Presence Of Prey Research Articles

Saugeye diets in southern reservoirs and insight for predatory control of stunted crappie

AbstractObjectiveSaugeye (Sauger Sander canadensis × Walleye S. vitreus) have been introduced in reservoirs for several purposes, including as a top‐down control to combat stunting in crappie Pomoxis spp. populations. However, no comprehensive diet evaluation has been completed in southern reservoirs. Our objectives were to assess variability in saugeye diet compositions, explore factors influencing crappie presence in saugeye diets, and investigate trends in prey size to inform management strategies regarding predatory control of crappie populations.MethodsWe collected 2638 saugeye diets from six Oklahoma reservoirs. We used permutational multivariate analysis of variance to test differences in diet compositions among saugeye lengths, study reservoirs, and seasons, and we used logistic regression models to correlate the presence of crappie in diets with saugeye size, season, crappie abundance, productivity, and turbidity. Finally, we used bivariate plots of diet indices and quantile regression to explore trends in prey importance and prey size relative to saugeye size.ResultSaugeye diet compositions were best explained by saugeye size, followed by study reservoir and season. Saugeye exhibited an ontogenetic shift from Inland Silverside Menidia beryllina to shad Dorosoma spp., and crappie were eaten infrequently in comparison. The presence of crappie prey in diets was most correlated with saugeye size (primarily large saugeye), followed by higher crappie abundance, lower reservoir productivity, and season (highest in fall). Saugeye consumed larger prey than most piscivores relative to predator size.ConclusionOur results indicated that dominant prey of saugeye transitioned from smaller‐bodied fishes to larger shad as they grew when both prey types were available, which may have implications for growth and recruitment. Ultimately, the low and variable use of crappie prey may lead to inconsistent predatory effects on crappie populations, and large saugeye may exert greater top‐down pressure on crappie in lakes with lower productivity or higher crappie abundance.

Selective depletion of Campylobacter jejuni via T6SS dependent functionality: an approach for improving chickens gut health

The targeted depletion of potential gut pathogens is often challenging because of their intrinsic ability to thrive in harsh gut environments. Earlier, we showed that Campylobacter jejuni (C. jejuni) exclusively uses the Type-VI Secretion System (T6SS) to target its prey such as Escherichia coli (E. coli), and phenotypic differences between T6SS-negative and T6SS-positive C. jejuni isolates toward bile salt sensitivity. However, it remains unclear how the target-driven T6SS functionality prevails in a polymicrobial gut environment. Here, we investigated the fate of microbial competition in an altered gut environment via bacterial T6SS using a T6SS-negative and -positive C. jejuni or its isogenic mutant of the hemolysin-coregulated protein (hcp). We showed that in the presence of bile salt and prey bacteria (E. coli), T6SS-positive C. jejuni experiences enhanced intracellular stress leading to cell death. Intracellular tracking of fluorophore-conjugated bile salts confirmed that T6SS-mediated bile salt influx into C. jejuni can enhance intracellular oxidative stress, affecting C. jejuni viability. We further investigated whether the T6SS activity in the presence of prey (E. coli) perturbs the in vivo colonization of C. jejuni. Using chickens as primary hosts of C. jejuni and non-pathogenic E. coli as prey, we showed a marked reduction of C. jejuni load in chickens cecum when bile salt solution was administered orally. Analysis of local antibody responses and pro-inflammatory gene expression showed a reduced risk of tissue damage, indicating that T6SS activity in the complex gut environment can be exploited as a possible measure to clear the persistent colonization of C. jejuni in chickens.

Insights into the diet and feeding behavior of immature polar cod (Boreogadus saida) from the under-ice habitat of the central Arctic Ocean.

