Variation In Diet Composition Research Articles

Spatial analyses of the influence of autocorrelation on seasonal diet composition of a marine fish species

Spatial autocorrelation is common in environmental factors, species distributions, and predator-prey interactions. Spatially autocorrelated distribution of prey and strong prey selectivity by predators may cause spatial autocorrelation of the fish diet shown as higher similarity among diets of fish caught nearby or in the same trip. We explore the importance of spatial autocorrelation analysis in understanding the fish diet composition and predator-prey interaction in diet analysis based on one example fish whitespotted conger (Conger myriaster) in the Yellow Sea and its prey species that have been monitored across seasons. Among the spatial estimators, the cluster-based estimator is used to quantify fish diet similarity from the same trip, and the spatial Gaussian and exponential autocorrelated estimators are used to test the hypothesis that fish diet similarity decreases over distance. The two types of spatially autocorrelated estimators performed better than spatially-independent and cluster-based estimators, with lower mean square errors in a cross-validation procedure. Prey selectivity related to the prey availability, and the spatial overlap between predator and prey were likely important factors affecting seasonal and spatial variations in diet composition of the example fish species. Cross-variograms indicated that whitespotted conger and some of its dominant prey species were positively spatially autocorrelated, which suggested fishes generally aggregated in areas of high prey density. Our study provides a practical basis for considering the effect of spatial characteristics in quantifying the diet composition likely linked to the environmental driven distributions of both fishes and their prey.

Diet Segregation between Sexes by a Gregarious Greater Antillean Bat, Phyllonycteris poeyi (Chiroptera: Phyllostomidae)

Phyllonycteris poeyi is endemic to Cuba and Hispaniola in the Greater Antilles, and it is among the most common and widespread bats of the Cuban archipelago. This species is an obligate cave dweller and forms the largest aggregations of bats found in Cuban caves; and could be considered a hot cave specialist. This high gregariousness could increase intraspecific competition of food resources. In this study, we examined the diet of P. poeyi at Cueva de los Majaes located in Baconao Biosphere Reserve in the southeastern region of Cuba. We hypothesized sexual diet variation as a way to reduce intraspecific competition. We estimated the percentage volume and frequency of occurrence of different food categories consumed by both sexes, using faecal analysis. Throughout the year, the diet of P. poeyi is a combination of fruits, pollen and insects; fruits of at least 17 plant species and flowers of five species are used by P. poeyi and the most frequent items were pollen of Roystonea regia and fruits of Piper aduncum and Piper umbellata. Insects occurred in the faeces of both sexes and their frequency and volume were low and did not differ between sexes. Although both sexes fed on similar food categories, we found significant variation in diet composition between sexes. Throughout the year, the majority of females mainly consumed fruits while males had preference for floral resources. We did not find differences in the sexes-reproductive season interaction, therefore the differences could not be attributed to changes associated to reproduction energetics. The average volume of fruits and pollen consumed by females were independent of the reproductive season, only significant differences were found in the consumption of insects, being the highest during the reproductive season. We conclude that this dietary partitioning behaviour between sexes of P. poeyi may be a strategy to maintain a high year-round gregariousness that could be critical to the viability of their large colonies in Cuban caves.

Varied diets, including broadleaved forage, are important for a large herbivore species inhabiting highly modified landscapes

Diet quality is an important determinant of animal survival and reproduction, and can be described as the combination of different food items ingested, and their nutritional composition. For large herbivores, human landscape modifications to vegetation can limit such diet-mixing opportunities. Here we use southern Sweden’s modified landscapes to assess winter diet mixtures (as an indicator of quality) and food availability as drivers of body mass (BM) variation in wild moose (Alces alces). We identify plant species found in the rumen of 323 moose harvested in Oct-Feb, and link variation in average calf BM among populations to diets and food availability. Our results show that variation in calf BM correlates with variation in diet composition, diversity, and food availability. A varied diet relatively rich in broadleaves was associated with higher calf BM than a less variable diet dominated by conifers. A diet high in shrubs and sugar/starch rich agricultural crops was associated with intermediate BM. The proportion of young production forest (0–15 yrs) in the landscape, an indicator of food availability, significantly accounted for variation in calf BM. Our findings emphasize the importance of not only diet composition and forage quantity, but also variability in the diets of large free-ranging herbivores.

