Opportunistic Feeding Strategy Research Articles

A tale from the Neogene savanna: Paleoecology of the hipparion fauna in the northern Black Sea region during the late Miocene

This paper investigates the paleoecology of the Neogene savanna in the northern Black Sea region during the late Miocene, focusing on the “Hipparion fauna” that inhabited the area. The study explores the dietary habits of various ungulates and carnivorans through dental mesowear and microwear patterns, aiming to infer aspects of trophic interactions and ecological niches occupied by different species. The research covers three sites that span from the late Khersonian (late Tortonian; MN11) to the late Maeotian (Messinian; MN13) stages. We report catastrophic bone accumulation at the Grebeniki and Cioburciu 1 sites. Results indicate a significant dietary diversity that is challenging the traditional assumptions about the “Hipparion fauna”. Rhinoceroses, specifically Chilotherium schlosseri and Aceratherium incisivum, are identified as true grazers, contradicting previous beliefs about their preference for forested or swampy ecosystems. The hipparions, traditionally considered open landscape foragers, are revealed as browsers or mixed-feeders. The study also highlights the diverse dietary traits among small antelopes, giraffids, and suids, emphasizing their adaptability to various environmental conditions. Data obtained on the hyaenid Adcrocuta eximia indicate a diet very similar to that of the bone-cracking spotted hyena. The microwear pattern of the cubs was very different from both adults and any other carnivorans used for comparison. The large felid Machairodus copei was characterized by a hypercarnivorous diet similar to lions, while smaller-size Ictitherium viverrinum was characterized by a more opportunistic feeding strategy. These findings suggest similarities and differences in feeding patterns between modern and Neogene savanna mammals. The presence of both grazing and browsing herbivores indicates a more heterogeneous landscape, with a mixture of open grasslands and denser vegetation. Additionally, the paper provides insights into the changing paleoenvironment, suggesting a transition from wooded grasslands to open landscapes during the late Miocene. Overall, this research contributes to a comprehensive understanding of the Neogene savanna ecosystem and challenges existing perceptions of the paleoecology of the “Hipparion fauna” in the northern Black Sea region.

Detailed analysis of prey taxonomic composition indicates feeding habitat partitioning amongst co-occurring invasive gobies and native European perch

One of the negative impacts of non-native invasive species on trophic interactions in an invaded ecosystem occurs via increased interspecific competition for food resources between the invader and local species of the same food niche. In freshwaters, there are usually several fish species that feed on similar food resources. Ponto-Caspian gobies are amongst the most successful and widespread invaders colonising European waterways. They have a wide food niche and an opportunistic feeding strategy, with a focus on benthic invertebrates and piscivory occurring occasionally mainly in the case of large individuals. Competition with native percids for food resources is predicted on the basis of high dietary overlap. However, studies published so far provide no unequivocal answer. In order to resolve this question, we conducted a comparative taxonomic analysis of gut content, with an emphasis on chironomids and amphipods, of the invasive monkey goby (Neogobius fluviatilis), racer goby (Babka gymnotrachelus) and the native Eurasian perch (Perca fluviatilis) occurring sympatrically in a large lowland European river, the Bug River in Poland. We found that each species forages in slightly different habitats, as indicated by the different composition of prey species in the gut content. This suggests feeding niche partitioning between the studied species facilitating their co-existence and reduction or avoidance of competition for food resources. Resource partitioning regarding prey types and foraging habitats is a mechanism for permitting the co-existence of closely-related alien gobies with similar food preferences in the invaded waters and co-occurrence with local species. This mechanism can contribute to their invasion success, as observed in European waters during the recent decades. We also demonstrate that precise prey identification to the lowest possible taxon is crucial to reveal the dietary overlap between co-occurring fish species and to predict the impact of alien invaders on native species through interspecific competition, as well as to recommend such an approach in studies upon fish foraging strategies.

