Sustainable management of predatory fish affected by an Allee effect through marine protected areas and taxation.

Ecological balance and stable economic development are crucial for the fishery. This study proposes a predator-prey system for marine communities, where the growth of predators follows the Allee effect and takes into account the rapid fluctuations in resource prices caused by supply and demand. The system predicts the existence of catastrophic equilibrium, which may lead to the extinction of prey, consequently leading to the extinction of predators, but fishing efforts remain high. Marine protected areas are established near fishing areas to avoid such situations. Fish migrate rapidly between these two areas and are only harvested in the nonprotected areas. A three-dimensional simplified model is derived by applying variable aggregation to describe the variation of global variables on a slow time scale. To seek conditions to avoid species extinction and maintain sustainable fishing activities, the existence of positive equilibrium points and their local stability are explored based on the simplified model. Moreover, the long-term impact of establishing marine protected areas and levying taxes based on unit catch on fishery dynamics is studied, and the optimal tax policy is obtained by applying Pontryagin's maximum principle. The theoretical analysis and numerical examples of this study demonstrate the comprehensive effectiveness of increasing the proportion of marine protected areas and controlling taxes on the sustainable development of fishery.

A systematic review and meta-analysis of unimodal and multimodal predation risk assessment in birds.

Despite a wealth of studies documenting prey responses to perceived predation risk, researchers have only recently begun to consider how prey integrate information from multiple cues in their assessment of risk. We conduct a systematic review and meta-analysis of studies that experimentally manipulated perceived predation risk in birds and evaluate support for three alternative models of cue integration: redundancy/equivalence, enhancement, and antagonism. One key insight from our analysis is that the current theory, generally applied to study cue integration in animals, is incomplete. These theories specify the effects of increasing information level on mean, but not variance, in responses. In contrast, we show that providing multiple complementary cues of predation risk simultaneously does not affect mean response. Instead, as information richness increases, populations appear to assess risk more accurately, resulting in lower among-population variance in response to manipulations of perceived predation risk. We show that this may arise via a statistical process called maximum-likelihood estimation (MLE) integration. Our meta-analysis illustrates how explicit consideration of variance in responses can yield important biological insights.

Low hunting costs in an expensive marine mammal predator.

Many large terrestrial mammalian predators use energy-intensive, high-risk, high-gain strategies to pursue large, high-quality prey. However, similar-sized marine mammal predators with even higher field metabolic rates (FMRs) consistently target prey three to six orders of magnitude smaller than themselves. Here, we address the question of how these active and expensive marine mammal predators can gain sufficient energy from consistently targeting small prey during breath-hold dives. Using harbor porpoises as model organisms, we show that hunting small aquatic prey is energetically cheap (<20% increase in FMR) for these marine predators, but it requires them to spend a large proportion (>60%) of time foraging. We conclude that this grazing foraging strategy on small prey is viable for marine mammal predators despite their high FMR because they can hunt near continuously at low marginal expense. Consequently, cessation of foraging due to human disturbance comes at a high cost, as porpoises must maintain their high thermoregulation costs with a reduced energy intake.

Costs of being a diet generalist for the protist predator Dictyostelium discoideum.

Consumers range from specialists that feed on few resources to generalists that feed on many. Generalism has the clear advantage of having more resources to exploit, but the costs that limit generalism are less clear. We explore two understudied costs of generalism in a generalist amoeba predator, Dictyostelium discoideum, feeding on naturally co-occurring bacterial prey. Both involve costs of combining prey that are suitable on their own. First, amoebas exhibit a reduction in growth rate when they switched to one species of prey bacteria from another compared to controls that experience only the second prey. The effect was consistent across all six tested species of bacteria. These switching costs typically disappear within a day, indicating adjustment to new prey bacteria. This suggests that these costs are physiological. Second, amoebas usually grow more slowly on mixtures of prey bacteria compared to the expectation based on their growth on single prey. There were clear mixing costs in three of the six tested prey mixtures, and none showed significant mixing benefits. These results support the idea that, although amoebas can consume a variety of prey, they must use partially different methods and thus must pay costs to handle multiple prey, either sequentially or simultaneously.

Incidence of eriophyid mites (Acariformes: Eriophyidae) and predatory mites (Parasitiformes: Phytoseiidae) in Florida citrus orchards under three different pest management programs.

