Predatory Strategies Research Articles

Predatory Search Strategy for Load Distribution of Multiple Chiller Water Units for the Purpose of Energy Saving

In this paper, two chiller water units connected in parallel working using the predatory search strategy was observed. Predatory search strategy has been applied to solve the optimal load distribution strategy problem for the cooling system constituted by multiple chiller water units, which has the characteristic such as complexity, constraint, nonlinearity, modeling difficulty, etc. Compared with the conventional method,the results indicated that the predatory search strategy algorithms has much less power consumption and is very suitable for application in air condition system operation.

Foraging movements of Audouin’s gull ( Larus audouinii) in the Ebro Delta, NW Mediterranean: A preliminary satellite-tracking study

A knowledge of the foraging strategies of marine predators is essential to understand the intrinsic factors controlling their distribution, abundance and their ecological function within the marine ecosystem. Here, we investigated for the first time the foraging movements and activity patterns of Audouin’s gull Larus audouinii by using satellite-tracking data from eight breeding adults in the main colony of the species worldwide (Ebro Delta, NW Mediterranean). Tagged gulls foraged in the marine area close to the breeding colony (62% of foraging locations) and in the terrestrial area of the Ebro Delta (mainly rice fields; 38% of foraging locations). The foraging activity patterns changed significantly throughout the day; lower from dusk through the first half of the night (19-1 h; 32% of active locations) and higher during the rest of the day (1–19 h; 75.5 ± 4.3% of active locations). These results confirm the foraging plasticity of this seabird and, based on previous information about the dietary habits of this species, we hypothesize how its time-dependent activity patterns and habitat use could be associated with variations in the availability of marine food resources (e.g. diel vertical migrations of pelagic fish) and the exploitation of terrestrial resources (e.g. American crayfish Procambarus clarkii).

Fuzzy Reliablity Optimization Design of Two Stage Planetary Gear System by Genetic Algorithm Based on Predatory Search Strategy

Fuzzy reliability analysis is regared as the theoretical basis. It takes the minimum volume and the maximum transmission efficiency as objective function．Then the mathematical model of fuzzy reliability optimal design on two stage planetary gear sets is set up. Genetic algorithm based on predatory search strategy is used to solve the fuzzy reliability mathematical model. Examples of calculation shows that the volume is decrease by 15%. The results imply the fuzzy reliability analysis is more scientific and reasonable in designing two stage planetary gear sets by using fuzzy reliability analysis.

Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae)

AbstractZhang, G. and Weirauch, C. 2011. Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae). —Acta Zoologica (Stockholm) 00: 1–10.For more than 50 years, specialized dermal glands that secrete sticky substances and specialized setae have been known from the legs of New World assassin bugs in the genus Zelus Fabricius (Reduviidae: Harpactorinae). The gland secretions and specialized ‘sundew setae’ are involved in enhancing predation success. We here refer to this predation strategy as ‘sticky trap predation’ and the specialized dermal glands as ‘sticky glands’. To determine how widespread sticky trap predation is among Reduviidae, we investigated taxonomic distribution of sticky glands and sundew setae using compound light microscopical and scanning electron microscopical techniques and sampling 67 species of Reduviidae that represent 50 genera of Harpactorini. We found sticky glands in 12 genera of Harpactorini and thus show that sticky trap predation is much more widespread than previously suspected. The sticky glands vary in shape, size and density, but are always located in a dorsolateral position on the fore tibia. Sundew setae are present in all taxa with sticky glands with the exception of Heza that instead possesses unique lamellate setae. The sticky trap predation taxa are restricted to the New World, suggesting a New World origin of this unique predation strategy.

