Impact Of Predation Research Articles

Complex Trophic Interactions in an Acidophilic Microbial Community.

Extreme habitats often harbor specific communities that differ substantially from non-extreme habitats. In many cases, these communities are characterized by archaea, bacteria and protists, whereas the number of species of metazoa and higher plants is relatively low. In extremely acidic habitats, mostly prokaryotes and protists thrive, and only very few metazoa thrive, for example, rotifers. Since many studies have investigated the physiology and ecology of individual species, there is still a gap in research on direct, trophic interactions among extremophiles. To fill this gap, we experimentally studied the trophic interactions between a predatory protist (Actinophrys sol, Heliozoa) and its prey, the rotifers Elosa woralli and Cephalodella sp., the ciliate Urosomoida sp. and the mixotrophic protist Chlamydomonas acidophila (a green phytoflagellate, Chlorophyta). We found substantial predation pressure on all animal prey. High densities of Chlamydomonas acidophila reduced the predation impact on the rotifers by interfering with the feeding behaviour of A. sol. These trophic relations represent a natural case of intraguild predation, with Chlamydomonas acidophila being the common prey and the rotifers/ciliate and A. sol being the intraguild prey and predator, respectively. We further studied this intraguild predation along a resource gradient using Cephalodella sp. as the intraguild prey. The interactions among the three species led to an increase in relative rotifer abundance with increasing resource (Chlamydomonas) densities. By applying a series of laboratory experiments, we revealed the complexity of trophic interactions within a natural extremophilic community.

There must be Some Kind of Way Out of Here: Towards ‘Reframing’ European Cormorant-Fisheries Conflicts

One of the most widespread and persistent environmental conflicts in Europe involves the Great Cormorant Phalacrocorax carbo. The ‘continental’ race P. c. sinensis comprises over 80% of the European breeding population and its numbers and geographical distribution have increased and expanded dramatically in recent decades. Consequently, Cormorants have increasingly come into conflict with fisheries interests across Europe, as many people believe that the birds are now so numerous that they cause declines in fish catches, with associated impacts on commercial and recreational fisheries. The Central European policy issue is thus how to deal with: (1) a large pan-European population of Cormorants, (2) very often breeding in some Member States but overwintering and preying upon fish in others, (3) where there is generally a lack of unequivocal scientific evidence for predation impact on fisheries and (4) where there are growing political calls for coordinated European management, whilst (5) many believe that the site-specific local/regional management advocated by some is ineffective. Using case examples and experiences from several pan-European studies and research networks, this paper describes the complexity of this issue and the diversity of associated opinions. Much of the controversy over Cormorants is fuelled by differences of opinion and, coupled with its persistence and entrenched nature, it has many of the characteristics of a so-called ‘intractable environmental conflict’. As such, this paper draws on a ‘reframing’ model proposed to deal with such situations and discusses the various ‘frames’ by which issues are viewed. It also proposes that future research might best focus on specific fisheries sectors that appear to be ‘hotspots’ for conflicts. Here, demonstration projects could involve a reframing exercise, coupled with new scientific research and practical experimentation within an adaptive management framework – one aim of which might be to increase the scope and geographical coverage of effective management activities.

The impact of predation on population dynamics of the Crested Ibis in the Qinling Mountains, Shaanxi, central China

Predation is one of the most important extrinsic factors acting upon animal populations and is a strong selective force in the evolution of form and function. Understanding the impact of predation on bird population dynamics is crucial for understanding the predation pressure of bird populations and implementing conservation strategies, especially for threatened or endemic bird species. In this paper, we sorted the predation events in the wild Crested Ibis population in Yangxian County, Shaanxi Province, from 1981 to 2021 and in the reintroduced Crested Ibis population in Ningshan from 2008 to 2021. With the use of age‐classified Leslie matrix models to simulate Crested Ibis populations under different predation pressures, the random population growth rate was estimated, and the impact of predation on population dynamics was evaluated. The results showed that snakes and raptors were the main predators of Crested Ibis in the wild and reintroduced populations, and the number of dead individuals was unevenly distributed within the three age classes in both the wild population (df = 2,χ2 = 13.236,p < 0.05) and reintroduced population (df = 2,χ2 = 49.273,p < 0.01). Predation caused a reduction in the potential annual population growth rate of 2.37% (confidence interval [CI]: 2.29–2.45) in the wild population and 2.88% (CI: 2.82–2.94) in the reintroduced population. The overall average growth rates of the wild and reintroduced populations derived from population model simulations were 12.84 and 18.13%, respectively, which suggested that the wild and reintroduced populations was increasing under the current predation pressure and that the impact of predation on the population was acceptable and sustainable.

