Main Predators Research Articles

Plant associated protists-Untapped promising candidates for agrifood tools.

The importance of host-associated microorganisms and their biotic interactions for plant health and performance has been increasingly acknowledged. Protists, main predators and regulators of bacteria and fungi, are abundant and ubiquitous eukaryotes in terrestrial ecosystems. Protists are considered to benefit plant health and performance, but the community structure and functions of plant-associated protists remain surprisingly underexplored. Harnessing plant-associated protists and other microbes can potentially enhance plant health and productivity and sustain healthy food and agriculture systems. In this review, we summarize the knowledge of multifunctionality of protists and their interactions with other microbes in plant hosts, and propose a future framework to study plant-associated protists and utilize protists as agrifood tools for benefiting agricultural production.

Local and landscape factors determining the abundance and richness of insect pests and arthropod predators in Bt and non-Bt soybean

Agricultural landscapes of the Pampas and Campos biome have changed considerably due to the expansion of annual crops over non-crop areas, soybean seeding and the adoption of lepidopteran-resistant varieties (Bt technology). These changes have a great impact on predatory and phytophagous arthropods, which have been scarcely studied in Uruguay. The following aspects were evaluated: (a) the effect of vegetation cover composition (landscape factor), Bt technology (varieties expressing Cry1Ac protein) and field margins (local factors), on the abundance of the main pests and predators of soybean; b) the role of refuge areas (non-Bt soybean) in determining the abundance and richness of arthropod predators in Bt soybean crops, and c) the effect of Cry1Ac protein on the biology, reproduction and feeding behavior of Piezodorus guildinii (Hemiptera: Pentatomidae). In the northern Uruguayan littoral, during two years, predators and pests were sampled in 90 commercial non-Bt and Bt soybean fields and refuge areas. Biological and reproductive parameters of P. guildinii fed with Bt soybean pods and their possible effect on feeding behavior were evaluated using the electrical penetration graph technique. The main results obtained were: a) i. Bt soybean presented lower abundance of defoliating lepidoptera, without affecting predator abundance; ii. Soybean predators’ abundance was negatively related to the proportion of this crop in the landscape, but positively related to natural grassland and other crops; iii. Predators’ abundance between margins and within soybean fields was positively associated; b) Bt predators’ abundance and richness was positively associated with their values in refuge areas, evidencing for the first time their role in the conservation of beneficial fauna; c) biological and reproductive parameters and feeding behavior of P. guildinii were not affected by the ingestion of Cry1Ac protein expressed in Bt soybean pods. These results contribute to the possibilities of ecological intensification designs of national and regional production systems through pest management approached from a landscape perspective.

Predation ability of Stratiolaelaps scimitus (Acari: Laelapidae) to Tyrophagus putrescentiae (Acari: Acaridae) on edible fungi

Tyrophagus putrescentiae is one of the major pests of many edible fungi, whereas Stratiolaelaps scimitus is one of its main natural predators, which can be used to control T. putrescentiae on edible fungi. In our study, the prey preference and predation ability of S. scimitus to T. putrescentiae were determined in the laboratory. The results showed that both female and male adults of S. scimitus preferred adults to larvae of T. putrescentiae. The daily consumption of female adults of S. scimitus was higher than that of male adult mites. The consumption and predation rates of female and male adult mites reached the maximum within the first hour, then gradually decreased. This research provided a theoretical basis for the mass breeding of S. scimitus and field control of T. putrescentiae for edible fungi.

Primate–Predator Interactions: Is There a Mismatch Between Laboratory and Ecological Evidence?

