The food, feeding habits and feeding structures of the whiting species Sillago sihama (Forsskål) and Sillago analis Whitley from Townsville, North Queensland, Australia

The diet, feeding habits and feeding structures of 519 Sillago sihama and 493 S. analis specimens collected from beaches and estuaries in the Townsville region are described. The species are carnivores on a wide range of benthic, epibenthic and planktonic prey. Both undergo size related dietary shifts; S. sihama from predominantly planktonic crustaceans in fish of less than 80 mm t.l . to polychaetes, penaeid and brachyuran crustaceans and molluscs at larger sizes; S. analis from a mixture of small Mesodesma eltanae and amphipods at sizes of less than 80 mm t.l . to predominantly M. eltanae and small quantities of penaeids and brachyuran crabs in larger fish. The dietary shift was not associated with migration from a nursery area.
While the species showed considerable overlap in the types of prey utilized, there were significant differences in the relative importance of shared components in their diets. The major difference was in the relative importance of the bivalve mollusc, M. eltanae. This was the dominant food of S. analis but of secondary importance in S. sihama. Associated with this basic difference in diet was a specialization of the pharyngeal dentition in S. analis to molariform crushing plates and a reduction of the gill rakers to vestigial knobs. In S. sihama , the pharyngeal teeth are sharp and pointed and the gill rakers normal.
The feeding activity of S. analis , but not S. sihama , is limited by the tidal cycle, a factor which may be a form of temporal partitioning.     

Dental morphology and diet in anuran amphibians from south India

The morphology of the jaw and palatine surfaces of eight species of metamorphosed anuran amphibians ( Microhyla ornata, M. rubra, Uperodon systoma, Tomopterna rolandae, Polypedates maculatus, Rana cyanophlycris, R. crassa and R. hexadactyla ) from a locality in south India, were examined by scanning electron microscopy. A relationship was observed between dentition (or its absence) and diet. In large prey feeders, there is a strong tendency towards the development of large secondary (or even tertiary) cusps, while myrmecophagous and termitophagous species lack teeth.
In the largely folivorous adults of Rana hexadactyla , secondary cusps are reduced to faint ridges and the tooth is cylindro-conical (as opposed to the recurved teeth with apices oriented lingually or distally in the insectivorous species). Although the phylogenetic relationships within members of the community are largely unknown, the oral armature is reflective of diet, and may represent adaptive suites.     

Functional morphology of bite mechanics in the great barracuda (Sphyraena barracuda)

The great barracuda, Sphyraena barracuda, is a voracious marine predator that captures fish with a swift ram feeding strike. While aspects of its ram feeding kinematics have been examined, an unexamined aspect of their feeding strategy is the bite mechanism used to process prey. Barracuda can attack fish larger than the gape of their jaws, and in order to swallow large prey, can sever their prey into pieces with powerful jaws replete with sharp cutting teeth. Our study examines the functional morphology and biomechanics of 'ram-biting' behavior in great barracuda where the posterior portions of the oral jaws are used to slice through prey. Using fresh fish and preserved museum specimens, we examined the jaw mechanism of an ontogenetic series of barracuda ranging from 20 g to 8.2 kg. Jaw functional morphology was described from dissections of fresh specimens and bite mechanics were determined from jaw morphometrics using the software MandibLever (v3.2). High-speed video of barracuda biting (1500 framess(-1)) revealed that prey are impacted at the corner of the mouth during capture in an orthogonal position where rapid repeated bites and short lateral headshakes result in cutting the prey in two. Predicted dynamic force output of the lower jaw nearly doubles from the tip to the corner of the mouth reaching as high as 58 N in large individuals. A robust palatine bone embedded with large dagger-like teeth opposes the mandible at the rear of the jaws providing for a scissor-like bite capable of shearing through the flesh and bone of its prey.     

Dietary partitioning promotes the coexistence of planktivorous species on coral reefs

Theories involving niche diversification to explain high levels of tropical diversity propose that species are more likely to co‐occur if they partition at least one dimension of their ecological niche space. Yet, numerous species appear to have widely overlapping niches based upon broad categorizations of resource use or functional traits. In particular, the extent to which food partitioning contributes to species coexistence in hyperdiverse tropical ecosystems remains unresolved. Here, we use a molecular approach to investigate inter‐ and intraspecific dietary partitioning between two species of damselfish (Dascyllus flavicaudus, Chromis viridis) that commonly co‐occur in branching corals. Species‐level identification of their diverse zooplankton prey revealed significant differences in diet composition between species despite their seemingly similar feeding strategies. Dascyllus exhibited a more diverse diet than Chromis, whereas Chromis tended to select larger prey items. A large calanoid copepod, Labidocera sp., found in low density and higher in the water column during the day, explained more than 19% of the variation in dietary composition between Dascyllus and Chromis. Dascyllus did not significantly shift its diet in the presence of Chromis, which suggests intrinsic differences in feeding behaviour. Finally, prey composition significantly shifted during the ontogeny of both fish species. Our findings show that levels of dietary specialization among coral reef associated species have likely been underestimated, and they underscore the importance of characterizing trophic webs in tropical ecosystems at higher levels of taxonomic resolution. They also suggest that niche redundancy may not be as common as previously thought.     

