Predatory Strategies Research Articles

A single predator multiple prey model with prey mutation

A multiple species predator-prey model is expanded with the introduction of a coupled map lattice for the prey, allowing the prey to mutate discretely into other prey species. The model is examined in its single predator, multiple mutating prey form. Two unimodal maps are used for the underlying dynamics of the prey species, with different predation strategies being used. Conclusions are drawn on how varying the control parameters of the model governs the overall behaviour and survival of the species. It is observed that in such a complex system, with multiple mutating prey, a large range of non-linear dynamics is possible.

Modeling of hunting strategies of the predators in susceptible and infected prey

A predator–prey model with epidemic prey and staged structure in the predators, where the predators are assumed to keep constant preference probability of predation on susceptible/infected prey, is formulated to study the hunting strategies of predators for maximum surviving rate as well as maximum density. Given that the disease is endemic among prey before the invasion of predators, global dynamics of the model are obtained and threshold dynamics determined by the predator’s net reproductive number RH are established: the predators go extinct if RH < 1; and predators persist if RH > 1. As an application, the hunting strategies of the predators for the maximum RH are studied, and it is shown that the predators should only hunt the susceptible prey when the disease is just slightly endemic, while if the disease is seriously endemic, they should only hunt the infected prey. Numerical simulations are performed to verify/support the theoretical results and to consider the hunting strategies of predators for their maximum density, for which it is shown that the predators should keep some proper preference probability on both susceptible and infected prey.

Dense understory dwarf bamboo alters the retention of canopy tree seeds

Tree seed retention is thought to be an important factor in the process of forest community regeneration. Although dense understory dwarf bamboo has been considered to have serious negative effects on the regeneration of forest community species, little attention has been paid to the relationship between dwarf bamboo and seed retention. In a field experiment we manipulated the density of Fargesia decurvata, a common understory dwarf bamboo, to investigate the retention of seeds from five canopy tree species in an evergreen and deciduous broad-leaved mixed forest in Jinfoshan National Nature Reserve, SW China. We found that the median survival time and retention ratio of seeds increased with the increase in bamboo density. Fauna discriminately altered seed retention in bamboo groves of different densities. Arthropods reduced seed survival the most, and seeds removed decreased with increasing bamboo density. Birds removed or ate more seeds in groves of medium bamboo density and consumed fewer seeds in dense or sparse bamboo habitats. Rodents removed a greater number of large and highly profitable seeds in dense bamboo groves but more small and thin-husked seeds in sparse bamboo groves. Seed characteristics, including seed size, seed mass and seed profitability, were important factors affecting seed retention. The results suggested that dense understory dwarf bamboo not only increased seeds concealment and reduced the probability and speed of seed removal but also influenced the trade-off between predation and risk of animal predatory strategies, thereby impacting the quantity and composition of surviving seeds. Our results also indicated that dense understory dwarf bamboo and various seed characteristics can provide good opportunities for seed storage and seed germination and has a potential positive effect on canopy tree regeneration.

Insights into Adaptations to a Near-Obligate Nematode Endoparasitic Lifestyle from the Finished Genome of Drechmeria coniospora.

Nematophagous fungi employ three distinct predatory strategies: nematode trapping, parasitism of females and eggs, and endoparasitism. While endoparasites play key roles in controlling nematode populations in nature, their application for integrated pest management is hindered by the limited understanding of their biology. We present a comparative analysis of a high quality finished genome assembly of Drechmeria coniospora, a model endoparasitic nematophagous fungus, integrated with a transcriptomic study. Adaptation of D. coniospora to its almost completely obligate endoparasitic lifestyle led to the simplification of many orthologous gene families involved in the saprophytic trophic mode, while maintaining orthologs of most known fungal pathogen-host interaction proteins, stress response circuits and putative effectors of the small secreted protein type. The need to adhere to and penetrate the host cuticle led to a selective radiation of surface proteins and hydrolytic enzymes. Although the endoparasite has a simplified secondary metabolome, it produces a novel peptaibiotic family that shows antibacterial, antifungal and nematicidal activities. Our analyses emphasize the basic malleability of the D. coniospora genome: loss of genes advantageous for the saprophytic lifestyle; modulation of elements that its cohort species utilize for entomopathogenesis; and expansion of protein families necessary for the nematode endoparasitic lifestyle.

