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India’s broad network of protected areas, which encompasses 4.93% of the country’s geographical area, is exposed to immense anthropogenic pressures that can create an imbalance and also hinder the prime objective of wildlife conservation and protection. The present study assesses some of these problems in relation to the Achanakmar Tiger Reserve (ATR). The main anthropogenic influence in ATR is the presence of eighteen core villages, five buffer villages, and 49 fringe villages in the periphery of the reserve area. The population density of the core zone was higher (16.0 people/km² ) as compared to the buffer zone (7.41 people/km2 ). Another important disturbance in the protected area is state highway 8 which bisects the entire core zone into two halves. This highway also connects the neighboring state of Madhya Pradesh and there is the continuous movement of traffic, which hampers the smooth movement of wild animals. ATR also has a wide network of tourist roads of 192 km passing through the core zone. The average population density of livestock in ATR is relatively high compared to the average population of wild ungulates. It creates competition between wild ungulates for food, and they are also under constant threat of infectious diseases. The livestock depredation by apex predators is one of the major reasons for man-wildlife conflict in ATR. The cattle kill incidences by both the apex predator (tiger and leopard) was 378 during the period of three years (2015 to 2018) and these incidences were recorded more in the core zone as compared to the buffer zone. In the present study, anthropogenic effects on ATR have been studied and evaluated. It concludes that for effective management and conservation of tigers in ATR, these aspects need to be considered. To restore the tiger population in ATR, there must be a proper balance between human (anthropogenic) approaches and conservation benefits for the effective sustainability of the protected areas. [ABSTRACT FROM AUTHOR]

Mercury, a toxic metal released by various human activities, exerts environmental stress through its bioaccumulation and biomagnification, particularly in marine habitats. South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) reproduce on the Atlantic coast of Uruguay. As top predators, they can accumulate toxic levels of mercury and are often used as sentinel species for monitoring ecosystem health. Fur seals prey on pelagic species, such as fish and squid, while sea lions consume coastal-benthic prey. We analyzed the total mercury concentration (THg) in hair and the trophic habits (δ13C and δ15N) of females from both species. The average THg concentration in adult female sea lions (30.5 ± 9.3 μg/g dry weight) was significantly higher than in fur seals (6.3 ± 2.5 μg/g dry weight). Additionally, the mean δ15N and δ13C values were significantly higher in sea lion (δ15N: 19.2 ± 0.6‰, δ13C: −13.8 ± 0.2‰) compared to fur seals (δ15N: 16.5 ± 0.5‰, δ13C: −15.5 ± 0.6‰). Our results suggest that different trophic levels and feedings areas affect the THg concentration in Uruguayan Otariids. Notably, at the intraspecific level, the THg concentration in sea lions increased with δ13C values, suggesting a link to coastal feeding habits. This indicates that coastal feeding behaviors, compared to feeding in pelagic environments, enhance mercury bioaccumulation in Otariids along the Uruguayan coast, with the discharge of freshwater from the Río de la Plata (one of the largest estuaries in South America) basin identified as a potential mercury source. THg concentrations found in female sea lion hair are the highest reported in Otariids globally. Mercury levels exceeded toxic thresholds observed in other mammals and could pose significant health risks. Our findings may explain why sea lions were particularly affected by the avian influenza outbreak in Uruguay compared to fur seals. Monitoring the declining sea lion population is crucial, making our results significant for integrated conservation and management strategies. [Display omitted] • Marine mammals are good sentinel species for monitoring Hg bioaccumulation. • Fur seals and sea lions prey on pelagic and coastal benthic species, respectively. • Hg accumulation in the hair of female sea lions was higher than in fur seals. • Hg levels in individual female sea lions rose with δ13C, indicating a link to coastal feeding habits. [ABSTRACT FROM AUTHOR]

The impacts and toxicological mechanisms of microplastics (MPs) or heavy metals on aquatic ecosystems have been the subject of extensive research and initial understanding. However, the combined toxicity of co-pollutants on organisms and cumulative toxic effects along the food chain are still underexplored. In this study, the ciliate protozoan Paramecium caudatum and zebrafish Danio rerio were used to represent the microbial loop and the higher trophic level, respectively, to illustrate the progressive exposure of MPs and cadmium (Cd2+). The findings indicate that MPs (ca. 1 ×105 items/L) containing with Cd2+ (below 0.1 µg/L) could permeate the bodies of zebrafish through trophic levels after primary ingestion by ciliates. This could cause adverse effects on zebrafish, including alterations in bioindicators (total sugar, triglycerides, lactate, and glycogen) associated with metabolism, delayed hepatic development, disruption of intestinal microbiota, DNA damage, inflammatory responses, and abnormal cellular apoptosis. In addition, the potential risks associated with the transfer of composite pollutants through the microbial loop into traditional food chain were examined, offering novel insights on the evaluation of the ecological risks associated with MPs. As observed, understanding the bioaccumulation and toxic effects of combined pollutants in zebrafish holds crucial implications for food safety and human health. [Display omitted] • MPs could transport Cd2+ into zebrafish via ciliate of the microbial loop. • Transfer of MPs+Cd2+ induced nutrient alterations within zebrafish. • MPs+Cd2+ disrupt the intestinal microbiota and lead to immune response. • The induction of apoptosis by MPs+Cd2+ is the key factor of toxicity in zebrafish. [ABSTRACT FROM AUTHOR]

The European catfish (Silurus glanis) is a large apex predator native to Eastern Europe. Increasing populations within and outside the species' native range in recent years, and its popularity with recreational anglers are fueling discussions about appropriate management. To understand the motivations of anglers and their views on different management strategies, an internet survey was conducted in southern Germany. The results showed that catfish anglers differ in several aspects from those targeting other species. For specialists, catfish fishing is a central part of life, and they invest significant time and money to catch trophy sized fish. Most catfish anglers think that their targeted species has no negative effect on the local fish community and practice catch and release, despite this practice being illegal in Germany. Large catfish are often released under the misapprehension that they are inedible. The findings of this study suggest that new fishery management approaches are needed in order to mitigate the impact of European catfish in southern Germany. A co-production approach actively incorporating anglers' perspectives will be essential in implementing education and incentives for catfish consumption alongside other aspects of fisheries management. • catfish anglers in southern Germany can be characterized as a specialized group. • they are partly unware of relevant catfish related fishery regulations. • they release most catfish, rendering targeted fisheries management ineffective. • angler education is needed. [ABSTRACT FROM AUTHOR]

Understanding the impacts of human actions on marine species and developing mitigation strategies are crucial conservation challenges. Many fish species, especially marine top predators, are already highly depleted and rely on population monitoring and conservation strategies for their maintenance. In this context, Marine Protected Areas can help recover target species and provide crucial information about population trends when human activities are restricted or managed. Here, we used the longest and most complete temporal series of reef fish data in the Southwestern Atlantic, comprising 16 years of underwater visual census sampling. We evaluated temporal trends in the density and biomass of the dusky grouper (Epinephelus marginatus), both inside and outside a no-take and no-entry Marine Reserve. Our findings reveal a consistent decline in density and biomass inside and outside the MPA over time, reaching alarmingly low densities and experiencing a steeper biomass decline in the last five years. Our results contradict global expectations of positive population recovery trends within MPAs. We highlight the adverse impacts of human activities on the dusky grouper population, including illegal fishing and habitat degradation. Additionally, we address the limited understanding of species' life stages, underscoring that their occurrence outside protected boundaries may render the entire population vulnerable to human pressures. Thus, to guarantee population recovery, stakeholders and researchers must take immediate action to increase knowledge of all life stages and improve ongoing strategies. • Despite conservation efforts over decades, the dusky grouper population is declining. • The population is declining in one of the oldest No-Take areas in the Southwestern Atlantic. • The situation worsened in the last 5 years of the 16-year time series studied. • The Reserve might be underperforming due to the disregard of local factors. • Current conservation strategies must be urgently reviewed. [ABSTRACT FROM AUTHOR]

