Shifts In Diet Composition Research Articles

Trophic downgrading of an adaptable carnivore in an urbanising landscape

Urbanisation critically alters wildlife habitat and resource distribution, leading to shifts in trophic dynamics. The loss of apex predators in human-transformed landscapes can result in changes in the ecological roles of the remaining mesocarnivores. Decreased top–down control together with increased bottom–up forcing through greater availability of anthropogenic foods can result in a predation paradox. Understanding these changes is important for conserving ecological function and biodiversity in rapidly urbanising systems. Here, we use stable isotope analysis to provide insight into longer term changes in trophic position, niche width and overlap of an elusive, medium-sized urban adapter, the caracal (Caracal caracal) in and around the city of Cape Town, South Africa. Using fur samples (n = 168) from individuals along a gradient of urbanisation we find that overall caracals have a broad isotopic dietary niche that reflects their large variation in resource use. When accounting for underlying environmental differences, the intensity of anthropogenic pressure, measured using the Human Footprint Index (HFI), explained variation in both food subsidy use (δ13C values) and trophic status (δ15N values). The significantly higher δ13C values (P < 0.01) and lower δ15N values (P < 0.001) of caracals in more urbanised areas suggest that predator subsidy consumption occurs via predictable, anthropogenic resource subsidies to synanthropic prey. These prey species are predominantly primary consumers, resulting in shifts in diet composition towards lower trophic levels. Further, caracals using areas with higher HFI had narrower isotope niches than those in less impacted areas, likely due to their hyperfocus on a few lower trophic level prey species. This pattern of niche contraction in urban areas is retained when accounting for caracal demographics, including sex and age. The removal of apex predators in human-transformed landscapes together with reliable resource availability, including abundant prey, may paradoxically limit the ecological influence of the remaining predators, and bring about a degree of predator trophic downgrading. The dampening of top–down control, and thus ecosystem regulation, likely points to widespread disruption of trophic dynamics in rapidly developing areas globally.

Association between dietary fat intake and colorectal cancer: A multicenter case-control study in Iran.

The evolving trends in colorectal cancer (CRC) as one of the most common malignancies worldwide, have likely been influenced by the implementation of screening programs and changes in lifestyle habits. Changing lifestyle, including the shift in diet composition with higher fat, sugar, and animal-source foods intake, led to an increasing burden of CRC in countries undergoing rapid socioeconomic improvement. Results for the link between specific fatty acids (FAs) and CRC are generally inconclusive and more limited in developing countries than elsewhere. This study aims to investigate the association between FA intakes and CRC and its anatomical subsites in a large Iranian case-control study. A food frequency questionnaire was used to collect information on dietary intake in 865 cases and 3206 controls. We conducted multivariate logistic regression models to calculate the odds ratio (OR) and 95% confidence interval (CI). We found positive association between CRC and high intake of dietary total fat (OR highest quartile Q4 = 1.77, 95% CI = 1.32-2.38), cholesterol (ORQ4 = 1.58, 95% CI = 1.22-2.05), and palmitoleic acid (ORQ4 = 2.16, 95% CI = 1.19, 3.91), and an inverse association with high intake of dietary heptanoic acid (ORQ4 = 0.33, 95% CI = 0.14, 0.79) and low intake of palmitic acid (OR lowest quartile Q2 = 0.53, 95% CI = 0.31-0.88). None of the fat variables were associated with rectal cancer. Our study suggests that the recommendation of limited consumption of fats may decrease the risk of CRC among the Iranian population.

Does the Diet of Sceloporus variabilis Vary Along an Elevational Gradient?

Studies of elevational variation in diets in lizards have often found shifts in diet composition among elevations. Herein, we studied the diets of Sceloporus variabilis from six populations found in a variety of habitats along an elevational gradient (3–1900 m) in Puebla and Veracruz, Mexico. Diets of S. variabilis for the six populations were similar at the order level, with hymenopterans and coleopterans being the most important prey items. However, the specific taxa at the family or genus level varied among the six populations. The presence of plant material in diets varied among the six populations, with the two lowest elevation populations and the highest elevation population containing the most of this material.