The abundance and diversity of eriophyid and phytoseiid mites in south and central Florida were assessed in six citrus orchards under three different pest management systems, conventional, organic, and untreated. Tree canopy, ground cover, and leaf litter were sampled every two months in two groves for each of the three pest management systems from April 2019 to February 2021. The citrus rust mite, Phyllocoptruta oleivora (Ashmead) represented 95 to 99% of the rust mites sampled in each grove except in one untreated orchard where it accounted for 45% of the samples (n = 938 total P. oleivora mounted specimens). The pink citrus rust mite, Aculops pelekassi (Keifer) was present in organic and untreated orchards at 5% and 28%, respectively, but absent from conventional orchards (n = 134 total A. pelekassi mounted specimens). Twenty-nine species of phytoseiid mites were identified from 1778 specimens. Thirteen species were present in the canopy, fifteen in the ground cover, and eighteen in the leaf litter with some common species among these habitats. In the tree canopy, Typhlodromalus peregrinus (39%), Euseius spp. (25%), and Iphiseiodes quadripilis (19%) were the dominant species. Typhlodromalus peregrinus (43%), Typhlodromips dentilis (25%), and Proprioseiopsis mexicanus (13%) were the major species in the ground cover. Species richness was lower in organic orchards (3.0) compared to conventional and untreated orchards (5.0 and 4.7, respectively). In the leaf litter, Amblyseius curiosus (26%), Proprioseiopsis carolinianus (15%), Chelaseius floridanus (14%), and Amblyseius tamatavensis (12%) were the most common species. Shannon index was significantly higher in conventional orchards (1.45) compared to organic and untreated orchards (1.02 and 1.05, respectively). Evenness was also higher in conventional orchards (0.86) compared to organic and untreated (0.72 and 0.68, respectively). Finding of several phytoseiids in abundance across pest management programs suggest the need for identifying their role in pest suppression particularly mites.

Social attributes shape antipredator behavior strategies in the ruddy ground-dove.

The cost-benefit of social behavior depends on group size and the social interaction. As group size increases, competition for resources increases, while individual vigilance may decrease due to the lower probability of individual predation or increased competition for resources. To test predictions of the "many eyes hypothesis" and the "competition hypothesis", we investigated the effects of social attributes on the vigilance, foraging, direct conflict and sex on social groups of ruddy ground-doves (Columbina talpacoti) in an urban area. We observed that the number of conspecifics did not influence individual foraging behavior, instead, the vigilance decreased as flock size increased. Moreover, the number of conflicts within the flock negatively affected individual vigilance. However, larger flocks exhibited more direct conflicts, and males were more frequently involved in social conflicts, regardless of the sex ratio of the flock. Finally, the investment in both vigilance and foraging was not influenced by the sex of the focal individual or the sex ratio of the flock. Our findings indicate that conspecific numbers and flock social organization significantly influence the cost-benefit dynamics of flocking behavior. Larger flocks enhance vigilance for predator detection but come at an individual cost due to increased resource competition and conflicts.

Counterintuitive prey strategies against predators with finite budgets: protection heterogeneity among sites matters more than their number.

Combining the search and pursuit aspects of predator-prey interactions into a single game, where the payoff to the Searcher (predator) is the probability of finding and capturing the Hider (prey) within a fixed number of searches was proposed by Gal and Casas (J. R. Soc. Interface 11, 20140062 (doi:10.1098/rsif.2014.0062)). Subsequent models allowed the predator to continue its search (in another 'round') if the prey was found but escaped the chase. However, it is unrealistic to allow this pattern of prey relocation to go on forever, so here we introduce a limit of the total number of searches, in all 'rounds', that the predator can carry out. We show how habitat structural complexity affects the mean time until capture: the quality of the location with the lowest capture probability matters more than the number of hiding locations. Moreover, we observed that the parameter space defined by the capture probabilities in each location and the budget of the predator can be divided into distinct domains, defining whether the prey ought to play with pure or mixed hiding strategies.

The relative importance of social information use for population abundance in group-living and non-grouping prey.