Flexible feeding patterns of copepod Centropages tenuiremis in fluctuating conditions: a possible survival strategy to cope with disturbance

Centropages tenuiremis is a species with a wide distribution range in disturbed coastal waters. However, due to a lack of dietary information, it remains unclear as to how they maintain such dominance in fluctuating conditions. In this study, C. tenuiremis was collected from the Daya Bay Nuclear Power Plant both in inlet and outfall regions at 06:00, 12:00 and 18:00 on April 27, 2011 and their in situ diet was analyzed using a PCR protocol targeting 18S ribosomal genes. Thirty-four species of prey organisms were identified totally, including Dinophyta, Baciliariophyta, Viridiplantae, Rhizaria, Apicomplexa, Chordata, Mollusca, Arthropoda and Fungi, indicating an obvious omnivorous feeding habit of C. tenuiremis. Centropages tenuiremis obviously exhibited spatial and temporal variations in diet composition. More plant prey (land plants and phytoplankton) were consumed in the morning (~50%), while more animal prey (metazoans and protozoans) were ingested at midday and night (60%–70%). Furthermore, a more diverse diet was detected in the outfall region (10–11 taxa), where the temperatures were relatively higher and more fluctuating, than in the control region (5–10 taxa). This finding indicated that C. tenuiremis could potentially expand its food spectrum under stressful condition. Specifically, C. tenuiremis exhibited phytoplankton preference (58.62%–67.64%) in the outfall region with a lower omnivory index (0.27–0.35) than in the control region (0.51–0.95). However, phytoplankton density was lower than that in the control region, suggesting a possible herbivorous tendency of C. tenuiremis under elevated temperatures to balance the energy acquirement and feeding effort. The flexible food choices of C. tenuiremis observed here could effectively buffer environmental fluctuations and might be an important survival strategy in coastal ecosystems.

Adaptations to prey base in the hypercarnivorous leopard cat Prionailurus bengalensis

Investigating biogeographical variations in diet composition can help understand the adaptability and generalism of species. Although the dietary adaptability of omnivorous mesocarnivores is well established, far less work has explored how more specialist hypercarnivores optimise their diets. By reviewing 11 studies of the leopard cat (Prionailurus bengalensis), we quantitatively examined how dietary composition varies over the wide range of biomes they occupy in Asia. Specifically, we contrasted the diet of the Iriomote Island sub-species (south-western Japan), where native rodents are absent, with that of the mainland. Leopard cat diet typically comprised mammals, birds, amphibians, reptiles, and invertebrates. In Iriomote Island, however, the low relative frequency of occurrence of small mammals (only introduced rats) was compensated by higher frequencies of reptiles and amphibians compared to the mainland. Consequently, trophic diversity and dietary niche breadth were higher for leopard cats in Iriomote Island than for the mainland. This shows that even hypercarnivorous species can use trophic plasticity to adapt to local prey availability. Given that rodent numbers often fluctuate substantially over time, the availability of alternative prey, such as herptiles, may be vital for the conservation of the leopard cat, and especially the critically endangered Iriomote cat. More generally, the trophic versatility of hypercarnivores must be considered when assessing their vulnerability to environmental change.

Temporal Measures in Cardiac Structure and Function During the Development of Obesity Induced by Different Types of Western Diet in a Rat Model.

