Number Of Prey Research Articles

Bifurcation analysis in a discrete predator–prey model with herd behaviour and group defense

<abstract><p>In this paper, we utilize the semi-discretization method to construct a discrete model from a continuous predator-prey model with herd behaviour and group defense. Specifically, some new results for the transcritical bifurcation, the period-doubling bifurcation, and the Neimark-Sacker bifurcation are derived by using the center manifold theorem and bifurcation theory. Novelty includes a smooth transition from individual behaviour (low number of prey) to herd behaviour (large number of prey). Our results not only formulate simpler forms for the existence conditions of these bifurcations, but also clearly present the conditions for the direction and stability of the bifurcated closed orbits. Numerical simulations are also given to illustrate the existence of the derived Neimark-Sacker bifurcation.</p></abstract>

Mechanisms leading to bursting oscillations in the system of predator–prey communities coupled by migrations

The purpose is to study the periodic regimes of the dynamics for two non-identical predator– prey communities coupled by migrations, associated with the partial synchronization of fluctuations in the abundance of communities. The combination of fluctuations in neighboring sites leads to the regimes that include both fast bursts (bursting oscillations) and slow oscillations (tonic spiking). These types of activity are characterized by a different ratio of synchronous and non-synchronous dynamics of communities in certain periods of time. In this paper, we describe scenarios of the transition between different types of burst activity. These types of dynamics differ from each other not so much in size, shape, and number of spikes in a burst, but in the order of these bursts relative to the slow-fast cycle. Methods. To study the proposed model, we use the bifurcation analysis methods of dynamic systems, as well as geometric methods based on the division of the full system into fast and slow equations (subsystems). Results. We showed that the dynamics of the first subsystem with a slow-fast limit cycle directly determines the dynamics of the second one with burst activity through a smooth dependence of regime on the number of predators and a non-smooth dependence on the number of prey. We constructed the invariant manifolds on which there are parts of dynamics with tonic (slow manifold) and burst (fast manifold) activity of the full system. Conclusion. We described the scenario for bursting with different waveforms, which are determined by the appearance of the fast invariant manifold and the location of its parts relative to the slow-fast cycle. The transitions between different types of burst are accompanied by a change in the oscillation period, the degree of synchronization, and, as a result, the dynamics becomes quasi-periodic when both communities are not synchronous with each other.

Effects of prey capture on the swimming and feeding performance of choanoflagellates

Locomoting organisms often carry loads such as captured prey or young. Load-carrying effects on high-Reynolds-number flight have been studied, but the fluid dynamics of load carrying by low-Reynolds-number microorganisms has not. We studied low-Reynolds-number load carrying using unicellular choanoflagellates, which wave a flagellum to swim and create a water current transporting bacterial prey to a food-capturing collar of microvilli. A regularized Stokeslet framework was used to model the hydrodynamics of a swimming choanoflagellate with bacterial prey on its collar. Both the model and microvideography of choanoflagellates showed that swimming speed decreases as number of prey being carried increases. Flux of water into the capture zone is reduced by bacteria on the collar, which redirect the water flow and occlude parts of the collar. Feeding efficiency (prey captured per work to produce the feeding current) is decreased more by large prey, prey in the plane of flagellar beating and prey near microvillar tips than by prey in other locations. Some choanoflagellates can attach themselves to surfaces. We found that the reduction in flux due to bacterial prey on the collars of these attached thecate cells was similar to the reduction in flux for swimmers.

