Variation In Diet Composition Research Articles

Lipid dynamics and trophic patterns inPleuragramma antarcticalife stages

AbstractThe aim of this study was to clarify the trophic patterns of the key speciesPleuragramma antarcticain the Dumont d’Urville Sea, through its development and possible changes according to sampling locations. Variability in diet composition of larvae, juvenile and adultP. antarcticawas analysed using fatty acid markers. Analysis of lipid class inP. antarcticareflected lipid accumulation with increasing size at all sampling stations. The fatty acid composition of triacylglycerol highlighted ontogenetic changes in the diet. Phytoplankton markers, such as C16PUFA:C16 and EPA:DHA ratios >1, and carnivorous markers in larvae suggested an omnivorous diet. Comparison between the fatty acid signature ofP. antarcticaolder stages (juveniles and adults) and zooplankton species using OPLS-discriminant analysis indicated that juveniles fed mainly on euphausiid larvae and to a minor extent on copepods, and confirmed that non-herbivorous copepods were the main prey for adults. Our results suggest that different feeding patterns and a generalist strategy inP. antarcticawith juveniles feeding on bigger prey than adults, probably as a result of prey availability according to their vertical segregation pattern.

Effects of population density and snow depth on the winter diet composition of sika deer

ABSTRACTThe understanding of population density and weather effects is fundamental for evaluating the population dynamics of ungulates. However, studies focusing on temporal variations in diet composition are limited. We investigated the effects of population density and snow depth on variation in the winter diet composition of 2 contrasting sika deer (Cervus nippon) populations in Oku‐Nikko and Ashio, Tochigi Prefecture, central Japan by monitoring diet composition for ≥15 years. The main food in Oku‐Nikko was dwarf bamboo (Sasa nipponica), which has a high crude protein content. This plant sometimes had low availability because of the combination of snow accumulation and reduced culm height associated with chronic grazing. The main food in Ashio was Japanese pampas grass (Miscanthus sinensis), which has a low crude protein content, but its availability was high because of high culm height and little snow accumulation. In Oku‐Nikko, snow accumulation and high deer density negatively affected the proportion of dwarf bamboo found in rumen contents, with the most significant effect found in calves. In Ashio, Japanese pampas grass composed a relatively high and constant proportion of the rumen contents when snow accumulation was ≤50 cm; however, it was negatively affected by snow accumulation of >50 cm. In addition, the utilization of Japanese pampas grass was reduced only when deer density was extremely high (>150 deer/km2). Our results clearly demonstrate that absolute density is not the sole factor that affects variation in the winter food selection of sika deer. The combined effects of snow depth and habitat quality, such as vegetation height, are overwhelmingly important in determining the winter diet composition of sika deer populations. © 2015 The Wildlife Society.

Trophic Niche and Feeding Strategy of the White Stork (Ciconia ciconia) during different Phases of the Breeding Season

Assessing feeding conditions and variations of diet composition over the breeding season is of great help in the understanding of the ecological niche of species. In meeting this aim, the White Stork's ( Ciconia ciconia) diet was studied based on the analysis of 87 regurgitation pellets collected from Batna (Northeast Algeria). A set of 2138 prey-items were identified and classified into 61 different prey-species belonging to seven classes, 13 orders, 29 families and 51 genera. The White Stork has a diverse diet (food niche breadth, FNB = 14.5, Shannon index H’ = 4.4 bits), mainly composed of arthropods, of which 94% of prey-items are insects that represent 8% of total prey biomass. The White Stork constantly fed on the remains of chicken foraged from rubbish dumps (biomass = 68.74%) and small mammals (biomass = 14.41%) as these prey categories constitute a source of high energy, particularly during the period of chick rearing. GLMs applied for diet characteristics revealed a significant variation in numbers of prey individuals between breeding phenological stages. While variations of other diet parameters (biomass, species richness, FNB, H’, H'max and evenness) were not statistically influenced by breeding phenology. All diet characteristics were significantly correlated with the period of chick development, which is the key period for breeding success; suggesting an increase in parental investment and feeding effort. Our findings suggest that the White Stork performs a balance in order to satisfy its food requirements by compensating reciprocally between intake of prey numbers and their biomass regardless of the phenological stage of reproduction.