Activity cycles and foraging behaviors of free-ranging sidewinder rattlesnakes (Crotalus cerastes): the ontogeny of hunting in a precocial vertebrate

Predators often employ a complex series of behaviors to overcome antipredator defenses and effectively capture prey. Although hunting behaviors can improve with age and experience, many precocial species are necessarily effective predators from birth. Additionally, many predators experience innate ontogenetic shifts in predatory strategies as they grow, allowing them to adapt to prey more appropriate for their increased size and energetic needs. Understanding how the relative roles of innate age-specific adaptation and learning have evolved requires information on how predation behavior develops in situ, in free-ranging predators. However, most of the research on the ontogeny of predation behavior is based on laboratory studies of captive animals, largely due to the difficulty of following newborn individuals in nature. Here, we take advantage of the unique tracks left by juveniles of a precocial viperid, the sidewinder rattlesnake (Crotalus cerastes), which we used to follow free-ranging snakes in the field. We recorded details of their ambush hunting behavior, and compared the behaviors of these juveniles to adult snakes that we monitored in the field via radio telemetry. Although juvenile and adult behaviors were similar in most respects, we did find that adults chose more effective ambush sites, which may be due to their increased experience. We also found that juveniles (but typically not adults) perform periodic tail undulations while in ambush, and that juveniles displayed slightly different activity cycles. Both of these latter differences are likely the result of age-specific adaptations for juveniles’ greater reliance on lizards versus small mammals as prey. We also compared the general predatory behavior of sidewinders to that of other species in the genus Crotalus. These findings will provide important baseline field information for more detailed empirical research on the ontogeny of predation behavior in precocial vertebrates.

Liquidity, resiliency and market quality around predictable trades: Theory and evidence

We extend the theory of strategic trading around a predictable liquidation by considering the role of market resiliency. Our model predicts that even a monopolist strategic trader improves market quality and increases liquidator proceeds if trades’ temporary price impacts are quickly reversed, and that competition among strategic traders strictly improves market quality. We provide related empirical evidence by studying prices, liquidity, and individual account trading activity around the large and predictable “roll” trades undertaken by a large exchange-traded fund (ETF). The evidence indicates narrower bid-ask spreads, greater order book depth, and improved resiliency on roll dates. We find that a larger number of individual trading accounts provide liquidity on roll dates, and do not find evidence of the systematic use of predatory strategies. On balance, the theory and evidence imply that traders supply liquidity to rather than exploit predictable trades in resilient markets.

Predator-prey body size relationship in temporary wetlands: effect of predatory insects on prey size spectra and survival

The effect of predators on prey size structure in aquatic communities has been well studied in lentic permanent habits, but less attention has been placed on temporary environments. The biota of seasonal Andean wetlands in Patagonia is basically formed by crustaceans, insects and pond-breeding amphibians. The dominant predators in these wetlands are macroinvertebrates, mostly aquatic insects. The main objectives of this study were to examine the seasonal and interannual variation in the body size of prey and predators in two temporary wetlands located in northwest Patagonia, during two consecutive hydroperiods and to evaluate the effect of different insect predators over different prey sizes and different ontogenetic stages of invertebrate and vertebrate prey. Prey size structure and predator size structure were affected by the wetland type and the sampling months and predator body size was not correlated with prey size structure. The experiments showed that small prey were the most impacted by predaceous insects and all predators showed size-limited predation. Although aquatic insects significantly reduced the number of prey in the predation experiments, they did not significantly affect the body size structure of prey in nature. In this sense, the diversity of aquatic insects with different predatory strategies could maintain the heterogeneity in prey size structure in the wetlands studied.

Accuracy of mandibular force profiles for bite force estimation and feeding behavior reconstruction in extant and extinct carnivorans.

Mandibular force profiles apply the principles of beam theory to identify mandibular biomechanical properties that reflect the bite force and feeding strategies of extant and extinct predators. While this method uses the external dimensions of the mandibular corpus to determine its biomechanical properties, more accurate results could potentially be obtained by quantifying its internal cortical bone distribution. To test this possibility, mandibular force profiles were calculated using both external mandibular dimensions ('solid mandible model') and quantification of internal bone distribution of the mandibular corpus obtained from computed tomography scans ('hollow mandible model') for five carnivorans (Canis lupus, Crocuta crocuta, Panthera leo, Neofelis nebulosa and the extinct Canis dirus). Comparison reveals that the solid model slightly overestimates mandibular biomechanical properties, but the pattern of change in biomechanical properties along the mandible remains the same. As such, feeding behavior reconstructions are consistent between the two models and are not improved by computed tomography. Bite force estimates produced by the two models are similar, except in C. crocuta, where the solid model underestimates bite force by 10-14%. This discrepancy is due to the more solid nature of the C. crocuta mandible relative to other carnivorans. Therefore, computed tomography improves bite force estimation accuracy for taxa with thicker mandibular corpora, but not significantly so otherwise. Bite force estimates derived from mandibular force profiles are far closer to empirically measured bite force than those inferred from jaw musculature dimension. Consequently, bite force estimates derived from this method can be used to calibrate finite-element analysis models.