The varied diet of the golden jackal (Canis aureus): Experiences from stomach analyses

The golden jackal population shows a rapid expansion in Europe during the recent decades, raising several management and conservation issues. Among others, the opportunistic feeding strategies might be a reason which is responsible for the invasive spreading and survival success of the species in various parts of Hungary. Our aim was to analyze the diet composition of the jackal through stomach content analysis to provide an insight about the evolution and behavioural adaptations of this mesopredator. The stomach samples were collected between 2003 and 2014 from different parts of Hungary. The percentage frequency of occurrence (%FO) as well as the biomass (%B) of the stomach content data were analyzed. Statistical analysis tests based on the presence and absence data of the remains of wild ungulates (cervids and wild boar) from seasonal data (winter-spring and summer-autumn) and between gender groups were conducted. Also, comparisons of the presence and absence data for the three main food categories (rodents, big game and vegetative/plant parts) were statistically tested.The results of the comparisons did not show any significant differences between the classes. This can be explained due to the high spatio-temporal variation of the data. The findings of our study shows the presence of a varied composition of food items such as rodents, insects, fruits, plant parts, ungulates (wild boar, cervids), reptiles (such as lizards and pond turtles), bird species (such as pheasants) as well as jaw remains of the red fox. It is noteworthy to mention in this context that majority of the ungulate remains from the stomach contents were associated with maggots, which indicated the presence of carrion consumption. Our study, based on varied diet composition, supports and confirms the opportunistic, scavenging and highly adaptive foraging of the golden jackal.

Functional and temporal facets of predation by marsh frogs across the aquatic–terrestrial ecotone of ponds and implications in the context of biological invasions

Abstract Freshwater vertebrate predators can exert trophic control over aquatic and littoral communities. Among these predators, post‐metamorphic anurans exhibit a biphasic trophic spectrum by foraging in both terrestrial and aquatic habitats. Many studies have described their diet through the classical taxonomic classification of prey. However, these singular diet habits imply a complex, time‐dependent, realised trophic niche in which predation pressure occurs over many consumers that fill diverse functional roles throughout the aquatic and terrestrial interface of ponds. Among anurans, marsh frogs (Pelophylax ridibundus) have been introduced outside their range in many countries and are now invading nationwide areas, particularly in western Europe. Focusing on their foraging specificities will therefore further the understanding of the trophic role of these alien taxa in pond environments that are highly colonised. We collected stomach contents from 761 marsh frogs from introduced populations in 19 ponds in southern France once a month over 4 months of their active period in the spring. The populations of marsh frogs were studied in a geographic area that was devoid of native water frogs and their origin tracks back as far as south‐eastern Europe (i.e., more than 1,000 km from the studied sites, as evidenced previously by genetic analyses). Marsh frogs exhibited generalist and opportunistic feeding strategies. The trophic niche was strongly asymmetrical and broader in the terrestrial environment than in the aquatic environment. However, predation occurred in communities of large freshwater macroinvertebrates and amphibians. Whereas the composition of the terrestrial diet exhibited strong seasonal variations, predation pressure was continuously exerted on the same aquatic organisms over time. Primary consumers and consumers at higher trophic levels frequenting aquatic benthic, vegetated, pelagic, and surface microhabitats were preyed upon, underlying the multidimensional extent of the predation spectrum. The diversified feeding strategies of alien marsh frogs highlight the extent of potential ecological control by predation on pond communities. Because of their wide trophic niche, they exert predation pressure on most pond organisms, triggering possible top‐down control of the overall aquatic communities. Our results show that the integration of the functional traits and microhabitats of consumed prey may aid in a better understanding of how predation by anurans may target specific components of pond communities. More particularly, this study raises concerns about the predatory role of introduced anurans in the context of biological invasions.

Insight into the trophic niche and prey contribution in the diet of Lutjanus griseus (Linnaeus, 1758) captured by artisanal fishing fleet in the central and southwest Gulf of Mexico