Abundant empirical and theoretical studies indicate that predation is a key driver of primate evolution. The Snake Detection Theory (SDT) posits that snakes have been the main predators of primates since the late Cretaceous and that they influenced the diversification and evolution of primates. Laboratory research focusing on the innate ability of primates to detect snakes amid complex visual stimuli has provided strong support for key tenets of the SDT. While this theory has greatly contributed to our knowledge of primate evolution, supporting experimental studies may have overly focused on snakes and disregarded other important predators. This potential sampling bias weakens the conclusion that primates respond with a specific (high) intensity to snakes compared to other predators. We reviewed the literature about primate-predator interactions under natural and experimental conditions. We listed the primate and predator species involved in natural versus experimental studies. Predation events on primates recorded in the field mainly involved other primates, then raptors and carnivorans. SDT-related experimental studies heavily focused on snakes as predator stimuli and did not include raptors. Other experimental studies largely used snakes and primates and to a lesser extent carnivorans. Apes were the most often tested primates in experimental studies, whereas other primate taxa were neglected. Moreover, predators used as stimuli in experimental studies were inaccurately identified, notably snakes. Altogether, our results show that SDT-related studies neglected most of the major natural predators of primates. SDT studies also focused on a handful of primate species, whereas the theory relies on comparisons among taxa. Finally, poor taxonomic information on snakes used as stimuli blurs the interpretation of their relationship with primates. We suggest that future studies test the SDT by presenting a wide range of predators to different primate species to improve our understanding of the complexity of predator–prey interactions.

Seasonal and inter-annual variation in exposure to peregrines (Falco peregrinus) for southbound western sandpipers (Calidris mauri)

BackgroundThe western sandpiper (Calidris mauri) is an early southbound migrant species in North America. The ‘peregrine avoidance’ hypothesis proposes that this timing evolved to reduce exposure to their main predator, the peregrine (Falco peregrinus), along the Pacific flyway.MethodsI evaluate this hypothesis based on 16 years of near-daily (June – October) measures of peregrine presence made on the Fraser River estuary, a major stopover in the Pacific northwest.ResultsExposure to peregrines is lowest for the earliest southbound western sandpipers, and rises steeply as peregrines en route from northern breeding areas begin to arrive in late July or August. Peregrine arrival timing varies greatly between years, shifting in step with the onset of spring along coastal Alaska. Peregrine presence on the Fraser estuary on any date is higher in years with earlier spring onset. On the median adult sandpiper passage date (day-of-year 198) this increases 17-fold over the inter-annual range between the earliest and latest peregrine arrival dates.ConclusionThe pattern of strong and predictable changes in the seasonal pattern of danger quantified here provides a further test of the hypothesis that danger affects migratory timing. Western sandpipers appear to anticipate the exposure level of southward migration, perhaps because they are able to observe spring onset on their Alaskan breeding grounds. They adjust the duration of parental care and length of the breeding season to keep the date of migratory departure from the Arctic relatively invariant in spite of large interannual variation in spring onset. While underway they also adjust aspects of migratory behavior. These observations support the ‘peregrine avoidance’ hypothesis, and suggest that western sandpipers are able to counter, at least partially, the higher migratory danger of early spring years.

Food habit of Tiger (Panthera tigris) in Tropical Moist Deciduous Forest of Dudhwa National Park, Uttar Pradesh, India

Tiger ( Panthera tigris ) is an endangered felid on the IUCN list. Habitat loss, landscape fragmentation, prey depletion, and poaching have contributed to the decline of the tiger in its entire range in Asia. In India also, it survives only in well-protected tiger reserves and gone or decreased drastically in less-protected areas. The same situation is seen in the terai arc landscape. Thus, accurate knowledge of a species' diet is essential for effective conservation and is vital for conservation initiatives like habitat prioritization, protection, and restoration. Scats analysis was used to determine the food habit of tigers in the tropical moist-evergreen forest of Dudhwa National Park, northern India. A total of 116 scats were collected and analyzed. Scat contents were analyzed in terms of the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 14 prey species were identified. In terms of frequency of occurrence and biomass, the most important prey species were barasingha ( Rucervus duvaucelii) and spotted deer ( Axis axis ), making up to 55% of biomass consumed. Domestic livestock contributed almost 10% to the diet of the tiger. The study revealed that tiger and leopard ( Panthera pardus ), the two main predators in Dudhwa Tiger Reserve, differentiate their niches by segregating the available resources as 55% of the tiger diet comprises barasingha and spotted deer. On the other side, leopard mainly feeds on spotted deer and rodents and may avoid direct competition from the tiger by shifting the space and diet, as revealed by another study in the same area.