Modelling of multi-agent coordination using crocodile predatory strategy

Multi-agent systems (MASs) are essential solutions for large-scale, complex problems as single agents are having limited capabilities and computing resources. In real-time problems, the agents have to take dynamic decisions during run-time and coordinate their actions accordingly. In such scenarios, conflicts between agents may arise while coordinating and collaborating dynamic action among them to achieve the goal and even after achieving the goal. To resolve such issues, a model is proposed in this paper which is motivated by the cooperative hunting and feeding behaviour of the crocodiles, i.e., utilises the predatory strategy of crocodiles.

Modelling of multi-agent coordination using crocodile predatory strategy

Multi-agent systems (MASs) are essential solutions for large-scale, complex problems as single agents are having limited capabilities and computing resources. In real-time problems, the agents have to take dynamic decisions during run-time and coordinate their actions accordingly. In such scenarios, conflicts between agents may arise while coordinating and collaborating dynamic action among them to achieve the goal and even after achieving the goal. To resolve such issues, a model is proposed in this paper which is motivated by the cooperative hunting and feeding behaviour of the crocodiles, i.e., utilises the predatory strategy of crocodiles.

Product Market Threats and the Value of Corporate Cash Holdings

We construct a model to show that predatory strategies by a financially strong rival can cause a financially weak firm to underinvest. This threat intensifies when the two firms produce similar products and share similar future investment opportunities. We show that cash holdings become more valuable by providing liquidity to fund investment opportunities as they emerge, thereby mitigating the underinvestment problem. Empirical evidence supports these model predictions. The value of cash is significantly higher for firms facing higher predatory threats. The results are robust to various controls for financial constraints, corporate governance, risk factors, and industry‐level measures of product market competition. An identification strategy that exploits exogenous variation in financial constraints further corroborates the causal effect of predatory threats on the value of cash.

Molecular phylogeny of Harpactorinae and Bactrodinae uncovers complex evolution of sticky trap predation in assassin bugs (Heteroptera: Reduviidae).

Sticky trap predation, the use of adhesive substances to trap and capture prey, is an intriguing yet poorly studied predatory strategy. Unique among known sticky trap predators, assassin bugs (Reduviidae) have evolved both exogenous and endogenous sticky trap predatory mechanisms: some trap their prey with sticky plant resins, some scavenge insects entrapped by sticky plant trichomes and others self-produce sticky secretions. The evolution of these different strategies in assassin bugs is poorly understood due to the lack of comprehensive phylogenies. We reconstruct a phylogeny of Reduviidae (141 taxa; >5000bp) focusing on the Harpactorinae and Bactrodinae that engage in sticky trap predation. Ancestral state reconstruction, and temporal and geographical divergence analyses show that sticky trap predation techniques in assassin bugs evolved at least seven times independently since the late Cretaceous: use of sticky plant trichomes evolved as many as four times, resin-use twice independently and once as a transition from trichome use, and 'self-stickiness' once. Exogenous and endogenous sticky traps first appeared in the Neotropics, with the two exogenous mechanisms (resin and trichome use) subsequently evolving independently in the Old World. This study illustrates, for the first time, the complex evolutionary pattern of sticky trap predation within assassin bugs.

The fall of high-frequency trading: A survey of competition and profits

We investigate high-frequency trading (HFT) strategies, inventorying the strategies already studied in the literature and introducing innovative strategies detected by private institutional research. To this end, we expand the existing classification, and we offer names for new categories. In a complementary but original manner, we introduce counter reactions from professional traders in response to HFT predatory strategies. These human answers reverse the usual framework of competition between high-frequency traders (HFTs) and low frequency traders (LFTs) and also widen this cadre to HFTs algos (predators) versus execution algos.This survey notes that a continuous increase in competition, between high-speed trading algorithms themselves through predatory strategies and from professional human traders adapting and building adequate responses has made the business more difficult and has led to shrinking profits for HFT. In the end, we believe that excessive competition and a change in the current regulation (favorable to HFT) could kill the goose that laid the golden egg.