Diet of a Population of Prairie Rattlesnakes (Crotalus viridis) in Kansas

This study examined prey items consumed and seasonal feeding events within a Prairie Rattlesnake (Crotalus viridis) population near Ulysses, Kansas, USA. A total of 183 specimens were collected over a period of three consecutive years (2012‒2015) during the active season from April to October. Most prey items consumed by this population were taken in spring between emergence from hibernacula and mating in early summer. Gravid females continued to take prey, likely opportunistically, while gestating. The only ontogenetic shift in diet composition was related directly to prey size. Larger snakes exhibited a preference for larger prey items. The two most abundant taxa in the diet of this population were Peromyscus spp (29.8%) and Sylvilagus spp (17.0%). Only one juvenile had consumed any prey within a week of capture.

Isotope-based inferences of skipjack tuna feeding ecology and movement in the southwestern Atlantic Ocean

Skipjack tuna (Katsuwonus pelamis) sustain a large-scale fishery in the southwest Atlantic Ocean (SWA), but information about its foraging ecology in this region is still limited. Here we use carbon (δ13C) and nitrogen (δ15N) stable isotope analysis of muscle from individuals collected in 2017–2018 (n = 383) to quantify diet composition and characterize movement patterns. We found a relatively small degree of variation in δ13C (range: -18.9 to −16.5‰) in comparison to δ15N values (6.7–14.7‰). At higher latitudes in the southern area (30–34°S), individuals had higher mean (±SD) δ15N values (12.2 ± 1.3‰) in comparison to those collected in the northern area (9.7 ± 1.5‰) between 20–26°S. At the northern area, isotope mixing models with informative priors showed that lanternfish (median: 50%) and krill (31%) were the primary foods. In the southern area, lanternfish (53%), krill (23%) and small pelagic fish (23%) were the primary food sources. Spatial shifts in diet composition were related to warming events that likely resulted in low abundance of sardines in the northern area. The latitudinal pattern in skipjack and krill δ15N values mirrored that of regional zooplankton isoscapes, suggesting residency at the timescale of isotopic turnover for muscle (~2–4 months), and that geographical variation in the baseline isotopic composition can be exploited to characterize seasonal movements of skipjack and other top marine consumers in this region.

How do forest management and wolf space-use affect diet composition of the wolf’s main prey, the red deer versus a non-prey species, the European bison?

We analyzed the effect of forest management and wolf (Canis lupus) space-use on diet composition of red deer (Cervus elaphus) and European bison (Bison bonasus) in Białowieża Primeval Forest (BPF), Poland. The red deer is the main prey species for the wolf, whereas the European bison is rarely preyed upon. As both species behave as intermediate feeders in BPF, we expected a large overlap in their diet composition. The red deer perceives the risk of wolf predation; thus, we hypothesized that its diet would change in relation to the intensity of wolf space-use, whereas bison’s would not. We compared diet composition between two contrasting management regimes: a national park managed as a protected area (no hunting, no forestry activities, restricted tourism), and an adjacent production forest managed for timber growth and extraction, where hunting on ungulates (but not wolves) does occur. We collected dung pellets of bison and red deer along transects in low and high wolf-use areas (with distance to settlements as proxy for wolf space-use) in both management types and analyzed diet composition using DNA-metabarcoding. In the national park both the bison and red deer had higher proportions of broadleaved tree species in their diet (bison 39%, red deer 42%) than in the managed forest (bison 26%, red deer 28%). The bison diet contained a higher proportion of shrubs, and specifically Rubus in the managed forest (shrubs 29%, Rubus 31%), compared to the national park (shrubs 21%, Rubus 8%). Only in the national park, red deer ate relatively more broadleaved tree species (51%) and fewer forbs (23%) in the high wolf-use area than in the low wolf-use area (33% broadleaved trees versus 37% forbs). Bison showed a qualitatively similar shift in diet composition as red deer, but the shift was not significant and also much smaller in extent. Our results indicate that forest management shapes the diet composition of both ungulate species. In addition, red deer showed larger shifts in diet composition than bison in high versus low wolf-use areas. This suggests that in addition to habitat differences, predation risk also plays a role in shaping the red deer diet. While earlier studies in BPF illustrated that wolves affect fine-scale deer foraging behavior, this study suggests this could potentially lead to changes in diet composition. We present alternative explanations for these diet shifts and urge others to look further into predation risk as a possible driver of dietary shifts in red deer.