Food habit of Tiger (Panthera tigris) in Tropical Moist Deciduous Forest of Dudhwa National Park, Uttar Pradesh, India

Tiger ( Panthera tigris ) is an endangered felid on the IUCN list. Habitat loss, landscape fragmentation, prey depletion, and poaching have contributed to the decline of the tiger in its entire range in Asia. In India also, it survives only in well-protected tiger reserves and gone or decreased drastically in less-protected areas. The same situation is seen in the terai arc landscape. Thus, accurate knowledge of a species' diet is essential for effective conservation and is vital for conservation initiatives like habitat prioritization, protection, and restoration. Scats analysis was used to determine the food habit of tigers in the tropical moist-evergreen forest of Dudhwa National Park, northern India. A total of 116 scats were collected and analyzed. Scat contents were analyzed in terms of the relative frequency of occurrence and the relative prey biomass consumed. A minimum of 14 prey species were identified. In terms of frequency of occurrence and biomass, the most important prey species were barasingha ( Rucervus duvaucelii) and spotted deer ( Axis axis ), making up to 55% of biomass consumed. Domestic livestock contributed almost 10% to the diet of the tiger. The study revealed that tiger and leopard ( Panthera pardus ), the two main predators in Dudhwa Tiger Reserve, differentiate their niches by segregating the available resources as 55% of the tiger diet comprises barasingha and spotted deer. On the other side, leopard mainly feeds on spotted deer and rodents and may avoid direct competition from the tiger by shifting the space and diet, as revealed by another study in the same area.

An Albino Deer in the Jungle: A Magical Creature and Where to Find Them

Albinism is a condition in which an animal’s skin, feathers, or fur is lighter in color than that of other animals of that species. We report a unique case of complete albinism in a red-brocket deer in the Brazilian Amazon rainforest. The individual, which we called a “magical creature,” lives inside a conservation area in one of the most deforested regions of the Brazilian Amazon. The survival of the albino red-brocket deer in the wild might be related to the fact that it is so rare! Possibly, its main predators, pumas and jaguars, are only familiar with colored red-brocket deer, so they might not be interested in eating a white one. Our article shows how important it is to monitor species diversity and to conserve habitats that support species diversity in endangered regions such as the Brazilian Amazon.

Does intercropping patterns of potato and safflower affect the density of Leptinotarsa decemlineata (Say), predators, and the yield of crops?

The impact of three intercrop patterns of potato (P), Solanum tuberosumL., and safflower (S), Carthamus tinctoriusL.: 4P:2S, 4P:4S, and 4P:8S (row ratios) along with single crops were examined on densities of the Colorado potato beetle (CPB),Leptinotarsa decemlineata(Say), biodiversity of predators, and yield profits over the growing season of potatoes in a randomized complete block design in 2019 and 2020 in Iran. The significant reduction in the densities of CPB (adults, eggs, and larvae) was seen in intercrops compared with single potato in either year. Accordingly, the damage index was decreased in intercrops than in single potato. Furthermore, intercrops resulted in an enhancement in the abundance of most predatory species of CPB, the Shannon diversity index (H΄), and the Pielou's evenness index (J'), especially in 4P:4S and 4P:8S than single potato. The values of R2 between the densities of CPB and the main predators were low (0.01 ≤ R2 ≤ 0.19) in June, whereas R2 values were significantly enhanced in July (0.13 ≤ R2 ≤ 0.71) and August (0.46 ≤ R2 ≤ 0.97). All intercrops delivered extra yield benefit compared with the single crops (LER ≥ 1.20 in 2019 and ≥ 1.18 in 2020). Our results disclosed that all intercrops, especially 4P:4S and 4P:8S could exercise in the controlling ofL. decemlineatain potato fields.

Intercropping flowering plants facilitate conservation, movement and biocontrol performance of predators in insecticide-free apple orchard