Структурні показники популяції окуня (Perca fluviatilis Linnaeus, 1758) Кременчуцького водосховища

Objective. Analysis of the structural parameters of the perch (Perca fluviatilis L.) population in the Kremenchuk Reservoir in the world of the development of the program of stocking large flat reservoirs of the Dnipro with juveniles of Far Eastern herbivorous fish, there was a need for methodical approaches to reduce the negative impact of small predators on the efficiency of planned stocking. Methodology. Primary materials related to the biology and fishing of perch were collected at the monitoring points of the Institute of Fisheries of the National Academy of Sciences. The basis of this article is the results of our own field research, which was carried out in the entire water area of the Kremenchuk Reservoir during 2016–2021. To determine the composition of catches in nets with different mesh sizes, the refined coefficient of annual commercial mortality was used. Results. The article establishes the general basic population indices of the perch (Perca fluviatilis L.) population in the Kremenchuk Reservoir. Acceptable indices of the perch population and the probability of its negative impact on the stocking of big-headed Chinese carps this year have been established. The scientific novelty of the work is due to the fact that effective stocking is currently possible only in the presence of scientifically based data, which can significantly affect the cost of planting material, and, as a result, the volume of work carried out. These basic principles are able to ensure the sustainable use of aquatic biological resources in natural reservoirs. Practical significance: the biological indices of the P. fluviatilis population presented in this work can be used to calculate the limits for perch commercial fishing in Kremenchuk Reservoir and to assess its negative impact on the stocked young fishes. Key words: perch, Kremenchuk Reservoir, length structure, catch per unit effort, commercial harvest.

CTENOPHORA <i>MNEMIOPSIS LEIDYI</i> A. AGASSIZ, 1865 POPULATION AND ITS PRESSURE ON ZOOPLANKTON IN OPEN AREAS OF THE BLACK SEA IN JULY - AUGUST 2017

The research both of the quantity and size structure of the invader Mnemiopsis leidyi (A. Agassiz 1865), as well as the mesozooplankton abundance, species diversity, the food spectrum, trophic relations, and predatory impact by M. leidyi on prey populations in the western and eastern sectors of the open Black Sea was carried out in July - August 2017. M. leidyi biomass varied from 92 to 250 g m during the period of maximum seasonal development. The food spectrum of M. leidyi was dominated by copepods Acartia spp. and Calanus euxinus (Hulsemann 1984). A clear spatial difference in the quantity of M. leidyi and zooplankton, the intensity of food consumption and predatory impact was observed. In the western offshore part of the sea, the high food ingestion rate by M. leidyi (the mean specific daily ration was 45.50±8.31% С) and intensive predatory impact on zooplankton (up to ~50% of Acartia sp. biomass) resulted in the strong decrease in mesozooplankton biomass. In contrast, in the eastern sector M. leidyi predation had no effect on zooplankton community maintaining daily grazing of ~6% Acartia spp. biomass.