The use of effect biomarkers has contributed to the understanding of the sublethal effects of contaminants on different organisms. However, the analysis of genotoxic markers as an indicator of organism and environmental health in sharks is underexplored. Thus, the present study investigated the relationship between the genomic damage frequency in erythrocytes and metal(loid) concentrations in whole blood of three shark species (Galeocerdo cuvier, Negaprion brevirostris and Ginglymostoma cirratum), taking into account climatic seasonality. The results showed that G. cuvier , an apex predator, presented the highest total erythrocyte genomic damage frequencies together with the highest mean whole blood concentrations of Al, Cd, Cr, Fe, Mn, Ni, Pb and Zn. The shark N. brevirostris also presented high levels of metal(loid), indicating a greater susceptibility to these contaminants in species that preferentially feed on fish. In contrast, G. cirratum , a mesopredator, presented the lowest erythrocyte damage frequencies and whole blood metal(loid) concentrations. The presence of micronuclei was the most responsive biomarker, and Al, As and Zn had an important effect on the genomic damage frequencies for all species evaluated. Zn concentration influenced the binucleated cells frequencies and Al concentration had an effect on the total damage and micronuclei frequencies in G. cuvier and N. brevirostris. Binucleated cells and blebbed nuclei frequencies were affected by As concentration, especially in G. cirratum , while showing a strong and positive correlation with most of the metals analyzed. Nonetheless, baseline levels of metal(loid) blood concentrations and erythrocyte genomic damage frequencies in sharks have not yet been established. Therefore, minimum risk levels of blood contaminants concentrations on the health of these animals have also not been determined. However, the high genomic instability observed in sharks is of concern considering the current health status of these animals, as well as the quality of the environment studied. [Display omitted] • The presence of micronuclei was the most responsive biomarker in sharks. • Al, As and Zn had an important effect on genomic damage frequencies in sharks. • Galeocerdo cuvier showed greater susceptibility to the metal(loid) analyzed. [ABSTRACT FROM AUTHOR]

Coastlines are susceptible to plastic and heavy metal pollution, which can accumulate from both marine and terrestrial sources. Shorebirds, top-level predators in these fragile ecosystems are considered as indicators of environmental health. Here, we tested the occurrence of microplastics and heavy metals in the droppings of ten regular wintering migrant shorebird species in Kadalundi-Vallikkunnu Community Reserve and adjoining sand beaches during November, December and January, each year, between 2019 and 2021. Heavy metals were analysed by Flame Atomic Absorption Spectrophotometer and the microplastic polymer compositions were identified using ATR-FTIR spectroscopy. We detected high concentrations of heavy metals such as Zinc, Copper, Cobalt, Chromium, Lead and Cadmium in droppings. Polyethylene, Polypropylene, Polystyrene, Poly Vinyl Chloride, Nitrile and Polyethylene terephthalate were the polymers identified. Polystyrene (42.6 %) and chromium (ranges between 7.83 and 88.45 mg/kg) were found to be the most abundant contaminants in most of the species. [Display omitted] • Microplastic and heavy metal co-occurrence observed in conspecific shorebird guano. • Elevated concentration of heavy metals exceeding environmental limits identified. • Six different microplastic polymers identified. • Polystyrene found to be the most abundant microplastic. • Chromium found to be the most abundant heavy metal. [ABSTRACT FROM AUTHOR]

Anticoagulant rodenticides (ARs) are one of the most toxic groups of compounds currently used worldwide for rodent pest control. Toxic baits are often, directly or indirectly, ingested by non-target animals, resulting in secondary poisoning and frequently affecting apex predators. Their presence in many species of raptors is quite common, particularly scavenger species, with some of these acting as sentinels for the presence of these substances in the environment. However, there is less data on the presence of ARs in Bonelli's eagle, one of the most endangered eagle species in Spain and which is experiencing a negative population trend in Europe. This medium-sized eagle feeds predominantly on live species, and rarely consumes carrion. In this study, 17 carcasses of Bonelli's eagles from the Eastern Spain were necropsied. Both first and second generation ARs in their livers were analyzed by HPLC-MS-TOF revealing that all the eagles studied had been exposed to at least 5 ARs, out of a total of 10 ARs analyzed, with 7 being the highest number of ARs detected in a sample. Second generation ARs were the most prevalent, particularly bromadiolone and brodifacoum, with the highest concentrations in 94% of the cases. More than a third of the eagles presented a liver concentration of greater than 200 ng/g ARs, suggesting AR poisoning. The elevated presence of these compounds in Bonelli's eagles could be a new cause of mortality for this species or could explain other causes of death, such as the increased mortality in power lines, and should be taken into account for their conservation. At the same time, the presence of these compounds in the environment also represents a risk to public health, as the most frequent species in the diet of Bonelli's eagle (rabbits and partridges) are also hunted and consumed by hunters and their families. [Display omitted] • Anticoagulant rodenticides (AR) are present in 100% of the Bonelli's eagles analyzed. • AR hepatic levels exceeded the potentially lethal threshold in 35% of the eagles analyzed. • A traumatic cause of death may be favoured by exposure to ARs. • ARs exposure is associated with increasing intensity of urbanization and rainfed agriculture. • Bonelli's eagles may be a good sentinel species of AR risk for humans. [ABSTRACT FROM AUTHOR]

Spotted hyaenas are generally considered to have resilience against injuries and pathogens, and the incidence of pathologies is scarcely reported. However, it is important for ecological studies and conservation efforts to have a clear overview of the physical threats that can occur in the life of a species. The present paper describes and interprets several osteopathologies in the crania of the spotted hyaena, Crocuta crocuta , in the collections of the Royal Museum for Central Africa (RMCA) in Tervuren, Belgium. Of the fifty-two specimens from central Africa examined, twenty-three (i.e., 44 %) of them showed evidence of pathologies, including injuries, congenital pathologies, and disease. Selected specimens were scanned using Computed Tomography and their internal cranial structures were studied. Here we describe and discuss the different types of pathologies evident in the crania of these hyaenas: craniosynostosis, microtia, osteomyelitis and periodontitis, as well as a trauma indicated by cranial fractures, dental fractures, and bite puncture marks. Some pathologies reported herein are novel for hyaenas, and there are some instances of multiple pathologies in the same individual. Implications of these pathologies, including the social interactions of hyenas, conservational threats, as well as biased data sampling, are highlighted. This study improves our knowledge of disease and trauma experienced by hyaenids, and provides a better understanding of their biology, and the potential threats faced by these iconic animals. This case study offers a comparative base for similar studies in other carnivorans, to clarify the pathological background of apex predators. • Spotted hyenas Crocuta crocuta show a wide range of cranial pathologies. • Newly recorded pathologies include brachycephaly and microtia. • Fractures are associated with diet and intraspecific competition. • Pathologies are connected with low social ranking and risk of human contact. [ABSTRACT FROM AUTHOR]

• Introducing the Normalized Reef Status Index (NRSI) for swift evaluation of fishing impact on reef fish populations. • Utilized the NRSI to assess 346 reefs across the Mexican Pacific, revealing the conservation status. • Results show Fully Protected areas maintain reefs with a trophic structure resilient to fishing pressures. • Predominantly, reefs scored below the NRSI average, indicating a widespread absence of key predatory species. • The study emphasizes the need for comprehensive marine conservation strategies to ensure sustainable coastal ecosystems. The trophic structure of ecosystems, reflecting biomass distribution across different levels, is paramount for understanding energy dynamics and community assemblages in marine environments. Typically, ecosystems devoid of external energy influx exhibit a bottom-heavy trophic pyramid, yet higher biomass systems often display a top heavy or concave distribution. Such structures are susceptible to alterations due to species turnover, trophic cascades, and anthropogenic impacts, particularly the phenomenon of 'Fishing down' the food web. Recognizing the trophic structure as a simplified yet potent indicator, we identify the necessity for a standardized, expedient method to assess reef health—a criterion fulfilled by our Normalized Reef Status Index (NRSI). The NRSI offers a novel metric for scientists and conservation practitioners to augment traditional reef health assessments. Utilizing the NRSI, we assessed the ecological status of 346 reefs across the Mexican Pacific. Our results demonstrated that only reefs within Fully Protected areas conform to the concave trophic structure indicative of low human interference. In stark contrast, unprotected reefs exhibited a depleted trophic architecture, often devoid of apex predators. This depletion not only threatens coastal livelihoods and food security but also disrupts the delicate balance of marine ecosystems critical to sustaining global ecological functions. Through the NRSI, we provide a robust, scalable tool for ongoing monitoring and conservation efforts, underscoring the urgent need to address human-induced trophic disruptions. [ABSTRACT FROM AUTHOR]