Diet of the fat dormouse (Glis glis) on the northern periphery of its distributional range

We studied the seasonal and annual variation in diet composition of the fat dormouse (Glis glis) in Lithuania, a locality situated on the northern periphery of the dormouse range and outside of the range of the European beech (Fagus sylvatica). After emergence from hibernation, dormice fed on oak acorns (from the previous year), inflorescences of various trees, vegetative parts of plants and food of animal origin (birds, their eggs and insects). In June, soft mast and seeds of birches supplemented the dormouse diet, and diet composition was the most diverse during this period. In July, raspberries and fruits of glossy buckthorn constituted the bulk of dormouse diet, but seeds of birches dominated in a specific year. Hard mast (mainly acorns) dominated the diet of G. glis from August until the beginning of hibernation in October. A high prevalence of acorns, comparatively high proportion of birch seeds and low proportion of food of animal origin in the diet, as well as feeding on fruits of glossy buckthorn, are specific features of feeding by G. glis in Lithuania. The diet of G. glis on the northern periphery of its range resembles its diet on the eastern periphery of the range where beech trees are also absent. According to the composition of G. glis diet, feeding conditions in both of these peripheral regions are poorer in comparison to central or southern regions.

From yellow perch to round goby: A review of double-crested cormorant diet and fish consumption at Three St. Lawrence River Colonies, 1999–2013

The number of double-crested cormorants (Phalacrocorax auritus) in the upper St. Lawrence River has increased markedly since the early 1990s. In 1999, a binational study was initiated to examine the annual diet composition and fish consumption of cormorants at colonies in the upper river. Since 1999, 14,032 cormorant pellets, collected from May through September each year, have been examined from St. Lawrence River colonies to estimate fish consumption and determine temporal and spatial variation in diet. Seasonal variation in diet composition within a colony was low. Prior to 2006 yellow perch was the primary fish consumed by cormorants in the upper St. Lawrence River. Round goby were first observed in cormorant diets in 2003 and by 2006 were the main fish consumed at two of the three colonies. The time interval it took from the first appearance of round goby in the diet at a colony to when goby were the dominant prey species varied by island, ranging from two to five years. Daily fish consumption at each cormorant colony increased significantly from the pre-round goby to post-round goby period. The mean annual biomass of yellow perch consumed decreased significantly during the post-round goby period at the three colonies. Reduced consumption of yellow perch by cormorants may alleviate suspected localized impacts on perch near some of the larger river colonies.

Summer Diel Diet and Feeding Periodicity of Four Species of Cyprinids in the Salmon River, New York

Abstract The diel diet composition and feeding periodicity of Luxilus cornutus (common shiner), Exoglossum maxillingua (cutlip minnow), Semotilus corporalis (fallfish), and Notropis hudsonius (spottail shiner) were examined in the Salmon River, New York over a 24 h period during the summer. Chironomids were the major prey of common shiner (60.6%) and cutlip minnow (54.7%), whereas terrestrial invertebrates (30.0%) and amphipods (38.4%) were the primary food of fallfish and spottail shiner, respectively. Diet overlap was high between common shiner and cutlip minnow (Morisita's index = 0.88) and moderate between fallfish and common shiner (0.54) and fallfish and cutlip minnow (0.50). Diel temperal variation in diet composition was greatest (0.64) for spottail shiner. Three species exhibited diel variation in food consumption. Fallfish had a distinct feeding peak, whereas peak food consumption of common shiner and cutlip minnow occurred over a more extended period. Spottail shiner did not have a distinct f...

