Prey Groups Research Articles

Comparative feeding analysis between the Chilean eagle ray Myliobatis chilensis (Philippi, 1982) and the Peruvian eagle ray Myliobatis peruvianus (Garman, 1913) from northern Peru

This study analyzed the diets of eagle rays in northern Peru to understand their intraspecific and interspecific feeding patterns, as well as their roles in the marine ecosystem. We obtained 109 stomachs with contents from Chilean eagle ray Myliobatis chilensis and 81 from Peruvian eagle ray Myliobatis peruvianus, between December 2020 and November 2021 in northern Peru (6º47'54"S and 79º59'30"W, San Jose, Lambayeque). The results show that M. chilensis has a benthic-pelagic feeding behavior with 14 prey families identified in its diet. The Peruvian anchovy Engraulis ringens, unidentified polychaetes, and families Onuphidae, Sternaspidae, Opheliidae, among others preys, were identified. On the other hand, M. peruvianus consumed Nassariidae, unidentified mollusks, unidentified polychaetes, and Veneridae, among other preys. We also found that both rays are secondary consumers with a restricted diet breadth (Bi < 0.6), where M. chilensis showed significant differences in diet by season and size class, while M. peruvianus only by size class. This study provides new information about eagle rays and is the first study to compare their diets. Furthermore, it also provides evidence of trophic segregation; however, given some overlap of some prey groups, low ecological redundancy. Finally, this study provides key information for the conservation of eagle rays in an important marine ecosystem in the eastern Pacific Ocean.

Disentangling direct and indirect effects of forest structure on biodiversity: Bottom‐up and top‐down effects between forestry, bats and their insect prey

Abstract Timber‐oriented forest management profoundly alters forest structure and composition, with complex effects on associated biodiversity. However, while species' responses to forest management and resulting structural characteristics have been the subject of numerous studies, direct and indirect effects that cascade through trophic levels are rarely disentangled. As insectivorous bats are particularly sensitive to changes in forest structure, that shape their available flight space, we investigated how forest structure, composition and management also indirectly modify their habitats, for example, by affecting important insect prey groups. We used structural equation models (SEMs) to test bat responses to forest composition, structure (forest heterogeneity, old‐growth attributes) and management intensity, quantifying direct and indirect prey‐mediated effects. For that, three bat guilds—short‐ (SRE), mid‐ (MRE) and long‐range echolocating (LRE) bats—and their prey insects (moths and ground beetles) were analysed from 64 sites in the Black Forest, Germany. We found guild‐specific effects on bats: While the structural heterogeneity of forests directly influenced the activity of bat guilds, the main influence of forest management, composition and structure was mediated through their prey‐groups. SRE activity responded to moths and LRE activity was associated with ground beetles, with positive effects of the insect groups' abundance, but negative effects of the same group's species richness. In addition, the SEM approach revealed a negative top‐down relationship between MRE activities and moths, suggesting predation or avoidance behaviour of moths. While forest management directly or indirectly increased prey insect abundance, it negatively affected the availability of roosting structures for bats. Synthesis and applications. The results highlight the indirect and positive effects of forest management on bats and support the important role of bats in insect regulation within continuous cover forests. Although forest management created small gaps that improved foraging habitats for most bats, it compromised the roosting functionality for bats. The ‘close‐to‐nature forestry’ currently prevalent in Europe mainly promotes continuous‐cover forests in mid‐successional stages. Expanding the forest management portfolio towards open and old‐growth forests would increase roosting opportunities and provide complementary foraging habitats for different bat species, while promoting high biodiversity in managed forest landscapes.

Foraging by predatory ants: A review.

In this review, we show that predatory ants have a wide range of foraging behavior, something expected given their phylogenetic distance and the great variation in their colony size, life histories, and nesting habitats as well as prey diversity. Most ants are central-place foragers that detect prey using vision and olfaction. Ground-dwelling species can forage solitarily, the ancestral form, but generally recruit nestmates to retrieve large prey or a group of prey. Typically, ants are omnivorous, but some species are strict predators preying on detritivorous invertebrates or arthropod eggs, while those specialized on termites or other ants often have scouts that localize their target and then trigger a raid. They can use compounds that ease this task, including chemical insignificance, mimicry, and venoms triggering submissive behavior. Army ants include 8 Dorylinae and some species from other subfamilies, all having wingless queens and forming raids. Dorylinae from the Old World migrate irregularly to new nesting sites. The foraging of most New World species that prey on the brood of other ants is regulated by their biological cycle that alternates between a "nomadic phase" when the colony relocates between different places and a "stationary phase" when the colony stays in a bivouac constituting a central place. Among arboreal ants, dominant species forage in groups, detecting prey visually, but can use vibrations, particularly when associated with myrmecophytes. Some species of the genera Allomerus and Azteca use fungi to build a gallery-shaped trap with small holes under which they hide to ambush prey.