Obesity is recognized worldwide as a complex metabolic disorder that has reached epidemic proportions and is often associated with a high incidence of cardiovascular diseases. To study this pathology and evaluate cardiac function, several models of diet-induced obesity (DIO) have been developed. The Western diet (WD) is one of the most widely used models; however, variations in diet composition and time period of the experimental protocol make comparisons challenging. Thus, this study aimed to evaluate the effects of two different types of Western diet on cardiac remodeling in obese rats with sequential analyses during a long-term follow-up. Male Wistar rats were distributed into three groups fed with control diet (CD), Western diet fat (WDF), and Western diet sugar (WDS) for 41 weeks. The animal nutritional profile and cardiac histology were assessed at the 41st week. Cardiac structure and function were evaluated by echocardiogram at four different moments: 17, 25, 33, and 41 weeks. A noninvasive method was performed to assess systolic blood pressure at the 33rd and 41st week. The animals fed with WD (WDF and WDS) developed pronounced obesity with an average increase of 86.5% in adiposity index at the end of the experiment. WDF and WDS groups also presented hypertension. The echocardiographic data showed no structural differences among the three groups, but WDF animals presented decreased endocardial fractional shortening and ejection fraction at the 33rd and 41st week, suggesting altered systolic function. Moreover, WDF and WFS animals did not present hypertrophy and interstitial collagen accumulation in the left ventricle. In conclusion, both WD were effective in triggering severe obesity in rats; however, only the WDF induced mild cardiac dysfunction after long-term diet exposure. Further studies are needed to search for an appropriate DIO model with relevant cardiac remodeling.

Ontogenetic variation in the diet of the anuran community from a semi-arid environment in the southeastern Chihuahuan Desert.

Although ontogeny influences dietary composition and trophic niche breadth in many anurans, its effects on diet have been little analyzed in sympatric species. In this study, we analyzed interspecific and ontogenetic variation in dietary composition and trophic niche width in an anuran community from a semi-arid environment. We found a more profound effect of species identity than body size on dietary composition, with the diet of four species dominated by formicids, that of two others by coleopterans and formicids, and that of the remaining species not dominated by specific prey types. We found ontogenetic changes in dietary composition in three of four species analyzed, in which consumption of some small insects decreased as predator size increased, regardless of species. Additionally, we did not find ontogenetic change in prey number consumed in any of the four species, but prey size increased with increasing predator size in all of them. Most species exhibited a narrow trophic niche, which was even narrower in adults in three of the four species analyzed. Costello’s modified plots revealed a high variation among individuals in termite consumption in Anaxyrus punctatus, and in more prey types in Spea multiplicata. Our results suggest that this community is not size-structured, and that ontogenetic diet shifts are mainly caused by passive sampling toward prey of different sizes. Finally, comparisons with previous data revealed an interpopulation pattern, in which trophic niche width contracts as aridity increases, possibly because of an increase in interspecific competition for trophic resources.

Dietary specialization depending on ecological context and sexual differences in Asiatic black bears.

The food habits of the Asiatic black bear (Ursus thibetanus) are well studied, but there is a little evidence of dietary specialization—that is, when individuals use a narrower set of resources compared to the population as a whole. To examine the dietary composition at the individual level, seasonal patterns of dietary specialization, and sex-based dietary differences in Asiatic black bears, we attached Global Positioning System (GPS) collars to 15 Asiatic black bears and collected their scats in Nagano Prefecture, Japan from 2017 to 2018. Our results showed that the dietary composition differed among individuals, although seasonal changes in dietary composition were observed at the population level. Dietary specialization was high in summer (resources less abundant) and low in spring and autumn (resources more abundant), indicating a relationship with general food abundance and the dietary diversity of bears. In spring, all bears consumed green vegetation and/or seed of Fagaceae family from previous autumn; in early- and late- summer, dietary composition, such as green vegetation, insects, and fruits, greatly differed among individuals. In autumn, most bears heavily depended on seeds of Fagaceae which is high-quality food for bears.Although we did not find statistical differences between sexes in terms of dietary specialization and diversity, we found variations in the timing of feeding on the Fagaceae family, being earlier in females compared with males. We also found considerable variation in dietary composition within sexes, suggesting that dietary specialization depends on multiple factors besides food abundance, food diversity, and sex.