Habitat management is an important approach suppressing pest via conservation biological control in agricultural systems. Intercropping flowering plants is a well- practiced habitat management measure, supporting predators with shelter, nectar, alternative prey and pollen. However, few studies systematically revealed predator’s conservation performance, transfer process and biocontrol ability by intercropping flowering plants in apple orchards. Here, an experimental model of intercropping flowering plants in apple orchard was planned for two consecutive years to response above questions. Four flowering plants conserve a different number and proportions of six main predator species (three ladybeetles (Propylaea japonica, Harmonia axyridis and Hippodamia variegata), one lacewing (Chrysoperla sinica), one hoverfly (Episyrphus balteatus) and one spider (Misumenops tricuspidatus)). By rubidium (Rb) marking technique, transfer rate of predators C. sinica from flowering plant Cnidium monnieri to apple trees were 79.5 % and 84.1 % in 2020 and 2021, respectively. Transfer rate of predators H. axyridis from flowering plant C. monnieri to apple trees were 74.2 % and 80.1 % in 2020 and 2021, respectively. By predator exclusion trials, the Biocontrol Services Index (BSI) was calculated in sampling date, in which the number of aphids on the caged and uncaged branch has significant difference in the four flowering plants and untreated control plots in 2020 and 2021, respectively. Thus, our results suggest that, intercropping flowering plants in insecticide-free apple orchard contributed to increase the number of predators and biological control of aphid Aphis spiraecola. These findings support that intercropping flowering plants as a promising management option could be implemented in apple orchards.

Main aerial top predator of the Andean Montane Forest copes with fragmentation, but may be paying a high cost

Large raptors are the most mobile top predators in fragmented landscapes and, consequently, they are key components of ecosystems. However, large raptors (e.g. eagles), requiring large areas of forested habitat, are also among the most threatened groups of raptors in the world and are directly and indirectly affected by habitat loss and fragmentation. The Black-and-chestnut Eagle ( Spizaetus isidori ) is a forest dependent species with a long period of natal dispersal. Here, we aim to assess home range size, mortality, and habitat selection of juvenile Black-and-chestnut Eagles during their natal dispersal in three populations within fragmented landscapes of the Tropical and Subtropical Andean Montane Forests of South America. During the first year of natal dispersal, juveniles occupied large home ranges (mean = 996.3 km 2 ; SD± 606; range = 294–2130 km 2 ). While juvenile eagles made their natal dispersal through fragmented landscapes, they consistently selected areas with higher remaining forest cover, medium elevations, and steeper slopes than the mean available in the landscape. Our study showed that juvenile eagles can tolerate a certain level of fragmentation during the natal dispersal period, although they also face high mortality during this same period. Four of the six (67 %) tagged juvenile eagles died during the study period. The high mobility of juvenile eagles may help maintain key ecosystem functions within fragmented landscapes of South America. In order to maintain viable populations of this top predator, it is urgent to mitigate non-natural mortality, mainly from direct human persecution, in fragmented landscapes. • Andean Montane Forests has lost around a half of its original vegetation cover. • Black-and-chestnut Eagle ( Spizaetus isidori ) is a highly mobile avian top predator. • Black-and-chestnut Eagle copes with fragmentation of the Andean Montane Forests. • Eagle mortality is very high and it is probably derived of habitat loss and fragmentation. • Understanding how top predators cope with fragmentation is needed for management.

Artificial selection for emamectin benzoate resistance in the biological control agent Orius laevigatus

Biological control is occasionally supplemented with insecticides treatments, which may have a significant impact on natural enemies. Typically, selective compounds are chosen to overcome lack of compatibility, but an alternative approach is the use of biocontrol agents resistant to pesticides. Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is the main predator used to control thrips and other small pests in greenhouses. The avermectin emamectin benzoate is a bioinsecticide developed for the control of lepidopteran pests, reported as moderately to highly toxic to O. laevigatus. Firstly, we studied the variation in susceptibility to emamectin benzoate in 32 wild and commercial populations of O. laevigatus. A 62.4-fold variation in response was found (LC50 from 0.8 mg L−1 to 49.9 mg L−1). The baseline LC50 was 4.8 mg L−1. Secondly, we exploited this intraspecific variation to select four distinct emamectin-resistant strains. After 41–47 selection cycles, four resistant strains were successfully obtained (LC50 = 104–203 mg L−1) compared to the reference population (LC50 = 4.7 mg L−1). The resistance was retained for 18 generations without insecticide exposure and was expressed in all life instars, especially from the 4th nymphal instar to adult. The emamectin-resistant strains did not show cross-resistance to abamectin. Inhibitors of the detoxification enzymes failed to restore susceptibility at the concentrations tested. Fecundity and predation capacity in the resistant strain was similar to those in a commercial population. The resistance obtained may be enough to allow survival of adults and nymphs of O. laevigatus exposed to treatments of emamectin benzoate across the crop season.