Grouping Behaviour and Anti-Predator Responses in the Helmeted Guineafowl Numida meleagris

Little is known about landbird group dynamics in response to predation. Here, we describe the interactions between the Helmeted Guineafowl (Numida meleagris) and its predators regarding the survival advantages grouping behaviour may provide. Livestream webcam observations were conducted in Madikwe Game Reserve (South Africa) from August 2020 to August 2021. Emphasis was placed on predator–prey interaction and its effect on group size and structure in a spatial framework. We hypothesise that while grouping is crucial for a number of daily activities in this highly social species, it might turn into a higher predatory pressure. We found, indeed, that the probability of attacks by black-backed jackals (Lupulella mesomelas) significantly increased with guineafowl group size, unlike what happened with raptors. Moreover, when attacked by jackals, the birds responded by standing close to each other. These results suggest, in line with the proposed hypothesis, that a trade-off occurs between the defensive function of grouping in this galliform and the probability of jackal attack that increases as a function of prey group size. Nevertheless, we argue that Helmeted Guineafowl cooperative social groups also play a role as a defensive strategy against predators, with the many-eyes and dilution effects likely compensating for the higher predatory pressure.

To pool or not to pool: Pooled metabarcoding does not affect estimates of prey diversity in spider gut content analysis

Abstract Gut content metabarcoding has provided important insights into the food web ecology of spiders, the most dominant terrestrial arthropod predators. In small invertebrates, like spiders, gut content analysis is often performed on whole body DNA extracts of individual predators, from which prey sequences are selectively enriched and sequenced. Since many spider species are generalist predators, large numbers of samples comprising individual spider specimens must be analysed to recover an exhaustive image of a spider species' prey spectrum, which is costly and time‐consuming. Pooled processing of bulk samples of multiple specimens has been suggested to reduce the necessary workload and cost while still recovering a representative estimate of the prey diversity. However, it is still unclear if pooling approaches lead to bias in recovering the prey spectrum and if the results are comparable with data from individually processed spiders. Here, we test the effects of metabarcoding pooled spider gut content on the recovered taxonomic diversity and composition of prey. Using a newly adapted primer pair, which efficiently enriches COI barcode sequences of diverse arthropod prey groups while suppressing spider amplification, we test if pooling leads to reduced taxonomic diversity or skewed estimates of prey composition. Our results show that pooling and individual processing recover highly correlated taxonomic diversity and composition of prey. The only exception are very rare prey items which were less well recovered by pooling. Our results support pooling as a cost‐effective and time‐efficient approach to recover the diet of generalist predators for population‐level studies of spider trophic interactions.

Diet Composition of Painted Comber Searranus scriba (Linnaeus 1758) in the Eastern-Central Adriatic Sea

Abstract The diet composition of painted comber Serranus scriba was studied in the eastern central Adriatic Sea. The stomach contents of 275 individuals with a total length (TL) between 10.8 and 24.1 cm, collected by a small beach seine from January to December 2017, were analyzed. The food items in stomachs belonged to seven prey groups: Gastropoda, Bivalvia, Polychaeta, Decapoda, Isopoda, Stomatopoda and Teleostei. Overall, decapods were the most important prey group (%IRI = 54.0), followed by teleosts (%IRI = 40.4%). All other prey groups had much lower %IRI values and thus were of less importance. Painted comber had a diverse diet, feeding on a higher number of prey items (H’ = 3.11), and can be considered an opportunistic feeder whose diet in the Adriatic Sea consists of different groups of benthic organisms, with a wide range of prey sizes and morphology. For fish of small and medium size (up to 20 cm TL), decapods were the most important prey, whereas large-sized individuals (&gt; 20 cm TL) mainly consumed teleosts. Decapods were the most important prey in spring, summer and autumn, whereas teleosts dominated in winter.