• Using criticality analysis a "hub index" was developed to identify species critical to ecosystem function. • The approach was tested on long-term diet data from around the world as well as model ecosystems. • The exact identity of hub species is system specific, but consistent through time over large areas. • Both top predators and forage species are often "hub species" that are key ecosystem connectors, which require management attention. • The method is robust to typical data uncertainties and reliable for management purposes. Ecosystem based fisheries management (EBFM) attempts to take a broader perspective to the management of natural resources. To date it has often focused on the status of specific stocks, species or habitats. Consideration of ecosystem structure has not received as much attention, but lessons from engineering suggest that indicators of structure can highlight whether critical connections in the ecosystem are receiving sufficient management attention. We apply concepts of criticality analysis and the identification of "hub nodes" in networks – which we call hub species – to model ecosystems and long-term diet data. This method highlights both top predators and connected forage species as key ecosystem connectors that need attention under EBFM. The exact identity of these species differs among systems, showing that this method can provide system specificity, which is a key attribute for the acceptance of EBFM tools. [ABSTRACT FROM AUTHOR]

Understanding species distributions is key for effective biodiversity conservation. We conducted a large-scale camera trapping survey in five systematic grids across central-eastern Namibia to identify drivers of large carnivore occupancy and to predict occurrence across a broader mixed-use landscape spanning 161,629 km2. Through targeted searches for intensive-use areas and pooling detections across camera trap stations, we reliably detected the most elusive carnivores. We identified a diminished large carnivore guild with the two top predators (lion (Panthera leo) and spotted hyena (Crocuta crocuta)) functionally absent, although present historically. While brown hyenas (Parahyaena brunnea) were omnipresent, we found local variations in guild composition. African wild dogs (Lycaon pictus) were more common near their resident population eastwards and in areas of greater vegetation productivity. The distribution of cheetahs (Acinonyx jubatus) was determined by the proportional cover of grass, consequently woody encroachment of grasslands may pose a threat. Leopard (Panthera pardus) occurrence was low in areas with a high human footprint, and high in areas with rugged terrain and greater vegetation productivity. The diminished large carnivore guild with contrasting species-habitat associations may enable persistence of subordinate carnivores, such as the cheetah and African wild dog, across this mixed-use landscape. However, we underscore the importance of multi-species conservation approaches to maintain ecological interactions. The large proportion (80 %) of suitable habitat identified, i.e. where probability of occupancy exceeded 0.5, is an encouraging outcome for the region's potential to hold value for carnivore persistence and potentially recolonization. Considering the limited space for protected area expansion, holistic conservation approaches are warranted to ensure viable large carnivore guilds and functional ecosystems. • Large-scale camera trap survey to identify drivers of large carnivore occurrence • Variations in guild composition with species-specific habitat associations • African wild dog, brown hyena, cheetah and leopard variably detected • Functional absence of lions and spotted hyenas despite historical presence • Habitat availability may support carnivore persistence and recolonization. [ABSTRACT FROM AUTHOR]

Marine organisms, especially top predators such as sharks, are susceptible to environmental pollutants like microplastics (MPs) and phthalate esters (PAEs), leading to ecosystem risks. Research on contamination in these apex species is, however, still limited. This study investigated MPs and PAEs in multiple shark species (Isurus oxyrinchus , Alopias superciliosus , Alopias pelagicus , Carcharhinus brevipinna , and Sphyrna zygaena) off Taiwan's eastern coast. Gastric tissue analyses revealed ubiquitous microplastics (2–31 particles), which positively correlated with body lengths and weights for Isurus oxyrinchus. Blue, fiber-shaped (1–2 mm), and rayon-based MPs are likely associated with textile fiber pollution. The PAEs concentration mean was 7035 ± 6829 ng/g, ww, having DEHP and DiNP as primary compounds. This study highlights pervasive contamination in Pacific Ocean sharks, emphasizing anthropogenic impact on top oceanic predators and providing essential insights for food safety and MP accumulation. [Display omitted] • Sharks, as top predators, are highly vulnerable to MPs and PAEs, posing significant ecosystem risks. • MPs and PAEs in various shark species off Taiwan's eastern coast. • Gastric tissue analyses revealed ubiquitous MPs (2–31 particles) in sharks • Mean PAE concentration was 7035 ± 6829 ng/g, ww, with DEHP and DiNP as primary compounds [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a naturally occurring heavy metal, but human activities and natural processes have led to increased pollution with Hg in the environment. Organic mercury, such as methyl mercury (MeHg), is considered more toxic than most inorganic mercury compounds. MeHg is rapidly taken up by aquatic organisms and bioaccumulates through the aquatic food web. The bioaccumulation causes high levels of MeHg in apex predators, such as pilot whales. Pilot whale meat is a traditional food source on the Faroe Islands; thus the consumption of pilot whale meat can lead to high Hg exposures in humans. The majority of the total Hg in pilot whale and fish is generally assumed to be MeHg. However, the relative amount of MeHg to total Hg can be highly variable. For risk assessment, it is relevant to know both the MeHg and the total Hg content. This study summarizes the knowledge of muscle MeHg concentrations relative to total Hg concentrations in pilot whales in the Faroe Islands. The pilot whale tissue was sampled during 1977–78, 1986–87, 2009–2010, and 2015. The 2015 samples included two pairs of fetuses/mothers. The results showed that the 1977–78 pilot whale muscle samples had lower relative concentrations of MeHg to total Hg compared to samples from the subsequent years. This discrepancy between early and later years could not solely be explained by increased demethylation related to concentration differences. Instead, the difference is more likely explained by variations in relative amounts of MeHg in prey of the pilot whales. In the fetuses the total Hg concentration was 20% of the Hg concentration in the mother. The relative MeHg concentrations in the fetuses were also lower (∼20%–30%) than in the mother. However, the MeHg to total Hg fraction in the fetus was similar or higher than in the mother. [Display omitted] • MeHg/TotHg ratios were analyzed in pilot whale muscle from Faroe Islands. • Higher relative ratios were observed in 1980's and 2009–2015 than in late 1970's. • Variation was likely related to different MeHg concentrations in prey. • MeHg concentrations were similar or higher in fetus compared to mother. [ABSTRACT FROM AUTHOR]

With the current possible presence of thousands of PFAS compounds in industrial emissions, there is an increasing need to assess the impacts of PFAS regulation of conventional PFAS on one hand and the exposure to emerging and yet unknown PFAS on the other. Today’s analytical methodologies using targeted approaches are not sufficient to determine the complete suite of PFAS present. To evaluate the presence of unknown PFAS, we investigated in this study the occurrence of an extended range of target PFAS in various species from the marine and terrestrial Norwegian environment, in relation to the extractable organofluorine (EOF), which yields the total amount of organofluorine. The results showed a varying presence of extractable fluorinated organics, with glaucous gull eggs, otter liver and polar bear plasma showing the highest EOF and a high abundance of PFAS as well. The targeted PFAS measurements explained 1% of the organofluorine for moose liver as the lowest and 94% for otter liver as the highest. PFCAs like trifluoroacetic acid (TFA, reported semi-quantitatively), played a major role in explaining the organic fluorine present. Emerging PFAS as the perfluoroethylcyclohexane sulfonate (PFECHS), was found in polar bear plasma in quantifiable amounts for the first time, confirming earlier detection in arctic species far removed from emission sources. To enable a complete organic fluorine mass balance in wildlife, new approaches are needed, to uncover the presence of new emerging PFAS as cyclic- or ether PFAS together with chlorinated PFAS as well as fluorinated organic pesticides and pharmaceuticals.

The article focuses on the reappearance of tigers in the Medog region, China, highlighting its importance for tiger conservation. It study conducted a camera trapping survey and collected socioecological data, confirming the presence of at least one adult male tiger within the region, emphasizing the need for conservation efforts to ensure their survival and potential population expansion.