The Importance of Collecting and Archiving Data on Domestic and Cultivated Organisms

At least 29% of the world’s terrestrial ecosystems have been significantly modified by human activity (Ellis 2011). Total livestock biomass is 15 times greater than that of wild mammals (Bar-On et al. 2018). Crops such as maize, soybean, rice, and wheat cover 23% of available agricultural land (Ritchie and Roser 2013). Even where land is not farmed, it is often converted to highly modified habitats such as urban ecosystems. Within the matrix of anthropogenic ecosystems spread around the world are many wild species (i.e., free-living, non-domesticated or feral). Some native species persist from the original ecosystems, while others colonize anthropogenic ecosystems including alien invasive species. Thus, wild flora and fauna in many areas are part of ecosystems that are dominated by, and often characterised by, the domestic and cultivated organisms that exist in them. Examples include large herbivores raised for milk and meat production, and omnivorous and carnivorous species such as both domestic and feral dogs and cats. Moreover, crops are typically grown in monoculture plots including tree plots in commercial forestry, and an enormous array of cultivated plants are grown in gardens, parks, and along streets in urban areas. Tellingly, in many ecosystems the domestic bee is the primary pollinator and domestic cats are the main predator. Domestic and cultivated organisms are not isolated from wild organisms and indeed they interact in many ways, including predation, parasitism, and herbivory, competition for biotic and abiotic resources, and pathogen transmission. If we are to understand modern ecosystems, clearly we cannot ignore the domesticated and cultivated components of ecosystems. So where are the observational data on these species? iNaturalist reluctantly tolerates them but does not publish them to the Global Biodiversity Information Facility (GBIF), eBird actively discourages recording them, and GBIF doesn’t encourage their submission either. Some information can be gleaned from land cover maps and remote sensing, but without knowing the specific species present in the land use category it is hard to build a holistic picture of an ecosystem. Data on domesticated and cultivated organisms have many uses, including horizon scanning and risk assessment for invasive species, understanding the impacts of invasive species, predicting the spread of disease, the spillover of disease to and from wild and domestic organisms, and many others (Groom et al. 2021). Evidently there are important components of ecosystems largely missing from our public databases. As data on biodiversity becomes more intergrated, such as implementing Digital Extended Specimens (Webster et al. 2021), it will become increasingly important to access data from all aspects of an ecosystem, included those that are domestic and cultivated. In this talk we will expand on why we should be mobilising such data. They can be published without ruining the integrity of data on wild organisms, so why don’t we embrace and use these fundamentally important, but much ignored, data?

A comparison of physical disturbance and pollution stressors in sandy beaches using nematode functional biological traits

Nematode functional traits and community structure approaches are receiving attention and being debated regarding the similarity in gained information. This work applied two nematode methods (i.e. functional traits, community structure) and sex ratios to investigate sandy beaches experiencing physical disturbances and anthropogenic stressors along the Alexandrian coast of Egypt. It is the first study to identify the Egyptian marine benthic nematodes to genus level yielding fourteen genera. This study addressed the following questions. (A) Which analyses of functional traits, community structure, or sex ratio could distinguish beaches experiencing natural disturbances from anthropogenic stressors? (B) What are the driving forces that govern nematode assemblages? Designated beaches were high pollution and energy (HPHE), high pollution but low energy (HPLE), and clean high energy (CHE). The study was conducted in March 2014, applying a stratified random sampling design and advanced multivariate analyses. Results revealed significant discrimination among and within beaches based on functional traits, community structure, and sex ratio. The functional traits (FBM) grouped data into two main groupings, predators and scavengers. Predators and cylindrical shape-tail types were found in high salinity moderately-sorted fine-grained sand dominant at HPHE and CHE. Scavengers and a variety of tail-shape types inhabited low saline water with well-sorted coarse sediment at HPLE. The community structure (CSM) revealed three groupings, as each beach had a specific assemblage based on its response to the measured physiochemical factors (salinity, pH, and temperature). Three genera were responsible for the high contribution across each beach Graphonema sp (HPHE), Enoplolaimus sp. (HPLE), and Oncholaimus sp. (CHE), as well as the co-sharing of Axnolaimus sp at HPLE. However, Axnolaimus sp and Oncholaimus sp showed the highest dissimilarity among beaches. The contribution of the measured factors was 53.8% (FBM) and 35.7% (CSM). Trophic guilds were anthropogenic stressors dependent and tail-shape type physically disturbing-related. However, nematode genera were species-specific to habitat type. The sex ratio was male-biased, and Juvenile-stages seemed to be temperature-dependent. The dissimilarity in the functional trait and community structure data recommend their application in biomonitoring and coastal restoration programs.