Polar cod (Boreogadus saida) is an endemic key species of the Arctic Ocean ecosystem. The ecology of this forage fish is well studied in Arctic shelf habitats where a large part of its population lives. However, knowledge about its ecology in the central Arctic Ocean (CAO), including its use of the sea-ice habitat, is hitherto very limited. To increase this knowledge, samples were collected at the under-ice surface during several expeditions to the CAO between 2012 and 2020, including the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. The diet of immature B. saida and the taxonomic composition of their potential prey were analysed, showing that both sympagic and pelagic species were important prey items. Stomach contents included expected prey such as copepods and amphipods. Surprisingly, more rarely observed prey such as appendicularians, chaetognaths, and euphausiids were also found to be important. Comparisons of the fish stomach contents with prey distribution data suggests opportunistic feeding. However, relative prey density and catchability are important factors that determine which type of prey is ingested. Prey that ensures limited energy expenditure on hunting and feeding is often found in the stomach contents even though it is not the dominant species present in the environment. To investigate the importance of prey quality and quantity for the growth of B. saida in this area, we measured energy content of dominant prey species and used a bioenergetic model to quantify the effect of variations in diet on growth rate potential. The modeling results suggest that diet variability was largely explained by stomach fullness and, to a lesser degree, the energetic content of the prey. Our results suggest that under climate change, immature B. saida may be at least equally sensitive to a loss in the number of efficiently hunted prey than to a reduction in the prey's energy content. Consequences for the growth and survival of B. saida will not depend on prey presence alone, but also on prey catchability, digestibility, and energy content.

Killer whales habitat suitability in the Iberian Peninsula and the Gulf of Biscay: Implications for conservation

This study addresses existing gaps in our understanding of the ecology of killer whales by investigating their habitat use dynamics in the Atlantic coastal waters of North Africa, the Iberian Peninsula, and the Gulf of Biscay. Despite previous research on their distribution during the Atlantic Bluefin tuna migration in the Strait of Gibraltar and adjacent waters, substantial knowledge gaps persist, particularly regarding their movement patterns beyond these regions and seasonal variations in habitat use. Utilizing killer whale occurrence records from 2020 to 2023 and considering environmental factors influencing prey presence, we employed seasonal spatial distribution models. MaxEnt models exhibited robust predictive performance, emphasizing distance to shore, depth, and sea surface temperature as key factors influencing killer whale habitat suitability. Spatial distribution patterns reveal a peak in coastal waters of the southern Iberian Peninsula and North Africa during winter and spring, with a significant shift northward and expansion during summer and autumn towards the Gulf of Biscay. This expansion suggests a broader distribution of killer whales in the Northeast Atlantic during warmer months, encompassing a diverse range of habitats. The research underscores a substantial interaction (47%) between killer whales and recreational vessels, posing concerns for both the killer whales and maritime safety. This study provides valuable insights on killer whale habitat use in the Atlantic waters from North Africa to the Gulf of Biscay, thereby supporting conservation and management efforts in the region.

Maintain the light, long-term seasonal monitoring of luminous capabilities in the brittle star Amphiura filiformis

The European brittle star Amphiura filiformis emits blue light, via a Renilla-like luciferase, which depends on the dietary acquisition of coelenterazine. Questions remain regarding luciferin availability across seasons and the persistence of luminous capabilities after a single boost of coelenterazine. To date, no study has explored the seasonal, long-term monitoring of these luminous capabilities or the tracking of luciferase expression in photogenic tissues. Through multidisciplinary analysis, we demonstrate that luminous capabilities evolve according to the exogenous acquisition of coelenterazine throughout adult life. Moreover, no coelenterazine storage forms are detected within the arms tissues. Luciferase expression persists throughout the seasons, and coelenterazine's presence in the brittle star diet is the only limiting factor for the bioluminescent reaction. No seasonal variation is observed, involving a continuous presence of prey containing coelenterazine. The ultrastructure description provides a morphological context to investigate the green autofluorescence signal attributed to coelenterazine during luciferin acquisition. Finally, histological analyses support the hypothesis of a pigmented sheath leading light to the tip of the spine. These insights improve our understanding of the bioluminescence phenomenon in this burrowing brittle star.