Evaluation of 15N and purine bases as microbial markers to estimate ruminal bacterial nitrogen outflow in dairy cows

The present study aimed to evaluate 15N and purine bases (PB) as markers for ruminal bacterial nitrogen (N) outflow in dairy cows. Additionally, the effects of calcium salts of fatty acids (CSFA) in diets with different levels of rumen degradable protein (RDP) on PB omasal flow, urinary recovery of purine derivatives (PD), and endogenous excretion of PD were evaluated. Eight ruminal cannulated Holstein cows, with 207 ± 23.6 (mean ± SD) days in milk, 618 ± 39.0 kg of body weight, and 33.4 ± 2.45 kg/d of milk yield were used in a replicated 4 × 4 Latin square design. Four treatments were arranged in a 2 × 2 factorial design to evaluate the following factors: CSFA addition [-CS: basal diet without CSFA; and + CS: with 33.2 g/kg dry matter (DM) of CSFA]; and the level of RDP (LRDP: low RDP, with 98 g/kg DM of RDP; and HRDP: high RDP, with 110 g/kg DM of RDP). Particle-associated bacteria (PAB) showed lower (P ≤ 0.008) 15N enrichment and purine N to total bacterial N ratio than liquid associated bacteria (LAB). Increasing RDP concentration reduced (P = 0.007) 15N enrichment and tended (P ≤ 0.095) to reduce PB concentration in bacterial pellets. Purine bases overestimated (P ≤ 0.002) LAB-NAN and total microbial flow but, regarding PAB-NAN flow, there was a trend of interaction (P = 0.067) between marker and fat supplementation effects. In the absence of fat supplementation, PB underestimated (P ≤ 0.05) the flow of PAB-NAN compared to 15N and failed to detect the negative effect of fat supplementation evidenced by 15N labeling. Omasal PB flow tended to increase (P = 0.061) in low protein degradability diets, but PD excretion was constant (322 ± 5,9 mmol/d, mean ± SE) regardless of diet and, as a result, urinary recovery of PB decreased (P = 0.007). Daily excretion of creatinine and endogenous PD was also unaffected by the diet and averaged 0.262 mmol/kg BW and 0.640 mmol/kg BW0.75, respectively. In conclusion, the response of PB and its urinary derivatives to variation in diet composition compared to 15N reveals their weaknesses in the estimation of microbial synthesis.

Hábitos alimenticios del sable Trichiurus lepturus en el Golfo de Urabá, Caribe colombiano

Se estudiaron los hábitos alimenticios del pez comercial Trichiurus lepturus, un mesodepredador con un papel importante en el flujo de energía en las redes tróficas costeras, con el objeto de contribuir al conocimiento de su ecología, herramienta para su conservación e insumo para el ordenamiento pesquero del Golfo de Urabá, en el noroeste de Colombia. Usando redes de enmalle se capturaron 320 individuos, de los que se obtuvieron 208 estómagos con contenido. El espectro alimenticio de la especie está integrado por 26 ítems, pertenecientes a tres grandes grupos taxonómicos: peces, crustáceos y moluscos. Entre estos, los engráulidos (Engraulidae) son el principal componente en todos los sitios de muestreo, sobresaliendo Centengraulis edentulus y varias especies del género Anchoa. Se encontró un traslape de presas entre los sitios, siendo evidente la importancia de las áreas de manglar para alimentación. Sin embargo, no hubo variación estacional ni diferencias entre sexos en la composición de la dieta, dado que los engráulidos, su principal presa, son uno de los recursos pesqueros más abundantes en el Caribe colombiano.

Nutritional composition of the diet of the western gorilla (Gorilla gorilla): Interspecific variation in diet quality.

To meet nutritional needs, primates adjust their diets in response to local habitat differences, though whether these dietary modifications translate to changes in dietary nutrient intake is unknown. A previous study of two populations of the mountain gorilla (MG: Gorilla beringei) found no evidence for intraspecific variation in the nutrient composition of their diets, despite ecological and dietary differences between sites. One potential explanation is that nutritional variability in primate diets requires greater ecological divergence than what was captured between MG sites, underpinning environmental differences in the nutrient quality of plant foods. To test whether Gorilla exhibits interspecific variation in dietary composition and nutrient intake, we studied the composition and macronutrients of the western gorilla (WG: Gorilla gorilla) staple diets and compared them with published data from the two MG populations. We recorded feeding time and food intake of four adult female WGs from one habituated group over a period of 11 months (December 2004-October 2005) at the Mondika Research Center, Republic of Congo, allowing for assessment of seasonal patterns of nutrient intake. Staple diets of WGs and MGs diverged in their dietary and macronutrient composition. Compared to MGs, the staple diet of WGs (by intake) contained higher proportions of fruit (43%) and leaf (12%) and a lower proportion of herb (39%), resulting in a higher intake of total nonstructural carbohydrate and fiber and a lower intake of crude protein. Staple gorilla fruits and herbs differed in nutrient quality between sites. Gorillas exhibit nutritional flexibility that reflects ecological variation in the nutrient quality of plant foods. Since dietary quality typically affects rates of growth and reproduction in primates, our results suggest that interspecific differences in nutrient intake and food quality may shape differences in gorilla nutrient balancing and female life history strategies.