But scientists can now infer the precise feeding habits of these apex predators by looking at the lipid (fatty acids) composition of the whales' blubber. Cover image: Two killer whales photographed in Vestmannaeyjar, Iceland, after feeding on a school of herring. Our research team collected biopsies from 200 individuals across the North Atlantic Ocean to reveal large variations in the whales' diets. [Extracted from the article]

Background: Energy demand for reproduction leads to a wide diversity of foraging and life-history strategy among wild animals, linking to a common objective to maximize reproductive success. Semelparous squid species in particular can use up to 50% of the total energy intake for reproduction. However, the energy acquisition strategy for reproduction is still a controversial issue regarding whether the squid shift in diet ontogenetically. Here we used Argentinean shortfin squid (Illex argentinus) as a case study to investigate the strategy of energy acquisition for reproduction, by analyzing energy density of the squid's reproductive tissues including ovary, nidamental glands and oviduct eggs, and stable isotopes and fatty acids of the squid's ovary. Results: The reproductive energy (the sum of the energy accumulated in ovary, nidamental glands and oviduct eggs) increased significantly with maturation. The ovary nitrogen stable isotopes (δ15N) showed a significant increase with maturation, but the increase by maturity stage was not equal to the typical enrichment of about 3‰ per trophic level. Isotopic niche width showed an increasing trend with maturation, and isotopic niche space exhibited greater overlap at advanced maturity stages. The relative amounts of 16:0, 20:5n3 and 20:4n6 in the ovary, tracing for carnivores and top predators, increased after the onset of maturation. The overall fatty acid profiles of the ovary showed significant differences among maturity stages, but obvious overlaps were found for mature squids. Mixed-effects model results revealed that reproductive energy was positively correlated with δ15N values. The reproductive energy was also positively related to the relative amounts of 18:0 and 20:4n6, respectively tracing for herbivores and top predators. Conclusions: Our results validate that the squid shifts to feed on higher trophic prey for reproduction as energy demand increases once maturation commences. However, the squid does not shift feeding habits at a trophic level but instead broadens prey spectrum, coupled with increasing intake of higher trophic prey items, to meet the energy demand for reproduction. Such energy acquisition strategy may be selected by the squid to maximize reproductive success by balancing energy intake and expenditure from foraging, warranting future studies that aim to clarify such strategy for reproduction among semelparous species. [ABSTRACT FROM AUTHOR]

Apex predators structure ecosystems by hunting mesopredators and herbivores. Their ecological influence is determined not only by the number of animals they kill, but also by how prey alter their behaviours to reduce risk. Predation risk is variable in space and time creating a landscape of fear. In Australia, dingoes hunt red foxes and suppress their populations. As both predators are commonly subjected to eradication programs, the question arises whether humans alter the risk dingoes pose to foxes and in turn alter the foxes' avoidance behaviours. We studied the spatio‐temporal activity patterns and wariness behaviours of foxes and dingoes at sites where they were protected (predator friendly), where they were persecuted (predator persecuted), and at sites where foxes were persecuted, and dingoes had been eradicated (dingo eradicated). The landscape of fear hypothesis predicts that foxes will be the most spatiotemporally restricted and most fearful at predator friendly sites, and least restricted and fearful at dingo eradicated sites. We found that fox occupancy was highest at dingo eradicated sites; and that they avoided times of heightened dingo activity at predator friendly sites more than at predator persecuted sites. Contrary to predictions, foxes were the least fearful (lowest frequency of cautious and vigilant behaviour) and most social (highest frequency of social interactions) at predator friendly sites. Our findings suggest that in the absence of persecution, mesopredators living with socially‐stable apex predators can anticipate and avoid risk, reducing the need for constant vigilance (i.e. fear). Where predators are protected, predator avoidance may be driven by knowledge rather than fear alone. [ABSTRACT FROM AUTHOR]

Energy sources and trophic interactions among vent fauna were investigated in deep-sea hydrothermal vents in the North Fiji Basin (NFB), Southwest Pacific, using stable sulfur, carbon, and nitrogen isotopes. A Bayesian isotope mixing model (MixSIAR) was used to quantify the proportions of energy sources for symbiont-bearing taxa. Based on these results, symbionts of host taxa such as the hairy snail Alviniconcha boucheti, black snail Ifremeria nautilei, and vent mussel Bathymodiolus sp. showed different carbon fixation pathways or nutrient preferences. We also observed niche partitioning among the omnivores by utilizing different resources or by occupying different microhabitats. For example, the squat lobster Munidopsis spp. occupied the bottom part of the chimney where dead shells were scattered around, as it was predatory to mussels. The scale worm Branchinotogluma segonzaci exploited energy from particulate organic matter or free-living bacteria on the chimney, whereas shrimp Rimicaris variabilis, which were clustered around I. nautilei and Echionelamus ohtai communities, had isotopic compositions similar to them. In contrast, limpets attached to I. nautilei did not share resources with snails and derived energy from mixed carbon sources. Among the vent fauna that we sampled, the crab was the top predator in the NFB, possibly consuming everything but with a lower preference for mussels. Overall, we found a non-overlapping diet or spatial niche of the vent fauna, with each taxon having a unique source or metabolism, or proportion. Such diversification in resource use may play an important role in sustaining the coexistence of species in a small area. [ABSTRACT FROM AUTHOR]

Market squid (Doryteuthis opalescens) constitute one of California's largest fisheries by landings and are an essential prey item for numerous top predators in the California Current ecosystem. However, extreme fluctuations in market squid abundance inhibit our ability to forecast local recruitment. We generate a species distribution model for market squid with data from an annual survey to examine the mechanisms behind the variability in their regional abundance and occurrence. Our results indicate juvenile market squid abundance was controlled by local recruitment in connection with sea surface temperature and upwelling dynamics, with finer spatial variability connected to the extent of upwelling dominated regions. Recent changes in these environmental factors also appear to contribute to the recent northward range expansion of market squid. Our spatiotemporally explicit model estimates of juvenile market squid abundance predicted the occurrence and abundance of older market squid in the diet of California sea lions (Zalophus californianus) and California fishery landings with as much skill as regional survey indices, suggesting the models are robust. Collectively, we provide mechanisms driving market squid variability throughout California's waters and an ecosystem assessment of this economically and ecologically critical species. [ABSTRACT FROM AUTHOR]

Mammals that use inland and coastal waters interact with people regularly, as they share similar habitats and resources. The Smooth-Coated Otter is an apex predator in the aquatic ecosystem that frequently interacts with local communities. When Cyclone FANI hit Balukhand Wildlife Sanctuary, which is close to the Eco-sensitive Nuanai area, in May 2019, this was one of the victim species witnessing a catastrophic population loss in Puri, Odisha. This is Odisha's first community-based conservation project. We conducted a semi-structured interview to examine people's perceptions and attitudes regarding the species, as well as to document the population's dangers. There was a huge threat to the species, but people are more aware now as a result of our research, and there are fewer threats. [ABSTRACT FROM AUTHOR]

Hunting and trapping of gray wolves (Canis lupus) has increased dramatically in the "lower 48" states of the United States. We assess the data used to justify the intense hunting pressure on wolves, and find an absence of accessible biological data. We find there is a clear need for more transparent reporting of livestock losses, wolf kills, and especially the numbers and types of nontarget species captured in traps set for wolves. Also lacking is a full accounting of benefits and costs of hunting wolves, with a noteworthy failure to incorporate the ecosystem functions served by wolves. As apex predators, wolves warrant multi‐objective management as opposed to management focused largely on livestock interests and concerns. [ABSTRACT FROM AUTHOR]