Examining the costs and benefits of male-male associations in a group-living equid

In feral horse (Equus caballus) populations, females can associate in year-round social groups with one male (single-stallion (SS) groups) or multiple males (multi-stallion (MS) groups). Given the expectation of intense male competition for mating opportunities, male-male associations raise questions regarding their supporting mechanisms and adaptive consequences. The function of MS groups has been highly debated which led to a series of conflicting hypotheses attempting to describe the relationship between the males, and the costs and benefits of this association in relation to SS groups. Based on previous studies, our goal was to compare the group size and stability, males’ defence behaviour against group outsiders and access to females, levels of male aggression to group members, and the activity budget and body condition of horses in MS and SS groups. Between the months of May to August (breeding season) from 2016 to 2021, we collected demographic and behavioural data from feral Garrano horses living in northern Portugal, where wolf (Canis lupus signatus) predation is an important factor. Contrary to mutualistic hypotheses, our results indicated that SS males had more breeding females than MS groups and group type did not influence female membership stability. However, dominant males in MS groups may be benefitting from the presence of another male via decreased effort in group defence and more resting time. We recorded less aggressive behaviours from dominant to subordinate males in MS groups when subordinates displayed more defensive behaviours against outsiders, but we found little evidence that subordinates were being rewarded with access to females, as proposed by reciprocal-altruism hypotheses. Females in MS groups did not suffer higher levels of male aggression when compared with SS females, and the number of males in the group had no significant influence on the time females spent grazing and resting, and ultimately on their body condition. Future research should explore how MS male associations shape male-female relationships, which could provide further insights to the existence and maintenance of subordinate males. This study is the first to report on predation impact by wolves in MS and SS groups, highlighting the need to further explore how different ecological pressures shape horse behaviour and social organization. Furthermore, our results provide information that can help improve the welfare of domestic horses and can make informed management decisions of feral and free-ranging horse populations, particularly in instances where males are targeted for removals. Considering the advantages, as well as costs, provided by extra males may be useful to managers and horse owners, who can then act accordingly and with the least disturbance to horse populations.

Green turtles nest survival: Quantifying the hidden predation

Trindade Island is the largest nesting site for green turtles Chelonia mydas in Brazil and one of the most important in the Atlantic ocean. The terrestrial crab Johngarthia lagostoma forages almost everywhere on the island, including the green turtle nesting beaches. Nothing is known about crab predation on sea turtle eggs at the time of nesting. We obtained unprecedented records of crab predation at sea turtle nests during the breeding seasons of 2017/18 and 2018/19. We analyzed through images and videos the behavior of the predatory species. Not only that, but we observed an average loss of 3 eggs per nest. The period from 0:00 to 3:00 h presented the highest risk of predation. The mortality rate in the egg stage related to neonates was 5% per nest, with an estimated predation impact of 21,600 eggs per season reproductive.

Metacommunity stability and persistence for predation turnoff in selective patches

Predation as an important trophic interaction of ecological communities controls the large-scale patterns of species distribution, population abundance and community structure. Numerous studies address that predation can mediate diversity and regulate the ecological community and food web stability through changes in the behavior, morphology, development, and abundance of prey. Since predation has large effects on persistence and diversity, the local loss or removal of predation in a community can trigger a cascade of extinctions. In ecological theory, the effect of predation removal has been well studied in foodwebs, but it remains unclear in the case of a spatially distributed community connected by dispersal. In this study, the interaction between local and spatial processes is taken into account, we present how a predation turnoff in selective patches affects the synchronized oscillatory dynamics of a metacommunity. Using a simple predator–prey metacommunity with a diffusive dispersal, we show the impact of predation on synchronized, asynchronized and source–sink dynamics. Our results reveal that predation turnoff in very few patches stabilizes the metacommunity by damping the perfectly synchronized oscillatory state into multicluster equilibrium (i.e., steady) states. In a source–sink behavior, predation turnoff in a source patch reduces the number of sink patches and changes the clusters. In general, predation turnoff in low number of patches shows non-zero equilibrium states in both prey and predator populations, whereas predation turnoff in a larger number of patches can lead to the complete extinction of predators. Moreover, prey density from the patches where predation is absent goes to a saturating state near the carrying capacity. Thus, this study stresses that predation turnoff in selective patches acts as a stabilizing mechanism to promote the metacommunity persistence.