Lutjanus griseus is a common species for fisheries of the Gulf of Mexico, and it is an effective vehicle to transport energy from low to top trophic levels in the ecosystem. The management of fish populations is based on the modeling and prediction of abundances. To accomplish this, trophic ecology results allow the understanding of habitat use and population expansions. To increase the knowledge in the trophic ecology of L. griseus, this study described its trophic niche, diet composition, and the prey contribution in the formation of muscle tissue. Results showed that the trophic niche in Veracruz was wider than in Campeche, this related to the consumption of prey in different habitats, coral reefs areas in Veracruz and seagrass beds in Campeche. According to the δ13C y δ15N values, in both regions the crustaceans were the most important group in the contribution of muscle tissue, however, it contrasted with the stomach content results, which suggested that the diet in Campeche was mainly composed of crustaceans, and in Veracruz of fishes. This difference could be related to the snapper’s movements, as they can be found in sea bottoms covered with seagrass, with high abundance of crustaceans, and sea bottoms composed of coral reefs with high diversity of fishes and other preys. Results highlight the generalist and opportunistic feeding strategy of L. griseus, this strategy allowed its population expansion to the north, consuming the available food source in the different habitats it occupied.

Opportunistic vs selective feeding strategies of zooplankton under changing environmental conditions.

The plankton community consists of diverse interacting species. The estimation of species interactions in nature is challenging. There is limited knowledge on how plankton interactions are influenced by environmental conditions because of limited understanding of zooplankton feeding strategies and factors affecting trophic interactions. In this study, we used DNA-metabarcoding to investigate trophic interactions in mesozooplankton predators and the influence of prey availability on their feeding behavior. We found that mesozooplankton feeding strategies vary within species across an environmental gradient. Some species, such as Temora longicornis consistently used a selective strategy, while diets of Centropages hamatus and Acartia spp. varied between stations, showing a trophic plasticity with the prey community. We found a dominance of Synechococcales reads in Temora's gut content and a high prey diversity for the cladoceran Evadne nordmanni. Our study shows the wide range of prey species that supports mesozooplankton community and helps to understand the spatial and temporal complexity of plankton species interactions and discriminate the selectivity ability of four zooplankton key species. Due to the central role of plankton in marine waters, a better comprehension of the spatiotemporal variability in species interactions helps to estimate fluxes to benthic and pelagic predators.

In situ microplastic ingestion by neritic zooplankton of the central Mexican Pacific

Microplastics (MPs) are present across the global ocean and can be encountered by many species, including zooplankton. Although they fall within the size range of zooplankton prey, there are few studies on MPs ingestion carried out in situ. In this study, we analyzed MPs ingestion during two seasons (rainy and dry) of organisms from 5 taxonomic groups of zooplankton from two bays of the Mexican central Pacific: Manzanillo and Navidad. In total, 2643 individuals were analyzed, and of those 23 individuals contained MPs. The ingestion rate by taxonomic group was 1 MP/36 copepods (0.02), 1 MP/30 decapods–mysis (0.03), 1 MP/29 decapods–megalopa (0.03), and 1 MP/200 fish larvae (0.005). No plastics were found in chaetognaths, amphipods, or decapods–zoea. The average length of the ingested particles was 468.1 ± 113.8 μm, with a minimum of 15.6 and a maximum of 647.6 μm. All MPs >300 μm were fibers, with diameters <50 μm. Fragments were the most abundant MPs (54.2%), followed by fibers (34.2%) and spheres (11.4%). Statistical analyses showed no significant differences (p > 0.05) between the bays or seasons. Using RAMAN spectroscopy, it was possible to identify 6 different types of polymers, with poly (ethylene:propylene) being the most abundant (42.8%). This polymer is commonly used to manufacture plastic bags, ropes and fishing nets. The results confirm that certain zooplankton groups are consuming MPs and suggest that omnivorous species are more likely to ingest MPs, possibly due to their capacity for foraging flexibility and opportunistic feeding strategies. However, the ingestion of MPs cannot be attributed to a single factor; it is necessary to consider variables such as the sampling area, feeding strategy, size, and seasonality to understand the dynamics of MPs ingestion by zooplankton groups.