Feeding and spatial behaviours of transhumant cattle in southern Benin: implications for the sustainable management of rangelands

Feed intake on pastures plays a vital role in cattle rearing in West Africa. However, the scarcity of pastures during the dry season may result in changing grazing behaviour by cattle. Therefore, we studied the management practices of transhumant herders on communal rangelands through monitoring of cattle herds’ behaviour in southern Benin. We expected changes in grazing behaviours of cattle and shifts in diet composition and diet overlaps between herds. Therefore, feeding and spatial behaviours of cattle were studied on six transhumant herds monitored daily, each during three consecutive days on communal rangelands of Djidja. In each herd, three adult cows of four to five years old were equipped with two GPS data loggers (GT-730FL-S) to monitor animals’ movements. The data loggers were set to record the positions of the animals every 10 s and direct observations of the animal activities were made. The results indicated that the activities of cattle varied greatly according to site (p < 0.05). Moreover, feed ingested varied with site. The ration was dominated by woody species with 70% Fabaceae, whereas shrubs and grasses were less represented, indicating a shift in diet. This analysis is required for better monitoring of grazing cattle.

Long-term temporal variation in the parasite community structure of metazoans of Pimelodus blochii (Pimelodidae), a catfish from the Brazilian Amazon.

The Amazon represents one of the most complex biomes in the world; however, the temporal variations in parasite community structure of fishes inhabiting this region remain poorly understood. Therefore, processes generating such variations are still unknown. The present study evaluated the long-term temporal variation of communitystructure of metazoan parasites of Pimelodus blochii collected in Iaco River, State of Acre (Southwestern Brazilian Amazon). A total of 196 parasites were collected over a 6-year period (2012-2017). Twenty-four different taxa of parasites were found, of which 5 Monogenea, 11 Nematoda, 3 Digenea, 1 Acanthocephala, 1 Cestoda, and 3 Crustacea. The overall species richness ranged from 4 in 2012 to 17 in 2016, in which nematodes (larvae and adults) showed higher numerical dominance, diversity, and species richness. However, the annual species richness was similar between the study years, except in 2016, where it showed a distinctly higher value. The overall parasite diversity was also different in 2012 and 2016, whereas the overall abundance differed in 2013 and 2017. The prevalence and abundance of some infracommunities of parasites varied over time. The temporal changes in the parasite community structure of P. blochii are probably related to variations in host-related features, i.e., body size and shift in diet composition as well as to the occurrence of parasites with distinct life history and biology (mainly monogeneans, digeneans, and nematodes). This is the first evaluation of a long-term temporal variation in the structure of the parasite community in fish from the Amazon.

Multiple Pathways to More Sustainable Diets: Shifts in Diet Composition, Caloric Intake and Food Waste

Our food choices, food production pathways and household behaviors together govern the impact that our diet has on our health as well as the environment. As the planetary population grows, there is an increasing awareness of the need to both improve the quality of our diets for health reasons and to reduce its impact on the earth. From the consumer perspective, however, it is not always clear which healthy diet options and behaviours contribute most to reductions in our dietary footprint. In this paper we model and contrast the impact of the current American diet and three recommended diets from the USDA Dietary Guidelines 2015-2020 on six dimensions of the dietary footprint: land area required, blue water use, fertilizer application, primary energy input, ammonia emissions and greenhouse gas emissions based on LCIA studies. For each diet we test the relative impacts of a shift in diet composition, caloric intake and the reduction in food waste on the dietary footprint. We find that there are multiple pathways to significantly reduce the environmental impact of our diets. Shifts in diet composition from the current diet to a vegetarian diet had the greatest impact on reducing the dietary footprint, however, combinations of reducing caloric intake from 2600kcal/d to 2000kcal/d combined with 50% reduction in food loss could achieve similar results in some cases. In line with results of other studies, we find that reducing red-meat and dairy contribute most to the dietary footprint. However, recommended increases in fruits and vegetables with dietary shifts are accompanied by significant increases in blue water use. We extrapolate our estimated of environmental impacts out to 2051 when the US population is set to reach 400 million people. By combining a number of incremental shifts in diet composition, intake level, and food loss, significant land currently under production could be spared from production for other uses while still providing a nutritious diet for all.