Theropods were the dominating apex predators in most Jurassic and Cretaceous terrestrial ecosystems. Their feeding ecology has always been of great interest, and new computational methods have yielded more detailed reconstructions of differences in theropod feeding behaviour. Many approaches, however, rely on well‐preserved skulls. Dental microwear texture (DMT) analysis is potentially applicable to isolated teeth, and here employed for the first time to investigate dietary ecology of theropods. In particular, we test whether tyrannosaurids show DMT associated with more hard‐object feeding than compared to Allosaurus; this would be a sign for higher levels of osteophagy, as has often been suggested. We find no significant difference in complexity and roughness of enamel surfaces between Allosaurus and tyrannosaurids, which conflicts with inferences of more frequent osteophagic behaviour in Tyrannosaurus as compared to other theropods. Orientation of wear features reveals a more pronounced bi‐directional puncture‐and‐pull feeding mode in Allosaurus than in tyrannosaurids. Our results further indicate ontogenetic niche shift in theropods and crocodylians, based on significantly larger height parameters in juvenile theropods which might indicate frequent scavenging, resulting in more bone–tooth contact during feeding. Overall, DMT is found to be very similar between theropods and extant large, broad‐snouted crocodylians and shows great similarity in feeding ecology of theropod apex predators throughout the Jurassic and Cretaceous. [ABSTRACT FROM AUTHOR]

Phthalate esters (PAEs) are emerging pollutants commonly found in plastic products. Thus, increasing plastic pollution in the marine environment amplify their entry and potential impacts on aquatic species. Likewise, pollutants may accumulate in top predators such as sharks and are highly consumed in many countries. Therefore, this study evaluated the concentrations of 10 PAEs plasticizers in commercially important Indian Ocean silky sharks Carcharhinus falciformis and their toxicity risks in children and adults. Results showed the concentrations of ΣPAEs in shark muscle ranging between 5,402–34,577 ng/g ww. PAEs in silky shark muscles appeared to be six times higher in locations near the coasts (islands) with higher anthropogenic impacts. Low molecular weight PAEs like DMP and DnBP dominated PAEs in shark muscle tissues. Moreover, the PAE levels in shark muscles did not significantly increase with length and weight, indicating their relative impacts in all shark sizes. For the estimate of the daily intakes (EDI), the DEHP was 32 μg/kg bw/day in preschool children and 23 μg/kg bw/day in adults (the DEHP Reference Dose (RfD) of 20 μg/kg bw/day). Toxicity risk assessment showed unacceptable levels indicating long-term dietary risks for consumers. [ABSTRACT FROM AUTHOR]

Artificial islands and reefs have been used in the Laurentian Great Lakes for over 40 years as a means of improving aquatic habitat; but research on their efficacy has primarily focused on their ability to increase the abundance of specific sportfish, top predators, or other keystone species. To understand the importance of islands in structuring the whole fish community, we took a holistic approach and analysed the effect of islands, location, and the interaction effect between the two in structuring fish communities in Hamilton Harbour, Lake Ontario using a 30-year electrofishing dataset. The effect of islands varied by location within the harbour, with some species showing a preference for islands in some locations while avoiding them in others. Island communities also tended to have significantly different species compositions, with higher index of biotic integrity scores and species richness, greater numbers of pollution intolerant fishes, centrarchids, and fewer generalist species. However, these results paled in comparison to the level of inter-annual variation in the fish community of the harbour, which has changed markedly over the 30-year time span. Taken together, our results highlight that while island creation can influence the fish community, the type and magnitude of effect will vary based on their distance to other suitable habitats (i.e., location within the system) and the design of the island itself. Further, the noted inter-annual variability emphasizes the importance of considering long time scales (> 10–20 years) when exploring fish community responses to habitat creation. Collectively, these results will help the design of more effective management strategies for restoring fish communities. [ABSTRACT FROM AUTHOR]

We present two models to monitor the health of ecosystems by assessing hazard from a persistent organic compound to a top predator species. Our diet model predicts the dietary exposure of American Mink (Neovison vison) to PCB toxic equivalents (TEQ) by combining concentrations in their prey using weighted average proportions consistent with literature-based mink diets. Our bioaccumulation model predicts the dietary exposure of mink to PCB TEQ based on each congener's total concentration in water (dissolved plus particulate fractions), the octanal/water partition coefficient (log Kow) of the compound, and the trophic levels of prey taxa. Both models predict mink dietary concentrations which can be directly compared with each other and with lowest observable adverse effects concentrations (LOAECs) to assess chronic and acute hazards of PCB TEQ to mink. By our choice of certain parameters in the bioaccumulation model, we forced it to match the diet model within less than 5% for Eighteenmile Creek in western New York State. When the two models were used for a similar creek about 25 km away, the differences in their predictions were of the same magnitude. [ABSTRACT FROM AUTHOR]

The Amur leopard (Panthera pardus orientalis) is a critically endangered top predator that struggles on the brink of extinction due to threats such as canine distemper virus (CDV), habitat loss, and inbreeding depression. Here we develop a viability analysis metamodel that combines a traditional individual-based demographic model with an epidemiological model to assess the benefits of alternative population management actions in response to multiple distinct threats. Our results showed an extinction risk of 10.3%-99.9% if no management actions were taken over 100 years under different levels of inbreeding depression. Reducing the risk of CDV infection in Amur leopards through the low-coverage vaccination of leopards and the management of sympatric domestic dogs could effectively improve the survival probability of the leopard population, and with habitat expansion added to these management measures, the population expanded further. Our findings highlight that protecting the Amur leopard necessitates a multifaceted synergistic effort, and controlling multiple threats together may significantly escalate overall viability of a species, especially for small-isolated threatened population. More broadly, our modeling framework could offer critical perspectives and scientific support for conservation planning, as well as specific adaptive management actions for endangered species around the world. In the absence of management strategies, canine distemper virus threatens the future existence of the endangered Amur leopard. [ABSTRACT FROM AUTHOR]

Scavenging by large carnivores is integral for ecosystem functioning by limiting the build-up of carrion and facilitating widespread energy flows. However, top carnivores have declined across the world, triggering trophic shifts within ecosystems. Here, we compare findings from previous work on predator decline against areas with recent native mammalian carnivore loss. Specifically, we investigate top-down control on utilization of experimentally placed carcasses by two mesoscavengers—the invasive feral cat and native forest raven. Ravens profited most from carnivore loss, scavenging for five times longer in the absence of native mammalian carnivores. Cats scavenged on half of all carcasses in the region without dominant native carnivores. This was eight times more than in areas where other carnivores were at high densities. All carcasses persisted longer than the three-week monitoring period in the absence of native mammalian carnivores, while in areas with high carnivore abundance, all carcasses were fully consumed. Our results reveal that top-carnivore loss amplifies impacts associated with carnivore decline—increased carcass persistence and carrion access for smaller scavengers. This suggests that even at low densities, native mammalian carnivores can fulfil their ecological functions, demonstrating the significance of global carnivore conservation and supporting management approaches, such as trophic rewilding. [ABSTRACT FROM AUTHOR]

Differences in hatching dates can shape intraspecific interactions through size-mediated priority effects (SMPE), a phenomenon where bigger, early hatched individuals gain advantage over smaller, late hatched ones. However, it remains unclear to what extent and how SMPE are affected by key environmental factors such as warming and predation risk imposed by top predators. We studied effects of warming (low and high temperature) and predation risk (presence and absence of predator cues of perch) on SMPE in life history and physiological traits in the cannibalistic damselfly Ischnura elegans. We induced SMPE in the laboratory by manipulating hatching dates, creating following groups: early and late hatchlings reared in separate containers, and mixed phenology groups where early and late hatchlings shared the same containers. We found strong SMPE for survival and emergence success, with the highest values in early larvae of mixed phenology groups and the lowest values in late larvae of mixed phenology groups. Neither temperature nor predator cues affected SMPE for these two traits. The other life history traits (development rate and mass at emergence) did not show SMPE, but were affected by temperature and predator cues. A tendency for SMPE was found for protein content, in the high temperature treatment. The other physiological traits (phenoloxidase activity and fat content) showed fixed expressions across treatments, indicating decoupling between physiology and life history. The results underline that SMPEs are trait-dependent, and only weakly or not affected by temperature and predation risk. [ABSTRACT FROM AUTHOR]