Survival of the sickest: selective predation differentially modulates ecological and evolutionary disease dynamics

Predators and parasites are critical, interconnected members of the community and have the potential to shape host populations. Predators, in particular, can have direct and indirect impacts on disease dynamics. By removing hosts and their parasites, predators alter both host and parasite populations and ultimately shape disease transmission. Selective predation of infected hosts has received considerable attention as it is recognized to have important ecological implications. The occurrence and consequences of preferential consumption of uninfected hosts, however, has rarely been considered. Here, we synthesize current evidence suggesting this strategy of selectively predating uninfected individuals is likely more common than previously anticipated and address how including this predation strategy can change our understanding of the ecology and evolution of disease dynamics. Selective predation strategies are expected to differentially impact ecological dynamics and therefore, consideration of both strategies is required to fully understand the impact of predation on prey and host densities. In addition, given that different strategies of prey selectivity by predators change the fitness payoffs both for hosts and their parasites, we predict amplified coevolutionary rates under selective predation of infected hosts compared to uninfected hosts. Using recent work highlighting the critical role that predators play in disease dynamics, we provide insights into the potential mechanisms by which selective predation on healthy individuals can directly affect ecological outcomes and impact long‐term host–parasite coevolution. We contrast the consequences of both scenarios of selective predation while identifying current gaps in the literature and future research directions.

Assessing the extent and public health impact of bat predation by domestic animals using data from a rabies passive surveillance program.

Domestic animals can serve as consequential conveyors of zoonotic pathogens across wildlife-human interfaces. Still, there has been little study on how different domestic species and their behaviors influence the zoonotic risk to humans. In this study, we examined patterns of bat encounters with domestic animals that resulted in submission for testing at the rabies laboratories of the Canadian Food Inspection Agency (CFIA) during 2014-2020. Our goals were specifically to examine how the number of bats submitted and the number of rabies positive bats varied by the type of domestic animal exposure and whether domestic cats were indoor or free-roaming. The CFIA reported 6258 bat submissions for rabies testing, of which 41.5% and 8.7% had encounter histories with cats and dogs, respectively. A much smaller fraction of bat submissions (0.3%) had exposure to other domestic animals, and 49.5% had no domestic animal exposure. For the bat submissions related to cats, and where lifestyle was noted, 91.1% were associated with free-roaming cats and 8.9% with indoor cats. Model results indicated the probability of a rabies-positive bat was the highest with a history of dog association (20.2%), followed by bats with no animal exposure (16.7%), free-roaming cats (6.9%), cats with unspecified histories (6.0%) and the lowest probability associated with non-free-roaming (indoor) cats (3.8%). Although there was lower rabies prevalence in bats associated with cats compared to dogs, the 4.8 fold higher number of cat-bat interactions cumulatively leads to a greater overall rabies exposure risk to humans from any free-roaming outdoor cats. This study suggests that free-roaming owned cats may have an underappreciated role in cryptic rabies exposures in humans and as a significant predator of bats. Preventing free-roaming in cats is a cost-effective and underutilized public health recommendation for rabies prevention that also synergistically reduces the health burden of other feline-associated zoonotic diseases and promotes feline welfare and wildlife conservation.

Protist feeding patterns and growth rate are related to their predatory impacts on soil bacterial communities.

Predatory protists are major consumers of soil micro-organisms. By selectively feeding on their prey, they can shape soil microbiome composition and functions. While different protists are known to show diverging impacts, it remains impossible to predict a priori the effect of a given species. Various protist traits including phylogenetic distance, growth rate and volume have been previously linked to the predatory impact of protists. Closely related protists, however, also showed distinct prey choices which could mirror specificity in their dietary niche. We, therefore, aimed to estimate the dietary niche breadth and overlap of eight protist isolates on 20 bacterial species in plate assays. To assess the informative value of previously suggested and newly proposed (feeding-related) protist traits, we related them to the impacts of predation of each protist on a protist-free soil bacterial community in a soil microcosm via 16S rRNA gene amplicon sequencing. We could demonstrate that each protist showed a distinct feeding pattern in vitro. Further, the assayed protist feeding patterns and growth rates correlated well with the observed predatory impacts on the structure of soil bacterial communities. We thus conclude that in vitro screening has the potential to inform on the specific predatory impact of selected protists.

