Food Niche Breadth Research Articles

Food Preference of Purple‐Spotted Bigeye (Priacanthus tayenus Richardson 1846) in Northern Coast of Java, Indonesia

ABSTRACTDiet is one of the essential information used in the management of fisheries resource. The objective of this study was to assess the dietary preferences, index of preponderance, trophic level, food niche breadth, and food overlap of purple‐spotted bigeye (Priacanthus tayenus) caught from the northern coast of Java, Indonesia. A total of 407 fish samples were collected from July to October 2023. Each fish sample was measured for total length and body weight. Fish were then dissected to determine sex, gut length, gut volume, and diet composition. Data analysis included relative gut length, diet composition, frequency of occurrence, trophic level, index of preponderance, food niche breadth, and food overlap. The result showed that the purple‐spotted bigeye is a carnivorous fish (trophic level ranges from 3.88 to 4.18), whose main food is fish and shrimp. Based on the niche breadth value, purple‐spotted bigeye from East Java were more diverse in finding food (niche breadth = 0.26) than from West Java (niche breadth = 0.06) and Central Java (niche breadth = 0.09). The purple‐spotted bigeye species from West Java and Central Java exhibited a high level of competition in their search for food, as indicated by a food overlap value of 0.998.

A Worldwide Review of Snowy Owl Feeding Ecology: The Importance of Lemmings and Voles in a Changing Climate

We compared Snowy Owl feeding ecology from 15 breeding season studies throughout Nearctic and Palearctic circumpolar regions. We used raw data and information theory to assess the owls’ feeding niche. Combined studies yielded 59,923 prey items, of which 59,585 were used for calculations. Overall, mean food niche breadth (FNB) was narrow: H′ = 1.95; R = 1.60, D = 0.526. In 10 of 15 studies, lemmings were > 71.8% of the owls’ diet. In four studies, Lemmus was > 90% of the diet, and in three studies Dicrostonyx was >90% of the diet. In three other studies, Lemmus represented 71.8%, 73.8%, and 84.0% of the diet. In one study, Lemmus and Dicrostonyx were about equal: 49.1% and 47.5%. In the four remaining studies, Microtus and Clethrionomys voles were important. In contrast, of 5888 winter prey items from seven North American studies, the mean FNB (H′ = 4.61) was twice that of 15 breeding season scores, FNB (H’ = 1.95). The Snowy Owl is primarily an obligate lemming predator for breeding. Changes to population ecology and distribution of lemmings due to climate change will have direct affects and effects on the Snowy Owls’ reproductive output. The conservation of Snowy Owls is the conservation of lemmings.

Wolves in the borderland – changes in population and wolf diet in Romincka Forest along the Polish–Russian–Lithuanian state borders

We assessed changes in the population size, density, and diet composition of wolves inhabiting the Romincka Forest (RF), an area of 480 km2 situated along the state border between Poland, Russian Federation (Kaliningrad), and Lithuania. We compared the results of our research in 2020–2021 with data from other projects conducted since 1999. We found that both packs living in RF had transboundary territories. The number of packs was stable over 21 years; the average pack size almost doubled (from 4–4.5 to 7.5–8 wolves per pack); the total wolf numbers increased 1.8 times, reaching 15–16 wolves; and the density increased 1.5 times up to 3.1–3.3 wolves/100 km2 in winter 2020/2021. Our analyses of 165 scats revealed that beavers Castor fiber made up 45.6% of food biomass in the wolf diet in 2020, which was 3.4 times more than in 1999–2004 (n = 84 scats,13.4%). Wild ungulates constituted 44.8% of the wolf food biomass in 2020, 1.6 times less than before (71.1%). In our study, among wild ungulates, wolves primarily consumed roe deer Capreolus capreolus (22.6% of food biomass), then wild boars Sus scrofa (13.7%), and red deer Cervus elaphus (5.0%), while moose Alces alces was eaten rarely (0.4%). We also recorded domestic dogs (4.9% of food biomass) and cattle (3.1%). The food niche breadth was wider (B = 2.31) than in the earlier period (B = 1.84), and the Pianka index showed moderate similarity in food composition between both periods (α = 0.816). In November 2022, due to the migration crisis, a 199 km impermeable fence along the state border with Kaliningrad was erected, which blocked access to 48% of the RF area that was regularly used by the resident wolf packs. This may cause wolf numbers to decrease and isolation from the central part of the Baltic wolf population to which they belong, according to our DNA analyses.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin.

The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Wild Ungulates Constitute the Basis of the Diet of the Iberian Wolf in a Recently Recolonized Area: Wild Boar and Roe Deer as Key Species for Its Conservation.