Decipher groundwater food web interactions by means of stable isotope and gut microbiome analyses

The traditional perception of groundwater food webs is that of short and poorly structured food chains extending to only few trophic levels. This is mainly attributed to the lack of light and the shortfall of substantial primary production as well as the shortage of dissolved organic carbon and nutrients. It is frequently argued that microbes form the basis of groundwater food webs. In reality, the obvious lack of comprehensive biofilms may point to detritus as the main common food source and an opportunistic and omnivorous feeding strategy with most groups and species. Also, the relative stability of groundwater environments may have led to low trait variability. However, recent research also contrasts the paradigm of poorly structured food chains against emerging convoluted mechanisms sustaining a great range of biotic diversity and functional complexity. In summary, understanding of the ecological and functional linkages among stygofaunal groups, and their interaction with the microbial community, is still in its infancy. Stygofauna sampled from three spots of a shallow alluvial aquifer in the vicinity of the Danube River in the city of Vienna, Austria, has been analyzed by means of bulk stable carbon and nitrogen isotope and gut microbiome analysis to disentangle food web interactions. Our preliminary data revealed the following pattern: plant material, terrestrial insects, and detritus show a narrow range in carbon (-32 to -25δ13C) and a wide range in nitrogen (-1.5 to 6.5 δ15N) isotope signatures. In terms of nitrogen isotope values, the next tropic level is represented by isopods and gastropods, followed by ostracods, oligochaetes and amphipods. The broader range of stygofauna in carbon isotope signatures indicate an additional food source; most probably microbes; gut microbiome analyses indicate differences with oligochaetes, gastropods, ostracodes, isopods and amphipodes, however, with a few individuals from the later three groups sharing a very similar gut microbiome; within the amphipods, there is obviously a difference in gut microbiome composition with species and sampling sites; carbon and nitrogen isotope signatures underline amphipod-species differences; microbiome diversity in all cases was less divers in the animal guts when compared to environmental water, sediment and detritus samples. plant material, terrestrial insects, and detritus show a narrow range in carbon (-32 to -25δ13C) and a wide range in nitrogen (-1.5 to 6.5 δ15N) isotope signatures. In terms of nitrogen isotope values, the next tropic level is represented by isopods and gastropods, followed by ostracods, oligochaetes and amphipods. The broader range of stygofauna in carbon isotope signatures indicate an additional food source; most probably microbes; gut microbiome analyses indicate differences with oligochaetes, gastropods, ostracodes, isopods and amphipodes, however, with a few individuals from the later three groups sharing a very similar gut microbiome; within the amphipods, there is obviously a difference in gut microbiome composition with species and sampling sites; carbon and nitrogen isotope signatures underline amphipod-species differences; microbiome diversity in all cases was less divers in the animal guts when compared to environmental water, sediment and detritus samples. Finally, we first collected evidence for anaerobic processes taking place in animal guts living in an oxic groundwater environment. In light of our data, putative groundwater food web interactions in the shallow alluvial aquifer are discussed.

Population dynamics and dietary habits of monkey goby (

Context Various aspects of the monkey goby (Neogobius fluviatilis) biology were studied but mainly in native marine and invaded freshwater bodies; however, in Ukraine, this species can be considered native in many freshwaters. Aim To investigate the population dynamics and dietary habits of N. fluviatilis in a freshwater habitat in its native range. Methods Samples were collected monthly in 2015–2016 and 2018 in a river flowing into the Kaniv reservoir (Dnieper River). Key results Goby abundance varied during a year and between years, depending on water temperature. Young of the year started appearing in June and reached the size of adult fish in October. N. fluviatilis had multiple spawnings occurring from May to August. Altogether, 70 taxa of prey organisms composed its diet, among which the most abundant prey were chironomids (57.7% in number). The diet of N. fluviatilis showed a clear ontogenetic shift from the consumption of benthic microcrustaceans to chironomids. Conclusions N. fluviatilis fed predominantly on prey inhabiting non-vegetated sand and mud substrate. The opportunistic feeding strategy, combined with time-expanded multiple spawnings, can facilitate the successive invasion and establishment of this species in new environments. Implications The obtained results can be used to predict the impact of N. fluviatilis on ecosystems in newly invaded areas.

