Search Results (315)

This study introduces a new class of coupled differential systems described by fractal–fractional Caputo derivatives with both constant and state-dependent delays. In contrast to traditional delay differential equations, the proposed framework integrates memory effects and geometric complexity while capturing adaptive feedback delays that vary with the system’s state. Such a formulation provides a closer representation of biological and physical processes in which delays are not fixed but evolve dynamically. Sufficient conditions for the existence and uniqueness of solutions are established using fixed-point theory, while the stability of the solution is investigated via the Hyers–Ulam (HU) stability approach. To demonstrate applicability, the approach is applied to two illustrative examples, including a predator–prey interaction model. The findings advance the theory of fractional-order systems with mixed delays and offer a rigorous foundation for developing realistic, application-driven dynamical models. Full article

The killer whale (Orcinus orca) is a crucial predator in marine ecosystems, affecting prey populations and overall ecosystem health. Since May 2020, Iberian killer whales in the Strait of Gibraltar have interacted unusually with pleasure boats, posing significant maritime safety challenges. Recognized as critically endangered by the IUCN, a conservation plan for these whales has been approved in Spain. This study analyzes media coverage of these interactions, as media can shape public opinion and influence policies regarding human–wildlife conflicts. A total of 107 news articles published between June 2022 and September 2024 in Spanish media were examined, focusing on the interactions between Iberian killer whales and boats. The research included six variables from prior studies to enhance understanding of media representation and its effects on conservation management. Findings suggest that media coverage often limits comprehension of orca behavior and their vulnerable status. Full article

Scorpions of the genus Tityus are a diverse and medically important group, but many aspects of their natural history, particularly feeding ecology, are poorly documented. A coherent understanding of their natural prey is crucial for interpreting the evolution of their potent venoms. During fieldwork in Quito, Ecuador, we recorded a predation event involving a specimen of Tityus pugilator Pocock, 1898, subduing a scolopendromorph centipede, Otostigmus sp. The centipede was still moving when found, indicating a recent envenomation. This observation adds to the limited knowledge of the genus’s feeding habits both locally and regionally, demonstrating that Tityus can prey on large and dangerous arthropods. This trophic relationship is worth noting as scorpions of this genus have evolved highly potent venoms. Further in-field observations are needed to fully explore this connection between diet and venom evolution in Tityus scorpions. Full article

This study investigates the defensive mechanisms employed by the freshwater flatworm Stenostomum sphagnetorum against the predatory ciliate, Coleps hirtus. Focusing on the role of the glandular secretions produced by S. sphagnetorum, the research demonstrates that the flatworm secretes mucus that acts as a barrier, disrupting predator attack. In particular, we show that: (1) S. sphagnetorum specimens artificially deprived of glandular secretions are significantly more susceptible to predation by C. hirtus than untreated specimens; (2) the secretion-deprived organisms consistently exhibit a significantly greater sensitivity to the main toxins employed by C. hirtus for predation, relative to untreated counterparts; (3) the characterization of the glandular secretion indicates that the mucus contains both neutral and acidic glycosaminoglycans, along with protein components, suggesting a complex chemical composition that may contribute to its protective function. Full article

Physical conditions in grain storage environments influence trophic interactions between predators and their prey and can affect the effectiveness of biocontrol agents. The study aimed to assess the potential of Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae), to manage Liposcelis decolor (Pearman) (Psocodea: Liposcelididae). Liposcelis decolor population suppression and X. flavipes progeny production were assessed at five predator–prey (P-P) ratios (0:240, 1:240, 2:240, 3:240, and 5:240), four temperatures (20, 24, 28, and 32 °C), and three relative humidities (RH) (63, 75, and 85%) over 40 days at 0:24 (L:D) photoperiod in the laboratory. Compared with the Control P-P ratio of 0:240 (no predators), prey suppression >97% was achieved across all predator release ratios. At 32 °C and 75% RH, which are the optimal conditions for L. decolor, 3985.13 ± 255.45 prey survived in the Control P-P ratio compared with 19.85 ± 2.47–115.73 ± 8.99 found for the four P-P ratios with the predator, representing prey reduction of 97.10–99.50%. Temperature influenced X. flavipes progeny production, which was greatest at 28 °C and a P-P ratio of 1:240. Suppression caused by X. flavipes demonstrates its potential as a biological control agent to manage psocid infestations in stored commodities. Full article