Diet diversity among five co-existing fish species in a tropical river: integration of dietary and stable isotope data

Diets were estimated from stomach contents and the MixSIR model using stable isotope values for five co-existing and abundant benthic fishes in relation to potential prey from a riffle habitat in a tropical river in eastern Thailand. Collectively, aquatic insects were of greatest dietary importance based on stomach contents and, except for one fish species, predicted from the MixSIR. The most prominent functional feeding insect groups in fish diets were collector-filterers and scrapers and, to a lesser extent, predators. MixSIR predicted shrimp to be the most important single dietary constituent for all fishes in contrast to stomach contents, which indicated they are a major item for only one species. MixSIR predicted plant material to be more important in fish diets than stomach contents where the composition of detritus was a concern. Differences in temporal feeding schedules, prey availability, species adaptations and others are important in understanding diet and in the construction of food webs. Stable isotope and dietary analysis provides a more accurate assessment of the food web structure and dynamics of tropical river ecosystems than either method alone.     

Chew,shake, and tear: Prey processing in Australian sea lions (Neophoca cinerea)

Pinnipeds generally target relatively small prey that can be swallowed whole, yet often include larger prey in their diet. To eat large prey, they must first process it into pieces small enough to swallow. In this study we explored the range of prey‐processing behaviors used by Australian sea lions (Neophoca cinerea) when presented with large prey during captive feeding trials. The most common methods were chewing using the teeth, shaking prey at the surface, and tearing prey held between the teeth and forelimbs. Although pinnipeds do not masticate their food, we found that sea lions used chewing to create weak points in large prey to aid further processing and to prepare secured pieces of prey for swallowing. Shake feeding matches the processing behaviors observed in fur seals, but use of forelimbs for “hold and tear” feeding has not been previously reported for other otariids. When performing this processing method, prey was torn by being stretched between the teeth and forelimbs, where it was secured by being squeezed between the palms of their flippers. These results show that Australian sea lions use a broad repertoire of behaviors for prey processing, which matches the wide range of prey species in their diet.     

Foraging behaviour and functional morphology of two scale-eating cichlids from Lake Tanganyika

The foraging behaviours of two Tanganyikan scale-eating cichlids, Perissodus straeleni and Perissodus microlepis , were observed in laboratory. Video analyses of their feeding behaviours showed the distinct differences in scale-eating action between the two species. Perissodus straeleni presses and shifts its mouth laterally along the body of the prey as the prey attempts to break free. In contrast, P. microlepis quickly rotates its body, with both jaws pressed tightly against the flank of the prey. Scanning electron microscopy of tooth shapes confirmed that dental morphology clearly differs between the two species: the teeth of P. straeleni are laminar and leaf-shaped with sharp edges along the lateral sides, whereas P. microlepis has thick, broad-based teeth with spine-like points in the upper corners. In addition, inspection of tooth condition in wild-caught fishes showed that the ratio of wearing teeth was significantly higher in P. straeleni than in P. microlepis . These results indicate that the functional morphology of the teeth plays an important role in their scale-eating actions; in P. straeleni , the sharp edges of the teeth appear to function as blades for scraping while shifting the mouth laterally along the body of the prey, whereas the spine-like projections on the teeth of P. microlepis appear to effectively catch scales while pressing and rotating the mouth, simultaneously wrenching off scales. These results clearly demonstrate that the different scale-eating behaviours of the two species are closely associated with the functional diversification of their jaw teeth.     

Diets and trophic guilds of small fishes from coastal marine habitats in western Taiwan

The diets and trophic guilds of small fishes were examined along marine sandy beaches and in estuaries at depths <1·5 m in western Taiwan, Republic of China. Copepods were the most frequently identified item in fish guts, indicating they are key prey for the fish assemblages studied. Piscivore, crustacivore, detritivore, omnivore, zooplanktivore and terrestrial invertivore trophic guilds were identified. The zooplanktivore guild contained the most fish species. Maximum prey size consumption was positively correlated with standard length (L_S) in seven species and at the assemblage level and negatively correlated with L_S in a single detritivorous species. The diet data and trophic guild scheme produced by this study contribute to an understanding of coastal marine food webs and can inform ecosystem‐based fisheries management.     