Linking body size and energetics with predation strategies: A game theoretic modeling framework

Predation is the ultimate survival game between the predator and prey. In this study, we use game theory as a modeling framework to demonstrate why and how different strategies in predation for both predator and prey are chosen based on body size and energetics. Two distinct and mutually exclusive strategies, active and passive, are considered for both players; hence the corresponding predation can be formulated as a 2×2 game. The payoffs are defined using energetics (energy gain and loss), with functional response to predator/prey body size. The game is formulated as a realistic general sum model and the numerical results of Nash equilibrium for different body sized predators and preys are calculated: in general, smaller sized predators and preys tend to use active strategy more often (mixed strategy equilibrium), and larger sized tend to choose active strategy exclusively (pure strategy equilibrium). The long-term evolutionary stability of the predator–prey system is also investigated, and the Nash equilibrium derived from these games are shown evolutionarily unstable. In summary, this study provides a unified modeling framework to study how animal body size and energetics determine predation strategies, and can easily extend to more complicated conditions, such as across multiple trophic levels.

Strand-feeding by coastal bottlenose dolphins (Tursiops truncatus) in the Gulf of Guayaquil, Ecuador

Strand-feeding as a predatory strategy was first observed in bottlenose dolphins, Tursiops truncatus, inhabiting waters of Spartina marshes of South Carolina and Georgia, United States. While a substantial body of documented observations exists for many regions of the world, current evidences and photo-documentation of these types of foraging behaviors by bottlenose dolphins in the Pacific coast of South America are scarce. To the best of our knowledge, behaviors resembling strand-feeding by bottlenose dolphins have been described very briefly without supporting photos in the inner estuary of the Gulf of Guayaquil. As a part of a long-term field study (2001-2011) on photo-identification, population ecology and monitoring of the bottlenose dolphin in the El Morro Mangrove and Wildlife Refuge, we provide some insights on its conservation, and photo-documented the occurrence of strand-feeding as a recurrent behavioral foraging tactic in this region of South America.

Adaptation of the spiders to the environment: the case of some Chilean species.

Spiders are small arthropods that have colonized terrestrial environments. These impose three main problems: (i) terrestrial habitats have large fluctuations in temperature and humidity; (ii) the internal concentration of water is higher than the external environment in spiders, which exposes them continually to water loss; and (iii) their small body size determines a large surface/volume ratio, affecting energy exchange and influencing the life strategy. In this review we focus on body design, energetic, thermal selection, and water balance characteristics of some spider species present in Chile and correlate our results with ecological and behavioral information. Preferred temperatures and critical temperatures of Chilean spiders vary among species and individuals and may be adjusted by phenotypic plasticity. For example in the mygalomorph high-altitude spider Paraphysa parvula the preferred temperature is similar to that of the lowland spider Grammostola rosea; but while P. parvula shows phenotypic plasticity, G. rosea does not. The araneomorph spiders Loxosceles laeta and Scytodes globula have greater daily variations in preferred temperatures at twilight and during the night, which are set to the nocturnal activity rhythms of these species. They also present acclimation of the minimum critical temperatures. Dysdera crocata has a low preferred temperature adjusted to its favorite prey, the woodlouse. Spider metabolic rate is low compared to other arthropods, which may be associated with its sit and wait predatory strategy particularly in primitive hunter and weavers. In mygalomorph spiders the respiratory system is highly optimized with high oxygen conductance, for example G. rosea needs only a difference of 0.12–0.16 kPa in the oxygen partial pressure across the air-hemolymph barrier to satisfy its resting oxygen consumption demands. Water loss is a significant stress for spiders. Paraphysa parvula shows an evaporative water loss 10 times more than usual when the temperature approaches 40°C and the participation of book lungs in this loss is about 60%. This species and others show seasonal changes in water loss accounted for by changes in cuticle permeability. The case of Chilean spiders shows how the ecophysiology in spiders is associated to their design and body size and how is affected by fluctuating Mediterranean environments, suggesting that the adaptive process can be seen as a route of optimizing the use of energy to cope with environmental restrictions imposed by the interaction with the terrestrial environment and lifestyle.

Importance of hunger and prey type on predatory behavior stages inCorythalia albicincta(Araneae: Salticidae)

Predators often adopt strategies to capture prey that reflect both the characteristics of the prey and their own hunger level. In generalist spiders of the family Salticidae, predatory behavior typically consists of four phases: orientation towards the prey, pursuit, crouching, and jumping to capture. In this study, we conducted laboratory experiments in order to determine whether predatory strategies change according to prey type and hunger level in Corythalia albicincta (F. O. Pickard-Cambridge 1901). We used adult specimens of both sexes to evaluate variation in capture jump distance, time spent on each predatory stage and attack efficiency, in terms of prey capture. Jump distance was greater with prey that can more readily escape (crickets and flies), compared to fly larvae. The duration of both latency and orientation was greater in larval trials than in the cricket and fly trials. Corythalia albicincta spent less time in a crouching position with flies and the total duration of the predation process was shorter with flies than with crickets or larvae. Numbers of failures, defined as the number of failed attacks before a spider captures a prey item in the test, was higher in spiders that had been starved for one day compared to those that had been starved for 7 and 15 days. Predatory strategies were modified according to movement patterns and prey speed, while hunger level affected predation efficiency.