A rapid shift to high-grain diet results in dynamic changes in rumen epimural microbiome in sheep

The rapid shift to high-grain (HG) diets in ruminants can affect the function of the rumen epithelium, but the dynamic changes in the composition of the epithelium-associated (epimural) bacterial community in sheep still needs further investigation. Twenty male lambs were randomly allocated to four groups (n = 5). Animals of the first group received hay diet and represented a control group (CON). Simultaneously, animals in the other three groups (HG groups) were rapidly shifted to an HG diet (60% concentrate)which continued for 7 (HG7), 14 (HG14) and 28 (HG28) days, correspondingly. Results showed that ruminal pH dramatically decreased due to the rapid shift to the HG diet (P <0.001), while, the concentrations of butyrate (P <0.001), lactate (P = 0.001), valerate (P = 0.008) and total volatile fatty acids (P = 0.001) increased. Diversity estimators showed a dramatic decrease after the shift without recovering as the HG feeding continued. The principal coordinates analysis showed that CON group clustered separately from all HG groups with the presence of significant difference only between HG7 and HG28 (P = 0.034). The non-parametric multivariate analysis (npmv R-package) deduced that the primary significant differences in phyla and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt)-predicted Kyoto Encyclopedia of Genes and Genomes (KEGGs) was attributed mainly to the diet composition (P <0.001, P = 0.001) compared to its application period (P = 0.140, 0.545) which showed a significant effect only on the genus (P = 0.001) and the operational taxonomic units (OTUs) level (P = 0.011). The Kruskal–Wallis test deduced that six phyla showed a significant effect due to the shift in diet composition. At the genus level, HG feeding altered the abundance of 12 taxa, four of which showed a significant variation due to the duration of the HG diet application. Similarly, we found that 21 OTUs showed significant variations due to the duration of the HG diet application. Furthermore, the genes abundance predicted by PICRUSt revealed that the HG feeding significantly affected seven metabolic pathways identified in the KEGG. Particularly, the abundance of gene families associated with carbohydrates metabolism were significantly higher in HG feeding groups (P = 0.027). Collectively, these results revealed that the rapid transition to an HG diet causes dramatic alterations in ruminal fermentation and the composition and function of ruminal epithelium-associated microbiome in sheep, while, the duration of the HG diet application causes drastic alterations to the abundance of some species.

Food Habits of Large Nektonic Fishes: Trophic Linkages in Delaware Bay and the Adjacent Ocean

Fish diets play a critical role in our understanding of aquatic trophic dynamics and are an important component in developing ecosystem-based approaches to fisheries management. Although large nektonic fishes exert top-down predator effects on the food web and typically support viable commercial and recreational fisheries, little is known about the diet of this guild. We evaluated the diets (6327 stomachs) of four nektonic predatory fishes (Pomatomus saltatrix [78–395 mm], Cynoscion regalis [91–520 mm], Morone americana [156–361 mm], and Morone saxatilis [82–785 mm]) in Delaware Bay and in the adjacent ocean. To assess ontogenetic, geographic, and interspecific variation in diets, observations from individual fish stomachs were clustered into species-size class groups, and dietary overlap was estimated using multivariate analyses. A shift in diet composition, as well as diversity, occurred along the estuarine gradient and into the adjacent ocean. Some prey were shared by most predators, including some crustaceans (dominated by Callinectes sapidus, mysids, and Palaemonetes spp.), fundulids (dominated by Fundulus heteroclitus), engraulids (dominated by Anchoa mitchilli), and clupeids (dominated by Brevoortia tyrannus). However, inter- and intra-specific variation in diet was observed as well. In particular, M. americana consumed fewer engraulids and clupeids, and many more and diverse types of invertebrates, while P. saltatrix consumed more clupeids and less invertebrates. The lack of overlap in diet between the four predators evaluated, and between size groups for each predator, supports previous evidence that these groups feed in trophic guilds defined by species and by size within a species. The highly variable diets for these predators suggest high resolution spatial data are necessary in order to quantify their most important prey and their role in coastal ecosystems.

Diet Niche Width and Individual Specialization of Brook Trout in Adirondack Lakes

AbstractWe evaluated diet niche width, individual diet specialization, and diet composition in six lake populations of Brook Trout Salvelinus fontinalis, a generalist predator known to exhibit benthic and pelagic trophic specialization. Population diet niche width was broad and similar across all lakes, contrasting with that of individual fish, which exhibited specialized diets in comparison with their population and other individuals. Overall, the degree of individual diet specialization was high compared with that of other fishes. The degree of individual diet specialization did not differ among study populations, although it was generally reduced in spring. Individual diet specialization was consistent across fish sizes despite observed shifts in diet composition with increasing fish length. Population diet composition varied among lakes but was consistent within lakes in all years during the 3‐year study period with regard to season and fish size. The consistency and stability in measures of population diet niche width, degree of individual diet specialization, and population diet composition for Brook Trout indicate that these metrics provide useful tools for characterizing fish foraging and measuring how it changes in response to biotic and abiotic perturbations.Received August 11, 2016; accepted January 20, 2017 Published online May 22, 2017