A Lotka–Volterra-type system with porous diffusion, which can be used as an alternative model to the classical Lotka–Volterra system, is under study. Multiparameter families of exact solutions of the system in question are constructed and their properties are established. It is shown that the solutions obtained can satisfy the zero Neumann conditions, which are typical conditions for mathematical models describing real-world processes. It is proved that the system possesses two stable steady-state points provided its coefficients are correctly specified. In particular, this occurs when the system models the prey–predator interaction. The exact solutions are used for solving boundary-value problems. The analytical results are compared with numerical solutions of the same boundary-value problems but perturbed initial profiles. It is demonstrated that the numerical solutions coincide with the relevant exact solutions with high exactness in the case of sufficiently small perturbations of the initial profiles. Full article

Predation plays a key organizational role in structuring plankton communities. However, predator diversity can lead to emergent effects in which the outcomes of predator–prey interactions are modified. The response of the plankton community to three different predator regimes at natural densities was investigated over a 10-day mesocosm experiment in a temperate, temporarily open/closed estuary in South Africa. The regimes included: (1) predation by the mysid, Mesopodopsis wooldridgei; (2) predation by larval Rhabdosargus holubi and (3) a combination of the two predators. M. wooldridgei are primarily copepod feeders, and juvenile R. holubi consume a broader diet including zooplankton, algae and invertebrate fauna. In the absence of predators, zooplankton grazing contributed to a significant decline in the phytoplankton size structure and total chlorophyll-a (Chl-a) concentration. The presence of the predators contributed to a decline in the total zooplankton abundances and biomass which dampened the grazing impact of the zooplankton on the total Chl-a, consistent with the expectations of a trophic cascade. There were no significant differences in the size structure of the phytoplankton community, total Chl-a concentration and the total zooplankton abundances and biomass between the different predator treatments, suggesting that the increase in predator diversity did not contribute to increased prey risk. These findings highlight both the direct and indirect ecological impacts of predators on plankton dynamics. Full article

Fish diel activity can affect the catch of fishing gear, such as gill nets, thereby influencing fishery resource assessment and management. This study investigated diel catch variations of primary fish species in Gehu Lake using monofilament trammel nets from April to November of 2016. Fish sampling occurred monthly, with nets set and fish caught at four-hour intervals in each month. The results showed that significant diel effects and diel × month interaction were found on Chinese silver carp (SC) and diel × month interaction on common carp (CC). Topmouth, humpback, and Wuchang bream (WB) displayed significantly higher catch per unit effort (CPUE) during twilight or daytime than at night, and no diel × month interactions were detected. For Chinese bighead carp (BC), Mongolian redfin (MR), Japanese grenadier anchovy (JGA), and crucian carp, no diel effect and diel × month interaction were observed. The study suggested that most activities occurring in daytime and at twilight were caused by visual orientation to prey for topmouth and humpback, and by the herbivorous feeding habitat of WB. Food competition between BC and JGA may drive a pronounced temporal partitioning of their diel activity. Overnight gillnet fishing could underestimate the population sizes of herbivores, such as WB, and visually oriented predators, for example, humpback, and might not influence the estimation for BC, JGA, and crucian carp. However, its effects on the stock estimation of SC and CC would vary with months. Notably, future winter investigations into diel catch in this lake could potentially augment the conclusions of the present study. Full article