Exploitation of environmental noise by an araneophagic assassin bug

Predatory arthropods that specialize in invading webs and preying on the resident spiders (‘araneophagic predators’) face special challenges. As webs are exceedingly good at transmitting vibrations, it is difficult for a web invader to move through the web and remain undetected by the spider. An araneophagic predator that generates vibrations in the web may risk prey escaping or even counterattacking. To increase the chances of an undetected approach, predators may exploit episodes of environmental noise to approach, while their prey’s ability to detect them is compromised (‘opportunistic smokescreen behaviour’). Here we provide the first experimental evidence of convergent opportunistic smokescreen behaviour in an araneophagic insect, Stenolemus bituberus Stal (Reduviidae), which preys on web-building spiders. We tested how two common types of environmental noise, wind and localized vibrations in the web, influence the predatory behaviour and success of assassin bugs when hunting spiders. We found that assassin bugs were more likely to catch the spider in the presence of wind. During episodes of environmental noise, assassin bugs stepped more often and walked in a more continuous manner, apparently exploiting the opportunity to approach while the prey’s sensory system is less able to detect the predator. Changes in predatory behaviour in the presence of environmental noise were not evident when S. bituberus was in an unoccupied spider web. This supports our hypothesis that noise-related timing of behaviour reflects decisions made as part of a predatory strategy, rather than responses to physical disturbance.

Specialized learning in antlions (Neuroptera: Myrmeleontidae), pit-digging predators, shortens vulnerable larval stage.

Unique in the insect world for their extremely sedentary predatory behavior, pit-dwelling larval antlions dig pits, and then sit at the bottom and wait, sometimes for months, for prey to fall inside. This sedentary predation strategy, combined with their seemingly innate ability to detect approaching prey, make antlions unlikely candidates for learning. That is, although scientists have demonstrated that many species of insects possess the capacity to learn, each of these species, which together represent multiple families from every major insect order, utilizes this ability as a means of navigating the environment, using learned cues to guide an active search for food and hosts, or to avoid noxious events. Nonetheless, we demonstrate not only that sedentary antlions can learn, but also, more importantly, that learning provides an important fitness benefit, namely decreasing the time to pupate, a benefit not yet demonstrated in any other species. Compared to a control group in which an environmental cue was presented randomly vis-à-vis daily prey arrival, antlions given the opportunity to associate the cue with prey were able to make more efficient use of prey and pupate significantly sooner, thus shortening their long, highly vulnerable larval stage. Whereas “median survival time,” the point at which half of the animals in each group had pupated, was 46 days for antlions receiving the Learning treatment, that point never was reached in antlions receiving the Random treatment, even by the end of the experiment on Day 70. In addition, we demonstrate a novel manifestation of antlions' learned response to cues predicting prey arrival, behavior that does not match the typical “learning curve” but which is well-adapted to their sedentary predation strategy. Finally, we suggest that what has long appeared to be instinctive predatory behavior is likely to be highly modified and shaped by learning.

Evolutionary branching and evolutionarily stable coexistence of predator species: Critical function analysis

On the ecological timescale, two predator species with linear functional responses can stably coexist on two competing prey species. In this paper, with the methods of adaptive dynamics and critical function analysis, we investigate under what conditions such a coexistence is also evolutionarily stable, and whether the two predator species may evolve from a single ancestor via evolutionary branching. We assume that predator strategies differ in capture rates and a predator with a high capture rate for one prey has a low capture rate for the other and vice versa. First, by using the method of critical function analysis, we identify the general properties of trade-off functions that allow for evolutionary branching in the predator strategy. It is found that if the trade-off curve is weakly convex in the vicinity of the singular strategy and the interspecific prey competition is not strong, then this singular strategy is an evolutionary branching point, near which the resident and mutant predator populations can coexist and diverge in their strategies. Second, we find that after branching has occurred in the predator phenotype, if the trade-off curve is globally convex, the predator population will eventually branch into two extreme specialists, each completely specializing on a particular prey species. However, in the case of smoothed step function-like trade-off, an interior dimorphic singular coalition becomes possible, the predator population will eventually evolve into two generalist species, each feeding on both of the two prey species. The algebraical analysis reveals that an evolutionarily stable dimorphism will always be attractive and that no further branching is possible under this model.

Predation on Recent Marine Ostracod Populations of Southwestern Spain

This paper analyzes evidences of predation observed in ostracod populations collected in the southwestern Spanish shelf (0–70 m depth). Examination of seventy-two samples and almost 17,300 specimens allowed recovering more than 135 bored valves and carapaces. Percentages of bored specimens are very low (< 2%), with the highest values in isolated samples with low to very low ostracod densities. Two main types of boreholes can be distinguished: a) Oichnus paraboloides Bromley, accounting for over 70% of the total boreholes; and b) Oichnus simplex Bromley. Boreholes are concentrated mainly in the central and dorsal areas of the valves. Borehole diameter shows a positive but not significant correlation with the sizes of the predated valves. This diameter is usually higher in shallow marine areas. Predation affects the most abundant species of this shallow marine environment (mainly adults and the last juvenile instars). Ornamentation seems to be secondary in the predatory strategy.