Seasonal dietary shifts and food resource exploitation by the hog badger (Arctonyx collaris) in a Chinese subtropical forest

Spatial and temporal fluctuations in the availability of food resources can affect adaptive foraging strategies substantially, with the potential to promote temporal dietary switching and specialisation among generalist carnivores. To understand this relationship better at the causal level, we examined spatial and temporal variation in diet composition and diversity in the hitherto little-known hog badger (Arctonyx collaris), in comparison to the environmental abundance of principal food resources, in a subtropical forest of central China. Here, hog badgers fed predominantly on earthworms and fruits, complemented with arthropod imagoes and invertebrate larvae, whereas vertebrate prey categories (mammals, birds and reptiles) were consumed infrequently. We observed strong seasonal variation in the consumption of different food categories. Earthworms predominated during spring, fruits in autumn, and earthworms, complemented by arthropods, in summer, with hog badgers apparently hibernating in winter. Fluctuation in dietary preferences between seasons and habitats correlated only partially with environmental food abundance; in autumn, when fruit abundance peaked, and despite a concomitant peak in earthworm abundance, hog badgers exhibited a dietary shift, indicating a preference for fruit, over earthworms. This resulted in autumnal minima in seasonal food niche breadth and evenness values. We conclude that, in this region, hog badgers exhibited a generalist diet but switched between food categories in response to changes in environmental seasonal abundance.

Diet of the Bannan CaecilianIchthyophis bannanicus(Amphibia: Gymnophiona: Ichthyophiidae) in the Mekong Delta, Vietnam

Abstract Ichthyophis bannanicus is a terrestrial caecilian, and little is known about many aspects of the ecology of this species. We investigated the correlation between diet and body size, spatiotemporal variation in dietary composition, diversity index of prey, and size dimorphism among populations for this species. Specimens (N = 135) were collected from May 2010 to April 2011 in the Mekong Delta, Vietnam. We found 178 prey items representing 11 unique families and discovered that the diet of I. bannanicus is composed mainly of small prey; the most important were Achatinidae, Lumbricidae, and Formicidae, with a combined importance index of 77%. Diet composition, prey size, and total prey volume in I. bannanicus changed between dry and rainy seasons and among regions (P < 0.001). Mean prey volume increased with body size and showed positive correlations (P < 0.001) between total length and mouth width and prey size consumed. The total dietary breadth of I. bannanicus was 4.52, and all six populations o...

Variation in diet composition during the breeding cycle of an Antarctic seabird in relation to its breeding chronology and that of its main food resource

This work had two aims related to the diet of brown skuas (Stercorarius antarcticus lonnbergi) breeding at Laurie Island (South Orkney Islands, Antarctic). The first aim was to explore whether there are changes throughout the breeding season. The second aim was to determine whether those changes relate to differences in food resource availability of their main prey, penguins, at different time periods of the penguins’ breeding cycles, or to different moments of the skuas breeding cycle, which may variably restrict the foraging activities of parents. Diet was analyzed from pellet samples grouped in two different ways. They were grouped in three periods defined for the skuas breeding cycle (laying and incubation; early parental care; later parental care), or the pellets were assigned to five periods based on the type of food resources available at the penguin colonies (eggs; eggs and small chicks; small and large chicks; large and fledged chicks; fledged chicks). A temporal variation in diet composition was evident from the analysis of contingency tables for both sample grouping methods. The more represented item in every period for both analyses was adult penguins, which may be related to the proposed cleaning function of the gut of penguin feathers. Both ways of grouping the samples suggest a relationship between the kind of resources available at the penguin colonies and the easiness of delivering them to the skuas chicks, reflected in a successive predominance of use of penguin eggs first and of penguin chicks and other birds later.