Prey targeted by lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica

AbstractFemale Weddell seals (Leptonychotes weddellii) display a mixed capital-income breeding strategy, losing up to 40% of their body mass between birthing and weaning their pups. How and when they regain energy stores, however, remains to be fully explored. To better understand the foraging by lactating Weddell seals, we fitted time-depth recorders and head-mounted cameras on 26 seals in Erebus Bay, Ross Sea, for ~ 5 days in November and December 2018 and 2019. We aimed to (1) identify prey species and foraging depth and (2) investigate relationships between seal physiology and demographics and probability of foraging. We recorded 2782 dives, 903 of which were &gt; 50 m, maximum depth was 449.3 m and maximum duration was 31.1 min. Pup age likely contributes to the probability of a lactating Weddell seal foraging (Est. = 1.21 (SD = 0.61), z = 1.97, p = 0.0484). Among 846 prey encounters, the most frequent prey items were crustaceans (46.2%) and Antarctic silverfish (Pleuragramma antarcticum, 19.0%); two encounters were observed with juvenile Antarctic toothfish (Dissostichus mawsoni, 0.2%). We identified substantial variability in foraging behaviour, individually and between locations, and found that lactating seals target many species and some may specialise on certain prey groups.

Reduced trophic niche breadth is associated with higher productivity in a recovering apex predator population

AbstractUnderstanding the trophic and demographic dynamics of apex predators is of paramount importance for ecosystem conservation. Apex predators are usually free from predation, and thus, the main driver of population dynamics is the availability of trophic resources, which affects breeding performance. Albeit food habits have been described in many apex species, the effects of changes in the trophic niche on long‐term demographic dynamics are poorly known. We describe the long‐term (N = 25 years) changes in trophic niche breadth of a recovering golden eagle population in a Mediterranean landscape (northern Spain) and search for potential correlates with their productivity (i.e., number of fledged eaglets per controlled pair) as a proxy for their breeding performance (N = 290 pair‐years). We identified a total of 3475 prey items from 77 species; rabbits, hares, and red‐legged partridges were the most frequent prey consumed (overall 51%), followed by roe deer (10%), red‐billed chough, red foxes, and woodpigeons, all of them with &gt;5%. Prey diversity in eagles' diet decreased during the study period. Consumption of rabbits and roe deer increased, while that of hares and partridges decreased; no significant trends were observed in the consumption of foxes, choughs, and woodpigeons. Prey diversity and red‐legged partridge consumption were negatively correlated with productivity at the territory level, while rabbits, corvids, and pigeons showed a strong positive relationship with productivity. The size of the territory showed the strongest positive relationship with productivity, while roughness was negatively correlated. Rabbits and ungulates showed negative and positive correlations with roughness, respectively, while predator consumption exhibited a negative relationship with the size of the territory. Our findings give insights into the potential trophic mechanisms driving the dynamics of recovering apex predator populations; a reduction in the trophic niche breadth toward specific groups of prey, which could be due to a higher availability and individual specificity toward these prey species, might enhance productivity at the territory level and, ultimately, influence population dynamics facilitating the recovery process. The remarkable increase in the consumption of wild ungulates, predators, and other apex consumers suggests that the current population recovery and reduced trophic niche breadth may facilitate this eagle population to exhibit its apex role and contribute to ecosystem functionality.

Domača mačka – tiha grožnja divjim živalim v primestni lokaciji Maribora

The monitoring of domestic cats' prey brought home was conducted between the 13th of March and the 1st of May 2023 in two residential areas near Maribor, Slovenia. This study aimed to provide information about the amount, diversity, and frequency of prey that the cats captured to identify the predatory impact of domestic cats in peri-urban areas. We present the results of the prey captured, whether the prey was brought alive or not, and whether it was eaten or not. We further provide information about the predation frequency of domestic cats concerning circadian activity, according to weather conditions and air temperature. The frequencies of various taxonomic groups of prey captured were described concerning land use in a location and species' biology. Our results include a total of 50 records of 12 species (3 species of birds and 9 of mammals). Domestic cats were more active during the mornings, on days without rain and the frequency of bringing home prey increased with higher temperatures.

Sailfish generate foraging opportunities for seabirds in multi-species predator aggregations.