Leopards at large: population density, habitat utilisation and spatio-temporal overlap of leopards (Panthera pardus) with competitors and prey in the Rajaji Tiger Reserve, northern India

Context In the vicinity of the western Rajaji Tiger Reserve, a significant rise in conflicts between humans and leopards has occurred. These conflicts have resulted in a substantial number of human deaths, with 60% attacks resulting in deaths over a 4-year period. Aims This study aims to examine any potential connection among the non-breeding tigers, leopards, prey, humans and the increased occurrence of conflicts. Methods To address this objective, we conducted an analysis to evaluate the density of leopards, as well as their spatial and temporal behaviour with respect to tigers, prey and humans through on-site habitat use, circular statistics, diel-overlap as well spatial niche breadth and spatial-niche overlap. Key results Our findings showed one of the highest leopard-density estimates (excluding cubs) (mean ± s.e.) of 23.7 ± 4.8 per 100 km2. When examining on-site habitat use by leopards, we found three variables that had a negative influence, namely, human presence, slope, and the presence of tigers. The presence of a large prey (sambar) had a positive influence. Leopards, exhibiting the highest spatial-niche breadth, demonstrated a small overlap with both tigers and humans, while displaying a significant diel overlap with sambar. The niche overlap was notably high with sambar, but very low with humans and tigers. Conclusions Although tigers locally created a zone of spatial and temporal avoidance, at the population level the leopards experienced a surge in numbers in response to the reduced tiger numbers, indicated by their high density. This could be a cause of high leopard movement into nearby human settlements. This unique scenario could have contributed to conflict. Implications Understanding the coexistence among different species and the impact of transient animals is crucial to develop effective management strategies to mitigate conflict. This approach would facilitate and ensure the long-term survival of diverse large carnivores in the tropical forests of southern Asia through sustained support for conservation from local communities.

A MODIFIED MAY–HOLLING–TANNER MODEL: THE ROLE OF DYNAMIC ALTERNATIVE RESOURCES ON SPECIES’ SURVIVAL

This paper investigates the dynamical behavior of the modified May–Holling–Tanner model in the presence of dynamic alternative resources. We study the role of dynamic alternative resources on the survival of the species when there is prey rarity. Detailed mathematical analysis and numerical evaluations, including the situation of ecosystem collapsing, have been presented to discuss the coexistence of species’, stability, occurrence of different bifurcations (saddle-node, transcritical, and Hopf) in three cases in the presence of prey and alternative resources, in the absence of prey and in the absence of alternative resources. It has been obtained that the multiple coexisting states and their stability are outcomes of variations in predation rate for alternative resources. Also, the occurrence of Hopf bifurcation, saddle-node bifurcation, and transcritical bifurcation are due to variations in the parameters of dynamic alternative resources. The impact of dynamic alternative resources on species’ density reveals the fact that if the predation rate for alternative resources increases, then the prey biomass increases (under some restrictions), and variations in the predator’s biomass widely depend upon the quality of food items. This study also points out that the survival of predators is possible in the absence of prey. In the theme of ecological balance, this study suggests some theoretical points of view for the eco-managers.

Predation on Baltic sea yolk-sac herring larvae (Clupea harengus) by the invasive ctenophore Mnemiopsis leidyi

Western Baltic spring spawning herring (Clupea harengus, L.) is a commercially important fish stock currently suffering a strong decline. Larval survival is essential for stock recruitment and can be substantially decreased by predation. The comb jelly Mnemiopsis leidyi A. Agassiz, 1865, is a lobate ctenophore which is invasive to the Baltic Sea and a known ichthyoplankton predator. However, predation on herring larvae in the Baltic Sea by M. leidyi has not been studied since its initial establishment in 2006. To address this knowledge gap, we conducted feeding experiments to investigate (1) the predation capability of M. leidyi on herring yolk-sac larvae, and (2) the influence of larval age, (3) predator size and (4) the presence of alternative prey on the clearance rate of M. leidyi on herring yolk-sac larvae. Our results showed that M. leidyi exhibited the ability to capture and digest herring larvae. The clearance rates of M. leidyi on herring larvae decreased with larval age and increased with predator size, while the presence of alternative prey had no effect on clearance rates. This finding suggests that M. leidyi can efficiently consume herring yolk-sac larvae under laboratory conditions. However, further investigations using mesocosm or field studies are necessary to evaluate the potential impact of M. leidyi on the mortality and recruitment of herring yolk-sac larvae under Baltic Sea field conditions.