Blubber fatty acids reveal variation in the diet of male Australian fur seals

Top-order predators play an important role in the structure and function of marine ecosystems. Optimal foraging theory predicts that predators will utilise foraging strategies that maximise their net energetic intake, and consequently, individuals within a population may utilise alternate strategies to target different prey resources. The present study investigated variation within the diet of 41 male Australian fur seals (Arctocephalus pusillus doriferus) using quantitative fatty-acid signature analysis (QFASA) of blubber. The study was conducted during the pre-breeding seasons of 2012 and 2013 and the non-breeding seasons of 2013 and 2014 at a colony on Kanowna Island (39°10′S, 146°18′E) in northern Bass Strait, southeastern Australia. QFASA models revealed that while males consumed prey commonly reported within the diet of Australian fur seals, elasmobranchs were more important than previously reported. Prey composition also varied between males which may reflect individuals using different strategies to target different resources, which ultimately broadens the trophic niche of a species and reduces intra-specific competition. Furthermore, substantial temporal variation in male diet was apparent presumably reflecting variation in the distribution, availability, and abundance of prey resources within Bass Strait at the time of sampling. Given that the energetic content of prey is expected to differ between species, temporal variation in dietary composition presumably has important implications for the growth and reproductive success of males.

Dietary composition and selection in the stream-breeding anuran assemblage from a tropical wet forest in eastern Mexico

In this study, we analyzed seasonal variation in dietary composition and diversity, structure along the trophic axis, and prey selection in a stream-breeding anuran assemblage from Mexico. It is composed of four morphologically diverse species: three strictly arboreal (Hyalinobatrachium fleischmanni, Ptychohyla zophodes, and Rheohyla miotympanum) and one that occupies several microhabitats (Lithobates vaillanti). Dietary composition did not differ between seasons, but it differed among the four species. Araneae, Orthoptera, Homoptera, and Lepidoptera (adults) were the prey that accounted for most of the variation. Dietary diversity was higher in the dry than in the rainy season in L. vaillanti, and was higher in this species than in the other three. In the dry season, arthropods were more abundant but less diverse in the environment, and L. vaillanti and R. miotympanum consumed less prey than in the rainy season. Furthermore, we detected that the frog assemblage was nonrandomly structured only in the dry season. Hyalinobatrachium fleischmanni strongly selected Homoptera and Orthoptera, but did not select prey by their size within the size range consumed. Ptychohyla zophodes and R. miotympanum strongly selected Lepidoptera (adults and larvae) and selected their prey by their size in the dry season. Our results overall suggest that interspecific competition could be a strong force in shaping type and quantity of food consumed between the two hylids. Additionally, we found a wider array of microhabitats used and prey types consumed than previously reported for L. vaillanti. Lastly, the relatively specialized diet of the three strictly arboreal species, and their selection towards insects sensitive to habitat changes (homopterans and lepidopterans), make them particularly vulnerable to changes in arthropod communities.

Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics

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 619:137-147 (2019) - DOI: https://doi.org/10.3354/meps12949 Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics Svein-Håkon Lorentsen1,*, Jenny Mattisson1, Signe Christensen-Dalsgaard1,2 1Norwegian Institute for Nature Research, 7485 Trondheim, Norway 2Department of Biology, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway *Corresponding author: shl@nina.no ABSTRACT: Seabird populations have declined worldwide, and several of the potential threats are of anthropogenic origin. To understand how changes in seabird populations relate to environmental conditions it is important to know the functional relationships between prey availability and foraging behaviour, prey choice and breeding performance over several years. This was studied by linking breeding success of European shag Phalacrocorax aristotelis to variation in diet composition, and investigating the underlaying mechanism driving this variation, primarily based on behavioural costs associated with foraging, such as foraging range and diving effort. We obtained demographic data and foraging trip metrics (using GPS-loggers and time-depth recorders) from a shag colony at Sklinna, Central Norway, during the 2011-2016 breeding seasons. Breeding population size was closely and positively correlated with breeding success, which in turn was positively correlated with the proportion of saithe Pollachius virens in the diet. When the dietary proportion of uncommon prey species increased, breeding success decreased. Breeding success was negatively influenced by increasing distance travelled and accumulated dive depths on an annual basis. Summed dive depths were greatest when prey species other than saithe dominated the diet. We found that in years with low availability of saithe fewer shags bred, and those that did had lower breeding success. This indicates that in years with poor feeding conditions, there might not be sufficient resources in the foraging area to support the whole breeding population of shags. KEY WORDS: Phalacrocorax aristotelis · Seabird diet · Saithe · Pollachius virens · Foraging range · Trip length · Dive depth Full text in pdf format Supplementary material PreviousNextCite this article as: Lorentsen SH, Mattisson J, Christensen-Dalsgaard S (2019) Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics. Mar Ecol Prog Ser 619:137-147. https://doi.org/10.3354/meps12949 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 619. Online publication date: June 04, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

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.

Spatial variation in trophic structure of nearshore fishes in Lake Michigan as it relates to water clarity

Nearshore water clarity, as measured by remotely sensed Kd(490), and stable C and N isotopes of several nearshore fishes differed across the Lake Michigan basin. Values of δ13C of round goby (Neogobius melanstomus), yellow perch (Perca flavescens), and spottail shiner (Notropis hudsonis) were depleted in the southeast where water clarity was low relative to the southwest where water clarity was greater. Bayesian analyses were used to evaluate spatial variation in diet composition and quantify the relationship between water clarity and the proportional importance of pelagic energy in fish diets. Water clarity in nearshore areas is likely related to variable riverine inputs, resuspension, and upwelling processes. While these processes may not directly impact δ13C or δ15N of nearshore fishes, we hypothesize that water clarity differentially affects benthic and pelagic algal production. Lower water clarity in the benthos and subsequently lower benthic productivity may be related to regional diet differences and increased reliance on pelagic energy sources. Mobile fishes such as alewife (Alosa pseudoharengus) may not be in isotopic equilibrium with regional prey sources and depart from spatial patterns observed in other nearshore fishes.

Variation in the diets of Japanese martens Martes melampus

Abstract We reviewed dietary data in the literature for Japanese martens Martes melampus from 21 study sites covering the entire geographic range of the species, tested for differences in the diets of martens in evergreen and deciduous forests, and described variation in main diets and dietary diversity in relation to geographical and environmental variables. Fruits, mammals, and insects occurred at the highest frequencies in faeces throughout the species’ range. Mammal prey items and non‐fruits were detected less frequently in scats collected in evergreen forests than in deciduous forests, while non‐fruits were detected more frequently in evergreen forests. Three environmental variables (mean temperature, variation in the normalised difference vegetation index [NDVI], and snow depth) had significant effects on variation in dietary composition, but the relative contribution of each variable varied among food items. Geographical variables, on the other hand, had no significant effects on variation in dietary composition. Mean temperature explained the variation in insect feeding, which increased in forests with moderate temperature. Snow depth explained the variation in feeding on non‐insects and other vertebrates; the former increased in forests with lower snow depth, while the latter increased in forests with higher snow depth. Variation in NDVI, on the other hand, had no effect on variation in feeding on a specific dietary category. The snow depth had a significant effect on the variation in dietary diversity, which became lower in forests with moderate snow depth. The high plasticity in the dietary composition and dietary diversity might represent a behavioural trait acquired by Japanese martens to allow them to expand their range into various forests with different food availabilities. When studying the variation in feeding behaviour of omnivorous carnivores, multiple environmental variables need to be considered equally.