Predator-prey relationships are fundamental components of ecosystem functioning, within which the spatial consequences of prey social organization can alter predation rates. Group-living (GL) species are known to exploit inadvertent social information (ISI) that facilitates population persistence under predation risk. Still, the extent to which non-grouping (NG) prey can benefit from similar processes is unknown. Here we built an individual-based model to explore and compare the population-level consequences of ISI use in GL and NG prey. We differentiated between GL and NG prey only by the presence or absence of social attraction toward conspecifics that drives individual movement patterns. We found that the extent of the benefits of socially acquired predator information in NG highly depends on the prey's ability to detect nearby predators, prey density and the occurrence of false alarms. Conversely, even moderate probabilities of ISI use and predator detection can lead to maximal population-level benefits in GL prey. This theoretical work provides additional insights into the conditions under which ISI use can facilitate population persistence irrespective of prey social organisation.

Muscle in the caterpillar Manduca sexta responds to an immune challenge, but at a cost, suggesting a physiological trade-off.

Although skeletal muscle is a specialized tissue that provides the motor for movement, it also participates in other functions, including the immune response. However, little is known about the effects of this multitasking on muscle. We show that muscle loses some of its capacity while it is participating in the immune response. Caterpillars (Manduca sexta) were exposed to an immune challenge, predator stress or a combination of immune challenge and predator stress. The expression of immune genes (toll-1, domeless, cactus, tube and attacin) increased in body wall muscle after exposure to an immune challenge. Muscle also showed a reduction in the amount of the energy storage molecule glycogen. During an immune challenge, the force of the defensive strike, an important anti-predator behaviour in M. sexta, was reduced. Caterpillars were also less able to defend themselves against a common enemy, the wasp Cotesia congregata, suggesting that the effect on muscle is biologically significant. Our results support the concept of an integrated defence system in which life-threatening events activate organism-wide responses. We suggest that increased mortality from predation is a non-immunological cost of infection in M. sexta. Our study also suggests that one reason non-immunological costs of infection exist is because of the participation of diverse organs, such as muscle, in immunity.

Assessment of predation risk through conspecific cues by anuran larvae.

Accurate assessment of predation risk is critical for prey survival during predator-prey interactions. Prey can assess predation risk by the presence of cues dropped by predators themselves, but they can also gather information about risk level through cues released by other prey, avoiding the hazard of being in close proximity to predators. In this study, we examine the ability of anuran larvae (Pelobates cultripes) to detect predation risk indirectly when they are in contact with conspecifics that have been recently exposed to chemical stimuli from natural predators (larvae of aquatic beetles). In a first experiment, we confirmed that larvae exposed to predator cues exhibited innate defensive behavior, indicating that they perceived the risk of predation and, thus, could potentially act as risk indicators for naïve conspecifics. In a second experiment, we observed that unexposed larvae paired with a startled conspecific adjusted their antipredator behavior, presumably by mirroring conspecifics' behavior and/or using chemical cues from their partners as a risk information source. This cognitive ability of tadpoles to assess predation risk through conspecific cues might play an important role in their interaction with predators, facilitating the early detection of potential threats to elicit appropriate antipredator responses and increase the chances of survival.

ECOfast - An integrative ecological evaluation index for an ecosystem-based assessment of shallow rocky reefs.

The degradation of marine ecosystems is a growing concern worldwide, emphasizing the need for efficient tools to assess their ecological status. Herein, a novel ecosystem-based ecological evaluation index of shallow rocky reefs is introduced and tested in the Aegean and Ionian Seas (NE Mediterranean). The index focuses on a specific set of pre-selected species, including habitat-forming, key, commercially important, and non-indigenous species, across a wide range of trophic levels (1.00-4.53). Data acquisition is conducted through rapid non-destructive SCUBA diving surveys to assess all macroscopic food web components (macroalgae, invertebrates, and fish). Two versions of the index, ECOfast and ECOfast-NIS, were developed, each applying a different approach to account for the impact of non-indigenous species. In our case study, the correlations between the two versions of the index and sea surface temperature, protection status, occurrence of carnivorous fish, and non-indigenous herbivores were assessed through generalized additive models (GAMs). The assessment assigned 93% (ECOfast) or 96% (ECOfast-NIS) of the sites to a moderate to bad ecological status, indicating an alarming situation in the shallow rocky reefs of the NE Mediterranean. Sites evaluated as poor or bad were characterized by extensive coverage of ephemeral macroalgae, absence or minimal presence of large indigenous carnivorous fish, and complete absence of one to three out of five invertebrate functional trophic groups. The community composition of macroalgae, herbivorous species, and carnivorous fishes differed between the 5 m and 15 m depth zones. Surface temperature and carnivorous fish occurrence were the most important tested predictors of the ecological status of shallow rocky reefs. The best GAMs showed that the ECOfast score declined with sea surface temperature and increased with the occurrence of carnivorous fish; ECOfast-NIS declined with sea surface temperature and the occurrence of non-indigenous fish and increased with the occurrence of carnivorous fish. The non-destructive and integrative nature of this approach, its speed of data acquisition and analysis, and its capacity to account for highly mobile predatory fish and non-indigenous species render the ECOfast index a novel, robust, and valuable tool for assessing the ecological status of shallow rocky reefs.

