Impact Of Predation Research Articles

An egg parasitoid interferes with biological control of tomato leafminer by augmentation of Nesidiocoris tenuis (Hemiptera: Miridae)

Tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious pest of tomato production in many parts of the world. The TLM has demonstrated capacity to evolve resistance to insecticides, and residues of these on tomato fruit pose hazards to human health, making biological control solutions an urgent priority. We assessed the biological control potential of the predatory bug Nesidiocoris tenuis (Reuter), in combination with the egg parasitoid Trichogramma brassicae Bezdenko at various release rates (0, 10 or 30 females/m2/week). Predators were released either 10 days before, or 10 days after, pest establishment. The predator lowered pest density only when it was released before the pest, but not to levels likely to retain the population below economic threshold. The parasitoid had no direct effect on pest density, but negatively affected the predator's impact on the pest, likely by reducing prey suitability and shifting feeding behavior toward more herbivory and/or cannibalism. Both pest and predator displayed negative density dependence; their population growth rates declined with increasing conspecific density. Our results indicate that N. tenuis should be augmented using a predator-in-first approach, and without simultaneous releases of egg parasitoids. Augmentation of N. tenuis will require integration with other tactics to provide adequate control of TLM, but has the potential for ancillary impacts on other tomato pests such as whiteflies and spider mites.

How Do Trait-Mediated Non-lethal Effects of Predation Affect Population-Level Performance of Mosquitoes?

Non-lethal, trait-mediated effects of predation impact prey behavior and life-history traits. Studying how these effects in turn influence prey demography is crucial to understand prey life-history evolution. Mosquitoes are important vectors that claim several million lives every year worldwide by transmitting a range of pathogens. Several ecological factors affect life-history traits of both larval and adult mosquitoes, creating effects that cascade to population-level consequences. Few studies have comprehensively explored the non-lethal effects of predation and its interactions with resources and competition on larval, adult, and population traits of mosquitoes. Understanding these interactions is important because the effects of predation are hypothesized to rescue prey populations from the effects of density-dependence resulting from larval competition. Aedes aegypti larvae reared at two different larval densities and subjected to three non-lethal predator treatments were monitored for survival, development time, and adult size through the larval stages to adult eclosion, and adult females were monitored for survival and reproduction through their first gonotrophic cycle. Intraspecific competition increased larval development time, yielded small-bodied adults, and reduced fecundity in individuals exposed to predatory chemical cues as larvae. Exposure to cues from a living predator affected both body size and latency to blood feed in females. Analysis of life-table traits revealed significant effects of competition on net reproductive rate (R 0) of mosquitoes. The interaction between competition and predator treatments significantly affected the cohort rate of increase (r) and the index of performance (r'). The index of performance, which estimates rate of population change based on the size-fecundity relationship, was significantly and positively correlated with r, but overestimated r slightly. Lack of significant effect of predator treatments and larval density on cohort generation time (T c) further suggests that the observed effects of treatments on r and r' were largely a consequence of the effects on R 0. Also, the significant effects of treatment combinations on larval development time, adult body size and fecundity were ultimately manifested as effects on life-table traits estimated from adult survival and reproduction.

Disentangling the trophic interactions between American bullfrogs and native anurans: Complications resulting from post‐metamorphic ontogenetic niche shifts