Understanding how prey and predator species partition activity patterns across time and space is essential for elucidating behavioral adaptation and ecological coexistence. In this study, we examined the diel and seasonal activity rhythms of two sympatric rodent species—Rhombomys opimus (Great gerbil) and Meriones meridianus (Midday gerbil)—and their primary predators, Otocolobus manul (Pallas’s cat) and Vulpes vulpes (Red fox), in a desert-steppe ecosystem on the northern slopes of the Qilian Mountains, China. Using over 8000 camera trap days and kernel density estimation, we quantified their activity intensity and spatiotemporal overlap. The two rodent species showed clear temporal niche differentiation but differed in their synchrony with predators. R. opimus exhibited a unimodal diurnal rhythm with spring activity peaks, while M. meridianus showed stable nocturnal activity with a distinct autumn peak. Notably, O. manul adjusted its activity pattern to partially align with that of R. opimus, whereas V. vulpes maintained a crepuscular–nocturnal rhythm overlapping more closely with that of M. meridianus. Despite distinct temporal rhythms, both rodent species shared high spatial overlap with their predators (overlap index OI = 0.64–0.83). These findings suggest that temporal partitioning may reduce predation risk for R. opimus, while M. meridianus co-occurs more extensively with its predators. Our results highlight the ecological role of native carnivores in rodent population dynamics and support their potential use in biodiversity-friendly rodent management strategies under arid grassland conditions. Full article

In this paper, we propose a diffusion-type predator–prey interaction model with harvest and disease in prey, and conduct stability analysis and pattern formation analysis on the model. For the temporal model, the asymptotic stability of each equilibrium is analyzed using the linear stability method, and the conditions for Hopf bifurcation to occur near the positive equilibrium are investigated. The simulation results indicate that an increase in infection force might disrupt the stability of the model, while an increase in harvesting intensity would make the model stable. For the spatiotemporal model, a priori estimate for the positive steady state is obtained for the non-existence of the non-constant positive solution using maximum principle and Harnack inequality. The Leray–Schauder degree theory is used to study the sufficient conditions for the existence of non-constant positive steady states of the model, and pattern formation are achieved through numerical simulations. This indicates that the movement of prey and predators plays an important role in pattern formation, and different diffusions of these species may play essentially different effects. Full article

Savanna systems are characterised by a community of large mammal herbivores with up to 30 species; coexistence is based on resource partitioning. In this paper we analyse the features of the landscape and plant structure which lead herbivores to use particular locations, a key to resource partitioning. The processes involved, top-down versus bottom-up, are well known for large species and small ones but not for medium-sized ones. We use two resident, medium-sized species, topi (Damaliscus lunatus jimela) and kongoni, (Alcelaphus buselaphus cokei) in the central woodlands of the Serengeti; selection of habitat by the residents is important for predator-prey interactions and for interactions among the grazers. Using Principal Component Analysis and Multiple Regression we develop highly predictive models which show that resource availability is the critical determinant of habitat selection in the dry season; and reduction in predation risk appears to be important in the wet season. These results show for the first time that habitat selection by the medium-sized herbivores is driven by different strategies in the two seasons. This contributes to understanding the processes involved in the dynamics of this globally important savanna system, a necessary foundation for management. Full article