Diet of the Little Owl (Athene noctua) during the pre-reproductive period in a semi-arid Mediterranean region

The assessment of feeding conditions and variations in diet composition over the pre-breeding period of birds plays a keyrole in the understanding of reproductive performance. Pellets regurgitated by the Little Owl, Athene noctua, were collected from Boulhilet (Batna, north-east Algeria). The analysis of 48 pellets resulted in the identification of 471 prey-items of 38 different species classified into 6 classes, 7 orders, 21 families, and 35 genera. Although the diet of the Little Owl mainly consists of arthropods, it is highly diverse (Food Niche Breadth = 14.5, Shannon index = 4.4 bits). Insects are made up 90% of the consumed food; however, they accounted only for 8% of the total biomass. Small mammal prey constituting a rich source of energy during the pre-breeding period, when other kinds of prey are not available due to cold conditions, made up 72% of the diet biomass. We found no significant variation in rodents as a component (number of prey-individuals, biomass, and prey-species richness, prey-s...

Seasonal diets of red foxes in a boreal forest with a dense population of moose: the importance of winter scavenging

In Scandinavia, an increased red fox Vulpes vulpes density during the last decades has been suggested to be caused by direct and indirect human influences on food availability. Recently, attention has been focused on the role of increasing scavenging opportunities due to intensified hunting of ungulates and the reestablishment of large carnivores. In our study, we investigated seasonal and annual variations in diet composition of red fox in Varaldskogen, SE Norway, an area with cyclic voles and a high density of moose Alces alces. Analyses of scats revealed significant differences among seasons in the occurrence of ungulates—mainly moose—and ungulates were the dominating food category during winter (44.9 % of all remains). Snow tracking of red fox (71 km) in winter confirmed the importance of ungulate carcasses, i.e. one case of scavenging per 3 km. The proportions of voles were high during all seasons (11.2–28.8 %); in spite of variation in available abundances, no significant seasonal or annual differences were detected. Other food categories with seasonal variation were birds, berries/seeds and amphibians/reptiles, all more common in snow-free seasons. Our study underlines the importance of ungulate remains during periods when the abundance and diversity of alternative food sources is low. Increased and stabilized populations of red foxes—mediated through remains from hunting and wolf kills from high moose populations—might have an important effect on the population dynamics of small game. Hence, we recommend that this relationship be given attention in future studies.

Feeding habits of Kammal thryssa Thryssa kammalensis (Bleeker, 1849) in the coastal waters of Gadeok-do, Korea

The feeding habits of Thryssa kammalensis was studied using 430 specimens collected from October 2010 to September 2011 in the coastal waters of Gadeok-do, Korea. T. kammalensis in the coastal waters of Gadeok-do was carnivorous predator and planktonic feeder with a wide variety of prey items such as arrowworm, copepods, crab larvae, shrimp larvae, and fish eggs. In addition, T. kammalensis consumed mainly arrowworm, copepods, crab larvae, shrimp larvae, fish eggs, and the diet also included small quantities of cladocerans, amphipods, bivalve larvae, mysids, and euphausiids. On the other hand, the body length (BL) of T. kammalensis specimens ranged from 5.9 to 15.1 cm. Size-related variations in dietary composition of T. kammalensis were not significant that overlap indexes of each major food items that showed very high values in all size classes, representing more than 0.80. Arrowworms were the dominant prey item in all sizes, and copepods were the next most frequent prey item consumed in all size classes. Seasonal changes in dietary composition of T. kammalensis were significant. However, overlap indexes of each major food items in some season showed very high values of 0.80 (between spring and winter) and 0.85 (between summer and autumn). Copepods were most frequently eaten in the spring and winter. Moreover, arrowworm were the dominant prey item in summer and autumn. Mean numbers of prey per stomach (mN/ST) changed significantly with size groups (P < 0.05), but mean wet weight of preys per stomach (mW/ST) showed an opposite tendency (P > 0.05).

How important are seabirds in the diet of black rats on islands with a superpredator?

This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats.