COMPOSICIÓN Y ESTRUCTURA DE LA DIETA DE PAVO OCELADO (MELEAGRIS OCELLATA) EN UN TERRITORIO AGROFORESTAL, CAMPECHE, MÉXICO

&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;: The Ocellated Turkey is a priority species because of its endemic status and being a strategic resource for local communities. An assessment of the state of its populations in the Yucatan Peninsula between 1980 and 2000 reports that the abundance decline is correlated with its weak dispersion capacity, habitat degradation, and availability of food resources. However, detailed information on its habitat requirements and trophic ecology is still very limited. Therefore, qualitative and quantitative information on the food resources consumed by &lt;em&gt;M. ocellata&lt;/em&gt; is essential for the implementation of management strategies aimed at promoting the conservation of the species. &lt;strong&gt;Objective:&lt;/strong&gt; In an agroforestry territory managed under the Mexican scheme of Units for Wildlife Conservation (UMA), the composition and structure of the Ocellated Turkey male diet were determined. &lt;strong&gt;Methodology:&lt;/strong&gt; The study site corresponds to UMA Las Flores, Campeche, Mexico. It is a communally owned agroforestry territory run by Mennonite colonies whose primary economic activities are soybean, sorghum, and maize agriculture. It has an area of 9600 ha, four thousand are farmlands and the rest of forest cover. The taxonomic composition of the male diet was evaluated analyzing food content present in the upper digestive tract (crop and gizzard) of 72 samples of male birds hunted during the breeding season (January to April 2019). The Relative Importance Index was estimated to quantitatively assess the importance of each food component and the Levins Index assessed the degree of specialization in the diet. &lt;strong&gt;Results: &lt;/strong&gt;According to the frequency of occurrence and abundance of the food components, we found that the male Ocellated Turkey presented a generalist and opportunistic feeding strategy; the stomach contents consisted of resources from the field crops, whose dietary composition was granivorous. Diet composition was based on the consumption of 39 vegetables belonging to 20 families of 12 orders. Of the six established food categories, the seeds registered the highest value with 94.49% of the total dry weight, being corn, sorghum, and a wild specie belonging to the Convolvulaceae family the most significant resources in the diet. &lt;strong&gt;Implications:&lt;/strong&gt; Our results help to determine the importance of agroforestry systems to meet food requirements and evaluate the trophic dynamics of the Ocellated Turkey, as well as the plasticity of the species to use food resources in different scenarios in space and time throughout its distribution range. &lt;strong&gt;Conclusion:&lt;/strong&gt; Information on the composition and abundance of food resources consumed by &lt;em&gt;M. ocellata&lt;/em&gt; males in an agroforestry system managed under UMA's Mexican scheme is important for understanding and redefining habitat requirements and trophic niche amplitude, to implement management strategies that promote the increase of their wild populations and sustainable hunting.&lt;/p&gt;

Midtrophic fish feeding modes at the poles: an ecomorphological comparison of polar cod (Boreogadus saida) and Antarctic silverfish (Pleuragramma antarctica)

The polar cod (Boreogadus saida) and the Antarctic silverfish (Pleuragramma antarctica) are pelagic fish endemic to the Arctic and Antarctica sea, respectively. Both species are abundant and play a central role as midtrophic wasp-waist species in polar ecosystems. Due to their biological and ecological characteristics (small size, complex life histories, relatively short generation cycles, movement capability, planktivorous diet, and importance as prey), the polar cod and the Antarctic silverfish are potentially good sentinels of ecosystem change. Changes in polar zooplankton communities are well documented. How changes impact ecosystems as a whole largely depend on the degree of diet specialization and feeding flexibility of midtrophic species. Here, we provide the ecomorphological characterization of polar cod and Antarctic silverfish feeding performances. A comparative functional ecology approach, based on the analysis of morpho-anatomical traits, including calculation of suction index and mechanical advantage in jaw closing, was applied to profile the feeding modes and flexibility of the two species. Ecomorphological evidence supports differences in food acquisition: the polar cod appears able to alternate particulate ram-suction feeding to a pump filter feeding, and the Antarctic silverfish results be both a particulate ram and a tow-net filter feeder. Both species exhibit opportunistic feeding strategies and appear able to switch feeding mode according to the abundance and size of the available prey, which is a clue of potential resilience to a changing environment.