Interspecific interactions among predators can shape ecological communities across trophic levels, including among predator guilds. The strength and directions of these interactions, however, may vary spatially and temporally in regions undergoing widespread landscape changes (e.g., urbanization, agricultural production). We investigated intraguild effects of coyotes (Canis latrans), a de facto apex predator, and land-cover changes on abundance indices of red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) using two long-term and independent time series: direct observations of canids by archery deer hunters (26 years) and harvest data from canid trappers (41 years) from across Illinois, USA. Abundance indices from both time series for red and gray foxes declined whereas coyote abundance indices increased, suggesting increasing coyote abundance may have led to decreases in fox population abundances. Empirical support among candidate models explaining fox declines was generally equivocal yet differed between fox species. Models including effects of coyote abundance were generally competitive for red foxes and estimated negative coyote effects even after controlling for declining farm size. The empirical support among our landscape hypotheses also varied by species despite increasing forest cover and farm size during our study. The estimated effects of coyote in our study were weaker than reported at more northerly latitudes suggesting that increasing coyote populations may not be fully responsible for observed declines in fox populations in the midwestern USA. [ABSTRACT FROM AUTHOR]

The Pantanal wetland harbours the second largest population of jaguars in the world. Alongside climate and land-use changes, the recent mega-fires in the Pantanal may pose a threat to the jaguars' long-term survival. To put these growing threats into perspective, we addressed the reach and intensity of fires that have affected jaguar conservation in the Pantanal ecoregion over the last 16 years. The 2020 fires were the most severe in the annual series, burned 31% of the Pantanal and affected 45% of the estimated jaguar population (87% of these in Brazil); 79% of the home range areas, and 54% of the protected areas within home ranges. Fires consumed core habitats and injured several jaguars, the Pantanal's apex predator. Displacement, hunger, dehydration, territorial defence, and lower fecundity are among the impacts that may affect the abundance of the species. These impacts are likely to affect other less mobile species and, therefore, the ecological stability of the region. A solution to prevent the recurrence of mega-fires lies in combating the anthropogenic causes that intensify drought conditions, such as implementing actions to protect springs, increasing the number and area of protected areas, regulating fire use, and allocating fire brigades before dry seasons. Destructive wildfires ravaged jaguar primary habitat, posing significant ecological threats to the species in the Pantanal wetland. [ABSTRACT FROM AUTHOR]

Coyotes Canis latrans have expanded their geographic range by 40% in the last 120 years, raising questions about their ecological impacts in the newly colonised areas. Despite a wealth of local knowledge on coyote diet in North America, we have little information about how and why diet might vary throughout the species' range.We conducted the first rangewide meta‐analysis of coyote diet by investigating how ecoregion, coyote mass, environmental conditions, presence of top predators and alternative food items are related to coyote dietary diversity, as well as consumption of small mammals, lagomorphs, vegetation and ungulates.Using data from 93 studies, we used generalised linear mixed models to determine which variables best explained coyote dietary patterns.Coyotes were generally more carnivorous in temperate forests than in other ecoregions, primarily due to greater ungulate consumption. Dietary diversity was most influenced via a negative effect of mammal consumption; coyote diet was more diverse in the spring and where human footprint was greater. There was minor variation in small mammal consumption, but lagomorph consumption was greater in spring and winter and when coyotes were larger. Vegetation consumption was greatest in summer and autumn. Ungulate consumption was positively related to coyote mass, snow cover and the presence of grey wolves Canis lupus.Both intrinsic and extrinsic factors were related to coyote diet. Larger coyotes ate larger foods, which parallels the relationship between mass and prey size across the carnivore guild. Wolves and humans have opposing effects on coyote diet. Coyotes seem to prioritise eating wild mammals, though more work is needed to quantify scavenging. Collectively, our findings emphasise the need for continued local or regional studies to understand the highly variable ecological effects of coyotes within the diverse ecosystems they currently inhabit and are poised to inhabit. [ABSTRACT FROM AUTHOR]

In this study a non-linear mathematical model is formulated to study and analyze an ecological system consisting of plants, insects preying on plants and insects natural enemy as predator. We analyze the dynamics of the system in a systematic manner. Here we have assumed that plants erow logistically. insect population depends on plants and predator population also depends on insects. We incorporate the gestation delay for predators in our proposed model. Positivity and boundedness of the system are established. The existence and stability of different equilibria are discussed. The existence of Hopfrbi furcation of the system is investigated. Then the proposed model is extended to stochastic model and simulation results for both stochastic and deterministic models are compared. [ABSTRACT FROM AUTHOR]

Ongoing environmental change across the Arctic is affecting many freshwater ecosystems, including small thaw ponds that support macroinvertebrates, thus potentially affecting important forage for fish and bird species. To accurately predict how fish and wildlife that depend on these macroinvertebrates will be affected by ecosystem change at high latitudes, understanding proximate factors that influence macroinvertebrate abundance is critical.To better understand factors that affect spatial and seasonal (i.e. phenology) patterns in abundance, we collected macroinvertebrates throughout the growing season of a single year from 33 thaw ponds on the Arctic Coastal Plain in northern Alaska. We used hierarchical N‐mixture models to provide detection‐corrected estimates of abundance (of the population exposed to sampling) in relation to pond type and seasonal patterns in environmental variables (i.e., cumulative water temperature, nutrient levels) for five taxonomic groups representing key food items for birds and fish—Anostraca (Arthropoda: Branchiopoda), Chironomidae (Insecta: Diptera), Cladocera (Arthropoda: Branchiopoda), Limnephilidae (Insecta: Trichoptera), and Physidae (Mollusca: Gastropoda).For three of five taxa (Anostraca, Cladocera, Limnephilidae), abundance varied across pond types and was lower in pond types where water temperatures increased more rapidly. Further, seasonal temperature profiles in ponds affected phenology, suggesting that seasonal patterns in abundance were influenced by changes in water temperature.These findings suggest that increases in water temperature in northern areas could alter macroinvertebrate phenology, possibly with consequences for upper level predators if availability of macroinvertebrate prey is reduced or shifted seasonally. Our results will facilitate improved predictions of how changing abiotic conditions could affect inland waters in northern areas, a critical need for conservation of Arctic wildlife and ecosystems. [ABSTRACT FROM AUTHOR]

Thinking flexibly is a skill that enables animals to adapt to changing environments, which enhances survival. Killer whales, Orcinus orca, as the ocean apex predator display a number of complex cognitive abilities, especially flexible thinking or creativity when it comes to foraging. In human care, smaller dolphins and other marine mammals have been trained to think creatively while under stimulus control. The results of these previous studies have demonstrated that bottlenose dolphins, Tursiops truncatus, can create original behaviors in response to an innovative cue. We trained and tested a total of nine killer whales from two different facilities on the innovate concept, using the same methodology. The killer whales ranged in age from 5 to 29 yrs with 4 females and 5 males. The results indicate that the killer whales demonstrated high fluency, originality, some elaboration, and flexibility in their behaviors. Individual variability was observed with younger animals demonstrating more variable behaviors as compared to the older animals. Males seemed to display less complex and lower energy behaviors as compared to females, but this impression may be driven by the age or size of the animal. These results support existing evidence that killer whales are dynamic in their thinking and behavior. [ABSTRACT FROM AUTHOR]

Species coexist only when occupying different ecological niches. We evaluated habitat and trophic niches in two recently diverged hybridizing avian apex predators, the declining Greater Spotted Eagle Clanga clanga (mainly found in contracting wetlands) and the more numerous Lesser Spotted Eagle Clanga pomarina (inhabiting mosaic farmlands). We tracked 24 Spotted Eagles, including interspecific hybrids, by GPS to estimate the home‐range size, land use composition and landscape structure in sympatric populations. In addition to information for landscape utilization, data for diet composition were evaluated. Home‐ranges of the two species were similar in size and open foraging habitats consisted mostly of agricultural landscape. However, landscape utilization of the Greater Spotted Eagle was largely driven by the composition of land‐use types, whereas the Lesser Spotted Eagle was mostly influenced by structural components of the landscape. Farmland‐dwelling voles accounted for the bulk of the diet in both species; however, subdominant prey classes differed. Hybrids exhibited intermediate or mixed features of home‐ranges and diets. Our results provide evidence for reduced niche partitioning and potential competition between the two Spotted Eagles, which may have been reinforced by anthropogenic habitat alteration. A closer examination of movement patterns revealed previously overlooked differences between closely related species with respect to landscape utilization strategies. [ABSTRACT FROM AUTHOR]