The behaviour and activity budgets of two sympatric sloths; Bradypus variegatus and Choloepus hoffmanni.

It is usually beneficial for species to restrict activity to a particular phase of the 24-hour cycle as this enables the development of morphological and behavioural adaptations to enhance survival under specific biotic and abiotic conditions. Sloth activity patterns are thought to be strongly related to the environmental conditions due to the metabolic consequences of having a low and highly variable core body temperature. Understanding the drivers of sloth activity and their ability to withstand environmental fluctuations is of growing importance for the development of effective conservation measures, particularly when we consider the vulnerability of tropical ecosystems to climate change and the escalating impacts of anthropogenic activities in South and Central America. Unfortunately, the cryptic nature of sloths makes long term observational research difficult and so there is very little existing literature examining the behavioural ecology of wild sloths. Here, we used micro data loggers to continuously record, for the first time, the behaviour of both Bradypus and Choloepus sloths over periods of days to weeks. We investigate how fluctuations in the environmental conditions affect the activity of sloths inhabiting a lowland rainforest on the Caribbean coast of Costa Rica and examined how this might relate to their low power lifestyle. Both Bradypus and Choloepus sloths were found to be cathemeral in their activity, with high levels of between-individual and within-individual variation in the amounts of time spent active, and in the temporal distribution of activity over the 24-hour cycle. Daily temperature did not affect activity, although Bradypus sloths were found to show increased nocturnal activity on colder nights, and on nights following colder days. Our results demonstrate a distinct lack of synchronicity within the same population, and we suggest that this pattern provides sloths with the flexibility to exploit favourable environmental conditions whilst reducing the threat of predation.

Epibionts provide their basibionts with associational resistance to predation but at a cost.

Epibiosis is increasingly considered a survival strategy in space-limited environments. However, epibionts can create a new interface between its host, environment and potential predators which may alter predator-prey relationships and biological functioning. Ex-situ experiments investigated the potential costs and benefits of epibiont barnacles on mortality and feeding rate of the mussel, Mytilus edulis, and its predator, the whelk Nucella lapillus. Mussels with living epibiont barnacles suffered no mortality from whelk predation, but when barnacles were absent, mortality was ∼21% over 48 days. Further comparisons revealed the structural complexity of barnacles provided mussels with protection from whelk predation, while the presence of living barnacles increased predator-prey encounters but led to predators targeting barnacles over mussels. Feeding trials revealed feeding rate increased by ∼24% in mussels with living epibionts over mussels with dead or without epibionts, indicating potential costs of hosting epibionts. Our results show that epibionts provide important associational resistance for mussels against whelk predation but a potential cost to the mussel of hosting epibionts requiring increased energy acquisition. These findings advance our understanding of associational resistance derived from epibionts and serve to highlight the potential trade-offs affecting basibiont functioning while showing the importance of positive ecological interactions in ecosystem structure and functioning.

The costs and trade-offs of optimal foraging in marine fish larvae.