Feeding ecology of the shortfin mako shark, Isurus oxyrinchus, in the Ecuadorian Pacific Ocean

Abstract Shortfin mako shark, Isurus oxyrinchus, is listed as an endangered species with declining global population. Thus, studies regarding its biology and ecology are important to recommend fishery management and conservation measures. This study aimed to determine the diet composition and feeding habits of I. oxyrinchus in Ecuadorian waters. Samples were obtained from Santa Rosa fishing port (Ecuador). The total length (LT), sex and sexual characteristics were recorded, and stomach contents were collected. A total of 142 individuals were recorded, comprising 81 females (104–295 cm LT) and 61 males (127–245 cm LT). A total of 24 prey species were identified, including crustaceans, cephalopods, teleosts and cetaceans. According to the Prey-Specific Index of Relative Importance (PSIRI), the main prey taxa were the ommastrephid squid, Dosidicus gigas (42.57%) and Sthenoteuthis oualaniensis (21.04%), followed by fish from the family Hemiramphidae (11.85%). Isurus oxyrinchus is a specialist predator that preferred a low number of prey (Bi = 0.25), both by sex (Bi; females = 0.29 and males = 0.34) and life stages (Bi; juveniles = 0.27 and adults = 0.37). The trophic overlap was medium for sexes (J = 0.54) and biological cycle phases (J = 0.42). Trophic level (TLk) was 4.47, indicating that I. oxyrinchus is a tertiary predator. This information will help in fisheries management based on an ecosystem approach, where this species fulfils an ecological role, and its interactions with other species allow us to understand how the flow of nutrients and energy occurs within an ecosystem.

Food web structure and microenvironment affect Chagas disease vector infection and abundance in a rural landscape

AbstractVector‐borne pathogen transmission is shaped by multiple abiotic and biotic factors. Understanding the relative importance of these factors on vector abundance and infection is important for developing vector‐borne disease control strategies. The crown of the Attalea butyracea palm provides a natural arboreal mesocosm suitable for studying how food web relations and microclimate affect Chagas disease vectors of the genus Rhodnius, which feed on vertebrate blood and interact with many vertebrate and invertebrate species, vegetation, and detritus within the palm crown. We performed a cross‐sectional, observational study of A. butyracea crowns using a community ecology network approach to evaluate abiotic and biotic conditions associated with Rhodnius pallescens abundance and infection with Trypanosoma cruzi, the Chagas disease etiologic agent. We collected 1098 R. pallescens from 105 A. butyracea crowns in rural landscapes of Panama. In a palm subset (N = 49), we recorded microclimate and habitat conditions and counted vertebrate and invertebrate species in order to characterize palm crown food webs. We used food web metrics, namely Generality (average number of prey per predator) and Vulnerability (average number of predators per prey) to evaluate associations between palm community trophic structure, vector predators, vector blood meal species composition, vector abundance, and vector T. cruzi infection. Field data analyzed with generalized linear models showed that vector abundance and infection in a given palm crown were influenced by a combination of geographic location, land‐use type, palm crown animal community composition, and microhabitat conditions. Vector abundance was negatively associated with increased overall palm crown community diversity. However, vector abundance was positively associated with the invertebrate predator and mammal community. R. pallescens Vulnerability score, which measures predation pressure on the vector within the palm crown, was positively associated with vector abundance. Vector infection with T. cruzi was positively associated with mammal presence; vectors in palms with mammals were about 25 times more likely to be infected with T. cruzi compared with vectors in palms without mammals. Our findings suggest that a holistic study of food webs and environmental variables at the local scale can provide useful information for vector‐borne disease management across a wide habitat range.

Citizen Science for the Study of Birds in Distinct Biomes: Diet of the Rufous-Tailed Jacamar (Galbula ruficauda) (Aves, Galbulidae) in Brazil