Shift in diet composition of Indian mackerel Rastrelliger kanagurta – an analysis in relation to climate change

The feeding regime of organisms depend on the plankton community structure which is being studied worldwide to assess the changes in marine ecosystem structure due to climate change or anthropogenic activities. An attempt is made here to study the seasonal and long term variation in feed composition of Indian mackerel over a period of 40 years and its relationship with sea surface temperature to elucidate structural changes in food composition if any over period of time and its relationship to the primary and secondary productivity in eastern Arabian Sea marine ecosystem. The diet study during 2011-2014 reported the domination of phytoplankton consisting of Coscinodiscus sp. consistently and the presence of macroplankton and fish larvae whereas the diet during 1960-1961 showed the dominance of zooplankton and copepods. It could be assumed that increase in sea surface temperature which resulted in dominance of phytoplankton community as reported elsewhere in the world is also observed in eastern Arabian Sea which is reflected in the diet regime of Indian mackerel. The results also indicate its facultative feeding behaviour by compensating the low value phytoplankton with high value macroplankton and hence can be considered as a resilient species with regard to climate change.

Chicken and Egg: Testing the Carbon Isotopic Effects of Carnivory and Herbivory

In bone, the spacing between δ13C in collagen and bioapatite carbonate is greater in herbivores than carnivores, with implications for understanding animal dietary ecology from surviving hard tissues. Two explanations have been proposed: varying diet composition or differences in physiology between herbivores and carnivores. We measured the isotopic effects of carnivorous and herbivorous diets on a single species, to test the effect of diet composition alone. Protein δ13C and δ15N and carbonate δ13C were measured on egg and bone from hens on different diets. Herbivorous hens had a +14.3‰ spacing between egg albumen and shell δ13C, compared to +12.4‰ for omnivorous hens, and +11.5‰ for carnivorous hens. The bioapatite–collagen Δ13C spacing was measured as +6.2‰ for herbivorous hens, and calculated as +4.3‰ for omnivorous hens, and +3.4‰ for carnivorous hens—similar to observed mammalian herbivore and carnivore bioapatite–collagen Δ13C differences. We conclude that a shift in diet composition from herbivory to carnivory in a single species does alter the bioapatite–collagen carbon isotopic spacing. Our data strongly suggest that this results from differences in the Δ13Cbioapatite–diet spacing, and not that of Δ13Ccollagen–diet.

Nymphal feeding habits of Perla madritensis Rambur 1842 (Plecoptera: Perlidae)

SummaryThe diet of Perla madritensis, endemic species of the northern half of the Iberian Peninsula, is described for the first time by means of a study carried out in north-western Spain. As other species of the genus Perla, this taxon behaves mainly as predator, with Chironomidae, followed by Baetidae, being the most abundant prey in its gut. Shifts in diet composition were detected in relation to size in this species, with smaller prey being replaced by larger ones such as Simuliidae and Leptophlebiidae when the nymphs become larger.

Prey size increases with nestling age: are provisioning parents programmed or responding to cues from offspring?

As offspring grow, parents often feed them with different sizes or taxa of prey to suit the changing nutritional or energetic demands. We investigated whether such changes in prey types were innate and inflexible or whether they were based on the proximate cue of offspring size. We created experimental broods in which parent blue tits Cyanistes caeruleus and pied flycatchers Ficedula hypoleuca received either older nestlings simulating rapid development or younger nestlings simulating delayed development. The size of prey increased over time in all brood types, suggesting a strong programmed pattern of foraging by parents. However, delayed broods were provisioned with smaller prey than control or advanced broods indicating some plasticity in the response by the parents to the size of nestlings. Although female birds brought smaller prey than male birds, both sexes showed the same rate of increase of prey size with time and brought similar types of prey items. The proportion of soft, digestible larva prey in the nestling diet decreased over time in pied flycatchers but increased in blue tits. Counter to the hypothesis that spiders provide unique and preferred nutrients for young nestlings, the proportion of arachnids in the diet did not change with nestling age for either species. The lack of treatment effect on the taxa of prey delivered suggests that temporal shifts in diet composition are not driven by the proximate cues of nestling age or size but that the feeding patterns are fairly innate and fixed in these altricial birds.