While various marine predators form associations, the most commonly studied are those between subsurface predators and seabirds, with gulls, shearwaters or terns frequently co-occurring with dolphins, billfish or tuna. However, the mechanisms underlying these associations remain poorly understood. Three hypotheses have been proposed to explain the prevalence of these associations: (1) subsurface predators herd prey to the surface and make prey accessible to birds, (2) subsurface predators damage prey close to the surface and thereby provide food scraps to birds, and (3) attacks of underwater predators lower the cohesion of prey groups and thereby their collective defences making the prey easier to be captured by birds. Using drone footage, we investigated the interaction between Indo-Pacific sailfish (Istiophorus platypterus) and terns (Onychoprion sp.) preying on schooling fish off the eastern coast of the Malaysian peninsula. Through spatio-temporal analysis of the hunting behaviour of the two predatory species and direct measures of prey cohesion we showed that terns attacked when school cohesion was low, and that this decrease in cohesion was frequently caused by sailfish attacks. Therefore, we propose that sailfish created a by-product benefit for the bird species, lending support to the hypothesis that lowering cohesion can facilitate associations between subsurface predators and seabirds.

Prey group defense and hunting cooperation among generalist-predators induce complex dynamics: a mathematical study.

Group defense in prey and hunting cooperation in predators are two important ecological phenomena and can occur concurrently. In this article, we consider cooperative hunting in generalist predators and group defense in prey under a mathematical framework to comprehend the enormous diversity the model could capture. To do so, we consider a modified Holling-Tanner model where we implement Holling type IV functional response to characterize grazing pattern of predators where prey species exhibit group defense. Additionally, we allow a modification in the attack rate of predators to quantify the hunting cooperation among them. The model admits three boundary equilibria and up to three coexistence equilibrium points. The geometry of the nontrivial prey and predator nullclines and thus the number of coexistence equilibria primarily depends on a specific threshold of the availability of alternative food for predators. We use linear stability analysis to determine the types of hyperbolic equilibrium points and characterize the non-hyperbolic equilibrium points through normal form and center manifold theory. Change in the model parameters leading to the occurrences of a series of local bifurcations from non-hyperbolic equilibrium points, namely, transcritical, saddle-node, Hopf, cusp and Bogdanov-Takens bifurcation; there are also occurrences of global bifurcations such as homoclinic bifurcation and saddle-node bifurcation of limit cycles. We observe two interesting closed 'bubble' form induced by global bifurcations due to change in the strength of hunting cooperation and the availability of alternative food for predators. A three dimensional bifurcation diagram, concerning the original system parameters, captures how the alternation in model formulation induces gradual changes in the bifurcation scenarios. Our model highlights the stabilizing effects of group or gregarious behaviour in both prey and predator, hence supporting the predator-herbivore regulation hypothesis. Additionally, our model highlights the occurrence of "saltatory equilibria" in ecological systems and capture the dynamics observed for lion-herbivore interactions.

Categorical data analysis using discretization of continuous variables to investigate associations in marine ecosystems

AbstractUnderstanding and predicting interactions between predators and prey and their environment are fundamental for understanding food web structure, dynamics, and ecosystem function in both terrestrial and marine ecosystems. Thus, estimating the conditional associations between species and their environments is important for exploring connections or cooperative links in the ecosystem, which in turn can help to clarify such directional relationships. For this purpose, a relevant and practical statistical method is required to link presence/absence observations with biomass, abundance, and physical quantities obtained as continuous real values. These data are sometimes sparse in oceanic space and too short as time series data. To meet this challenge, we provide an approach based on applying categorical data analysis to present/absent observations and real‐number data. The real‐number data used as explanatory variables for the present/absent response variable are discretized based on the optimal detection of thresholds without any prior biological/ecological information. These discretized data express two different levels, such as large/small or high/low, which give experts a simple interpretation for investigating complicated associations in marine ecosystems. This approach is implemented in the previous statistical method called CATDAP developed by Sakamoto and Akaike in 1979. Our proposed approach consists of a two‐step procedure for categorical data analysis: (1) finding the appropriate threshold to discretize the real‐number data for applying an independent test; and (2) identifying the best conditional probability model to investigate the possible associations among the data based on a statistical information criterion. We perform a simulation study to validate our proposed approach and investigate whether the method's observation includes many zeros (zero‐inflated data), which can often occur in practical situations. Furthermore, the approach is applied to two datasets: (1) one collected during an international synoptic krill survey in the Scotia Sea west of the Antarctic Peninsula to investigate associations among krill, fin whale (Balaenoptera physalus), surface temperature, depth, slope in depth (flatter or steeper terrain), and temperature gradient (slope in temperature); (2) the other collected by ecosystem surveys conducted during August–September in 2014–2017 to investigate associations among common minke whales, the predatory fish Atlantic cod, and their main prey groups (zooplankton, 0‐group fish) in Arctic Ocean waters to the west and north of Svalbard, Norway. The R code summarizing our proposed numerical procedure is presented in S4S1.