Data obtained by citizen scientists have been used by researchers to study the natural history of tropical birds in several countries. For example, this approach has been increasing the knowledge about their feeding ecology, as many photographs show birds holding prey with their foot and/or bill. Due to this, the diet of numerous bird species can be examined with citizen science data. The Rufous-tailed Jacamar (Galbula ruficauda) is a forest bird species widely distributed throughout the Neotropics, and its diet was scarcely quantified in a few localities. This study aimed to investigate the diet of the Rufous-tailed Jacamar in three Brazilian biomes: the Caatinga, the Cerrado and the Atlantic Forest. Searches for photographs with evidence of feeding activities were done in February 2021 in the WikiAves and eBird databases, the major citizen science projects regarding birds found in Brazil. For each selected record, the captured prey was tentatively identified to the taxonomic Order level, and the date of obtention was classified as part of dry or rainy periods. The chi-square test was used to compare the numbers of prey of distinct insect orders in different periods and biomes. A total of 283 feeding records were obtained by citizen scientists in the Caatinga (12%) and surrounding portions of the Cerrado (45%) and the Atlantic Forest (43%). Captured prey comprised seven insect orders, and 15% of them could not be identified. In the Cerrado, the most numerous prey in its diet were those of the orders Lepidoptera and Odonata, followed by Hymenoptera and Hemiptera, in both the dry and rainy periods. On the other hand, substantial seasonal variation was observed in the Atlantic Forest. Records with Lepidoptera were more numerous than those with other insects in the dry period, while Hymenoptera had more records than other orders in the rainy period. In the Caatinga, prey with more records were those of the orders Odonata, Lepidoptera and Hymenoptera. This study suggests that photographic records available in citizen science databases, such as WikiAves and eBird, can be used to improve our knowledge about the diet of birds found in the Neotropics.

Modeling the Dynamics of a Ratio-Dependent Leslie–Gower Predator–Prey System with Strong Allee Effect

In this paper, the dynamics of a ratio-dependent predator–prey model with strong Allee effect and Holling IV functional response is investigated by using dynamical analysis. The model is shown to have complex dynamical behaviors including subcritical or supercritical Hopf bifurcation, saddle-node bifurcation, Bogdanov–Takens bifurcation of codimension-2, a nilpotent focus or cusp of codimension-2. The codimension-2 Bogdanov–Takens bifurcation point acts as an organizing center for the whole bifurcation set. The coexistence of stable and unstable positive equilibria, homoclinic cycle is also found. Our analysis shows that the ratio-dependent model may collapse suddenly due to certain parameter variation, i.e. the numbers of predator and prey will decrease sharply to zeroes after undergoing a short time of sustained oscillations with small amplitudes. Of particular interest is that the coalescence of saddle-node bifurcation point and Hopf bifurcation point may indicate the occurrence of relaxation oscillations and the critical state of extinction of predator and prey. Numerical simulations and phase portraits including one-parameter bifurcation curve and two-parameter bifurcation curves are given to illustrate the theoretical results.

Feeding by larval fish: how taxonomy, body length, mouth size, and behaviour contribute to differences among individuals and species from a coastal ecosystem

AbstractData on individual stomach contents were used to describe length-dependent differences in feeding success of larvae of 11 species of fish found in coastal Newfoundland, Canada. Copepods dominated the diet with a gradual shift from nauplii to copepodites in all species. Differences in feeding success in both prey number and gut fullness among individual larvae was linked to increasing individual diet diversity in all taxa, although there was a weak decline in mean prey size. Maxilla and body length, within and among taxa, have a dominant positive influence on the potential feeding success of larval fish. In addition to differences in average stomach weight, the variability in number of prey per stomach among individuals indicates that each species perceives their prey environment in different ways. Taxonomic proximity had limited effect on differences in feeding success among taxa. The results suggest that behavioural differences among individuals and taxa, that likely reflect swimming capacity and/or prey perception/capture ability, are likely to be important elements contributing to feeding success. Body and mouth size may represent key characteristics that should be considered in evaluating differences in feeding success among species as well as among individuals within and among cohorts.