Multiple stressors: negative effects of nest predation on the viability of a threatened gull in different environmental conditions

The majority of the world's seabirds show substantial population declines, but a detailed understanding of the phenomenon is lacking. A potentially important mechanism that has received momentum lately is nest predation. This study aimed to assess the population viability of a threatened population of the lesser black‐backed gull Larus fuscus fuscus under different scenarios for nest predation and environmental conditions. We merged results from statistical analyses of 16 years of empirical data with a Leslie model, emphasising the impact of predation at the nesting stage. In the model, we quantified the effect of multiple stressors on the viability of the lesser black‐backed gull according to the IUCN Red List's 'Vulnerable' criteria (30% reductions in population size over < 3 generations). First, the empirical analyses showed that the estimated apparent survival probability, which showed declining temporal trends, was on average 0.862 and 0.470 for adults and juveniles, respectively. The average clutch size in the absence and presence of nest predation was 2.836 and 0.935 eggs nest−1, whereas the average number of fledglings nest−1 was 0.452, respectively. Nest predation and chick production showed a concave‐up temporal trend, whereas clutch size showed no trend. Second, based on the predictive models, we documented multiple stressor effects: nest predation was the single‐most‐important stressor, but its adverse effect was severely amplified when environmental conditions were poor. When important nest predators were present, L. f. fuscus met the 'Vulnerable' criteria. Nonetheless, when nest predation was absent or low, the status of our population was following IUCN Red List's 'Least Concern' criteria (its official status). Nest predation played a vital role in limiting population growth – a finding that is likely to be relevant for several other seabirds in northern Europe.

Downstream Economic Implications of Predation in the South African Red Meat Industry

Globally, predation is an important and ongoing problem facing the livestock sector. This study estimated the downstream economic impact of predation in the South African red meat industry using a recent South African Social Accounting Matrix (SAM) and a partial equilibrium model. Due to predation the total output decreased by R 3,806 million and R 648 million for large (cattle) and small livestock (sheep and goat), respectively. The result implies that the loss of livestock due to predation reduces the number of livestock available for marketing and the presence of predators influences the level and intensity of best management practices employed by the red meat industry. The findings of this study, which looked at the macroeconomic implications of predation in the South African red meat industry, as well as the biodiversity and ecology aspects of predation, could help government and policymakers develop appropriate policies and mitigation strategies to reduce prediction and prioritize strategies that will help lessen the impact of predation.

Trophic interactions between predatory protists and pathogen-suppressive bacteria impact plant health.

Plant health is strongly impacted by beneficial and pathogenic plant microbes, which are themselves structured by resource inputs. Organic fertilizer inputs may thus offer a means of steering soil-borne microbes, thereby affecting plant health. Concurrently, soil microbes are subject to top-down control by predators, particularly protists. However, little is known regarding the impact of microbiome predators on plant health-influencing microbes and the interactive links to plant health. Here, we aimed to decipher the importance of predator-prey interactions in influencing plant health. To achieve this goal, we investigated soil and root-associated microbiomes (bacteria, fungi and protists) over nine years of banana planting under conventional and organic fertilization regimes differing in Fusarium wilt disease incidence. We found that the reduced disease incidence and improved yield associated with organic fertilization could be best explained by higher abundances of protists and pathogen-suppressive bacteria (e.g. Bacillus spp.). The pathogen-suppressive actions of predatory protists and Bacillus spp. were mainly determined by their interactions that increased the relative abundance of secondary metabolite Q genes (e.g. nonribosomal peptide synthetase gene) within the microbiome. In a subsequent microcosm assay, we tested the interactions between predatory protists and pathogen-suppressive Bacillus spp. that showed strong improvements in plant defense. Our study shows how protistan predators stimulate disease-suppressive bacteria in the plant microbiome, ultimately enhancing plant health and yield. Thus, we suggest a new biological model useful for improving sustainable agricultural practices that is based on complex interactions between different domains of life.