Understanding the biodiversity of aquatic communities and the underlying mechanisms that shape biodiversity patterns and community dynamics is crucial for the effective conservation and management of freshwater ecosystems. However, traditional survey methods often fail to comprehensively capture species diversity, particularly for low-abundance taxa. Moreover, studies integrating both metazoan and fish communities at fine spatial scales remain limited. To address these gaps, we employed a multi-marker eDNA metabarcoding approach, targeting both the 12S and 18S rRNA gene regions, to comprehensively investigate the composition of metazoan and fish communities in the Yujiang River. A total of 12 metazoan orders were detected, encompassing 15 families, 21 genera, and 19 species. For the fish community, 32 species were identified, belonging to 25 genera, 10 families, and 7 orders. Among these, Adula falcatoides and Coptodon zillii were identified as the most prevalent and abundant metazoan and fish species, respectively. Notably, the most prevalent fish species, C. zillii and Oreochromis niloticus, are both recognized as invasive species. The Bray–Curtis distance of metazoa (average: 0.464) was significantly lower than that of fish communities (average: 0.797), suggesting higher community heterogeneity among fish assemblages. Beta-diversity decomposition indicated that variations in the metazoan and fish communities were predominantly driven by species replacement (turnover) (65.4% and 70.9% for metazoa and fish, respectively) rather than nestedness. Mantel tests further revealed that species turnover in metazoan communities was most strongly influenced by water temperature, while fish community turnover was primarily affected by water transparency, likely reflecting the physiological sensitivity of metazoans to thermal gradients and the dependence of fish on visual cues for foraging and habitat selection. In addition, a co-occurrence network of metazoan and fish species was constructed, highlighting potential predator-prey interactions between native species and Corbicula fluminea, which emerged as a potential keystone species. Overall, this study demonstrates the utility of multi-marker eDNA metabarcoding in characterizing aquatic community structures and provides new insights into the spatial dynamics and species interactions within river ecosystems. Full article

The analysis of activity patterns is a valuable tool for understanding the temporal organization of mammal communities, which is determined by biological requirements, resource availability, and competitive pressures both within and between species. Research on this ecological aspect can contribute to the development of effective conservation strategies. Cloud forest is an ecosystem of high biological relevance, as this provides habitat for a wide diversity of species in Mexico, including endemic, emblematic, and threatened taxa. Our main objectives were to analyze mammalian activity patterns and predator–prey relationships in the cloud forest of the El Cielo Biosphere Reserve, Tamaulipas, Mexico. From 2018 to 2020, twenty camera trap stations were installed, and independent photographic records were obtained, divided into 24 one-hour intervals, and subsequently classified as diurnal, nocturnal, crepuscular, or cathemeral. Temporal activity was estimated using circular statistics in RStudio v4.3.1, and activity overlap between major carnivores and their prey was assessed using the ‘overlap’ package in R. A total of 18 medium- and large-sized mammal species were recorded in this study. The activity of four species was seasonally influenced, with a predominantly nocturnal pattern observed during the dry season. The activity overlap analysis revealed potential temporal similarity between predators and their prey. For example, Panthera onca exhibited a high overlap with Mazama temama (Δ = 0.83), Puma concolor with Nasua narica (Δ = 0.91), and Ursus americanus with M. temama (Δ = 0.77). These findings suggest that the activity patterns of certain species can be influenced by seasonality and that large predators may favor specific prey whose activity overlaps with their own. Full article

In the scenario that requires the biological control of pests using predatory enemies, predators not only prey on pests directly but also can affect the population fitness of pests through indirect non-consumptive effects (predation risk effects). However, the impact of predation risk effects varies depending on the mode of stress imposed by natural enemies and the state of the stressed pests. Herein, we exposed aphids (Periphyllus koelreuteriae) at different stages to various cues from the multicolored Asian lady beetle (Harmonia axyridis) to assess the effects of different predation risks on P. koelreuteriae development and reproduction. We found that the effect of predation risk on aphid developmental time was clearly stage-dependent. When 1st-instar nymphs were exposed to predator cues, their developmental time was prolonged only in the early stages (1st–3rd instar nymphs). Similarly, when third-instar nymphs were stressed, only the current stage (third instar) showed a developmental delay, while fourth-instar nymphs and adult aphids were not significantly affected. Additionally, aphids at different stages perceive predation risk differently. Nymphs cannot recognize visual cues from predators, but can perceive odor cues. In contrast, adult aphids are sensitive to a variety of predator cues, including visual ones. Predation risk caused aphids to shorten their adult lifespan and reduce reproductive output, but it increased the proportion of diapause offspring. This study highlights the importance of considering how predation risk affects multiple life stages and physiological changes, which are important for gaining insights into the mechanisms of predator–prey interactions and for comprehensively assessing the ability of lady beetles to regulate aphid populations. Full article