics P. Saint-George and T. To. The computer center of the University of Minnesota provided computer time for simulations.

A mechanical model of island colonization is developed which takes explicit notice of the geometry of the potential source populations on the mainland. The model treats both active and passive dispersers colonizing islands off peninsulas, along straightline shores, and within lakes. The primary conclusion is that distance offshore is an inadequate descriptor of colonization rate. Colonization rate can decline rapidly with distance offshore; it can decline only slowly; in some cases it can even increase.

Etude quantitative de l'approvisionnement de Macropus giganteus et de M. robustus dans divers habitats en deux sites differant par la qualite de l'herbe. La quantite consommee dans un habitat est correlee positivement a l'abondance de la categorie d'aliment prefere (feuilles de graminees riches en proteines). Les deux especes different dans leur utilisation de quelques graminees de haute qualite

The effects of manganese nodules on concentration fields in adjacent pore waters and sediments are investigated theoretically with a three-dimensional (axisymmetric) diffusion-reaction model. The nodules are idealized as impermeable and poorly permeable disks and hemispheres. The first part of this paper examines the organic matter and coupled pore water oxygen fields in order to evaluate the local redox conditions under an isolated nodule. Oxygen is allowed to disappear on a free surface that is calculated as an output of the model. In sediments that become suboxic, like those at MANOP site C, the model predicts that pore waters neighboring a nodule are markedly more depleted in oxygen than in its absence. Although these reduced conditions may remobilize metals that would be available for nodule growth, these same conditions would appear to favor nodule dissolution. Typically, the presence of a nodule raises the local position of the zero-oxygen surface, but it is deeper than expected for large nodules on sediments containing only highly reactive organic matter. The redox changes calculated for an isolated nodule on a hypothetical, but representative, oxidized abyssal red clay appear inadequate to raise the redox boundaries enough to facilitate metal transport from reduced regions deeper in the sediment. In the later part of the paper the model is used to evaluate the influence of a nodule field on the outward flux of dissolved silica from a siliceous ooze. Although the flux attenuation is generally modest, some dense packings observed in the Pacific should produce substantial reductions (>35%), which should promote opal preservation.

The data that Hanski and Peltonen present are directly relevant to the issue of the dependence of island colonization upon the geometry of the nearby mainland. It does indeed, as they claim, seem unlikely that shrews and other active dispersers would leave the mainland at all points with equal probability. One would expect a dispersing terrestrial animal with a given compass orientation to follow the shore as long as it could manage to go approximately in the desired direction and to cross the water barrier at which point the shore turns sharply away from the chosen bearing, which is precisely the circumstance posed by a peninsula. Other shoreline anomalies, such as rivers or mountains, should have much the same effect. In fact anything which makes the cost of continued along-shore travel high should induce movement across water. The statistical analysis Hanski and Peltonen apply to their data adequately reveals the inaccuracy of the assumption that every unit of shoreline generates an equal number of dispersers, at least for such active dispersers as shrews. I take issue with some aspects of their test. If one will test qualitative predictions of mathematical theory, one must pay fairly close attention to the appropriate values of the parameters. The first prediction put to the test is that islands off straight-line shores have dramatically higher colonization rates than islands off peninsular tips. For islands in lakes, this is an appropriate prediction of the theory only if the organism's maximum dispersal distance is a small fraction of the lake's radius. Since the organisms in question are capable of dispersing 500-1000 m (Hanski 1986), this means the lake must be quite large. The second prediction to be tested is that active dispersers in lakes can show increases in colonization with increasing distance from shore. This prediction is logically valid only in the circumstance where the maximum dispersal distance is a substantial fraction of the lake's radius, and this means that the lake must be relatively small. I am not familiar with the lakes from which Hanski gathered these data, but it seems unlikely that the conditions generating these two qualitative predictions could exist simultaneously. This implies that the data can reflect negatively on one of these predictions but not on both. I suspect that the test of the distance argument is the weaker of the two. Theory serves a variety of purposes in ecology. My purpose in this case was not to generate precise predictions. Every organism and every landscape have unique attributes, and a precise model will need to include them. My intention rather was "... to raise a question. Is it enough when comparing the biotas of islands and testing various theories explaining their diversities, to consider distance offshore as an adequate measure of isolation when mainland geometries differ?" (Taylor 1987: 230) Hanski and Peltonen have confirmed my opinion that it is not.

The association of individuals of different social classes of the wallaroo was examined on two properties (Lana and Newholme) in the New England Tablelands of New South Wales. The density of wallaroos on Lana was seven times greater than that on Newholme. Individuals of different social classes differed in the extent to which they were found alone. More animals were seen alone on Newholme than on Lana but this increase was not uniform over the social classes. Individuals of different social classes did not associate at random. Association patterns differed for individuals in groups of different size. No differences in habitat use were found between different social classes during grazing periods; however, during sheltering periods a greater proportion of large adult males was found in areas with many rocks compared with medium adult males or adult females with young-at-foot. The adaptive significance of the pattern of association of social classes is discussed.