Wildlife alter their behaviors in a trade-off between consuming food and fear of becoming food themselves. The risk allocation hypothesis posits that variation in the scale, intensity and longevity of predation threats can influence the magnitude of antipredator behavioral responses. Hunting by humans represents a threat thought to be perceived by wildlife similar to how they perceive a top predator, although hunting intensity and duration varys widely around the world. Here we evaluate the effects of hunting pressure on wildlife by comparing how two communities of mammals under different management schemes differ in their relative abundance and response to humans. Using camera traps to survey wildlife across disturbance levels (yards, farms, forests) in similar landscapes in southern Germany and southeastern USA, we tested the prediction of the risk allocation hypothesis: that the higher intensity and longevity of hunting in Germany (year round vs 3 months, 4x higher harvest/km2/year) would reduce relative abundance of hunted species and result in a larger fear-based response to humans (i.e., more spatial and temporal avoidance). We further evaluated how changes in animal abundance and behavior would result in potential changes to ecological impacts (i.e., herbivory and predation). We found that hunted species were relatively less abundant in Germany and less associated with humans on the landscape (i.e., yards and urban areas), but did not avoid humans temporally in hunted areas while hunted species in the USA showed the opposite pattern. These results are consistent with the risk allocation hypothesis where we would expect more spatial avoidance in response to threats of longer duration (i.e., year-round hunting in Germany vs. 3- month duration in USA) and less spatial avoidance but more temporal avoidance for threats of shorter duration. The expected ecological impacts of mammals in all three habitats were quite different between countries, most strikingly due to the decreases in the relative abundance of hunted species in Germany, particularly deer, with no proportional increase in unhunted species, resulting in American yards facing the potential for 25x more herbivory than German yards. Our results suggest that the duration and intensity of managed hunting can have strong and predictable effects on animal abundance and behavior, with the potential for corresponding changes in the ecological impacts of wildlife. Hunting can be an effective tool for reducing wildlife conflict due to overabundance but may require more intensive harvest than is seen in much of North America. [ABSTRACT FROM AUTHOR]

The mesopredator release hypothesis predicts that abundance of smaller predators should increase in the absence of larger predators due to release from direct killing and competition. However, the effects of top predators on mesopredators are unlikely to operate in isolation but interact with other factors such as primary productivity of the landscape and human activities. We investigate factors influencing activity indices of a top predator (dingo) and an introduced mesopredator (red fox) in forests of south-eastern Australia. We used generalised linear models to investigate the effects that net primary productivity, proximity to freehold land and poison baiting campaigns directed at dingoes had on fox and dingo activity. Baiting was the best predictor of activity for both dingoes and foxes. Dingo activity was variable but typically lower at baited sites. Fox activity varied within a lower range at a majority of sites compared to the dingo but was typically higher at the baited sites. Positive responses of foxes to dingo control are consistent with the mesopredator release hypothesis and suggest in this region dingoes may have greater suppressive effect on fox populations than poisoning campaigns directed towards dingoes. Our results suggest that removal of dingoes may be counter-productive for biodiversity conservation because it may lead to higher activity of foxes. Summary Here, we investigate factors influencing activity indices of a top predator (dingo) and an introduced mesopredator (red fox) in forests of south-eastern Australia. Lethal baiting was the best predictor of activity for both dingoes and foxes. Our results suggest that removal of dingoes, via lethal baiting, may be counter-productive for biodiversity conservation because it may lead to higher activity of foxes. [ABSTRACT FROM AUTHOR]

In nearly every ecosystem, human predators (hunters and fishers) exploit animals at extraordinarily high rates, as well as target different age classes and phenotypes, compared to other apex predators. Demographically decoupled from prey populations and technologically advanced, humans now impose widespread and significant ecological and evolutionary change.In this paper, we investigate whether there is evidence that humans provide complementary services and whether ecosystem services of predators can be maintained by humans where wild predators are lost. Our objective is to contribute to two key ecological themes: the compatibility of human harvesting within ecosystems and management approaches in consideration of the intentional or unintentional loss of predators.We reviewed evidence for five key effects of predators: natural selection of prey, disease dynamics, landscape effects, carbon cycling and human well‐being. Without carefully designed management strategies, such changes can impose harm to ecosystems and their constituents, including humankind.Ultimately, we applied this information to consider management paradigms in which humans could better support the role of, and potentially behave more like, apex predators and discuss the challenges to such coexistence. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aquaculture environments harbor complex bacterial communities that are critical for the growth and health of culture species. Apex predators are frequently added to aquaculture ponds to improve ecosystem stability. However, limited research has explored the effects of apex predators on the composition and function of bacterioplankton communities, as well as the underlying mechanisms of community assembly. Using 16S ribosomal RNA (rRNA) high-throughput sequencing, we investigated bacterioplankton communities of crustacean aquaculture ponds with and without apex predators (mandarin fish, Siniperca chuatsi) throughout the culture process. In addition to investigating differences in bacterioplankton communities, we also explored variations in environmental adaptation, functional redundancy, and community stability. Significant differences were observed in bacterioplankton composition among different cultural stages; there was an increase in Bacteriobota and fermentation-related bacteria, but a decrease in Firmicutes and pathogens in the middle stages of aquaculture. Apex predators increased the abundance of organic matter degradation bacteria and decreased pathogens. Bacterioplankton communities under apex predator disturbances had a wider environmental breadth, indicating broader environmental adaptation. Moreover, functional prediction and network analyses revealed that communities under apex predator disturbances were less functionally redundant and unstable. Based on the null model, stochastic processes drove community assembly during aquaculture, whereas apex predators elevated the contribution of deterministic processes. Greater changes in nitrate in culture ponds caused by apex predator disturbances were decisive in controlling the balance between stochasticity and determinism in community assembly. Our study provided insight into the mechanisms underlying bacterioplankton community assembly in aquaculture systems in response to apex predator disturbances. [ABSTRACT FROM AUTHOR]

The daily activity patterns of animals are modulated by external factors such as habitat selection, temporal niche selection, prey availability and predation risk. Furthermore, different species show a variety of responses to human disturbance; therefore, to understand the effects of human activities on wildlife, it is crucial to consider the disturbance characteristics (e.g. type, frequency, timing and location of human activity). Our objective was to evaluate whether vehicles on forest roads altered the daily temporal activity patterns of three apex predators; Eurasian lynx (Lynx lynx), the grey wolf (Canis lupus) and brown bear (Ursus arctos), using an extensive camera trap data set collected across a gradient of forest roads and wildlife trails in the Croatian part of the Dinaric mountains. We expected a low temporal overlap between humans and apex predators but predicted this even lower at sites where vehicles are present. Consistent with our expectations, the general overlap in temporal activity of all three apex predators and humans was low, the former being primarily active at night/dawn/dusk hours and the latter during daylight hours. In contrast, our results showed similarity in the temporal activity of all three predators on wildlife trails and forest roads where human activity was more frequent and diverse. [ABSTRACT FROM AUTHOR]

The chemical industry is the leading sector in the EU in terms of added value. However, contaminants pose a major threat and significant costs to the environment and human health. While EU legislation and international conventions aim to reduce this threat, regulators struggle to assess and manage chemical risks, given the vast number of substances involved and the lack of data on exposure and hazards. The European Green Deal sets a 'zero pollution ambition for a toxic free environment' by 2050 and the EU Chemicals Strategy calls for increased monitoring of chemicals in the environment. Monitoring of contaminants in biota can, inter alia: provide regulators with early warning of bioaccumulation problems with chemicals of emerging concern; trigger risk assessment of persistent, bioaccumulative and toxic substances; enable risk assessment of chemical mixtures in biota; enable risk assessment of mixtures; and enable assessment of the effectiveness of risk management measures and of chemicals regulations overall. A number of these purposes are to be addressed under the recently launched European Partnership for Risk Assessment of Chemicals (PARC). Apex predators are of particular value to biomonitoring. Securing sufficient data at European scale implies large-scale, long-term monitoring and a steady supply of large numbers of fresh apex predator tissue samples from across Europe. Natural science collections are very well-placed to supply these. Pan-European monitoring requires effective coordination among field organisations, collections and analytical laboratories for the flow of required specimens, processing and storage of specimens and tissue samples, contaminant analyses delivering pan-European data sets, and provision of specimen and population contextual data. Collections are well-placed to coordinate this. The COST Action European Raptor Biomonitoring Facility provides a well-developed model showing how this can work, integrating a European Raptor Biomonitoring Scheme, Specimen Bank and Sampling Programme. Simultaneously, the EU-funded LIFE APEX has demonstrated a range of regulatory applications using cutting-edge analytical techniques. PARC plans to make best use of such sampling and biomonitoring programmes. Collections are poised to play a critical role in supporting PARC objectives and thereby contribute to delivery of the EU's zero-pollution ambition. [ABSTRACT FROM AUTHOR]