When can we expect natural habitats to enhance pest control by generalist predators? Insights from a simple, simulated agricultural landscape

Many field studies have reported that natural habitats in the agricultural landscape are associated with increased predator abundance and/or decreased crop pest load. However, recently published meta-analyses have found mixed results, with natural habitats being associated with increased pest loads as often as decreased loads. We investigate possible reasons for these conflicting results using a mechanistic model that simulates the dynamics of a generalist, omnivorous predatory bug and a plant bug pest in a landscape consisting of a 1 km2 annual field crop monoculture bisected by a 60 m wide natural habitat strip. The model simulates the movement of adult predators in the landscape via both trivial movement and long-distance dispersal, along with the movement of energy and egg reserves carried by those predators. We simulate multiple scenarios varying the presence or absence of floral resources and alternate prey in the natural habitat and crop, and the presence or absence of overwintering refuges for the predator and pest insect in the natural habitat. Food resources provided to the predator by the natural habitat did not enhance natural control in adjacent crops. When the natural habitat served as an overwintering refuge for predators, natural control of pests was enhanced if food resources were available in the crop for those predators. Availability of alternate prey was more important to the predator than floral resources. Early-season crop pest loads were always increased when pest insects overwintered in the natural habitat, however early-season availability of pest insects enhanced natural control across the whole-season. Overall, crop pest loads were highly variable across simulation scenarios, reproducing the conflicting results from field research.

Broad-scale impacts of coastal mega-infrastructure project on obligatory inshore delphinids: A cautionary tale from Hong Kong

Inshore marine habitats experience considerable anthropogenic pressure, as this is where many adverse effects of human activities concentrate. In the rapidly-changing seascape of the Anthropocene, Hong Kong waters at the heart of world's fastest developing coastal region can serve as a preview-window into coastal seas of the future, with ever-growing anthropogenic footprint. Here, we quantify how large-scale coastal infrastructure projects can affect obligatory inshore cetaceans, bringing about population-level consequences that may compromise their long-term demographic viability. As a case in point, we look at the construction of world's longest sea crossing system and broad-scale demographic, social and spatial responses it has caused in a shallow-water delphinid, the Indo-Pacific humpback dolphin (Sousa chinensis). Soon after the infrastructure project began, dolphins markedly altered their home range near construction sites such that these waters no longer functioned as dolphin core areas despite the apparent presence of prey, indicating that anthropogenic impacts outweighed foraging benefits. The contraction of key habitats has in turn led individuals to interact over spatially more constricted area, reshaping their group dynamics and social network. Although there was no apparent decline in dolphin numbers that could be detected with mark-recapture estimates, adult survival rates decreased drastically from 0.960 to 0.904, the lowest estimate for these animals anywhere across the region to date, notably below the previously estimated demographic threshold of their long-term persistence (0.955). It is apparent that during an advanced stage of this coastal infrastructure project, dolphins were under a major anthropogenic pressure that, if sustained, could be detrimental to their long-term persistence as a viable demographic unit. As effective conservation of species and habitats depends on informed management decisions, this study offers a valuable lesson in environmental risk assessment, underscoring the implications of human-induced rapid environmental change on obligatory inshore delphinids—sentinels of coastal habitats that are increasingly degraded in fast-changing coastal seas.

Depth and temperature preferences of meagre, Argyrosomus regius, as revealed by satellite telemetry.