Geometric optimization for prey–predator strategies

This paper investigates several strategies for prey and predator in both bounded and unbounded domains, assuming they have the same speed. The work describes how the prey should move to escape from the predator and how predator should move to catch the prey. The approach is agent-based and explicitly tracks movement of individuals as prey and predator. We show that the prey escapes one or two competing predators, while might be caught in the case of three predators. The paper also describes a strategy for finding a well camouflaged static prey which emits signals.

Behavioural responses of Iberian midwife toad tadpoles (Alytes cisternasii) to chemical stimulus of native (Natrix maura and Squalius pyrenaicus) and exotic (Procambarus clarkii) predators

Predation can be an important force of selection, resulting in the evolution or learning of antipredator defences in amphibian larvae. In the laboratory, we compared the behavioural responses of the tadpoles of Alytes cisternasii subjected to the chemical stimulus of an exotic predator, Procambarus clarkii, with the responses to the chemical stimuli of two of its native predators, the snake Natrix maura and the fish Squalius pyrenaicus, which employ different predation strategies. Tadpoles reacted more intensely to N. maura and then to P. clarkii, with no significant responses to S. pyrenaicus. The alteration in the use of the vertical axis of the aquaria was the antipredator behaviour more frequently used towards both native and exotic predators, and the adopted behaviour was adequate to the activity period and predation strategy of each predator. Alytes cisternasii tadpoles reacted to P. clarkii, a predator introduced about 20 years ago in the study area. These reactions may result from a micro-evolutionary process, but may also be a fortuitous response to a non-familiar cue. We can also not discard the possibility of learning by tadpoles since, due to the reproductive characteristics of this species, it was not possible to collect egg masses before their release in the aquatic environment.

Optimal foraging theory predicts diving and feeding strategies of the largest marine predator

Accurate predictions of predator behavior remain elusive in natural settings. Optimal foraging theory predicts that breath-hold divers should adjust time allocation within their dives to the distance separating prey from the surface. Quantitative tests of these models have been hampered by the difficulty of documenting underwater feeding behavior and the lack of systems, experimental or natural, in which prey depth varies over a large range. We tested these predictions on blue whales (Balaenoptera musculus), which track the diel vertical migration of their prey. A model using simple allometric arguments successfully predicted diving behavior measured with data loggers. Foraging times within each dive increased to compensate longer transit times and optimize resource acquisition. Shallow dives were short and yielded the highest feeding rates, explaining why feeding activity was more intense at night. An optimal framework thus provides powerful tools to predict the behavior of free-ranging marine predators and inform conservation studies. Copyright 2011, Oxford University Press.

Home range evolution and its implication in population outbreaks

We investigated the phenomenon of population outbreaks in a spatial predator-prey model, and we found that pattern formation and outbreaks occur if the predators have a limited neighbourhood of interaction with the preys. The outbreaks can display a scale-invariant power-law tail, indicating self-organized criticality. We have also studied the system from an evolutionary point of view, where the predator home range is a hereditary trait subjected to mutations. We found that mutation drives the predator home range area to an optimal value where pattern formation and outbreaks are still present, but the latter are much less frequent. We developed analytical approximations using mean field and pair correlation techniques that indicate that the predation strategy is crucial for existence of this optimal home range area.