A partial food web involving predatory gastropods on a Pacific fringing reef

An analysis of the feeding habits of a diverse assemblage of predatory gastropods on a Guam fringing reef, shows that seven major prey categories are eaten, namely polychaetes, sipunculans, gastropods, bivalves, crustaceans, ophiuroids, and fish. The three largest feeding groups are the polychaete feeding guild which mainly consists of species of Conus, the gastropod guild dominated by species of the Muricidae and the sipunculan guild consisting mainly of the Mitridae. There is considerable dietary overlap between members of feeding guilds, but interaction between guilds is low and accounted for by the relatively few generalist species in the community.     

Chirocentrodon bleekerianus (Teleostei: Clupeiformes: Pristigasteridae), a small predaceous herring with folded and distinctively oriented prey in stomach.

Predaceous fish-eating species of the order Clupeiformes have a large mouth with well-developed teeth, and reach the greatest sizes within their families (up to 90 cm). We found that the pristigasterid Chirocentrodon bleekerianus, a small clupeiform (about 10 cm) from the tropical SW Atlantic, is able to prey on proportionally large clupeoid fishes and caridean shrimps. Fish preys are folded in the stomach of this herring, their heads and tails pointing toward the predator's head. This distinctive orientation of fish prey is also recorded for some small to medium-sized, fish-eating species of the tropical freshwater order Characiformes with canine-like teeth similar to those found in C. bleekerianus.     

Feeding ecology and dietary comparisons among three sympatric Neotrygon (Myliobatoidei: Dasyatidae) species

The diets of Neotrygon picta, Neotrygon kuhlii and Neotrygon annotata are described using trophic level analysis, index of relative importance (I(RI) ) and non-metric multidimensional scaling ordination (nMDS). They were secondary consumers with trophic levels of between 3·55 and 3·58. Carids were the most important prey category in the diets of N. picta (82·0%I(RI) ) and N. annotata (69·4%I(RI) ); Polychaeta (72·3%I(RI) ) was the most important prey category for N. kuhlii. A significant difference was detected between the volumetric dietary data of all three species (ANOSIM, global R-statistic = 0·742, P < 0·01) and between sequential N. picta and N. kuhlii size classes (ANOSIM, global R-statistics = 0·367-0·403, P < 0·01). Changes in polychaete and carid prey proportions were the primary sources of diet variability. Dietary differences may be linked to variations in disc width, mouth morphology and feeding strategies. This study provides insights into the level of variability within and between the diets and feeding behaviours of Neotrygon species, and the potential for resource partitioning to occur when these species coexist.     

Patterns of morphological traits shaping the feeding guilds in the intertidal mudflat fishes of the Indian Sundarbans

Broad-scale patterns of resource utilization and the corresponding morphological evolution is a result of an integral relationship among form and function. In addition, there is also an inherent role of the latter in determining species co-interaction and assemblage pattern that forms an integral aspect of ecological research. The present study aimed to evaluate the ecomorphological relationship among 37 fish species inhabiting the intertidal mudflats of the Indian Sundarbans by outlining the following objectives: (i) identifying and characterizing feeding guilds/groups and (ii) understanding the inter-relationship between morphometry with (a) the established feeding guild classifications and (b) observed prey taxa (that characterizes these feeding groups) for determining the role of morphometry in prey acquisition followed by (iii) the evaluation of their potential phylogenetic convergence among the species. For the first objective, two approaches for feeding guild classification were made (3-Guild and 8-Guild) for assessing the prediction accuracy of morphological characters in identifying the different guilds. While the former was based on troph values, the latter classification mode relied on the similarities in diet composition among the different fish species. For addressing the second objective, we employed two different models namely, linear discriminant (LDA) and redundancy analysis (RDA). While the LDA model tested the prediction accuracy of morphological traits in classifying the different feeding guilds, RDA was applied to model the correlation between the morphological traits and the prey categories. In the LDA model, morphological characters showed higher accuracy (78.4%) in classifying three feeding groups rather than eight feeding groups (73%). Following this, the RDA model (explaining 79.78% of constrained variance) showed gill raker intensity, protrusion length, head depth, caudal peduncle, eye diameter and inter-orbital distance to be highly associated with selection of specific prey types by species, thereby characterizing a particular feeding guild. However, generalized linear models testing for correlation between troph value and feeding groups showed substantial variation (90.35%) in the dietary index being explained by the 8-Guild classification. Hence, our study maintains the assumption that broad morphological differentiation acts as one of the underlying processes resulting in dietary variations that results in the varying modes of resource utilization by the coexisting species, thereby determining the structure of a trophic guild. Furthermore, it also suggests that in terms of prey abundance or selectivity, the 8-Guild model is much more conducive in representing the feeding habits of the species while the morphological traits reflected a relatively broader scheme of classification, (i.e., 3-Guild model) with certain traits being phylogenetically conserved within these groups.     