Argyrosomus regius (commonly referred to as meagre), is one of Europe's largest coastal bony fish species and supports important recreational and commercial fisheries in the Atlantic and Mediterranean coasts. Demand for this species, and more recently for their swim bladders, has led to regional population declines and growing importance as an aquaculture species. Despite intense research in captivity, little is known about the spatial ecology of A. regius's wild population, including basic information such as vertical migrations and depth/temperature preferences. Previous research based on indirect data suggests a seasonal habitat shift from shallow to deeper waters, but this has never been validated through direct high-resolution movement data. In this study, we tagged 13 adult A. regius with pop-up satellite archival tags in the South of Portugal, which successfully returned data from 11 individuals including high-resolution data from six recovered tags (mean, range: 167 days, 28-301 days). We found that adults of this population spend 95.2% of their time between 5 and 75 m depth (mean ± SD, 30.9m ± 18.3m) and do not venture beyond 125 m. Across seasons, A. regius move across water temperatures between 13.3 and 24.8°C with a preferred thermal range between 14 and 18°C where they spent 75.4% of their time. The inferential modelling using this electronic data validated previous hypotheses by showing significant differences between a shallower and warmer summer habitat vs. a deeper and cooler winter habitat. Visual investigation of the diel effects on depth preferences suggests subtle changes in depth use between day and night during the warmer months of the year. We speculate that these patterns are in response to the species' behavioural ecology and physiology, reflecting the seasonal changes in water stratification and presence of prey, as well as on the species reproduction, which results in summer spawning aggregations in shallower areas.

Key processes required for the different stages of fungal carnivory by a nematode-trapping fungus.

Nutritional deprivation triggers a switch from a saprotrophic to predatory lifestyle in soil-dwelling nematode-trapping fungi (NTF). In particular, the NTF Arthrobotrys oligospora secretes food and sex cues to lure nematodes to its mycelium and is triggered to develop specialized trapping devices. Captured nematodes are then invaded and digested by the fungus, thus serving as a food source. In this study, we examined the transcriptomic response of A. oligospora across the stages of sensing, trap development, and digestion upon exposure to the model nematode Caenorhabditis elegans. A. oligospora enacts a dynamic transcriptomic response, especially of protein secretion-related genes, in the presence of prey. Two-thirds of the predicted secretome of A. oligospora was up-regulated in the presence of C. elegans at all time points examined, and among these secreted proteins, 38.5% are predicted to be effector proteins. Furthermore, functional studies disrupting the t-SNARE protein Sso2 resulted in impaired ability to capture nematodes. Additionally, genes of the DUF3129 family, which are expanded in the genomes of several NTF, were highly up-regulated upon nematode exposure. We observed the accumulation of highly expressed DUF3129 proteins in trap cells, leading us to name members of this gene family as Trap Enriched Proteins (TEPs). Gene deletion of the most highly expressed TEP gene, TEP1, impairs the function of traps and prevents the fungus from capturing prey efficiently. In late stages of predation, we observed up-regulation of a variety of proteases, including metalloproteases. Following penetration of nematodes, these metalloproteases facilitate hyphal growth required for colonization of prey. These findings provide insights into the biology of the predatory lifestyle switch in a carnivorous fungus and provide frameworks for other fungal-nematode predator-prey systems.

Diet composition and feeding strategy of larvae and juveniles of green riffle goby, Stiphodon elegans in Cimaja Estuary, Indonesia

Green riffle goby, Stiphodon elegans, is an amphidromous goby living in Cimaja River, Sukabumi. Postflexion and juvenile stages of this species migrate from the sea to the river estuary for the recruitment process both in the day and nighttime. The presence of prey strongly influences the success of the recruitment process. The present study, therefore, aims to reveal the diet preferences and feeding strategies of postflexion larvae and juveniles of the green riffle goby during the recruitment process. Postflexion larvae and juveniles of S. elegans were collected day and nighttime using a lift net from December 2020 to May 2021 in the Cimaja River estuary. A total of 13,955 larvae and juveniles were captured. For diet analysis, 455 fish larvae and juveniles were analyzed, consisting of 47 larvae (8.9-11.8 BL) and 408 juveniles (11.9-21.8 BL). The diet composition of postflexion larvae comprised five genera from three different classes of benthic microalgae and zoobenthic. In comparison, fish juveniles’ prey composition comprised 15 genera from 5 different classes of benthic microalgae and zoobenthic. The postflexion larva tends to be more specialized than the juvenile in utilizing prey. There is no significant difference in the diet composition and feeding strategy of postflexion larvae and juveniles during the day and nighttime (p>0.05).