Mixed evidence for nest masquerading in the Blue Manakin (Chiroxiphia caudata)

Masquerading is a camouflage strategy in which the prey (here, the nests) have visual similarities to inedible objects or structures present in the surrounding environment to avoid correct identification by visually oriented predators. Here we investigate whether masquerading occurs in nests of the Atlantic Forest endemic Blue Manakin Chiroxiphia caudata, whose nests resemble pendent tufts of moss or debris. The number of tufts in a 3‐m radius was the main parameter explaining nest‐site choice, and nest monitoring with infra‐red digital camera‐traps revealed that the main nest predators were visually oriented. However, daily nest survival rate was negatively associated with the number of tufts around nests. Despite the mixed evidence for nest masquerading in this situation, it remains possible that this strategy is involved in the evolution of nest characteristics and of nest‐site choice in bird species whose nests resemble nest‐like structures present in their habitats, and we suggest developing further studies to test for the occurrence of masquerading.

Bacteriota and Antibiotic Resistance in Spiders.

Simple SummaryThe microbiomes of insects are known for having a great impact on their physiological properties for survival, such as nutrition, behavior, and health. In nature, spiders are one of the main insect predators, and their microbiomes have remained unclear yet. It is important to explore the microbiomes of spiders with the positive effect in the wild to gain an insight into the host–bacterial relationship. The insects have been the primary focus of microbiome studies from all arthropods. Although the research focused on the microbiome of spiders is still scarce, there is a possibility that spiders host diverse assemblages of bacteria, and some of them alter their physiology and behavior. According to our findings, there is a need for holistic microbiome studies across many organisms, which would increase our knowledge of the diversity and evolution of symbiotic relationships. Antimicrobial resistance is one of the most serious global public health threats in this century. Therefore, the knowledge and some information about insects and their ability to act as reservoirs of antibiotic-resistant microorganisms should be determined in order to ensure that they are not transferred to humans. It is important to monitor the microbiome of spiders found in human houses and the transmission of resistant microorganisms, which can be dangerous in relation to human health.Arthropods are reported to serve as vectors of transmission of pathogenic microorganisms to humans, animals, and the environment. The aims of our study were (i) to identify the external bacteriota of spiders inhabiting a chicken farm and slaughterhouse and (ii) to detect antimicrobial resistance of the isolates. In total, 102 spiders of 14 species were collected from a chicken farm, slaughterhouse, and buildings located in west Slovakia in 2017. Samples were diluted in peptone buffered water, and Tryptone Soya Agar (TSA), Triple Sugar Agar (TSI), Blood Agar (BA), and Anaerobic Agar (AA) were used for inoculation. A total of 28 genera and 56 microbial species were isolated from the samples. The most abundant species were Bacillus pumilus (28 isolates) and B. thuringensis (28 isolates). The least isolated species were Rhodotorula mucilaginosa (one isolate), Kocuria rhizophila (two isolates), Paenibacillus polymyxa (two isolates), and Staphylococcus equorum (two isolates). There were differences in microbial composition between the samples originating from the slaughterhouse, chicken farm, and buildings. The majority of the bacterial isolates resistant to antibiotics were isolated from the chicken farm. The isolation of potentially pathogenic bacteria such as Salmonella, Escherichia, and Salmonella spp., which possess multiple drug resistance, is of public health concern.

Winter browsing in absence of an apical predator: Do high moose densities compromise tree regeneration?