Abstract The American bullfrog, Lithobates catesbeianus (Shaw, 1802), is considered one of the world's worst invaders because of its potential to affect native fauna adversely, especially amphibians, through predation, competition, breeding interference, and disease transmission. Here, the potential impact of introduced American bullfrogs (juveniles and adults) on native adult green frogs, Pelophylax kl. esculentus (Linnaeus, 1758), was investigated in a pond ecosystem by means of stomach‐content and stable‐isotope analyses. Specifically, this study was aimed at assessing the impact of the American bullfrog on native green frogs in terms of predation and competition (i.e. feeding ecology and habitat use), and uncovering changes in interspecific interactions linked to the ontogenetic dietary–habitat shifts of the invaders. Stomach contents and isotope analyses suggest that L. catesbeianus changes trophic position in the food chain and undergoes ontogenetic dietary–habitat shifts during its life cycle. The species therefore has the potential to exert a double impact on native green frogs: as a predator at the adult stage and as a competitor (for food and habitat use) at the juvenile stage. Stomach‐content and isotope analyses gave similar results, suggesting that the predation impact by adult American bullfrogs on green frogs is mediated by the presence of the alien red swamp crayfish, Procambarus clarkii (Girard, 1852). Juvenile American bullfrogs and native amphibians overlap in their diet composition and in their habitat use, suggesting the existence of potential competition between the two species. Ontogenetic dietary–habitat shifts in the American bullfrog, local conditions, and trophic interactions should be seriously considered in management approaches to promote the long‐term coexistence of L. catesbeianus and native amphibians. Such management options have been neglected in the literature, and are worthy of further investigation to understand their efficacy on native species.

Impact of shorebird predation on intertidal macroinvertebrates in a key North African Atlantic wintering site: an experimental approach

Shorebirds, as migratory aquatic birds and top predators in intertidal ecosystems, can be affected by global environmental changes and escalations in local impacts on coastal lagoons and estuarine trophic networks. Many shorebirds winter in North African Atlantic coastal sites, most likely because these locations provide constant and reliable food supplies with less energy costs in comparison with the wintering sites of northern Europe. Although more information is available for other important southern coastal sites (e.g. Saharan Atlantic coastal desert and Guinean mangroves coast), very little information is available for the North African Atlantic coast. Here, we focus on the impact of shorebird predation on benthic macroinvertebrates in a major wintering site in this area—Sidi Moussa coastal lagoon, Morocco—using an exclosure experiment. For most of the macroinvertebrate species there was no significant effect of the exclusion of shorebird predation. Overall, our results do not show evidence that predation by shorebirds influenced the overall standing biomass of the benthic community. This may indicate that the benthic productivity is high enough to provide constant and reliable food supplies for non-breeding shorebirds.

Влияние предшественника на показатели качества зерна яровой мягкой пшеницы

Влияние предшественника на показатели качества зерна яровой мягкой пшеницы

Foxes, voles, and waders: drivers of predator activity in wet grassland landscapes

Impacts of generalist predators on declining prey populations are a major conservation issue, but management of this situation is constrained by limited knowledge of the factors influencing predator distribution and activity. In many declining populations of ground-nesting waders, high levels of nest and chick predation are preventing population recovery. Red foxes, Vulpes vulpes, are the main predator but their primary prey is small mammals. On wet grasslands managed for breeding waders, small mammals are concentrated in tall vegetation outside of fields, and nests closer to these patches are less likely to be predated. To assess whether these patterns result from fox attraction to small mammals, and thus the potential for management of tall vegetation to influence nest predation rates, we quantify seasonal and spatial variation in fox and small mammal activity in relation to tall vegetation patches. Across wet grassland sites, tall vegetation patches of any size (> 0.05 ha) supported small mammals and small mammal activity increased throughout the wader breeding season, while the use of fox track plots within fields declined seasonally. Although within field fox track plot use did not vary with distance to tall vegetation, over the 1064 nights of trail camera recording, foxes were seen in areas with tall vegetation on 13 nights compared with short vegetation on only two nights. These findings suggest that lower predation rates of lapwing nests close to tall vegetation could reflect fox attraction to areas with small mammal activity, but any such effects would primarily operate later in the breeding season, and may therefore primarily influence late nests and chicks.

Assessment of potential impact of domestic cats on small mammals in a protected insular area

Abstract The presence of domestic cats in natural areas is considered one of the main reasons for species loss, especially on islands and among native small non-volant mammals, birds and reptiles. However, in this study, we detected values opposite to those expected for species richness, abundance, and diversity among different areas when considering the presence or absence and density of these felines. We also observed that in the evaluated environments, prey availability did not influence consumption of small mammal species. Our results reinforce the theory of domestic cats’ behaviour as being opportunistic and generalist predators. In addition, we only recorded the presence of exotic species in the faeces of cats; that is, we did not capture exotic species in the traps. The close relationship between these exotic species and anthropogenic environments indicates that felines are likely hunting in areas close to the homes where they live. Assessing the impact of predation by domestic cats on native fauna is important for the development and implementation of strategic resource management and to minimize long-term impacts.