Anthropogenic pressure on large carnivores and their prey in the highly threatened forests of Tanintharyi, southern Myanmar

AbstractThe Tanintharyi Region in southern Myanmar is rich in biodiversity yet is facing threats from varying degrees of anthropogenic pressure. In this research we examine how anthropogenic pressures are influencing large carnivores (tiger Panthera tigris, leopard Panthera pardus and dhole Cuon alpinus) and their major prey species (wild pig Sus scrofa, muntjac Muntiacus spp., sambar Rusa unicolor, gaur Bos gaurus and banteng Bos javanicus) in the Lenya Reserved Forest and adjacent areas of Sundaic forest. We used data from camera-trap surveys during May 2016–March 2018 and logistic regression to analyse the relationships between the presence of large carnivores and explanatory variables such as human disturbance, landscape variability and changes in prey distribution. Tiger presence was positively associated with the occurrence of gaur and distance to villages. The occurrence of prey did not explain the detection of leopards in the study area. We suspect this was because leopards have a broad diet, including arboreal primates, and their prey was not fully recorded in our camera-trap survey. Dholes were positively associated with wild pigs and the total number of prey but not associated with forest type and landscape variables. To restore the carnivore population and conserve the biodiversity of this area, effective protection of predators and habitat management for large ungulates are crucial.

Data for "Track and dive-based movement metrics do not predict the number of prey encountered by a marine predator"

Data for "Track and dive-based movement metrics do not predict the number of prey encountered by a marine predator"

Impact of elevated CO2 on feeding potential of wolf spider against brown planthopper (Nilaparvata lugens)

An experiment was conducted at Department of Entomology, Indian Agricultural Research Institute, New Delhi during 2015–16 and 2016–17 to study the impact of elevated CO2 on functional response of wolf spider, Pardosa pseudoannulata (Boesenberg and Strand, 1906) against brown planthopper, Nilaparvata lugens (Stal, 1854) (Hemiptera: Delphacidae). Spider feeding rate on BPH was higher in jar arena compared to microcosm arena both under ambient CO2 and elevated CO2 conditions. Regression of number of attacked prey (1/Ha) upon prey density per unit area (H) over time duration of experiment (T) in microcosm and in jar arena under ambient and elevated CO2 revealed type II functional response. Attack rate, maximum attack rate and efficiency parameters were higher and handling time was lower in both jar arena and microcosm under elevated CO2 condition compared to ambient CO2 condition. Simultaneously, predators might have consumed more number of preys due to their poor nutrient quality under elevated CO2 compared to ambient CO2. It was revealed that with increase of predator density within the same prey density in same area under both ambient and elevated CO2 conditions, the prey control might have optimized. This information generated would support the planthopper management by regulating predator number for increased predator efficiency.

Ladybird-Mediated Indirect Interactions between Two Aphid Species When Using a Banker Plant System

Banker plant systems have the advantages of introducing natural enemies preventively and maintaining by providing alternative prey, thus controlling the pests sustainably. Banker plant systems are usually composed of three factors: a banker (secondary) plant, an alternative prey, and a shared predator (attacking an alternative prey on the secondary plant, and the targeted pest on the crop). However, for most banker plant systems, there is a lack of understanding regarding the dynamic relationship among these elements, with detrimental effects on practical applications. Therefore, in this study, the control of Myzus persicae on Capsicum annum by the Coccinella septempunctata–Megoura japonica–Vicia faba banker plant system was used as the research system. The effects of different release time of predators, different initial numbers of alternative prey (Me. japonica) and different initial ratios of target pests/alternative prey on the indirect interaction of two aphids and the biological control effect of shared predators were tested. The occurrence of indirect interactions between the two aphid preys, the impact on population dynamics, and biological control effectiveness of the shared predator C. septempunctata were investigated. When the initial numbers of both species of aphids were equal (200 each), the delay between aphid and C. septempunctata introduction in the cage had no effect on My. persicae, but Me. japonica showed lower numbers when testing the least time between predatory introductions. When the numbers of the two aphids were manipulated, the My. persicae population was significantly reduced by the predator only at a ratio of My. persicae to Me. japonica < 1, while initial ratios ≥ 1 enabled My. persicae population growth. In 1–6 days, the control effect of C. septempunctata was the best. Principal component analysis showed that the experimental time, initial numbers of Me. japonica, and relative numbers of Me. japonica affected the predation of My. persicae by C. septempunctata. In addition, when the initial aphid ratio was greater than 1/4, C. septempunctata was able to effectively control My. persicae. Overall, our study confirmed the number-mediated indirect interaction (apparent competition) relationship and its impact on prey population dynamics. We provide useful information for optimizing banker plant systems, to boost biocontrol of aphid pests.