Bifurcation analysis of a Leslie-type predator–prey system with prey harvesting and group defense

In this paper, we investigate a Leslie-type predator–prey model that incorporates prey harvesting and group defense, leading to a modified functional response. Our analysis focuses on the existence and stability of the system’s equilibria, which are essential for the coexistence of predator and prey populations and the maintenance of ecological balance. We identify the maximum sustainable yield, a critical factor for achieving this balance. Through a thorough examination of positive equilibrium stability, we determine the conditions and initial values that promote the survival of both species. We delve into the system’s dynamics by analyzing saddle-node and Hopf bifurcations, which are crucial for understanding the system transitions between various states. To evaluate the stability of the Hopf bifurcation, we calculate the first Lyapunov exponent and offer a quantitative assessment of the system’s stability. Furthermore, we explore the Bogdanov–Takens (BT) bifurcation, a co-dimension 2 scenario, by employing a universal unfolding technique near the cusp point. This method simplifies the complex dynamics and reveals the conditions that trigger such bifurcations. To substantiate our theoretical findings, we conduct numerical simulations, which serve as a practical validation of the model predictions. These simulations not only confirm the theoretical results but also showcase the potential of the model for predicting real-world ecological scenarios. This in-depth analysis contributes to a nuanced understanding of the dynamics within predator–prey interactions and advances the field of ecological modeling.

Multiple methods of diet assessment reveal differences in Atlantic puffin diet between ages, breeding stages, and years

IntroductionAtlantic puffin (Fratercula arctica, hereafter “puffin”) reproductive success in the Gulf of Maine (GoM) has declined following a recent oceanographic regime shift that has led to rapid warming and increasingly frequent marine heatwaves. Concurrent changes in both the regional forage fish community and puffin chick diets and provisioning rates suggest that inadequate prey resources may be driving this decline. Traditional, noninvasive methods of diet assessment, however, are unable to determine seabird diet at many age classes and breeding stages.MethodsTo determine what prey GoM puffins were feeding on during two years of marine heatwave conditions, we assessed puffin diet using two complementary methods: traditional, observational methods that utilize bill-load photography and emerging methods employing fecal DNA metabarcoding. We then examined the effect of methodology, age, breeding stage, and year on puffin diet composition. ResultsWe identified a strong correlation between the composition of chick diet as estimated through traditional and emerging methods, supporting the interpretation of DNA relative read abundance as a quantitative metric of diet composition. Both methods identified the same dominant prey groups yet metabarcoding identified a greater number of species and offered higher taxonomic resolution. Additionally, metabarcoding revealed adult puffin diet during the incubation period for the first time. Although puffin adults and chicks fed on many of the same prey types, adults consumed a greater variety of taxa and consumed more low quality prey types than they provisioned chicks.DiscussionFor both age classes, diet varied both between and within years, likely reflecting changes in the local forage fish community in response to environmental variability. Puffins exploited unusual abundances of typically-uncommon prey during these two years of marine heatwave conditions, yet low puffin productivity suggests the observed dietary plasticity was not fully able to compensate for apparent prey shortages. Continued refinement of molecular methods and the interpretation of the data they provide will enable better assessments of how seabirds of diverse ages and breeding stages are adapting to changing prey communities.

Dynamical analysis of a modified Leslie–Gower predator–prey model with disease in prey incorporating a prey refuge and treatment

In this paper, we present and assess a predator–prey Leslie–Gower model including disease, refuge and treatment in prey population. There are two groups of prey: those who are susceptible and infected. It is hypothesized that prey population is affected by diseases and refuge, and grows logistically in the absence of predators. Infected prey population receives treatment. The predators’ growth rate is governed by the modified Leslie–Gower dynamics. The dynamical attributes of the resulting system are boundedness, positivity of solutions, extinction criteria, existence and (local and global) stability. Biology uses mathematical analysis to identify the possible attributes of equilibrium points. The focus of this study is to assess how treatment and refuge affect the populations of ill prey, susceptible prey, predators and treated prey. The numerical simulation indicates that the influence of treatment, and refuge change the dynamics of the system (2.1). Extensive numerical simulations were performed to validate our analytical findings by using the Mathematica and MATLAB software.