Predation Fear, Prey Behavior, and Community Structure: A Brief Review of Their Relationship

Predation Fear, Prey Behavior, and Community Structure: A Brief Review of Their Relationship Hamenya Mpemba, Henry Karanja, Guangshun Jiang Abstract The main aim of this research is to review the relationship between predation fear, prey behavior, and community structure or assembly. The relationship between prey and predator is shaped around the risk of predation. A non-consumptive impact of predators on their prey seems to be more extensive and diverse, with significant consequences for community structure and function of the ecosystem. Predators have a strong direct and indirect effect on ecological communities by intimidating their prey. Ecological context including habitat structure and identity of species have influenced the strength and nature of non-consumptive effects and hence it may alter the outcome of intimidation of predator. Further, this study uses secondary data collection methods. The relationship between predation fear and aging behavior of prey, reproduction behavior of prey and territorial defense strategies of prey are detailed in the prior literature review. Since a wide range of wildlife is under existential crisis especially the predators, there is a need to understand the predator-prey relation. In the future, this work can be detailed by collecting the primary data source through a quantitative approach among various investigators. Full Text: PDF DOI: 10.15640/aijb.v7n1a1

Comparing the predatory impact of captive–bred and free–living yellow spotted mountain newt (Neurergus microspilotus) on the larval green toad (Bufotes variabilis)

Comparing the predatory impact of captive–bred and free–living yellow spotted mountain newt (Neurergus microspilotus) on the larval green toad (Bufotes variabilis)

Temperature Induced Predation Impact of Mosquitofish (Gambusia affinis) on Growth, Development, and Survival of Larvae and Tadpole of Bufotes variabilis (Amphibia: Anura)

There are increasing evidences documenting the negative impact of exotic species including mosquitofish, Gambosi affinis, in Iran. Meanwhile, recent climate change in freshwater ecosystems in arid and semi-arid regions such as Iran is expected to cause undesirable impact. We conducted experiments in 2 levels of temperature and predator density including: high temperature/high predator (HT/HP), high temperature/ low predator (HT/LP), low temperature/high predator (LT/HP), and low temperature/low predator (LT/LP) that carried out within 20 days. Larval growth rate was highest at the HT/HP (0.29 mm/day), development stage was slowest at the LT/HP treatment (Gosner: 28.33 ± 0.33), and survival rate was lowest at HT/HP treatment (0.00%). Except for the significant impact of predator density on survival, B. variabilis was tolerant of both predator density and increased temperature and there was no interaction between predator density and increased temperature in term of growth, development and survival. But, combined effects of temperature and predator density showed significant effects on growth, metamorphosis, and survival over time.

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

VIABILITY OF THE POPULATIONS OF PERDIX PERDIX L. AT MT. FRUŠKA GORA AND SREMSKA RAČA, REPUBLIC OF SERBIA

UDK: 639.124(497.11)
 Perdix perdix L. (also known as the Grey partridge, English partridge, and Hungarian partridge) populations have been declining for years in natural habitats and areas in which this species of wildlife has been introduced. Hunting grounds at the base of Mt. Fruška Gora and Sremska Rača in the Republic of Serbia provide excellent conditions for its breeding. In addition to the data from hunting records about population quantity of the P. perdix, a direct monitoring allows a relevant inside to its' quantity in hunting associations’ hunting grounds. The decline of population quantity is mostly the result of the use of chemicals for protection of agricultural crops (10%), destruction of nests and bird eggs (12.5%), and the failure to implement failure wildlife-protection measures, by forbidding the hunt of P. perdix (5%) , and the use of poisons on agricultural crops, such as the forbidden poison Furadan (5%). Although no significant results have been obtained on the impact of predators and abandoned animals on the reduction of P. perdix population, there is a justified concern by hunting associations’ in terms of finding ecologically and biologically viable solutions for impact on predators on feathered game, and especially abandoned dogs. The results of the study were obtained by the method of directly determining the number of P. perdix in the crop fields, in the hunting grounds of L.D. "Fazan Mala Remeta", L.D. "Fazan" Jazak, L.D. "Stejanovci" Stejanovci, L.D. "Zec" Vrdnik and L.D. "Srndać" Sremska Rača. The obtained results directly the need to introduce the principle of integral protection of P. perdix, which implies control over the implementation of measures for the protection of agricultural crops and the implementation of P. perdix protection measures during the organization of hunting on other game species in hunting grounds.