Prey stage preference and functional response of Neoseiulus striatus (Acari: Phytoseiidae) on Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae, is one of the most serious phytophagous mites affecting maize in China. Recently, a species of predatory mite, Neoseiulus striatus Wu (Acari: Phytoseiidae), was found on maize plants in Inner Mongolia. To understand the potential of N. striatus as a biocontrol agent agsinst T. urticae, prey stage preference of N. striatus for T. urticae and functional response of N. striatus to T. urticae were explored in a climate chamber set at 25 ± 1 °C, 60 ± 5% RH, and a 16:8 h (L:D) photoperiod. The immature stages (eggs, larvae and nymphs) of T. urticae were used to avoid the influence of oviposition of female adults on the experimental results. In the no-choice experiment, N. striatus consumed significantly more larvae than on the other prey stages of T. urticae. At same time, in the choice experiment, N. striatus also significantly preferred larvae, followed by eggs and then nymphs of T. urticae. Neoseiulus striatus displayed a type II functional response on all immature stages of T. urticae. The number of prey consumed by N. striatus increased with the increase in prey density. In contrast, the predation rate of N. striatus decreased with increasing prey density, indicating that the proportions of prey consumed by N. striatus were higher at lower prey densities. Meanwhile, the highest attack rate of N. striatus was recorded when it fed on larvae of T. urticae, whereas the shortest handling time of N. striatus was recorded when it fed on eggs of T. urticae. In conclusion, N. striatus appears to be a promising natural enemy against T. urticae, especially at low prey densities. Thus, releasing N. striatus at the early occurrence of T. urticae may be an efficient method for suppressing the population of T. urticae and prevent their establishment on maize.

Rainforest carnivore ecology in a managed forest reserve: Differential seasonal correlates between habitat components and relative abundance

Studies of relationships between seasons and Neotropical carnivore distributions tend to focus on water and prey availability without considering other habitat components such as escape, foraging, and resting cover. Our goal was to evaluate habitat characteristics that may be important for predicting the seasonal (dry or rainy) relative abundance of four commonly captured Neotropical carnivores (i.e., jaguar [Panthera onca], puma [Puma concolor], ocelot [Leopardus pardalis], and grey fox [Urocyon cinereoargenteus]) in Chiquibul Forest Reserve in Belize, Central America. We used trail camera data and random-effect Poisson models to investigate how prey ratios (number of prey detections/total detections), cover (e.g., logs and stumps used for hiding cover from predators), vegetation structure, and environmental site characteristics (e.g., site harvest-history, slope, aspect) were related to carnivore relative abundance. Both prey ratios and vegetation structure appeared in supported models more frequently than other environmental site characteristics and were negatively correlated with carnivore relative abundance. Supported models differed for each season for all species except jaguars for which mammalian prey ratios and prey cover at sites was always negatively correlated with jaguar relative abundance. Carnivores appeared to avoid sites where vegetation created ideal escape and hiding cover for prey even though prey may be less abundant. Our data suggest that vegetation structure and composition can create conditions conducive to carnivore foraging and that these characteristics can differ by season in the tropics.