Variation in Prey Delivered to Common Black-Hawk (Buteogallus anthracinus) Nests in Arizona Drainage Basins

Abstract Understanding how raptor diets vary across local and regional scales can be important when human actions have the potential to alter prey abundances. We combined data on prey delivered to 16 Common Black-Hawk (Buteogallus anthracinus) nests in three tributaries of the Verde River, Arizona, in 2008 and 2009 with similar data reported previously (1994) for three other Arizona drainage basins to better understand variation in diet composition within and across drainage basins. Within the three drainage basins studied in 2008 and 2009, nests clustered into two groups: those along Fossil Creek, where fish and amphibians were common, and those in Wet Beaver and Oak Creek drainage basins, where reptiles and nonnative crayfish were more abundant. When data from all six drainage basins were combined, drainage basins again clustered into two groups, with prey deliveries in one cluster dominated by fish and amphibians and in the other cluster by reptiles. These results confirm the opportunistic nature of pr...

Mitochondrial activity, hemocyte parameters and lipid composition modulation by dietary conditioning in the Pacific oyster Crassostrea gigas

Several parameters can affect membrane lipid composition in bivalves, including diet. Although two fatty acids (FA) 22:6n-3 and 20:5n-3 are essential membrane components, they are sparingly synthesized by bivalves and must be obtained from their diet. Here, effects of dietary modifications of membrane lipid composition were studied at both cellular and subcellular levels in the oyster Crassostrea gigas. To this end, we compared oysters fed two monoalgal diets that differed markedly in their FA composition and a mix of both. As expected, algae impacted phospholipids, in particular 22:6n-3 and 20:5n-3, reflecting differences of dietary microalgae FA composition. Meantime, total saturated FA, total monounsaturated FA, total polyunsaturated FA and total non-methylene-interrupted FA varied little and phospholipid class composition was only slightly affected by diets. Measures made in hemocytes indicated that only mitochondrial membrane potential was affected by diets. Total ROS production as well as mitochondrial superoxide production did not differ with diet. There was no difference in phosphorylating (state 3) and non-phosphorylating (state 4) rates of oxygen consumption rates or in cytochrome c oxidase activity of mitochondria isolated from gills between the three diets. Similarly, neither cytochromes a, b, c or c1 content nor citrate synthase activities were changed, suggesting that number and morphology of mitochondria were not affected by dietary treatment. These results suggest that oysters could possess high homeostatic capabilities, at both cellular and subcellular levels, to minimize the effect of dietary FA and related membrane lipid FA modifications on mitochondrial functions. These capabilities could be a means to face variations in diet composition in their natural environment and to preserve important oyster physiological functions such as growth and reproduction.

Constancy and change in marine predator diets across a shift in oceanographic conditions in the Northern California Current

Variable ocean conditions can greatly impact prey assemblages and predator foraging in marine ecosystems. Our goal was to better understand how a change in ocean conditions influenced dietary niche overlap among a suite of midtrophic-level predators. We examined the diets of three fishes and one seabird off central Oregon during two boreal summer upwelling periods with contrasting El Nino (2010) and La Nina (2011) conditions. We found greater niche specialization during El Nino and increased niche overlap during La Nina in both the nekton and micronekton diet components, especially in the larger, more offshore predators. However, only the two smaller, more nearshore predators exhibited interannual variation in diet composition. Concurrent trawl surveys confirmed that changes in components of predator diets reflected changes in the prey community. Using multiple predators across diverse taxa and life histories provided a comprehensive understanding of food-web dynamics during changing ocean conditions.