Importance of hunger and prey type on predatory behavior stages inCorythalia albicincta(Araneae: Salticidae)

Predators often adopt strategies to capture prey that reflect both the characteristics of the prey and their own hunger level. In generalist spiders of the family Salticidae, predatory behavior typically consists of four phases: orientation towards the prey, pursuit, crouching, and jumping to capture. In this study, we conducted laboratory experiments in order to determine whether predatory strategies change according to prey type and hunger level in Corythalia albicincta (F. O. Pickard-Cambridge 1901). We used adult specimens of both sexes to evaluate variation in capture jump distance, time spent on each predatory stage and attack efficiency, in terms of prey capture. Jump distance was greater with prey that can more readily escape (crickets and flies), compared to fly larvae. The duration of both latency and orientation was greater in larval trials than in the cricket and fly trials. Corythalia albicincta spent less time in a crouching position with flies and the total duration of the predation process was shorter with flies than with crickets or larvae. Numbers of failures, defined as the number of failed attacks before a spider captures a prey item in the test, was higher in spiders that had been starved for one day compared to those that had been starved for 7 and 15 days. Predatory strategies were modified according to movement patterns and prey speed, while hunger level affected predation efficiency.

Outrun or Outmaneuver: Predator-Prey Interactions as a Model System for Integrating Biomechanical Studies in a Broader Ecological and Evolutionary Context.

Behavioral studies performed in natural habitats provide a context for the development of hypotheses and the design of experiments relevant both to biomechanics and to evolution. In particular, predator-prey interactions are a model system for integrative study because success or failure of predation has a direct effect on fitness and drives the evolution of specialized performance in both predator and prey. Although all predators share the goal of capturing prey, and all prey share the goal of survival, the behavior of predators and prey are diverse in nature. This article presents studies of some predator-prey interactions sharing common predation strategies that reveal general principles governing the behaviors of predator and prey, even in distantly related taxa. Studies of predator-prey interactions also reveal that maximal performance observed in a laboratory setting is not necessarily the performance that determines fitness. Thus, considering locomotion in the context of predation ecology can aid in evolutionarily relevant experimental design. Classification by strategy reveals that displaying unpredictable trajectories is a relevant anti-predator behavior in response to multiple predation strategies. A predator's perception and pursuit of prey can be affected indirectly by divergent locomotion of similar animals that share an ecosystem. Variation in speed and direction of locomotion that directly increases the unpredictability of a prey's trajectory can be increased through genetic mutation that affects locomotor patterns, musculoskeletal changes that affect maneuverability, and physical interactions between an animal and the environment. By considering the interconnectedness of ecology, physical constraints, and the evolutionary history of behavior, studies in biomechanics can be designed to inform each of these fields.

3D computational mechanics elucidate the evolutionary implications of orbit position and size diversity of early amphibians.

For the first time in vertebrate palaeontology, the potential of joining Finite Element Analysis (FEA) and Parametrical Analysis (PA) is used to shed new light on two different cranial parameters from the orbits to evaluate their biomechanical role and evolutionary patterns. The early tetrapod group of Stereospondyls, one of the largest groups of Temnospondyls is used as a case study because its orbits position and size vary hugely within the members of this group. An adult skull of Edingerella madagascariensis was analysed using two different cases of boundary and loading conditions in order to quantify stress and deformation response under a bilateral bite and during skull raising. Firstly, the variation of the original geometry of its orbits was introduced in the models producing new FEA results, allowing the exploration of the ecomorphology, feeding strategy and evolutionary patterns of these top predators. Secondly, the quantitative results were analysed in order to check if the orbit size and position were correlated with different stress patterns. These results revealed that in most of the cases the stress distribution is not affected by changes in the size and position of the orbit. This finding supports the high mechanical plasticity of this group during the Triassic period. The absence of mechanical constraints regarding the orbit probably promoted the ecomorphological diversity acknowledged for this group, as well as its ecological niche differentiation in the terrestrial Triassic ecosystems in clades as lydekkerinids, trematosaurs, capitosaurs or metoposaurs.