Nesting ecology and nesting success of resident and endemic tropical birds in the Dominican Republic

Despite Hispaniola's high rates of avian endemism and its importance to supporting global biodiversity, relatively little information is available on the basic biology and ecology of its resident birds, particularly the 31 species endemic to the island. Here we describe the nesting ecology and nesting success (n = 643 nests) of species of resident and endemic birds occurring in southwestern Dominican Republic, spanning 4 major habitat types over an elevational gradient from sea level to ∼1,750 m: desert thorn scrub, dry broadleaf forest, pine forest, and montane cloud forest. We quantify nesting success in terms of daily nest survival and cumulative survival probabilities for 14 resident species (3 endemic) and describe life history metrics for these species, including clutch size and length of incubation and brooding. We compare nest success among habitats and highlight the large impact of introduced mammalian predators in all habitats studied. Nesting success was generally lower than in temperate areas, but comparable to other studies of nesting success in the Neotropics, with a mean cumulative survival probability for all open-cup nesting species of 33.6%. Nest failure due to predation varied by species but was overall notably high, ranging from 73% to 100% of all failed nests. Predation was primarily attributable to nonnative mammals introduced via European colonization.

Comparing the predatory impact of captive–bred and free–living yellow spotted mountain newt (Neurergus microspilotus) on the larval green toad (Bufotes variabilis)

espanolLa cria en cautividad de especies amenazadas es un practica importante en la conservacion, pero no esta claro si los programas de cria en cautividad a largo plazo pueden afectar a determinados atributos fundamentales de la eficacia biologica de las especies como la capacidad de depredacion. En el presente estudio se estudian experimentalmente los efectos de la capacidad de depredacion de tritones del Kurdistan adultos nacidos en cautividad (CBN) y de individuos obtenidos directamente de la naturaleza (FLN) en la supervivencia y el crecimiento de renacuajos de sapo verde mantenidos en cuatro tratamientos de densidad de depredadores, que contenian cero, uno, dos y tres tritones. El grupo de tritones FLN mostro una tasa de depredacion rapida dependiente de la densidad de depredadores que conllevo que las tasas de supervivencia de los renacuajos en las densidades de control, baja, media y alta fueran, respectivamente, del 81%, el 74%, el 60% y el 17%. El grupo CBN tuvo una menor tasa media de depredacion sobre los renacuajos de B. variabilis, cuya tasa de supervivencia disminuyo hasta el 83%, el 81%, el 82% y el 77% para los tratamientos con cero, uno, dos y tres tritones, respectivamente. Sin embargo, a diferencia del grupo FLN, esta tasa de depredacion aumento significativamente con el tiempo y paso de 0,37 a 0,60 renacuajos por dia. Por otra parte, la tasa de crecimiento de los renacuajos criados con depredadores del grupo FLN fue significativamente superior a la de los renacuajos criados en contenedores de control sin depredadores. Como conclusion, nuestros resultados sugieren que la exposicion de individuos nacidos en cautividad del triton del Kurdistan a sus presas potenciales enriquece el medio ambiente y puede ser util para elaborar programas mas eficientes de cria en cautividad y reintroduccion de esta especie de anfibio muy amenazada. EnglishCaptive breeding of endangered species is an important conservation tool, but it is not clear how long–term captive breeding can influence fitness attributes such as predatory ability. We experimentally investigated the predatory impact of adult captive–bred newts (CBN) and adult free–living newts (FLN) on the survival and growth of larval green toad (B. variabilis) in four predator density treatments containing none, one, two, or three newts. FLNs performed a rapid density–dependent predation, yielding average survival rates of tadpoles in no, low, medium, and high densities to 81%, 74%, 60% and 17%, respectively. CBNs had an average lower predation rate on B. variabilis tadpoles with a decrease in survival rate of tadpoles to 83%, 81%, 82% and 77% for 0, 1, 2 and 3 predator treatments, respectively. However, contrary to FLNs, they exhibited a significant increase in predation rate with time from 0.37 to 0.60 tadpoles per day. In addition, the growth rate of tadpoles reared with predators for the FLN group was significantly higher than the growth rate of tadpoles reared in control containers without the predator. In conclusion, our findings suggest that exposing captive–born adult yellow spotted mountain newts to their potential prey enriches the environment, and may be a useful approach in the development of more efficient captive breeding and reintroduction programs for this highly endangered amphibian.