Dormice (Gliridae) in the diet of predators in Eurasia: a review

Dormice are widely distributed through Eurasia and Africa, but their abundance varies considerably. In many regions, dormice are rare, and their role in ecosystems is considered to be unimportant. The aim of this study was to evaluate the significance of dormice in the diet of predators in the Palaearctic (excluding Japan). A total of 540 sources, containing information on dormice in the diet of predators was analysed. Countries of Southern and Central Europe had the largest numbers of target sources. Dormice were recorded in the diet of 57 predator species: 21 mammals, 13 owls, 18 diurnal birds and 5 reptiles. Owls hunting in the forests, particularly the Tawny Owl (Strix aluco), are the main dormouse predators. The highest proportion of dormice in the diet of predators was recorded in the Mediterranean region, where Edible Dormice (Glis glis) are abundant and some other dormouse species are sympatric. In particular periods, dormice may be an alternative prey for predators such as Tawny Owl and even Lynx (Lynx lynx). It was supposed previously that predation was an important cause of high winter mortality in dormice, but analysis of publications showed that dormice were rather seldom recorded in the winter diet of predators. Thus, the exact impact of predators on winter mortality of dormice remains unclear. The role of dormice in the diet of predators depends on dormouse abundance. In areas where dormice are rare, it is trivial. However, predators catching even individual females, may have a significant impact on dormouse reproductive success.

Impact of seasonality and ladybird predators on the population dynamics of Mugo pine aphids

Impact of seasonality and ladybird predators on the population dynamics of Mugo pine aphids

Trophic relationships in the zooplankton – gelatinous zooplankton food chain in the shelf areas of the Crimean coast of the Black Sea

The seasonal and spatial dynamics of the key trophic characteristics were studied (food spectrum, feeding rate, and predatory impact on mesozooplankton) for populations of the jellyfish Aurelia aurita (Linnaeus, 1758) and ctenophore Mnemiopsis leidyi A. Agassiz, 1865. The investigation was carried out during four cruises of the RV “Professor Vodyanitsky” in the shelf areas of Crimean Peninsula in January to October 2016. The area was divided into inner (depth of < 50 m) and outer (51–150 m) shelves. To study the food spectrum and feeding rate of gelatinous predators, the composition of food items in the gastric cavity was analyzed under a binocular microscope. Daily ration (R, mg C·ind.−1·day−1) was calculated by the formula: R = Bz × DT−1 × 24, where Bz is zooplankton biomass in the predator gastric cavity (mg), and DT is zooplankton digestion time (h). Predatory impact of gelatinous zooplankton was estimated by the values of daily ration and mesozooplankton biomass. Zooplankton was sampled with a Juday plankton net with mouth diameter of 38 cm and mesh size of 140 µm. Vertical net hauls were performed: at the inner shelf stations, from the sea surface down to the bottom; at the outer shelf stations, down to the boundary of the hydrogen sulfide zone (δt = 16.2 conventional units according to a Sea-Bird probe). In the samples fixed with 4 % formalin solution, zooplankton abundance, its taxonomic composition, and size–age structure were quantified by standard method. In the food spectrum of the jellyfish, seasonal differences were revealed: predominance of Bivalvia veligers in winter and spring and wide species composition of Crustacea and other groups of prey in summer. The feeding rates of the studied species were similar: specific daily rations in winter, spring, and autumn did not exceed tenth of a percent of the carbon content in the body. Both species fed at a maximum rate in summer on the outer shelf: the specific rations reached 12.9 and 5.1 % C of the body for the jellyfish and ctenophore, respectively. A. aurita and M. leidyi populations consumed 0.2 to 5 % of the fodder zooplankton biomass per day; it did not result in a drastic reduction in zooplankton abundance and provided favorable feeding conditions for small planktivorous pelagic fish.