In a warming world, both the metabolic rates of ectotherm predators and the phenology of their prey organisms is subject to change. Knowledge on how intrinsic and extrinsic factors govern predator-prey interactions is essential in order to understand how the environment regulates the vital rates of consumers. Controlled experiments, however, simultaneously testing behavioural and growth responses of the larvae of fish and other ectotherm organisms in different feeding regimes are scarce. Prey size (PS) selection was determined for young Atlantic herring Clupea harengus L. larvae offered 100- to 850-µm copepods Acartia tonsa at five different concentrations. In separate, 4- (13°C) or 7-day (7°C) trials, the effect of prey size on larval foraging behaviour, specific growth rate (SGR) and biochemical condition (RNA:DNA, RD, a proxy for individual instantaneous growth) was tested. Preferred (selected) PS was similar at all prey concentrations but increased from 3% to 5% predator length with increasing larval size. At various temperatures, dome-shaped relationships existed between PS and larval RD (and accordingly SGR). Compensatory changes in foraging behaviour (pause and feeding strike frequencies) existed but were not adequate to maintain positive SGR when available prey were substantially smaller than those preferred by larvae. A physiology-based model predicted that larvae depended more heavily on optimal prey sizes at the colder versus warmer temperature to grow well and that the profitable prey niche breadth (the range in prey sizes in which growth was positive) increased at warmer temperatures. Seemingly subtle match-mismatch dynamics between ectotherm predators and their preferred prey size can have large, temperature-dependent consequences for rates of growth and likely survival of the predator. To the best knowledge, this was the first study to directly quantify the "costs and trade-offs" of optimal foraging in marine fish larvae.

Hydrology-mediated ecological function of a large wetland threatened by an invasive predator.

Invasive species are one of the greatest threats to ecosystems, disrupting ecosystem function and leading to the collapse and extinction of native species. While populations of native fishes in the Everglades are tied to the system's natural hydrological dynamics, Asian Swamp Eels (Monopterus albus/javanensis) are drought-resistant fish first reported from Florida in 1997 and the Everglades in 2007. Using a 26-year dataset that included a 13-year baseline period prior to swamp eel arrival in Taylor Slough, we assessed population changes of common small fishes and decapods that are important prey for larger vertebrate predators. After invasion, populations of two crayfishes collapsed by >95 %, two fishes declined by >80 %, two fishes had intermediate declines of 44-66 %, and three species remained unchanged. Species most strongly reduced were those dependent on predator-free habitats at the onset of the wet season, indicating drought-resistant swamp eels have introduced novel predator effects and disrupted the hydrology-mediated production of aquatic animals that are prey for many larger predators. Ongoing Everglades restoration is designed to restore hydrological conditions that support production of crayfishes and fishes, and nesting wading birds reliant on them. Water management may have facilitated the invasion of swamp eels. Our results suggest that the continued spread of swamp eels may result in adverse consequences for Everglades trophic dynamics and potentially diminish benefits expected from the $20B+ restoration.

Optimal prey switching: Predator foraging costs provide a mechanism for functional responses in multi-prey systems.

Foragers must balance the costs and gains inherent in the pursuit of their next meal. Classical functional response formulations describe consumption rates driven by prey density and are naive to predator foraging costs. Here, we integrated foraging costs into functional responses to add mechanism and precision to foundational ideas. Specifically, using a model system with a single predator and two prey, we express a functional response emerging from variable energy and time costs of each predation phase: searching, attacking, or consuming prey. The utility of our model is explored through a focused example where prey can exert variable influence on predator foraging costs through antipredator traits. Dissimilarity between prey in their foraging costs influence the energy gain rate of the predator through optimal prey switching. We found that a small subset of prey antipredator traits and density conditions generated a stabilizing Type III (sigmoidal) functional response-the pattern often thought to typify a generalist predator switching between prey species. The sigmoid functional response occurred for highly profitable prey only when the costly prey (1) were at a high density and (2) their antipredator traits increased energy or time costs following an encounter. We outline testable predictions regarding foraging costs from our model. We provide guidance on how to apply optimal foraging theory to empirical scenarios where predator foraging costs vary due to prey type, predator type, or environmental conditions. Our framework represents a synergy of foundational and contemporary theory across disciplines, facilitating the discovery of shared principles and context-dependent variation across varied predator-prey systems.

[Médecine Tropicale et Santé Internationale takes a stand against editorial predation]. / Médecine Tropicale et Santé Internationale s'engage contre la prédation éditoriale.