Trophic interactions between common minke whales (Balaenoptera acutorostrata) and their prey during summer in the northern Barents Sea

Global warming is causing rapid change in marine food webs, particularly at northern latitudes where temperatures are increasing most rapidly. In this study, the diet of common minke whales Balaenoptera acutorostrata was assessed both in terms of short-term (morphological analyses of digestive tract contents) and longer-term (tissue chemical markers: fatty acids and stable isotopes) prey use in the northern Barents Sea to see if they are prey shifting. Samples (blubber cores, muscle, and stomach contents) were obtained from 158 common minke whales taken during Norwegian commercial whaling operations during summer over the period 2016–2020. Two prey items, capelin Mallotus villosus and krill (primarily Thysanoessa sp.), dominated the stomach contents in the entire period of investigation, which included sampling both in June and in August, similar to findings from earlier studies. A few gadoids were also observed in the whale stomachs. Lower blubber fatty acid (FA) contents in 2016/2017 as compared with 2018/2019 were observed. This is most likely explained by differences in sampling time (June in 2016/2017 vs August in 2018/2019, i.e., after a longer feeding period during the summer in the latter case). This explanation also fits with the fact that FA profiles of the 2018/2019 whales were more similar to the FA profiles of the potential prey, presumably reflecting the two months longer assimilation time for these whales. Multidimensional mixing models based on carbon and nitrogen isotope composition of the most likely prey groups suggested that the whales ate mostly krill in four of the five sampling years. In 2018 there were indications of a higher proportion of gadoid fish, showing some dietary flexibility. The trophic level of the whales’ feeding, as interpreted from the nitrogen isotope values, was positively correlated with blubber thickness suggesting that fish-eaters tended to assimilate more energy than whales that focused more exclusively on lower trophic prey. The variation suggested by different dietary analyses methods − stomach contents, fatty acids, and stable isotopes – most likely reflects different turnover times, with muscle stable isotopes likely representing several months of dietary integration, while lipid stores are more dynamic and may represent weeks, and stomach contents represent feeding events during the last few hours. The change in diet of minke whales from small pelagic fishes (in the past) to a greater quantity of krill and demersal fish (seen in this study) suggests that the whales are responding to the ongoing borealization of the Barents Sea ecosystem.

Methods for comparing theoretical models parameterized with field data using biological criteria and Sobol analysis

Prey–predator models are frequently developed to investigate trophic webs and to predict the population dynamics of prey and predators. However, the parameters of these models are often implemented without empirical data and may even be chosen arbitrarily. Commonly, only a few parameters are tested regarding their sensitivity and it is rare to read about the comparison between different prey–predator models (i.e. predation function structure). Here, we propose a method to compare four prey–predator models designed for two populations. We then apply this method to select the more biologically plausible one to model a simplified agricultural trophic system, including one predator compartment (the red fox Vulpes vulpes) and one prey group compartment (small mammals). These models are based on four Holling functional responses for the predation interaction and take the prey intrinsic growth rate into account through a Verhulst logistic function. Most parameters’ values (like attack rates or growth rates) were calculated from field data or based on literature review. We then used Sobol indices to conduct parameter exploration around mean parameter values to investigate and compare the model dynamics responses. Our first results showed that under our assumptions, the two most relevant models for our case study are the saturated Holling I and II models. We were also able to discriminate that among the 6 scaled parameters that vary, the model outputs are particularly sensitive to four of them (κ: saturation rate of the environment, Tr1: characteristic intrinsic decay time of the predators, Tc: characteristic growth time of the predator via the predation on the prey and λ: saturation rate of a predator’s stomach per time unit) and much less sensitive to two others (Tr2: characteristic intrinsic growth time of the prey and Ta: characteristic decay time of the prey due to the predation). These first encouraging results open the way for the next step, which will be to adapt this model construction to more complex prey–predator systems, with several predator and/or several prey compartments.