Habitat utilization and feeding ecology of small round goby in a shallow brackish lagoon

We examined small-scale distribution and feeding ecology of a non-native fish species, round goby (Neogobius melanostomus (Pallas, 1814)), in different habitats of a coastal lagoon situated in the south-western Baltic Sea. First observations of round goby in this lagoon were reported in 2011, 3 years before the current study was conducted, and information on this species’ basic ecology in different habitats is limited. We found that mainly juvenile round gobies are non-randomly distributed between habitats and that abundances potentially correlate positively with vegetation density and thus structural complexity of the environment. Abundances were highest in shallower, more densely vegetated habitats indicating that these areas might act as a refuge for small round gobies by possibly offering decreased predation risk and better feeding resources. Round goby diet composition was distinct for several length classes suggesting an ontogenetic diet shift concerning crustacean prey taxa between small (≤ 50 mm total length, feeding mainly on zooplankton) and medium individuals (51–100 mm, feeding mainly on benthic crustaceans) and another diet shift of increasing molluscivory with increasing body size across all length classes. Differences in round goby diet between habitats within the smallest length class might potentially be related to prey availability in the environment, which would point to an opportunistic feeding strategy. Here, we offer new insights into the basic ecology of round goby in littoral habitats, providing a better understanding of the ecological role of this invasive species in its non-native range, which might help to assess potential consequences for native fauna and ecosystems.

Trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico

We describe the diet, feeding strategy, and trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico during both the warm and cold seasons. A total of 4,547 stomachs were collected, with 1,921 empty stomachs being discarded. According to the stomach content analysis, 95 prey items were identified and grouped into 70 food categories belonging to crustaceans, mollusks, fish, polychaetes, and echinoderms. The Smith index value and high prey diversity indicated that the 11 fish species exhibited a generalist opportunistic feeding strategy in both survey seasons. Low values of dietary overlap were recorded, and only a few significant cases of dietary overlap were found in the interaction between some rays (Urotrygonidae) and flatfish species (Pleuronectiformes). The availability and abundance of prey resources in the environment and the generalization of niche breadth allows the demersal predator community of the soft shallow bottoms to coexist without any evident competition for trophic resources.

Seasonal variability of stable isotope values and niche size in tropical calanoid copepods and zooplankton size fractions

The seasonal variability of stable isotope values (δ15N and δ13C), ∆15N values, and niche width of calanoid copepod species, three zooplankton size fractions and seston were assessed from samples obtained monthly between January and December 2012 at a coastal sampling site in the Eastern Tropical Pacific off Mexico (19°09′03″ N, 104°44′50″ W). Twenty calanoid copepod species were analyzed, 15 of which were sampled in both the cool, productive ‘mixed’ period and the warm, oligotrophic ‘stratified’ period. While copepod δ15N and ∆15N values were higher during the mixed period, seston δ15N values did not differ between periods. The δ13C values indicated a seasonal difference between a priori-defined groups of oceanic and coastal copepod species. The seasonal variations of both the isotopic niche (Bayesian ellipses) values and Layman metrics in tropical copepods and zooplankton fractions suggested an opportunistic feeding strategy responding to the local coupled physical–biological seasonal processes. During the productive mixed period, the trophic web was more robust and stable, and a wider niche was observed. Contrary to commonly reported responses to environmental conditions, we found a more complex mesozooplankton food web during the productive period and a shorter web during the oligotrophic period, highlighting the importance of researching trophic dynamics in coastal tropical ecosystems.

Trophic ecology of albacore tuna (Thunnus alalunga) in the western tropical Indian Ocean and adjacent waters

In this study we investigated the trophic ecology of albacore tuna in the western Indian Ocean and adjacent Atlantic waters based on stomach content analysis using a reconstituted length and weight of prey approach. From 686 non-empty stomachs collected between 2001 and 2015 across three biogeographic provinces, we describe the diet composition of albacore tuna, analyse its feeding habits and investigate the structure and diversity of mid-trophic-level communities. Epipelagic fish were found to be the principal prey by number and reconstituted weight; cephalopods were the second important prey group. Small organisms prevailed in the diet of albacore tuna, with predation on juvenile fish commonplace. Albacore tuna exhibits a flexible, opportunistic feeding strategy, from ram filter feeding on abundant schooling prey to visual predation on large individuals. Prey species richness varied highly across the region. Oligotrophic conditions within the subtropical gyre of the Indian Ocean generated the most diverse mid-trophic-level communities, with less diverse communities occurring in productive areas. Albacore tuna occupies a similar trophic niche throughout the global ocean, foraging on the same prey families and even species. This study indicates overall temporal stability of the Indian Ocean and south-east Atlantic ecosystems where principal prey species remain unchanged over decades.