Seasonal variation in prey preference,diet partitioning and niche breadth in a rich large carnivore guild

Large carnivore community structure is affected by direct and indirect interactions between intra-guild members. Co-existence between different species within a carnivore guild may occur through diet, habitat or temporal partitioning. Since carnivore species are highly dependent on availability and accessibility of prey, diet partitioning is potentially one of the most important mechanisms in allowing carnivores to co-exist. Intra-guild interactions may vary over time as carnivore prey preference and diet overlap can change due to seasonal changes in resource availability. We conducted scat analysis to compare the seasonal changes in prey preference, diet partitioning and niche breadth of four large carnivore species, namely leopard Panthera pardus, spotted hyena Crocuta crocuta, brown hyena Parahyaena brunnea and wild dog Lycaon pictus in central Tuli, Botswana. Large carnivores in central Tuli display a high dietary overlap, with spotted hyena and brown hyena displaying almost complete dietary overlap and the other carnivore species displaying slightly lower but still significant dietary overlap. Dietary niche breadth for both hyena species was high possibly due to their flexible foraging strategies, including scavenging, while leopard and wild dog showed a relatively low niche breadth, suggesting a more specialised diet. High dietary overlap in central Tuli is possibly explained by the high abundance of prey species in the area thereby reducing competition pressure between carnivore species. Our research highlights the need to assess the influence of diet partitioning in structuring large carnivore communities across multiple study sites, by demonstrating that in prey rich environments, the need for diet partitioning by carnivores to avoid competition may be limited.     

Feeding habits and niche partitioning in a predator guild composed of tigers, leopards and dholes in a temperate ecosystem in central Bhutan

We describe the food habits, niche overlap and prey preferences in a predator guild comprised of tigers Panthera tigris , leopards Panthera pardus and dholes Cuon alpinus in a mountainous region of central Bhutan. Scat analyses revealed that these predators consumed 11 different prey species including livestock and rodents, of which leopards consumed 11. The combined relative occurrence of the three species, sambar Cervus unicolor , muntjac Munticus muntjac and wild pig Sus scrofa , constituted 42.7, 33.7 and 71.1% of the tiger, leopard and dhole diets, respectively, while livestock comprised 44.5, 73.4 and 15.9% of the prey consumed, respectively. Regression equations from earlier feeding trials were used to estimate the relative biomass and the numbers of prey consumed. Results showed that sambar featured more frequently than did muntjac and wild pig in the diets of tiger, leopard and dhole and contributed more relative biomass than did muntjac and wild pig. Sambar, muntjac and wild pig together provided 36.9, 28 and 63.1% of the biomass consumed by tigers, leopards and dholes respectively. All else being equal, there was evidence that all three predators ate livestock less than might have been expected on the basis of the abundance and high biomass of this prey category in the area. There was a high dietary niche overlap between the predators (Pianka's overlap index of 0.58–0.92), with a greater overlap between the two felid species than between the felids and the canid. This study provides evidence of a substantial diet overlap among the three sympatric carnivores, and thus highlights the potential for high intra-guild competition among them, especially given the relatively low density of prey.     

Zooplankton populations and the diets of three Chaoborus species (Diptera, Chaoboridae) in a tropical lake

SUMMARY. 1. Zooplankton populations in a small, natural, tropical lake are dominated by a few, small-sized taxa including the copepod Thermo- cyclops consimilis , the cladoceran Moina micrura and several rotifer species.
2. Moina micrura and adults of Thermocyclops consimilis undergo diel vertical migrations within the water column. Population densities of T. consimilis show marked intra-annual variations which may to some extent be related to variations in rainfall and to lunar periodicities In predator abundance.
3. The diets of Chaoborus lavae include other Chaoborus , Cladocera, Copepoda. Rotifera and the dinoflagellate Peridinium. The diets of late instars of the largest species, edulis , were dominated by Crustacea, while those of the two smaller species. C, ceratopogones and C. anomalus , were dominated by Rotifera and the dinoflagellate alga Peridinium , as were the diets of early instars of all species. Algae have not been previously reported to be a large component of the diet of Chaoborus populations in nature.
4. Some of the dietary differences among Chaoborus instars and species are related to the size of each prey species in relation to the mouth gape of each instar. However, there are also important differences in electivity among instars of different species of the same size.     