Over the last decades, the increasing intensity of timber harvesting and the changes in forestry practices have impacted the population dynamics of many wildlife species. Moose (Alces alces americana) densities have strongly increased, leading to an extensive pressure on vegetation but also to the growing popularity and socioeconomic benefits of sport hunting. On the south shore of the St. Lawrence River, eastern Québec (Canada), moose densities have been on a constant rise for 3 decades, reaching unprecedented levels due to the absence of its main predator (wolf Canis lupus), conservative sport hunting regulations (females protected 1 year out of 2) and increases in early seral forests induced by logging. Resource managers now need to find the balance between ensuring adequate regeneration of cutblocks and maintaining quality habitat to support the hunting industry, a task that requires identifying the level of use and damages on commercial tree species, and the variables related to such damages. We evaluated the effect of 4 common silvicultural treatments and time elapsed since treatment on proxies of resource use and suitability for moose in the mixed forest of the Bas-Saint-Laurent region. Besides silvicultural treatments, we evaluated the effect of various characteristics – at the stand and landscape scales – on the habitat use of moose and the damage they caused in 440 sampling plots. We found no difference in use and damage between all types of treatment, suggesting that local conditions vary between replicates of a given treatment. At the stand scale, variations of occurrence of browsed commercial and non-commercial stems and severe damages to commercial stems were strongly related to forage diversity, relative nitrogen availability and the proportion of alternative species that are browsed. At the landscape scale, the area occupied by naturally regenerating stands around our sample plots increased the occurrence of severe damages to commercial species. The variations in occurrence and in the number of moose feces were best explained by relative moose density and the proportion of browsed stems. Our results showed the importance of considering stands characteristics to provide quality habitat for moose. We recommend that managers avoid the aggregation of naturally regenerating stands, and prioritize high-density plantations without pre-commercial thinning or low-density plantations to reduce the probability of severe damage by moose. These approaches promote stand diversity, forage quality and availability, and favor quality habitat for moose while ensuring maximum timber yield from planted spruce, which is not targeted by moose browsing.

Effects of Roach Rutilus rutilus Collapse on Abundance, Distribution and Diet of Great Cormorants Phalacrocorax carbo in a Large River in North-West Europe

Aquatic habitats are subject to multifactorial changes including global warming, invasive species colonisation, modification of organic and micro-pollutant discharge and, for large rivers in Europe, drastic physical modification (e.g. channelisation, impoundments). The Meuse River in Belgium is one of these multi-stressed environments, in which recent decreases of fish populations were observed, with the loss of 90% of Roach Rutilus rutilus biomass in only a few years. In the light of this fish stock collapse, diet modification and local population evolution of a key avian predator, the Great Cormorant Phalacrocorax carbo, were examined. The diet composition and daily consumption rates of the Great Cormorants feeding in the river were largely similar to that seen before the fish population collapsed. Numbers of wintering Great Cormorants decreased by 90%, as did Roach numbers, and thus the predation pressure was adjusted to the decreased fish availability. The number of night-roosts and locations remained unchanged and no redistribution to adjacent habitats was observed at the regional scale. We suggest a bottom-up chain of responses where a fish collapse forced a reduction in Cormorant numbers, being the main piscivorous avian predator, rather than a modification of Cormorant prey composition and/or a local redistribution to adjacent wetlands (top-down). The factors that govern the establishment of a small and productive breeding population remain to be explained, but we hypothesise that the start of breeding could well have been alleviated by the large decrease in number of wintering birds.

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.

Top-down control of planktonic ciliates by microcrustacean predators is stronger in lakes than in the ocean

Planktonic ciliates are major components of pelagic food webs in both marine and freshwaters. Their population dynamics are controlled ‘bottom-up’ by prey availability and ‘top-down’ by microcrustacean predators. In oceans, copepods are the main ciliate predators while in lakes cladocerans are the typical predators. The efficacy by which these functionally different predators control ciliate population dynamics is debated. We, therefore, investigated experimentally the grazing of three microcrustacean predators with different feeding modes on five freshwater ciliates. We then performed a meta-analysis to assess if our findings can be generalised for aquatic ecosystems. We hypothesized that top-down control is stronger in lakes than in the ocean. We find that: (i) average ingestion rates of marine and freshwater microcrustaceans do not differ; (ii) clearance rates of freshwater cladocerans decrease with ciliate size but increase with ciliate size in freshwater copepods; (iii) clearance rates of the marine microcrustaceans is unrelated to ciliate cell size. These findings have implications for the functioning of freshwater and marine food webs: (i) the ciliate—microcrustacean link is stronger in lakes than in the ocean, and (ii) globally top-down control of ciliates is unlikely in the ocean.