Diet and feeding strategy of Northeast Atlantic mackerel (Scombrus scomber) in Icelandic waters.

Predator-prey relations, as well as the trophic ecology of highly migratory marine species, is important to understand their impact on the ecosystem. Conventional methods were used to study the diet composition and feeding strategy of the Northeast Atlantic mackerel (Scombrus scomber), during their summer feeding migration to Icelandic waters in 2009–2014. In addition, generalised additive modelling (GAM) was used to determine which biological and environmental factors contribute to the variation of their stomach weight in the years 2011–2014. From the dietary analysis, we found that calanoid copepods (especially Calanus finmarchicus) were the most important contributor to the overall diet of mackerel in the years studied. Although in some years and areas, they also preyed heavily on larger prey items such as euphausiids, amphipods and megalopa larvae of crab and shrimp. The GAM showed that temperature and the time the day of sampling were significant explanatory variables for the stomach weight, while zooplankton biomass did not seem to have much influence. The Northeast Atlantic mackerel are ferocious feeders upon copepods, as well as exhibiting an overall opportunistic feeding strategy. During their feeding migration in Icelandic waters, they were found to feed on the most dominant species available to them.

Opportunistic feeding strategy in wild immature chimpanzees: Implications for children as active foragers in human evolution

Modern human (Homo sapiens) children are generally considered to be dependent on older individuals for foods, even after weaning. However, recent studies of hunter-gatherer societies have reported that children can also acquire food by themselves, although the degree of self-provisioning by children differs among groups and is considered a facultative adaptation. To investigate the dependence of children on older individuals for food and the importance of self-provisioning in early hominins, I examined feeding behavior in wild, immature chimpanzees (Pan troglodytes schweinfurthii). I studied 19 mother-offspring chimpanzee pairs in the Mahale Mountains National Park, Tanzania for approximately 22 months. Feeding behavior and interactions between mothers and their offspring were recorded. The results supported these three predictions: (1) immature chimpanzees need to feed more frequently than mothers because of increased basal metabolic rate and immature stomach capacity; (2) mothers provide effective opportunities to feed on high-quality food items which are similar to those of the mothers'; and (3) when feeding independently of their mothers, immature chimpanzees consume highly accessible food including non-adult foods nearby mothers to avoid getting lost and physical burden as with self-provisioning of human children in hunter gatherer societies. During non-simultaneous feeding bouts, immature individuals frequently consumed pith and wood. They may be valuable food items for immature individuals during their growth stage because they can be consumed year round and contain relatively higher crude ash and protein amounts, which may enable immature chimpanzees to manage the confines of their immature bodies, preventing them from matching adult feeding rhythms. This opportunistic feeding strategy is similar to self-provisioning by human children in hunter-gatherer societies. These results suggested that early hominin children performed self-provisioning based on opportunistic feeding strategies, and contributed to their food consumption by snacking in accordance with their metabolic needs and physical confines.

Seasonal trophic ecology of the dominant Antarctic coral Malacobelemnon daytoni (Octocorallia, Pennatulacea, Kophobelemnidae)

Antarctic ecosystems present highly marked seasonal patterns in energy input, which in turn determines the biology and ecology of marine invertebrate species. This relationship is stronger at lower levels of the food web, while upper levels may be less dependent on primary production pulses. The pennatulid Malacobelemnon daytoni, is one of the most abundant species in Potter Cove, Antarctica. In order to assess its trophic ecology and energetic strategies, its biochemical (carbohydrates, proteins and lipids), Fatty Acid (FA) and Stable Isotope (SI) (δ15N and δ13C) compositions were studied over a year-round period. The FA and SI profiles suggest an omnivorous diet and opportunistic feeding strategy for the species. These results, together with biochemical analysis (higher lipid and carbohydrate concentration observed in July and October 2009), support the hypothesis that resuspension events may be an important source of energy, reducing the seasonality of food depletion periods in winter. The evidence presented here gives us a better insight into the success that this species has in Potter Cove and under the current environmental changes experienced by the Antarctic Peninsula.