Sensitivity of Hydra vulgaris to Nanosilver for Environmental Applications

Nanosilver applications, including sensing and water treatment, have significantly increased in recent years, although safety for humans and the environment is still under debate. Here, we tested the environmental safety of a novel formulation of silver nanoparticles functionalized with citrate and L-cysteine (AgNPcitLcys) on freshwater cnidarian Hydra vulgaris as an emerging ecotoxicological model for the safety of engineered nanomaterials. AgNPcitLcys behavior was characterized by dynamic light scattering (DLS), while Ag release was measured by inductively coupled plasma mass spectrometry (ICP-MS). H. vulgaris (n = 12) subjects were evaluated for morphological aberration after 96 h of exposure and regeneration ability after 96 h and 7 days of exposure, after which the predatory ability was also assessed. The results show a low dissolution of AgNPcitLcys in Hydra medium (max 0.146% of nominal AgNPcitLcys concentration) and highlight a lack of ecotoxicological effects, both on morphology and regeneration, confirming the protective role of the double coating against AgNP biological effects. Predatory ability evaluation suggests a mild impairment of the entangling capacity or of the functionality of the tentacles, as the number of preys killed but not ingested was higher than the controls in all exposed animals. While their long-term sub-lethal effects still need to be further evaluated on H. vulgaris, AgNPcitLcys appears to be a promising tool for environmental applications, for instance, for water treatment and sensing.

Feeding Niche and Predator–Prey Size Relationship in the Whiptail Lizard Aspidoscelis lineattissima (Squamata: Teiidae) in Insular and Continental Populations of the Mexican Pacific

We explore the feeding habits of two populations of the lizard Aspidoscelis lineattissima from two localities (Cocinas = island and Xametla = mainland) under the hypothesis that in an insular environment, there is less selection of food, because it is a relatively comfortable environment to forage due to the presence of few competitors and predators. We also examine the predator–prey size relationship in this lizard species with the intention of distinguishing possible ontogenetic changes in the choice of prey sizes in the two localities. In stomach contents of the lizards from mainland, a total of 2,616 prey items were recorded, while on the island, 1,357 prey items were found. This number of prey was divided into 18 categories for the mainland and 20 for the island. In general terms, the most important prey in the diet of lizards from both localities were Isoptera, Coleoptera (adult and larvae), Araneae, Orthoptera, Hymenoptera (ants and others), Blattodea, and Diptera. Island lizards presented a greater amount of plant material in their stomach contents. The breadth of the food niche was greater on the island than on the mainland. Although statistically there were no differences regarding food overlap between localities, the highest overlap values between groups (age classes and sexes) were found on the mainland. We found a positive relationship between morphological variables of the lizards (snout–vent length, head width, and head length) with the maximum and mean values of the prey volume in both localities. This reveals an ontogenetic change that indicates that as lizards grow, they add a greater quantity of large prey to their diet and at the same time eat smaller prey. These results showed that the diet of the lizards from both localities was similar to other species of the genus. The feeding habits of a species in contrasting environments is evidence that is helpful for understanding the foraging patterns more clearly, and the possible connection with its life history characteristics, shedding more light on the hypothesis of niche amplitude and the optimal foraging theory.

Impact of native and invasive cyclopoid predators in relation to the diversity of the zooplankton community

Abstract The ecological impact of invasive species may be less in communities with high species diversity. We hypothesized that the feeding rates of an invasive copepod would be unaffected by high species diversity of prey in the medium as compared with a native species which would have reduced feeding rates under similar conditions. The biotic resistance to prey consumption was evaluated by testing consumption rate of the invasive species: Mesocyclops pehpeiensis and the native species: Mesocyclops longisetus curvatus, Acanthocyclops americanus, Eucyclops sp. and Microcyclops dubitabilis separately exposed to two treatments: high diversity with 13 prey species (rotifers and microcrustaceans) and low diversity with three prey species (determined on the basis of previous studies on zooplankton diversity in Mexican water bodies). We also tested the prey preference index of M. pehpeiensis in the absence and presence of the native copepod M. longisetus curvatus. M. pehpeiensis consumed the same number of prey in both treatments, regardless of high or low diversity conditions, whereas the four native species consumed less prey in the high diversity than the low diversity treatments. High community diversity may not represent an obstacle to the successful establishment of the invasive exotic copepod M. pehpeiensis.