Predation and prey preference of the exotic snail Anentome helena on two freshwater snails: implications for species invasion

Aim: The aim of the present study was to estimate the probable impact of predation of the exotic snail Anentome helena on two co-occurring freshwater snails, Racesina luteola and Physella acuta, in the laboratory set-up. Methodology: In the initial experiment, the predatory efficiency of A. helena was observed using R. luteola and P. acuta as prey, separately, under varying prey and predator densities. In the following experiment, the prey snails were provided in both conspecific and heterospecific conditions with different predator densities to deduce the prey preference of A. helena, if any. Results: The experiments show that A. helena can consume a considerable number of R. luteola and P. acuta. The predation rate of A. helena varied significantly (p< 0.0001) with different sizes of prey, prey and predator densities. Although the predation rate differed among conspecific and heterospecific prey conditions, A. helena did not demonstrate any significant prey preference towards any of the prey. Interpretation: The study revealed that the chance dispersal of predator A. helena from household aquaria to natural habitats may directly impact the population of the freshwater snail R. luteola and P. acuta.

Adult mosquito predation and potential impact on the sterile insect technique

The sterile insect technique is a promising environmentally friendly method for mosquito control. This technique involves releasing laboratory-produced sterile males into a target field site, and its effectiveness may be affected by the extent of adult mosquito predation. Sterile males undergo several treatments. Therefore, it is vital to understand which treatments are essential in minimizing risks to predation once released. The present study investigates the predation propensity of four mantis species (Phyllocrania paradoxa, Hymenopus coronatus, Blepharopsis mendica, Deroplatys desiccata) and two gecko species (Phelsuma standingi, P. laticauda) on adult Aedes aegypti, Ae. albopictus and Anopheles arabiensis mosquitoes in a laboratory setting. First, any inherent predation preferences regarding mosquito species and sex were evaluated. Subsequently, the effects of chilling, marking, and irradiation, on predation rates were assessed. The selected predators effectively preyed on all mosquito species regardless of the treatment. Predation propensity varied over days for the same individuals and between predator individuals. Overall, there was no impact of laboratory treatments of sterile males on the relative risk of predation by the test predators, unless purposely exposed to double the required sterilizing irradiation dose. Further investigations on standardized predation trials may lead to additional quality control tools for irradiated mosquitoes.

Small monsters: Insect predation limits reproduction of yellow‐bellied toad Bombina variegata to ponds in their earliest successional stage

Abstract The disappearance and deterioration of amphibian breeding habitats is a major cause of their global extinction. In Europe, this problem affects the yellow‐bellied toad Bombina variegata, which inhabits small ponds in the early stages of succession, where no predatory invertebrate species normally occur. Nonetheless, as habitats, small temporary ponds are highly endangered, a situation that is intensifying with urban spread. A system of 13 pairs of artificial ponds was constructed in 2012 for the breeding of B. variegata with the aim of reconnecting disjunct populations. During the 2 years of the study, one of the twin ponds was regularly cleared of emergent vegetation and invertebrates. The survival rates of the tadpoles released in the cleared and uncleared ponds were analysed. The survival rate of the tadpoles released into the cleared ponds was higher than of those introduced into the uncleared ones. Tadpole survival rates were also higher in new, single ponds, constructed in 2013. The lower survival rates of the introduced tadpoles are best explained by the presence of predatory aquatic invertebrates, particularly the large diving beetle Dytiscus marginalis. Experimentally obtained consumption rates indicate that one Dytiscus larva is capable of destroying a typical clutch of B. variegata tadpoles within a few hours, much faster than any of the other insect predators tested. The impact of freshwater invertebrates on tadpoles is frequently studied but rarely quantified. For conservation measures to be effective, quantitative standards need to be applied that describe the impact of predation in a predictable manner. Construction of artificial small ponds is broadly accepted as an important conservation measure compensating for the disappearance of natural amphibian breeding sites. This function of artificial ponds may be substantially enhanced by the periodic removal of invertebrate predators.