Using light as a lure is an efficient predatory strategy in Arachnocampa flava, an Australian glowworm

Trap-building, sit-and-wait predators such as spiders, flies and antlions tend to have low standard metabolic rates (SMRs) but potentially high metabolic costs of trap construction. Members of the genus Arachnocampa (glowworms) use an unusual predatory strategy: larvae bioluminesce to lure positively phototropic insects into their adhesive webs. We investigated the metabolic costs associated with bioluminescence and web maintenance in larval Arachnocampa flava. The mean rate of CO(2) production (VCO(2)) during continuous bioluminescence was 4.38 μl h(-1) ± 0.78 (SEM). The mean VCO(2) of inactive, non-bioluminescing larvae was 3.49 ± 0.35 μl h(-1). The mean VCO(2) during web maintenance when not bioluminescencing was 8.95 ± 1.78 μl h(-1), a value significantly lower than that measured during trap construction by other predatory arthropods. These results indicate that bioluminescence itself is not energetically expensive, in accordance with our prediction that a high cost of bioluminescence would render the Arachnocampa sit-and-lure predatory strategy inefficient. In laboratory experiments, both elevated feeding rates and daily web removal caused an increase in bioluminescent output. Thus, larvae increase their investment in light output when food is plentiful or when stressed through having to rebuild their webs. As light production is efficient and the cost of web maintenance is relatively low, the energetic returns associated with continuing to glow may outweigh the costs of continuing to attract prey.

Morphology and distribution of the ampullary electroreceptors in wobbegong sharks: implications for feeding behaviour

The electrosensory capabilities of wobbegong sharks are of particular interest, partly because very little is known about their behavioural ecology and specifically because of their unusual ambush predatory strategy and benthic lifestyle. While several biological functions of electroreception have been proposed, less consideration has been given to the functional significance of interspecific differences in the morphology and topographic distribution of the ampullary organs. The morphology of the ampullary organs was examined in four species of wobbegong shark, and the distribution of electroreceptive pores was mapped in two species. The ampullary systems of wobbegongs are similar in morphology to other marine elasmobranchs. The number of alveoli per ampullae is not significantly different between the four species; however, differences are seen between ampullary cell size in some species. Ampullary pore distribution patterns are relatively unique, with the majority of pores occurring on the dorsal region of the head. Wobbegongs feed primarily on demersal teleost fishes, and as the benthic and well-camouflaged wobbegong remains motionless, these fish could be easily detected by the dorsal pores when swimming within range.

Predation in off-patent drug markets

In 2009, Sanofi-Aventis, whose generic subsidiary is Winthrop, merges with the generic firm, Zentiva. This article fills the gap in the theoretical literature concerning mergers in pharmaceutical markets. To prevent generic firms from increasing their market share, some brand-name firms produce generics themselves, called pseudo-generics. We develop a Cournot duopoly model by considering the pseudo-generics production as a mergers' catalyst. We show that a brand-name company always has an incentive to purchase its competitor. The key insight of this article is that the brand-name laboratory can increase its merger gain by producing pseudo-generics beforehand. In some cases, pseudo-generics would not otherwise be produced and this production is then a predatory strategy.

Prey nutrient composition has different effects on Pardosa wolf spiders with dissimilar life histories

The nutritional composition of prey is known to influence predator life histories, but how the life history strategies of predators affect their susceptibility to nutrient imbalance is less investigated. We used two wolf spider species with different life histories as model predators: Pardosa amentata, which have a fixed annual life cycle, and Pardosa prativaga, which reproduce later and can extend development across 2 years. We fed juvenile spiders of the two species ad libitum diets of one of six Drosophila melanogaster fly types varying in lipid:protein composition during three instars, from the start of the second instar until the fifth instar moult. We then tested for interactions between predator species and prey nutrient composition on several life history parameters. P. amentata completed the three instars faster and grew larger carapaces and heavier body masses than P. prativaga, but the two species responded differently to variation in prey lipid:protein ratio. Duration of the instars increased when feeding on protein-poor prey in P. amentata, but was unaffected by diet in P. prativaga. Likewise, the effect of diet on body composition was more pronounced in P. amentata than in P. prativaga. Prey nutrient composition thus affected the two species differently. During macronutrient imbalance P. amentata appear to prioritize high growth rates while experiencing highly variable body compositions, whereas P. prativaga maintain more constant body compositions and have slower growth. These can be seen as different consequences of a fixed annual and a plastic annual-biennial life cycle.