When the aggressiveness degree modifies the intraguild predation magnitude

In agroecosystems, intraguild predation (IGP) is an ecological interaction that can reduce the effectiveness of biological control programs. Since aggressiveness is correlated with a higher attack rate, it is suspected to influence IGP occurrence. To understand the consequences of increased aggressiveness on the IGP, we used two artificially selected lines of the generalist predator, Nabis americoferus (one aggressive and one docile). We hypothesized that IGP is positively correlated to aggressiveness. Individuals of N. americoferus were tested individually with an intraguild prey (IGPrey), Orius insidiosus, and in the absence or presence of an extraguild prey (XGPrey), third instars of Lygus lineolaris. Firstly, the attack rate of N. americoferus on O. insidiosus was recorded for 15 min and then the IGP after a period of 24 h. We found that aggressive individuals performed a higher attack rate and IGP than docile ones even with the presence of XGPrey. Whereas docile individuals did not display a strong IGP in the absence of XGPrey, it increased significantly when they were introduced. Our results suggest that IGP is positively correlated to a high aggressiveness. Additionally, it seems that docile individuals are more prone to adjust their behavior according to environmental conditions. Finally, the implications of aggressiveness degree for the predator–prey dynamic is discussed.

Polistes dominula (Hymenoptera: Vespidae) paper wasps detect native grasshoppers using olfactory cues

AbstractPolistes dominula is an invasive social wasp that preys on the grasshopper Dichroplus elongatus, which constitutes a potential agricultural pest in Northwest Patagonia. This grasshopper feeds on a wide variety of plants, the ‘Dandelion’ (Taraxacum officinale) being one of the main food resources. In this study, by means of a Y‐tube olfactometer, we analysed the use of olfactory cues by P. dominula in the detection of grasshoppers. Specifically, we evaluated the attractiveness of live grasshoppers, their traces (i.e. leaves with herbivory traces + prey faeces or only faeces) and herbivory‐free leaves. The results showed that foragers equally chose olfactory cues emitted by grasshoppers and leaves with herbivory traces + faeces and herbivory‐free leaves, suggesting that the leaves of the host plant also have an important role in the searching behaviour. The current research is the first to demonstrate that the invasive paper wasp orients its search towards either the presence of grasshopper prey or the volatiles of plant leaves. These findings shed new light on predator‐prey interactions mediated by olfactory cues in P. dominula, which may play a biological role as a natural controller of D. elongatus, phytophagous pest in the invaded ecosystems.

Modelling the biological control of tomato root-knot nematode by predatory mites in the presence of an alternative prey

Modelling the biological control of tomato root-knot nematode by predatory mites in the presence of an alternative prey

Intra- and inter-specific interactions between <i>Coccinella transversalis</i> and <i>Cheilomenes sexmaculata</i> in relation to prey abundance

In the present study, we investigated the feeding rate and the effect of intra- and inter-specific interactions between adults, 3rd and 4th instar larvae of the coccinellids, Coccinella transversalis and Cheilomenes sexmaculata to its conspecific and heterospecific combinations under laboratory conditions. Cannibalism and the effect of interaction were investigated using the multiplicative risk model. Aphidophagous predators and their instars were kept alone, paired with conspecifics, and heterospecifics combinations in the absence and presence of prey (aphid, Aphis gossypii). In the presence of aphids, the combined release of these predator species revealed that except for (3rd × 3rd) and (4th× 4th) intraspecific combination of both predators, the observed consumption was lower than the expected consumption. In the case of interspecific combination, the observed consumption was significantly lower than expected and it indicated the antagonistic effect of both the predators in later instars in the presence of sufficient prey population. In the absence of the prey, intra-specific cannibalism was lowest between adults of both the species and highest among C. transversalis 3rd × C. transversalis adult and C. sexmaculata 3rd × C. sexmaculata adult. The interspecific predation was highest between C. transversalis adult × C. sexmaculata 3rd instar and lowest between adults of both species. The results suggest that C. transversalis was more a successful aphid predator, being able to find aphids more quickly and consume more of them compared to C. sexmaculata. As there was less intraspecific cannibalism among C. transversalis and individual consumption is also high, it is considered to play a significant role as a biocontrol agent in aphid management.