Diet niche relationships among North American grassland and shrubsteppe birds

Summary We consider the dietary relationships of the numerically dominant breeding bird species in four North American grassland/shrubsteppe habitats, sampled over 2–3 consecutive years. Overall, the diets of these species contained primarily insects: orthopterans comprised 29% of the diet biomass, coleopterans 24%, and lepidopteran larvae 23%, while seeds contributed 15% of the average diet. These diets varied substantially, however, and we evaluated several aspects of this variation. Intersexual differences in diets within a species were few, despite the occurrence of significant sexual size dimorphism in several species. For many species, however, there were substantial shifts in dietary composition between years at a given location; overall, the average between-year similarity of species' dietary composition was 70%. Different species exhibited rather different diet patterns. Horned Larks were relatively omnivorous, had broad diet composition niches, and varied considerably in diets between different locations. Meadowlarks were also broad-niched and geographically variable in their diets, but were the most highly carnivorous of the species we considered. Dietary niche breadths of Grasshopper Sparrows were intermediate, but diet composition was rather stable, both between years and between locations. Chestnut-collared Longspurs exhibited narrow diet niches, but substantial annual variation: each year this species apparently exploited a different but limited set of prey types rather heavily. Larger avian predators generally consumed a broader array of functional groups of prey, but did not differ in the taxonomic variety of their diets from small birds. Variation in diet composition between individuals within local populations was considerable; in most species, an individual contained on the average 30–40% of the prey taxa represented in entire population smaples.Patterns of dietary overlap among species were quite inconsistent from year to year at most locations, although at the shrubsteppe site overlap among all species present was consistently quite high. Relatively few cooccurring species pairs exhibited low diet overlap. The degree of diet niche overlap was unrelated to body size differences of the birds, despite as much as six-fold differences in weight among some coexisting species. Relationships of the bird species on another dimension of the trophic niche, prey size, also differed substantially between sites and years. The ranking of co-occurring species by the mean sizes of the prey they consumed generally did not parallel their rankings by body sizes, and in some cases the smallest and the largest species present ate prey of similar sizes. At the shrubsteppe site, all the breeding species exhibited quite similar frequency distributions of prey sizes in their diets.As species number and diversity increased in the breeding avifaunas, diet niche breadths generally decreased, species packing by prey size decreased, and diet composition niche overlap remained relatively unchanged. These trends are in at least partial agreement with predictions of diffuse competition theory, but the patterns were derived from broad inter-site comparisons of overall site averages, and the relationships generally did not hold within local assemblages of species. In general, our attempts to match values of dietary niche features with site characteristics failed to demonstrate close agreement with the predictions of prevailing ecological theory based upon assumptions of resource limitation and competition. Instead, our findings seem generally most consistent with the suggestion that food is not normally limiting to bird populations in these systems, and individuals and populations are exploiting the food resources in an opportunistic fashion, which leads to considerable individual, between-year, and between-location variation in diet compositions and interspecific overlaps.Our attempts to discern clear relationships that accord with theoretical expectations in these avian assemblages are thwarted by our lack of detailed information on the resource base and by the lack of clear tests that will separate alternative hypotheses of community organization and structuring. We suggest that these complications may compromise the findings of many community studies.     

Feeding ecology of the waterbirds in a tropical mangrove in the southeast Gulf of Mexico

ABSTRACT

Species that exploit the same type of environmental resources are defined as a guild, which have similar needs in the use of food or habitat. It was analyzed the diet of five waterbirds’ offsprings species (Neotropic Cormorant (Nannopterum brasilianus), Reddish Egret (Egretta rufescens), Boat-billed Heron (Cochlearius cochlearius), Snowy Egret (Egretta thula) and Great Egret (Ardea alba)), by prey identification and calculated the relative importance, overlap and breadth diet. The general diet of the piscivorous guild consisted of 17 fish species from 13 genera and eight families. The highest overlap was between the Reddish Egret and Boat-billed Heron. Fish species dominated the diets of all studied waterbirds, Poecilia velifera was the most abundant prey species in each of the birds, suggesting that they are abundant in the wetlands system of northern Yucatan. Diet overlap in waterbirds species depends on the use of resources and feeding habitat. Since reproductive success largely depends on the availability of food resources, mainly of resident or estuarine fishes. The information about diet is important for the conservation of waterbirds.     

Diet composition of two larval headwater stream salamanders and spatial distribution of prey

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Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.