Predation of the round goby (Neogobius melanostomus Pallas, 1814) on Atlantic herring eggs in the Western Baltic Sea

ABSTRACTThe Ponto-Caspian round goby (Neogobius melanostomus Pallas, 1814) is a prominent invasive species in many European waters. Eggs of the Western Baltic Spring Spawning Atlantic herring might be attractive prey for the invasive round goby during the spawning season. However, investigations of the small fish fauna in an important spawning area of herring, which was characterized by high densities of macrophytes, indicated a spatio-temporal mismatch of round goby and herring spawn in spring, at least on some of the known important spawning beds situated on vegetated sandy bottoms. In contrast, a spatio-temporal overlap between round gobies and herring spawn was observed in a more structured area, characterized with stones, where round gobies’ stomachs were sampled. Further field study results suggest that large round gobies (> 10 cm) do not feed on herring eggs, while smaller round gobies (< 10 cm) do so. To support these results, we conducted laboratory feeding experiments with round gobies. When C. crangon, M. edulis and herring eggs were offered simultaneously, round gobies preferred C. crangon. M. edulis was preferred over herring eggs when C. crangon was absent. The predatory impact of the round goby on herring eggs seems to be of minor importance compared to other species, such as three-spined stickleback or perch. Applying the same data, different food ‘preference indices’ revealed a discrepancy in preference between indices. Therefore, we propose a modified food preference index (mE), taking into account four important parameters and combining benefits of two commonly applied indices.

Can the common fisheries policy achieve good environmental status in exploited ecosystems: The west of Scotland demersal fisheries example

The latest reform of the Common Fisheries Policy (CFP) which regulates the exploitation of fish stocks in European waters entails a move from the traditional single stock management towards Ecosystem Based Fisheries Management (EBFM). Meanwhile the Marine Strategy Framework Directive dictates that Good Environmental Status (GES) should be achieved in European waters by 2020. Here we apply an EBFM approach to the west of Scotland demersal fisheries which are currently facing several management issues: depleted stocks of cod (Gadus morhua) and whiting (Merlangius merlangus), increased predation from grey seals (Halichoerus grypus), and large bycatch of juvenile whiting by crustacean fisheries. A food web ecosystem model was employed to simulate the outcomes of applying the traditional single stock fishing mortalities (F), and management scenarios which explored F ranges in accordance with the CFP. Ecosystem indicators were calculated to assess the performance of these scenarios towards achieving GES. Our results highlight the importance of considering prey-predator interactions, in particular the impact of the top predators, cod and saithe (Pollachius virens), on juvenile cod and whiting. The traditional single stock approach would likely recover cod, but not whiting. Exploring the F ranges revealed that a drastic reduction of juvenile whiting bycatch is necessary for the whiting stock to recover. Predation from grey seals had little impact overall, but did affect the timing of cod and whiting recovery. With the exception of whiting, little difference was observed between the single stock scenario, and the best scenario identified towards achieving GES. The findings advocate for the use of ecosystem modelling alongside the traditional single stock assessment models used for tactical decision making in order to better inform fisheries management.

Metrics of progress in the understanding and management of threats to Australian birds.