Detecting the invisible through DNA metabarcoding: The role of gelatinous taxa in the diet of two demersal Antarctic key stone fish species (Notothenioidei)

AbstractGelatinous zooplankton (GZP), i.e., ctenophores, cnidarian medusae, chaetognaths, appendicularians and salps, are considered climate change winners. This becomes particularly obvious in the Southern Ocean, which has undergone a significant shift from a krill‐based to a salp‐based ecosystem over the last decades. A better knowledge on the role of gelatinous invertebrates as prey is needed to predict the impact of such a gelatinous shift. Until recently, GZP was considered as a “trophic dead end”. However, their true importance in diets has remained unresolved due to the rapid digestion of their watery and soft tissues in predators' stomachs. In this study, we want to validate the paradigm shift from GZP being considered as “survival food” to be considered a “regular” prey item for two demersal fish species (Notothenia rossii and N. coriiceps) of Potter Cove, South Shetland Islands, using a multimarker (COI and 18S) metabarcoding approach. We found that GZP taxa commonly occurred in the diets of both species, represented by pelagic tunicates (appendicularians, salps), cnidarians, chaetognaths and ctenophores. Salps were the most abundant prey group, preyed upon by each individual of both species, reaching 98.7% relative read abundance for 18S. We recovered a wide range of different taxa in their diets, from primary producers to highly abundant invertebrates, thus the two nototheniid species can be regarded as “natural samplers” of the ecosystem in study. Finally, we want to point out the importance of multimarker metabarcoding approaches for broad ecological assessments, given the differential amplification and sequencing success of different markers for specific groups and the unequal taxonomic coverage of the reference databases. The output of each marker was highly complementary, since an important prey item such as salps, was only detected with 18S, while other taxa (e.g., Arthropoda) were represented with a higher taxonomic resolution with COI.

First evidence of scavenging behaviour in Ichthyosaura alpestris (Laurenti, 1768)

The alpine newt is an opportunistic predator whose diet consists predominantly of aquatic and terrestrial invertebrates with Crustacea, Plecoptera, Collembola, Diptera, Isopoda and Gastropoda being the predominant prey groups. Consumption of amphibian eggs and larvae are another common food source. Here, we report the first documented case of adult Ichthyosaura alpestris feeding on a rodent carcass, thus adding to its menu a prey item that belongs to the Class Mammalia, while showcasing the previously unknown scavenging behaviour. This finding suggests that rodent carcasses can serve as an important resource for nutrients in remote, high-altitude populations of the alpine newt.

Sugar-coated survival: N-glycosylation as a unique bearded dragon venom resistance trait within Australian agamid lizards

In the ongoing evolutionary arms race between predators and prey, adaptive innovations often trigger a reciprocal response. For instance, the emergence of α-neurotoxins in snake venom has driven prey species targeted by these snakes to evolve sophisticated defense mechanisms. This study zeroes in on the particular motifs within the orthosteric sites of post-synaptic nicotinic acetylcholine receptors (nAChR) that confer resistance to α-neurotoxins, often through structural alterations of nAChR. This research examined Australian agamid lizards, a primary prey group for Australian elapid snakes, which are subject to predatory selection pressures. We previously showed that Pogona vitticeps (Central bearded dragon) was resistant to α-neurotoxic snake venoms through a steric hindrance form resistance evolving within the nAChR orthosteric, specifically through the 187–189NVT motif resulting in the presence of N-glycosylation, with the branching carbohydrate chains impeding the binding by the neurotoxins. This adaptive trait is thought to be a compensatory mechanism for the lizard's limited escape capabilities. Despite the significance of this novel adaptation, the prevalence and evolutionary roots of such venom resistance in Australian agamids have not been thoroughly investigated. To fill this knowledge gap, we undertook a comprehensive sequencing analysis of the nAChR ligand-binding domain across the full taxonomical diversity of Australian agamid species. Our findings reveal that the N-glycosylation resistance mechanism is a trait unique to the Pogona genus and absent in other Australian agamids. This aligns with Pogona's distinctive morphology, which likely increases vulnerability to neurotoxic elapid snakes, thereby increasing selective pressures for resistance. In contrast, biolayer interferometry experiments with death adder (Acanthophis species) venoms did not indicate any resistance-related binding patterns in other agamids, suggesting a lack of similar resistance adaptations, consistent with these lineages either being fast-moving, covered with large defensive spines, or being arboreal. This research not only uncovers a novel α-neurotoxin resistance mechanism in Australian agamids but also highlights the complex dynamics of the predator-prey chemical arms race. It provides a deeper understanding of how evolutionary pressures shape the interactions between venomous snakes and their prey.