Warnings against predatory journals get stronger. Designed to capture manuscripts with the promise of rapid publication, the main aim of these journals is to charge abusive publication fees. Sometimes boasting imaginary impact factors, they are not indexed and offer no guarantee of visibility, accessibility or durability of the published article. Above all, they have no concern for the rigor and scientific integrity of the work they publish.

Predator- and killed prey-induced fears bear significant cost to an invasive spider mite: Implications in pest management.

BACKGROUND: The success of biological control using predators is normally assumed to be achieved through direct predation. Yet it is largely unknown how the predator- and killed prey-induced stress to prey may contribute to biological control effectiveness. Here, we investigate variations in life-history traits and offspring fitness of the spider mite Tetranychus ludeni in response to cues from the predatory mite Phytoseiulus persimilis and killed T. ludeni, providing knowledge for evaluation of the nonconsumptive contribution to the biological control of T. ludeni and for future development of novel spider mite control measures using these cues. RESULTS: Cues from predators and killed prey shortened longevity by 23-25% and oviposition period by 35-40%, and reduced fecundity by 31-37% in T. ludeni females. These cues significantly reduced the intrinsic rate of increase (rm ) and net population growth rate (R0 ), and extended time to double the population size (Dt ). Predator cues significantly delayed lifetime production of daughters. Mothers exposed to predator cues laid significantly smaller eggs and their offspring developed significantly more slowly but these eggs had significantly higher hatch rate. CONCLUSION: Predator- and killed prey-induced fears significantly lower the fitness of T. ludeni, suggesting that these nonconsumptive effects can contribute to the effectiveness of biological control to a great extent. Our study provides critical information for evaluation of biological control effectiveness using predators and paves the way for identification of chemical odors from the predator and killed prey, and development of new materials and methods for the control of spider mite pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Avoiding costly mistakes in groups: The evolution of error management in collective decision making.

Individuals continuously have to balance the error costs of alternative decisions. A wealth of research has studied how single individuals navigate this, showing that individuals develop response biases to avoid the more costly error. We, however, know little about the dynamics in groups facing asymmetrical error costs and when social influence amplifies either safe or risky behavior. Here, we investigate this by modeling the decision process and information flow with a drift-diffusion model extended to the social domain. In the model individuals first gather independent personal information; they then enter a social phase in which they can either decide early based on personal information, or wait for additional social information. We combined the model with an evolutionary algorithm to derive adaptive behavior. We find that under asymmetric costs, individuals in large cooperative groups do not develop response biases because such biases amplify at the collective level, triggering false information cascades. Selfish individuals, however, undermine the group's performance for their own benefit by developing higher response biases and waiting for more information. Our results have implications for our understanding of the social dynamics in groups facing asymmetrical errors costs, such as animal groups evading predation or police officers holding a suspect at gunpoint.

Modelling the role of predation on disease burdens of prey.

Research Highlight: Brandell, E. E., Cross, P. C., Smith, D. W., Rogers, W., Galloway, N. L., MacNulty, D. R., Stahler, D. R., Treanor, J. & Hudson, P. J. (2022). Examination of the interaction between age-specific predation and chronic disease in the Greater Yellowstone Ecosystem. Journal of Animal Ecology, 00, 1-12. https://doi.org/10.1111/1365-2656.13661. Predation can alter disease dynamics in prey. If predators select for infected individuals, they can reduce disease burdens. In other cases, predators can increase disease burdens via various mechanisms such as altered prey behaviour. The influence of predation on disease dynamics is a result of interactions among various traits of the predators, prey and the pathogen itself. For example, pathogens tend to vary with age and predators typically select for certain age classes. Thus, the overlap between ages selected by predators and those infected will likely contribute to any effects of predation on reducing disease burdens. In this paper, Brandell et al. (2022) develop a model to evaluate the predator cleansing effect given age-based variation in pathogens and predation. The model was developed for Chronic Wasting Disease (CWD) infections in deer and elk facing predation by cougars and grey wolves in the Greater Yellowstone Ecosystem. The results indicate that predators can reduce CWD outbreak size, especially if selecting for infected individuals. CWD is an always fatal disease and this work suggests that predators could reduce disease burdens in cervids. The model is also applicable to other systems and promises to further our understanding of the role of predation on disease in prey, as well as drive future empirical studies.