Effect of Transgenic Cotton Expressing Bt Cry1Ac or Cry1Ab/Ac Toxins on Lacewing Larvae Mediated by Herbivorous Insect Pests.

A simple food chain (plant, insect pests, and predatory arthropods) in an agro-ecosystem was set up here as a model system to elucidate the potential effect of transgenic Bacillus thuringiensis (Bt) cotton on non-target organisms. The system included transgenic/non-transgenic cotton, neonate larvae of three herbivorous insects (Spodoptera exigua, Helicoverpa armigera, and S. litura), and predatory lacewing larvae (Chrysopa spp.), which represent the first, second, and third trophic levels, respectively. The results showed that transgenic treatments and different densities of prey had significant effects on both body-weight gain of neonate herbivorous larvae and the number of prey captured by lacewing larvae, respectively. It was found that Bt toxin could persist at the third trophic level in lacewing larvae. The diet mixture bioassay showed that body-weight gain of lacewing larvae was significantly affected by various treatments, especially at lower concentrations of plant-expressed Bt toxin in the diet mixture, which caused significant decreases in body-weight gain. In contrast, synthetic Bt toxin at higher concentrations in the diet did not show this effect. Thus, we inferred that Bt toxin indirectly affected the growth of the lacewings and the lacewings may not be susceptible to Bt toxin or are able to metabolize it.

Trophic ecology of Gymnodactylus geckoides Spix, 1825 (Squamata, Phyllodactylidae) from Caatinga, Northeastern Brazil

The diet of lizards is mainly composed of arthropods. It can be affected by biotic and abiotic factors, which influence the energy supply provided by the composition of the animal´s diet. The richness and abundance of many arthropod species can be influenced by environmental seasonality, especially in the Caatinga ecoregion, due to the rainfall regimes. The present study aims to describe aspects of the seasonal and morphological variation in the lizard Gymnodactylus geckoides diet and their energy content. We collected 157 individuals (63 females, 68 males, and 26 juveniles) at the Catimbau National Park, Northeastern Brazil, of which 72 were analyzed for the dry season and 59 for the rainy season. Our data indicates Isoptera to be the most common prey in G. geckoides’s diet. Energy content, prey number was higher in the dry season, whereas prey volume and glycogen content increased in the rainy season. Proteins and lipids did not show marked differences. The present study represents the first effort to understand variations in G. geckoide’s trophic ecology, indicating that this specie presents a wide variation in their diet, especially when considering seasonal factors, revealing their needs and restrictions according to prey availability and environmental conditions.

Diet shifting of tortoise-eating Golden Eagles (Aquila chrysaetos) in southeastern Bulgaria

Top predators may adapt their diets to changes in prey availability where human-induced environmental changes are intense. This long-term study of the breeding-season diet of Golden Eagle (Aquila chrysaetos) in the Strandzha Mountains analyzed shifts in diet caused by the population decline in principal prey species, the tortoises (Testudo hermanni and T. graeca). Tortoises comprised 50.0% of the eagle diet by prey number in the 1990s, but that share collapsed to 5.8% in 2014–2021. During this later interval, Golden Eagles preyed more intensively on lighter-weight prey such as Northern White-breasted Hedgehog (Erinaceus roumanicus, an increrase of 28.2% by number) and Edible Dormouse (Glis glis, an increase of 14.9% by number). Hedgehogs predominated in the diet of an individual eagle nest site for the first time in 1998 and became the principal prey in 2014–2021. Differences in food niche breadth and proportions of mesopredators between tortoise- and hedgehog-dominated individual annual diets were not significant, corresponding to a low level of food stress. The only eagle with an annual diet dominated by Squamata (snakes and lizards) was an exception, having the widest food niche. Young domestic ungulates have almost completely disappeared from eagle diets at the same as the reduction of tortoises, corresponding to a concurrent decline of livestock farming. The results obtained here have relevance to conservation management of both predator and prey populations.