Physiological responses and lipid storage of the coral Lophelia pertusa at varying food density

ABSTRACTDespite the importance of the cold-water coral Lophelia pertusa to deep-sea reef ecosystem functioning, current knowledge of key physiological responses to available food resources is scarce. Scenarios with varying food density may help to understand how corals deal with seasonal variations in the dark ocean and might be used to study consequences of anthropogenic activities potentially affecting food availability. Thus, the physiological responses of L. pertusa to varying food (Artemia salina nauplii) concentration, ranging from 20% to 300% of carbon equivalent turned over by basal coral respiration, were investigated. A starvation group was also included. Measurements of respiration, growth, mucus production, and energy reserves (storage fatty acids) were performed at several time intervals over 26 weeks. In general, data showed a stronger effect of experimental time on measured responses, but no significant influence of food density treatment. In starved corals, respiration rate declined to 52% of initial respiration, while skeleton growth rate was maintained at the same rate as Artemia-fed corals throughout the investigation. Mucus production measured as the sum of dissolved organic carbon (DOC) and particulate organic carbon (POC) was also similar across food treatments, but POC production exceeded that of DOC at the highest food density. No marked effect was observed on storage fatty acids. These results confirm that L. pertusa is highly resilient to environmental conditions with suboptimal food densities over a time scale of months. Regulation of several physiological processes, including respiration and mucus production, possibly in combination with an opportunistic feeding strategy, contributed to this tolerance to maintain viable corals. Thus, it appears that L. pertusa is well adapted to life in the deep sea.

Trophic niche of the invasive red king crab Paralithodes camtschaticus in a benthic food web

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 565:113-129 (2017) - DOI: https://doi.org/10.3354/meps12023 Trophic niche of the invasive red king crab Paralithodes camtschaticus in a benthic food web Mona M. Fuhrmann*, Torstein Pedersen, Einar M. Nilssen Department of Arctic and Marine Biology, UiT–The Arctic University of Norway, 9037 Tromsø, Norway *Corresponding author: mona.m.fuhrmann@uit.no ABSTRACT: Understanding the trophic ecology of an invasive species is important for risk assessment. The red king crab Paralithodes camtschaticus is both a valuable fishery resource and a potential threat to native biota in the Barents Sea. We combined gut content analysis and stable carbon and nitrogen isotope analysis to study feeding strategy, variation in resource use and niche overlap within the benthic food web of Porsangerfjord (70.1° to 70.9°N, 25° to 26.5°E) on the northern Norwegian coast. This fjord has experienced recent invasion by the red king crab. Sediment-dwelling bivalves and polychaetes dominated gut contents of the red king crab with respect to occurrence, and the wide range of prey from multiple trophic levels revealed a generalist, opportunistic feeding strategy. There were differences in diet related to crab size and foraging location, reflecting habitat choice and depth distribution of crabs during their life cycle. Small crabs, feeding in shallow water, relied to a larger extent on littoral species such as sea urchins and gastropods. The estimated mean trophic level for red king crab in Porsangerfjord was 3.1 (range 2.7-3.5). There was no evidence of a pronounced ontogenetic niche shift in stable isotopes, with local effects concealing possible overall size effects. Competition may arise with native anomuran species (e.g. Lithodes maja), large predatory asteroids and gastropods, all of which overlapped with red king crab in isotopic niche. A low overlap in isotopic niche between red king crab and fish suggests that they exploit different major food resources and that predatory fish occupy a higher trophic position than the red king crab in Porsangerfjord. KEY WORDS: Decapod · Diet · Stable isotopes · Trophic ecology · Trophic level · Introduced species · North Atlantic Full text in pdf format Supplementary material PreviousNextCite this article as: Fuhrmann MM, Pedersen T, Nilssen EM (2017) Trophic niche of the invasive red king crab Paralithodes camtschaticus in a benthic food web. Mar Ecol Prog Ser 565:113-129. https://doi.org/10.3354/meps12023 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 565. Online publication date: February 17, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.