Diet Composition and Breeding Success of the Black-Winged Kite on the Lleida Plains in Relation to Population Size

We monitored the number of pairs and the diet of Black-winged Kite Elanus caeruleus on the Lleida Plains (Catalonia, NE Spain) from 1998 to 2012. We examined the diet by means of pellet analysis. Nesting was irregular with peak numbers in some years (2009-2010). We found a positive relationship between the percentage of rodents in the diet and breeding success, an inverse relationship between dietary breadth and breeding success, a negative relationship between dietary breadth and the percentage of rodents in the diet and no significant variation in diet composition or breeding success between low kite population and high kite population years. All of this was consistent with the response of a specialist predator taking advantage of rodent outbreaks. We conclude that the breeding of the Black-winged Kite on the Lleida Plains is more consistent with the existence of irruptive events than with a real colonization of the area.—Llorente-Llurba, E., Bota, G., Pujol-Buxo, E., Bonfil, J., Galvez, M., Montes, G., Bas, J., Moncasi, F., Pont, F. & Manosa, S. (2019). Diet composition and breeding success of the Black-winged Kite on the Lleida Plains in relation to population size. Ardeola, 66: 33-50.

Diet of benthivorous fish and prey availability in streams of the Pirapó River basin-PR

Abstract Aim This study aimed to investigate the diet of seven species of fish that consume predominantly benthic macroinvertebrates, and the availability of these organisms in the environment. We analyzed the occurrence of trophic segregation between species and the correlation between the abundance of macroinvertebrates in the diet and in the environment. Methods Fish and macroinvertebrates were sampled in three streams of the Pirapó River basin (Upper Paraná River - Brazil). Differences in diet composition between species were tested using a multivariate permutation analysis of variance (PERMANOVA). A Spearman Correlation was performed to test the relation between the abundance the macroinvertebrates consumed and those available in the environment. Results All species mainly consumed aquatic insect, and significant interspecific variations in diet composition were found for most of them. For five out of the seven species of fish analyzed no significant correlation was detected between the abundance of macroinvertebrates in the environment and in the diet. Conclusions The results showed that most of the species segregate and their diets are not positively correlated with the abundance of preys in the environment, indicating that the most consumed macroinvertebrates were not the most abundant in the environment. These results suggest that the fish species select the macroinvertebrates, and that the morphological and behavioral characteristics of both predators and prey are important in feeding fish from streams.

Diet Variability of Steelhead/Rainbow Trout in a Coastal Basin in Central California: Relative Importance of Seasonal, Spatial, and Ontogenetic Variation

AbstractDiets of stream‐dwelling salmonids vary at multiple spatial and temporal scales, but the relative importance of different sources of variation has rarely been evaluated for a population. In a small coastal basin in central California, we sampled diets of steelhead/Rainbow Trout Oncorhynchus mykiss monthly for a year from two reaches that differed in the presence of streambed travertine (calcium carbonate) to determine the relative magnitude of spatial, seasonal, and ontogenetic variation in consumption and diet composition. Seasonal parameters (cosine function terms for months in periodic regression and multivariate models) and fish size (FL) were greater sources of variation than differences between the two study reaches, and seasonal and ontogenetic patterns were evident despite high interindividual variability. Seasonal parameters explained the most variation in diet composition, which varied in an orderly pattern over the year. Consumption was highest in spring and summer for both aquatic and terrestrial prey, and seasonal parameters accounted for more variation than fish size for consumption of aquatic prey but this was reversed for terrestrial prey and total consumption. The main ontogenetic trend was increased consumption of terrestrial invertebrates: from 15‐20% of the energy consumed by 60–100‐mm fish to 60% of the energy consumed by fish larger than 160 mm. In addition, diet breadth (taxonomic richness and prey size) and the degree of variation among individuals also increased with fish size. Diet differences between sites were relatively small and included higher consumption of aquatic invertebrates at the site without travertine in 4 months and modest differences in the relative abundances of common prey taxa. Although seasonal and ontogenetic patterns were evident, interindividual variation was the dominant scale of diet variation, and diets of individual fish ranged from specialized to generalized relative to the population. Based on these findings, O. mykiss appeared to be opportunistic feeders that took advantage of diverse aquatic and terrestrial prey available in these study reaches.