How area restricted search of a pelagic seabird changes while performing a dual foraging strategy

Movements and foraging strategies of marine predators should cope with the hierarchical spatial distribution of resources. Therefore, in order to predict the at-sea distribution of aerial predators, it is crucial to understand the factors governing trajectory decisions at different scales. Using first passage time (FPT) analysis on precision tracking information (GPS-loggers data) we were able to examine the foraging strategy of Cory's shearwaters Calonectris diomedea and to detect the adoption of area-restricted search (ARS), measuring the scale and duration of this behaviour. Data were collected from three different populations foraging in different oceanographic conditions. During long excursions birds only commuted between their colony and prey patches, while on their short movements birds increased the amount of looping movements. On short trips, birds addopted ARS behaviour at an average scale of 18 km and at a second nested scale of around 2 km. When engaging in long trips, first scale of ARS occurred on average at about 67 km of radii and than a second nested scale at a radii of 24 km. Overall, the different populations showed foraging patterns matching the habitats exploited: a) at smaller scales of ARS, sea-surface temperature, chlorophyll-a concentration and depth influenced the time of residence (i.e. FPT) of birds (with variations at a population level); b) at larger scales of ARS, FPT increased within regions of higher gradients of sea-surface temperature, chlorophyl-a concentration and depth. This study demonstrates that Cory's shearwaters adopt scale-dependent adjustments of movement in relation to the hierarchical distribution of the environment they exploit, matching the scale and duration of ARS with the hierarchical distribution of the environmental features.

COLLUSION AND PREDATION UNDER THE CONDITION OF STOCHASTIC BANKRUPTCY

In this paper, on the basis of the framework of repeated games, we consider the strategic interaction between firms that may face financial constraints and go into bankruptcy when they earn low profit. We demonstrate that under asymmetric information concerning the financial constraints of the rival firm, firms adopt a pricing pattern wherein they switch to high (or collusive) prices after maintaining low prices for some periods. There are always such predatory pricing strategies sustained as equilibria when firms are sufficiently patient. We also show that the set of feasible and individual rational payoffs becomes narrower than that of the ordinal repeated games.

Defence reactions of Apis mellifera ligustica against attacks from the European hornet Vespa crabro

The predatory behaviour of Vespa crabro hornets on the honeybee Apis mellifera ligustica and the counter strategy of the prey were observed and described in two apiaries of 27 and 41 colonies in Central Italy. Observations were carried out in the second half of October and accompanied by experiments aimed at determining the mechanisms of honeybee defence. We confirmed that V. crabro represents a relatively mild predator for A. mellifera ligustica but it can have a considerable impact on already debilitated colonies. Hornet predatory strategy is to spot then swoop on returning foragers. Honeybee defence centres on forming packed aggregations of individuals near the hive opening, which probably deters the wasps from entering. Coordinated behaviour by the bees, which cling together in groups, can knock the approaching hornets down, which are then totally covered by the bees. This balling behaviour has the effect of over-heating the predator whose lethal thermal limit is about 44 °C, although other factors, such as carbon dioxide emission and the release of venom by the honeybees, may also contribute to the death of the hornet. Comparing the differences and similarities of this behaviour with those observed in other species of Apis and Vespa reveals that these two species are an interesting model for the study of the evolutionary arms race.

Niche partitioning in orbweaving spiders Meta menardi and Metellina merianae (Tetragnathidae)

Hypogean habitats are relatively simple exhibiting low diversity, low production and relative constancy of environmental factors, and are therefore appropriate for studying species coexistence in situ. We investigated the coexistence of two closely related, similarly sized orb-weaving spider species, Meta menardi and Metellina merianae, living syntopically in a Slovenian cave. We studied the annual dynamics of both species within a mixed population, and the impact of the ambient temperature, relative humidity, airflow and illumination, and compared their trophic niches to legacy data on prey of both species from 55 caves in Slovenia. We predicted a large overlap in their spatial niches and substantial differences in their temporal and trophic niches. We found that their spatial niches overlap greatly with few exceptions, mostly on the dates of notable meteorological changes in the cave but that their temporal niches differ significantly with r-strategy resembling epigean annual dynamic in M. merianae and a steady low abundance course in M. menardi within the cave. We also found that different predatory strategies significantly segregate their trophic niches: M. merianae uses a typical orb-weaving hunting strategy, while M. menardi combines web hunting with off-web hunting. Our findings suggest that both the diverse dynamics and trophic niches enable the coexistence of M. menardi and M. merianae despite their similar spatial niches, and that M. menardi, in particular, is optimally adapted to the epigean/hypogean ecotone.