Although evidence-based approaches have become commonplace for determining the success of conservation measures for the management of threatened taxa, there are no standard metrics for assessing progress in research or management. We developed 5 metrics to meet this need for threatened taxa and to quantify the need for further action and effective alleviation of threats. These metrics (research need, research achievement, management need, management achievement, and percent threat reduction) can be aggregated to examine trends for an individual taxon or for threats across multiple taxa. We tested the utility of these metrics by applying them to Australian threatened birds, which appears to be the first time that progress in research and management of threats has been assessed for all threatened taxa in a faunal group at a continental scale. Some research has been conducted on nearly three-quarters of known threats to taxa, and there is a clear understanding of how to alleviate nearly half of the threats with the highest impact. Some management has been attempted on nearly half the threats. Management outcomes ranged from successful trials to complete mitigation of the threat, including for one-third of high-impact threats. Progress in both research and management tended to be greater for taxa that were monitored or occurred on oceanic islands. Predation by cats had the highest potential threat score. However, there has been some success reducing the impact of cat predation, so climate change (particularly drought), now poses the greatest threat to Australian threatened birds. Our results demonstrate the potential for the proposed metrics to encapsulate the major trends in research and management of both threats and threatened taxa and provide a basis for international comparisons of evidence-based conservation science.

Using functional responses to quantify notonectid predatory impacts across increasingly complex environments

Predation is a key biotic interaction that influences both the structure and functioning of ecosystems, and is relevant in the biological control context. Levels of habitat complexity in aquatic ecosystems are highly variable and can profoundly affect predator-prey interactions through the presence of prey refugia, which can in turn reduce predatory efficacy. Here, we use functional responses (FRs, resource use under different resource densities) to quantify the predatory impact of the notonectid Anisops debilis towards larvae of the mosquito Culex pipiens under a habitat complexity gradient. Anisops debilis displayed a potentially population-destabilising Type II FR towards larval C. pipiens prey across the habitat complexity gradient. Attack rates were highest in simple environments, however handling times were not significantly affected by habitat complexity. Maximum feeding rates of A. debilis towards C. pipiens larvae were thus robust to habitat complexity variations. Our results demonstrate the substantial predatory impacts of notonectids towards larval mosquito prey irrespective of habitat complexities, which may assist in the biological control of pests and vectors in aquatic systems.

Dye another day: the predatory impact of cyclopoid copepods on larval mosquito Culex pipiens is unaffected by dyed environments.

Culex mosquitoes are especially evasive of predators when ovipositing. Black pond dyes are known to profoundly attract their oviposition and this study looked at the combination of predator presence and pond dye. Our results indicate that predatory impacts of cyclopoid copepods are unaffected by the presence of pond dye. Their use in synergy with dye may facilitate population sinks characterized by high rates of oviposition coupled with high predation rates. This may increase the vulnerability of mosquitoes to predation at the landscape level and is pertinent given that oviposition site selectivity is currently the greatest hindrance to effective larval mosquito control.

Size-dependent functional response ofXenopus laevisfeeding on mosquito larvae

Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often, predators of the same species are assumed to be functionally equivalent, despite considerable individual variation in predator traits known to be important for shaping predator–prey interactions, like body size. This assumption may greatly oversimplify our understanding of within-species functional diversity and undermine our ability to predict predator effects on prey. Here, we examine the degree to which predator–prey interactions are functionally homogenous across a natural range of predator body sizes. Specifically, we quantify the size-dependence of the functional response of African clawed frogs (Xenopus laevis) preying on mosquito larvae (Culex pipiens). Three size classes of predators, small (15–30 mm snout-vent length), medium (50–60 mm) and large (105–120 mm), were presented with five densities of prey to determine functional response type and to estimate search efficiency and handling time parameters generated from the models. The results of mesocosm experiments showed that type of functional response of X. laevis changed with size: small predators exhibited a Type II response, while medium and large predators exhibited Type III responses. Functional response data showed an inversely proportional relationship between predator attack rate and predator size. Small and medium predators had highest and lowest handling time, respectively. The change in functional response with the size of predator suggests that predators with overlapping cohorts may have a dynamic impact on prey populations. Therefore, predicting the functional response of a single size-matched predator in an experiment may misrepresent the predator’s potential impact on a prey population.