Comparison of Diet Among Reintroduced and Wild Juvenile Alligator Snapping Turtles (Macrochelys temminckii) and Adult Female Ouachita Map Turtles (Graptemys ouachitensis)

Abstract Reintroductions are increasingly utilized in conservation, but the experiences and environments to which animals are exposed prior to release can significantly impact the success of such efforts. We investigated differences in the diet of reintroduced juvenile alligator snapping turtles (Macrochelys temminckii) relative to juveniles from a wild population. In addition, we compared the diet of adult female Ouachita map turtles (Graptemys ouachitensis) to reintroduced M. temminckii with whom co-occurrence was recently reestablished and wild juvenile M. temminckii in a river system where the species have enjoyed long-term sympatry. There were differences in diversity and richness of the diet of M. temminckii at the two study sites that could be due to dissimilarity in foraging experience. There was greater overlap in diet of M. temminckii and G. ouachitensis at the site of reintroduction than at the site of long-term sympatry that corresponded to variation in composition of diet. Such a difference c...

Diet and prey selectivity of the red mullet, Mullus barbatus (Pisces: Mullidae), from the southern Tyrrhenian Sea: the role of the surf zone as a feeding ground

The diet and prey selectivity of the red mullet, Mullus barbatus, on a sandy bottom of the Tyrrhenian Sea were examined, in respect of season, size and depth, focusing on the use of the surf zone as a feeding ground. Stomach contents of 99 specimens collected by beach seine (in the surf zone) and 568 specimens collected by trawl net (at 10, 20 and 30 m depths) were analysed. The overall diet of M. barbatus was dominated by crustaceans, mainly gammarids, while molluscs and polychaetes are secondary prey taxa. The diet composition of red mullet at each specific depth was related to the availability of prey in the benthic community: mysids were mostly preyed on in the surf zone, while gammarids, decapods and copepods were the principal crustacean prey organisms at other investigated depths. Red mullet in the surf zone mainly preyed on mysids and bivalves in summer and on cumaceans, gammarids and polychaetes in winter. At the other depths, seasonal variation in diet composition reflected the fluctuations of gammarid abundance in the environment; no differences in diet by size were detected. As a result, M. barbatus in the southern Tyrrhenian Sea can be considered as an opportunistic predator of benthic organisms, relying predominantly on crustaceans.

Fish diet composition in floodplain lagoons of an Australian dryland river in relation to an extended dry period following flooding

Floodplain rivers worldwide are threatened by loss of connectivity to their floodplains and hence reduced benefits from floodplain energy subsidies. Dryland rivers with ‘boom and bust’ ecological responses to flooding and extended dry periods may be particularly vulnerable. This paper describes variations in dietary composition of three fish species of contrasting trophic position in dryland floodplain lagoons with variable flood inundation and drying histories. The study species were Ambassis agassizii - a microphagic carnivore, Leiopotherapon unicolor - a carnivore/omnivore, and Nematalosa erebi - an algivore/detritivor. Despite the range of food items recorded in fish guts, each species fed mostly on relatively few food categories and few food items within each category. Most of the spatial (i.e. among lagoons) and temporal dietary variation was associated with different proportional contributions of these food items. Given the absence or low magnitude of flooding during the study period, temporal changes in diets of the three species are probably the result of successional changes in composition of invertebrate prey as the dry season progressed. The focus of each fish species on relatively few food categories and a few reliable food items within each category may be the most profitable foraging strategy when food resources are limiting in progressively drying floodplain lagoons.

Diel variation in summer habitat use, feeding periodicity, and diet of subyearling Atlantic salmon in the Salmon River Basin, New York

The habitat use, diet composition, and feeding periodicity of subyearling Atlantic salmon (Salmo salar) was examined during both day and night periods during summer in tributaries of Lake Ontario. The amount of cover used was the major habitat variable that differed between day and night periods in both streams. At night subyearling Atlantic salmon were associated with significantly less cover than during the day. Principal Component Analysis showed that habitat selection of subyearling Atlantic salmon was more pronounced during the day in both streams and that salmon in Orwell Brook exhibited more diel variability in habitat use than salmon in Trout Brook. Subyearling salmon fed primarily from the benthic substrate on baetids, chironomids, and leptocerids. There was a substantial amount of diel variation in diet composition with peak feeding occurring from 0400h to 0800h on July 21–22, 2008.