How do macroconsumers interact with insect shredders in streams? A laboratory test using shrimp and caddisfly larvae that build cases with different organic materials

Negative interactions between macroconsumers and detritivores can influence organic matter processing in streams. We evaluated how the shrimp Macrobrachium potiuna affects the shredding activity and survival of larvae of Phylloicus major and Triplectides gracilis, two caddisfly species that build cases with leaf pieces and tree sticks, respectively. We also evaluated whether the shredding activity of the shrimp changes in the presence of potential prey. We hypothesized that (i) M. potiuna would constrain the rates of leaf consumption and FPOM production of P. major more than T. gracilis and (ii) the shredding activity of the shrimp would increase in the presence of larvae. Laboratory trials were carried out in feeding arenas containing one shrimp, three larvae of one caddisfly species, and leaf discs of Miconia chartacea as food. The visual and chemical stimuli from the shrimp did not change the rates of leaf consumption and FPOM production of either larva. However, when physical contact was allowed, the survival rate of P. major was 35.7 %, while all individuals of T. gracilis remained alive. The shredding activity of M. potiuna was low and observed only in the presence of P. major. These results suggest that although larvae of P. major are less protected against predation, M. potiuna does not constrain the activity of either shredder. Therefore, top-down effects of this macroconsumer on detritus-based food webs dominated by case-building caddisfly shredders are likely context dependent.

Prey–predator optimal harvesting mathematical model in the presence of toxic prey under interval uncertainty

This paper explores a multispecies prey–predator harvesting system based on Lotka–Volterra model with two preys (palatable and toxic prey) and one predator with interval biological parameters. Due to the enhancement in resource availability, prey–predator system becomes destabilized theoretically (the paradox of enrichment). Also, a prey may become toxic for the predator due to a little change in the resource stoichiometry. The presence of toxic prey influences the growth of the predator as well as that of a palatable prey. Thus the dynamics of prey–predator system is significantly affected by the presence of such toxic prey. Again, due to lack of precise numerical data of the biological parameters an interval number based mathematical toxic prey–predator model is developed and then discussed the dynamical behaviour of the model. Then, we observe the existence of different points of equilibrium and also the stabilities at these points of equilibrium of the system are presented. Also, the bionomic equilibrium of the harvesting model has been analysed. Next, the optimal harvest policy is carried out and obtained the solution in the interior equilibrium point using Pontryagin’s maximum principle. All important analytical findings are demonstrated through computer simulation using MATLAB followed by discussions and conclusions.

DNAmetabarcoding illuminates the contribution of small and very small prey taxa to the diet of lions

AbstractKnowledge of food web interactions is essential for understanding the role of carnivores in an ecosystem and designing appropriate conservation and management strategies to preserve them. These interactions can only be understood by studying carnivores' diets and obtaining comprehensive and unbiased diet data. For large carnivores—which typically rely on large herbivores as prey—the role of smaller prey species has not received attention. This study aims to quantify the contribution of small (5–50 kg) and very small (<5 kg) prey taxa in the diet of lions (Panthera leo melanochaita) in four Kenyan National Parks (NPs). We use DNA metabarcoding to achieve higher‐resolution insights into prey composition, which is less biased toward large prey species compared to traditional methods, such as carcass counts. Our study identified 24 prey taxa in a total of 171 lion fecal samples. Small and very small prey taxa together contributed 18.7% out of 278 prey occurrences in all fecal samples, with comparable small prey presence (ranging from 8% to 15%) in the diet for each NP studied. This approach proved to be useful in detecting small and very small prey species in the diet of lions and can therefore be used in future research to uncover the diverse diet composition of these large carnivores. The consistent presence of smaller prey species in the diet indicates that lions generally supplement their large prey diet with smaller prey.