Sharks are top predators and play an important role in the regulation of marine ecosystems at lower trophic position. Mustelus californicus, Sphyrna zygaena, and Isurus oxyrinchus prove to be important fishery resources along the western coast of Baja California Sur and cohabit the same coastal areas, probably sharing resources. However, our knowledge about ecological dynamics of multiple species coexisting and sharing similar habitat resources is still limited, particularly for predators such as sharks. Therefore, this study focuses on the analysis of trophic ecology of the sharks species, using carbon (13C) and nitrogen (15N) stable isotope values in muscle tissues coupled with trace element concentration (Hg, Se, and Cd) in muscle and hepatic tissues of sharks. The values of δ13C (M. californicus −17.3 ± 1.1‰, S. zygaena −17.9 ± 0.5‰, and I. oxyrinchus −18.3 ± 0.3‰) and δ15N (M. californicus 18.2 ± 1.1‰, S. zygaena 18.4 ± 0.9‰, and I. oxyrinchus 17.8 ± 1.1‰) indicated that these species feed in the Gulf of Ulloa all throughout the year, and for extended periods with similar habitat use and trophic niche. The above-mentioned statement is also a conclusion supported by the significant correlation between isotopic and trace element concentrations in the muscular tissues in all studied species. Thus, the results of the present study emphasize the habitat and niche characteristics of three sympatric sharks off the coast of Baja California Sur, Mexico. [ABSTRACT FROM AUTHOR]

Felids are the top predators in the environments they inhabit. They entered South America at the Pliocene-Pleistocene boundary, but their fossil record in Uruguay, although informative, is scarce. In the present contribution, three new materials (two hemimandibles and an isolated first lower molar) assigned to Panthera onca (Linnaeus, 1758) are described. This material came from Quaternary sediments (Sopas, Dolores, and Libertad Formations) from several localities in Uruguay. Based on this material, different aspects of the paleobiology and paleoecology of jaguars are discussed. Remains of these felids were previously listed but never described; thus, the material analyzed here is the first fossil records reliably determined for P. onca in Uruguay. These felids would have shared an ecological niche with other large carnivores during the late Pleistocene in Uruguay, such as saber-toothed cats (Smilodon populator Lund, 1842; S. fatalis Leidy, 1868), Puma concolor Linnaeus, 1771, and short face bears Arctotherium Burmeister, 1879; and they would have fed upon medium-sized herbivores, principally in vegetated environments. [ABSTRACT FROM AUTHOR]

The angular roughshark, Oxynotus centrina (Linnaeus, 1758), is a rarely encountered deep‐sea demersal shark species. It is listed as "Critically Endangered" in the IUCN's regional assessment for the Mediterranean. Like other sharks and rays, the angular roughshark is subject to by‐catch in demersal trawl and longline fisheries. This study contributes new knowledge on (a) its occurrence, size and sex information; and (b) its feeding ecology in the Sea of Marmara. Data were collected on total length (TL), total weight (TW) and sex from unpublished research survey reports performed intermittently from 1994 to 2020. According to the data, O. centrina was mainly recorded from the muddy sand bottom type in the southwest region of the Marmara Sea, which has higher biodiversity of macrobenthic species than other regions. Different methodological approaches were conducted to understand its feeding, such as DNA metabarcoding and isotope analysis to identify its prey spectra and assign a trophic level. Sampled specimens were full of liquid in their stomachs without any discernible visually identifiable prey items. The metabarcoding analyses were also unsuccessful in identifying any prey items. Trophic position calculation based on nitrogen isotope in muscles highlighted that O. centrina has the highest trophic position compared to the other sharks and rays in the Sea of Marmara. Although it was found mainly feeding on polychaetes and sipunculids species from previous studies, the δ15N values made the authors cautious about the possibility of this species feeding on low trophic‐level benthic invertebrates. Because the authors could not observe the presence of shark vitellus in the stomachs and could not succeed in DNA identification for prey, this study highlights high δ15N values similar to top predators for O. centrina. The authors conclude that this species strategically feeds mainly on shark eggs to fulfil its nutritional requirements with minimum energy expenditure in line with its slow‐moving behaviour and mouth morphology. [ABSTRACT FROM AUTHOR]

Animals exhibit variation in their space and time use across an urban–rural gradient. As the top‐down influences of apex predators wane due to human‐driven declines, landscape‐level anthropogenic pressures are rising. Human impacts can be analogous to apex predators in that humans can drive increased mortality in both prey species and carnivores, and impact communities through indirect fear effects and food subsidies. Here, we evaluate the time use of a common mesocarnivore across an urban–rural gradient and test whether it is influenced by the intensity of the use of a larger carnivore. Using multiple camera‐trap surveys, we compared the temporal response of a small carnivore, the raccoon (Procyon lotor), to the larger coyote (Canis latrans) in four study areas across Michigan that represented a gradient of pressure from humans. We found that raccoon time use varied by study area and was most unique at the rural extreme. Raccoons consistently did not shift their activity pattern in response to coyotes in the study area with the highest anthropogenic pressures despite the considerable interannual variation, and instead showed stronger responses to coyotes in more rural study areas. Temporal shifts were characterized by raccoons being more diurnal in areas of high coyote activity. We conclude that raccoons may shift time use in the presence of coyotes, dependent on the level of anthropogenic pressure. Our results highlight that the variation in raccoon time use across the entirety of the urban–rural gradient needed to be considered, as anthropogenic pressures may dominate and obscure the dynamics of this interaction. [ABSTRACT FROM AUTHOR]

Killer whales (Orcinus orca) are marine apex predators distributed across the world's oceans. In the last 40 years, researchers have increasingly differentiated killer whales into ecotypes based on genetics, morphology, behaviour, acoustic repertoire, habitat, and trophic ecology. While killer whale ecotypes in the Northern Hemisphere are well studied, the recognition of distinct killer whale forms in the Southern Hemisphere is mainly limited to Antarctic waters. Although present in less studied regions, such as along the Atacama Desert coast in the Southeast Pacific Ocean, limited information is available regarding their biology or trophic ecology. Herein, multiple lines of evidence are presented for killer whale predation on marine mammals in northern Chile. Using information from systematic boat-based surveys, whale-watching tour surveys, and reports from fishermen/citizen scientists, 19 killer whale sightings are reported along the coast of northern Chile (from the Arica and Parinacota region in the north to the Atacama region in the south). Killer whales were photo-identified as corresponding to the Southern Hemisphere Type A-like ecotype according to their dorsal fin shape and white eye patch. One killer whale pod, which included two males, one female, one juvenile, and one calf, was resighted six times from 2016 to 2021 in northern Chile and was observed hunting South American sea lions (Otaria flavescens), dusky dolphins (Lagenorhynchus obscurus), and long-beaked common dolphins (Delphinus cf. capensis). Killer whales were observed taking advantage of large aggregations of sea lions associated with the offshore purse-seine fishery. Adult killer whales used the hulls of fishing vessels to prevent sea lions from escaping. Photo-identification analysis of a fin whale (Balaenoptera physalus) catalogue from Mejillones Peninsula showed that 2.6% of all identified whales had apparent rake marks from killer whale teeth on their dorsal fins. These data show that Type A-like killer whales in northern Chile prey on several species of marine mammals. [ABSTRACT FROM AUTHOR]