Assimilation of Oil-Derived Elements by Oysters Due to the Deepwater Horizon Oil Spill

During and after the Deepwater Horizon Oil Spill (DWHOS), oysters (Crassostrea virginica) were exposed to oil and susceptible to incidental consumption of surface and subsurface oil materials. We determined the contribution of oil materials from the DWHOS to diet of oysters by comparing carbon (C) and nitrogen (N) stable isotope ratios in oyster shell to ratios in suspended particulate matter (SPM) and in fresh and weathered oil. Average δ(13)C and δ(15)N values in oyster shell (-21 ± 1‰ and 9-11‰, respectively) were consistent with consumption of naturally available SPM as opposed to values in oil (-27 ± 0.2‰, 1.6 ± 0.4‰). Stable isotope ratios in oyster adductor muscle were similar to shell for δ(15)N but not δ(13)C, suggesting either a recent shift in diet composition or differential assimilation of C between tissue types. We found no evidence of assimilation of oil-derived C and N and, therefore, no evidence of an oyster-based conduit to higher trophic levels. Trace elements in shell were inconclusive to corroborate oil exposure. These findings are not an indication that oysters were not exposed to oil; rather they imply oysters either did not consume oil-derived materials or consumed too little to be detectable compared to natural diet.

Seasonal Variability in Trypsin and α-amylase Activities Caused by the Molting Cycle and Feeding Habits of Juvenile Pink Shrimp Farfantepenaeus duorarum (Burkenroad, 1939)

ABSTRACT In view of the relationship between shifts in diet composition and the activity of digestive enzymes in penaeid shrimp, the present study focused on the analysis of digestive trypsin and α-amylase activities of wild Farfantepenaeus duorarum (Burkenroad, 1939) juveniles and their changes in phenotypic expression, during the molt cycle as endogenous factor and their changes due to different feeding regimes (exogenous factor) in relation with δ13C and δ15N isotopic signature as an index of food assimilation induced by the seasonal availability of food items in the nursery area. Wild juveniles of F. duorarum were captured from April 2007 to February 2008, in the Celestun coastal lagoon, Yucatan, Mexico. Samplings were carried out considering all quarters of the lunar cycle and in each of the recognized seasons for this region: dry, rainy, and the Nortes (North Wind). Copepods and amphipods were the main source of food for juveniles of F. duorarum. Values of δ13C in the muscular tissue were near -20‰ ...

The foraging ecology of larval and juvenile fishes

Knowledge of the foraging ecology of fishes is fundamental both to understanding the processes that function at the individual, population and community levels, and for the management and conservation of their populations and habitats. Furthermore, the factors that influence the acquisition and assimilation of food can have significant consequences for the condition, growth, survival and recruitment of fishes. The majority of marine and freshwater fish species are planktivorous at the onset of exogenous nutrition and have a limited ability to detect, capture, ingest and digest prey. Improvements in vision, development of fins and associated improvements in swimming performance, increases in gape size and development of the alimentary tract during ontogeny often lead to shifts in diet composition. Prey size, morphology, behaviour and abundance can all influence the prey selection of larval and juvenile fishes. Differences in feeding behaviour between fish species, individuals or during ontogeny can also be important, as can inter- and intraspecific interactions (competition, predation risk). Temporal (diel, seasonal, annual) and spatial (microhabitat, mesohabitat, macrohabitat, regional) variations in prey availability can have important implications for the prey selection, diet composition, growth, survival, condition and, ultimately, recruitment success of fishes. For fish populations to persist, habitat must be available in sufficient quality and quantity for the range of activities undertaken during all periods of development. Habitats that enhance the diversity, size ranges and abundance of zooplankton should ensure that sufficient food resources are available to larval and juvenile fishes.

Feeding Ecology of Acanthochelys spixii (Testudines, Chelidae) in the Cerrado of Central Brazil

Abstract We studied the diet of Acanthochelys spixii in a wild population in the Cerrado of central Brazil for 19 months, investigating ontogenetic, sexual, and interindividual variation. The diet consisted mainly of nymphs of Odonata, although other insects, amphibians, and plant material were also present. We observed no ontogenetic shifts in diet composition (e.g., no shift from carnivorous juveniles to herbivorous adults), which can be related to the high abundance of prey at the study site. There was no association between prey size and turtle carapace length, with larger animals still taking small prey. Dietary niche overlap was high, and there was no difference in niche breadth between sexes. However, differences in diet composition suggested differential habitat use, with males using more the periphery and females using more the center of ponds. Diet composition varied more among males than among females, which can result from higher diversity of prey at the pond margins, higher movement rates, or...