The Iberian wolf (Canis lupus signatus) is recolonizing historical distribution areas after decades of absence. As in other human-dominated landscapes, finding a balance to protect this species by favoring recolonization and mitigating human-wildlife conflicts is a challenge. Since wolves are often generalist opportunistic predators, we studied their diet composition in central Spain to evaluate the consumption of domestic ungulates and provide reliable data that could help local authorities to deal with the current wolf-cattle ranchers conflict and coexistence. Diet composition (% prey occurrence, % prey ingested biomass) was analyzed through the identification of prey hairs present in 671 scats collected between 2017 and 2021. The wolves fed more on wild ungulates (82% occurrence) than domestic ones (18%). Wild boar (Sus scrofa, 44% occurrence) and roe deer (Capreolus capreolus, 35%) were the most consumed prey. The wolves positively selected these two species. The wolves' diets varied between seasons, years, and forest regions, but a diet based on wild ungulates predominated over domestic ones. Food niche breadth showed variations depending on seasons and years. Preserving the availability and diversity of wild ungulates may favor reducing livestock attacks and would be an achievable goal that would help to conserve this species and reduce conservation conflicts.

The Food Niche Overlap and Interspecific Relationship between the Sympatric Tibetan Macaque and Grey Snub-Nosed Monkey.

Assessing the trophic niche and interspecific relationships between related species and determining how the species maintain differences in nutritional niches while coexisting in the same area are important topics in ecological research. Therefore, exploring the mechanism of food resource utilization, competition and coexistence among species distributed in the same region is important. In this study, we used fecal samples and metagenome sequencing technology to study the plant feeding habits and coexistence mechanisms of Tibetan macaques (Macaca thibetana) and grey snub-nosed monkeys (Rhinopithecus brelichi) within the same area. In the winter of 2020, we collected a total of 40 fecal samples from Tibetan macaques and grey snub-nosed monkeys; of those, 29 samples were considered valid and were analyzed using DNA metabarcoding. The results showed that in winter, Tibetan macaques consumed plants from 117 families and 184 genera, whereas grey snub-nosed monkeys consumed plants from 109 families and 165 genera. Diversity analysis revealed that there was a significant difference in the food composition of Tibetan macaques and grey snub-nosed monkeys. Tibetan macaques had a broader food niche width than grey snub-nosed monkeys at the family and genus levels. In winter, the food niches of Tibetan macaques and grey snub-nosed monkeys almost entirely overlapped (0.99). Our research provides detailed dietary data for Tibetan macaques and grey snub-nosed monkeys and valuable information that can aid in conservation efforts targeting these species.

An assessment of the diet of Brown Fish-Owl Ketupa zeylonensis (J.F. Gmelin, 1788) (Aves: Strigiformes: Strigidae) from two localities in the foothills of the Western Ghats of Goa, India

The Brown Fish-Owl Ketupa zeylonensis is a large nocturnal bird of prey that has a vast distribution range. However, there is a significant literature gap on the ecology of this species in the Western Ghats ecoregion, particularly in regard to its food spectrum. In the present study, we assessed the diet composition of this species in the foothills of the Western Ghats of Goa, India. The diet was evaluated by analysing the undigested prey remains in regurgitated pellets obtained from the banks of forest streams and roosting sites. A total of 104 pellets were collected from two localities that exhibited similar landscape characteristics. Our analysis indicated that crabs contributed to a significant proportion of the diet of the species (75.47%), followed by amphibians (frogs, 8.02%), fishes (7.08%), reptiles (snakes, 2.83%), birds (2.36%), scorpions (1.89%), and insects (Odonata, 0.47%). Additionally, 1.89% (n = 4) of the prey items could not be identified due to their disintegrated nature. Furthermore, an assessment of Food Niche Breadth (FNB) indicated that K. zeylonensis exhibited a high degree of specialization in terms of its diet in the study areas.

Comparative gastrointestinal organ lengths among Amazonian primates (Primates: Platyrrhini).

The morphological features of the gastrointestinal tract (GIT) in mammals reflect a species' food niche breadth and dietary adaptations. For many wild mammals, the relationship between the structure of the GIT and diet is still poorly understood, for example, the GIT for frugivorous primates is usually classified as unspecialized and homogeneous. Here, we compare the GIT structure of 13 primate species from the three families of extant platyrrhines (Atelidae, Pitheciidae, and Cebidae) in Amazonia, and discuss possible evolutionary adaptations to different diets and trophic niches. We measured the length of the esophagus, stomach, small intestine, large intestine, cecum, colon, and rectum of the digestive tracts of 289 primate specimens. We determined the allometric relationships of the different tubular organs with the total length of the GIT as a proxy of specimen body size. Allometric parameters were used to establish the quotients of differentiation of every organ for each primate specimen. There was a high differentiation in structure of the digestive organs among genera. Alouatta specimens clearly separated from the other genera based on dissimilarities in gastric, colonic, and rectal quotients, likely linked to the fermentation of plant contents. In contrast, all cebines (Sapajus, Cebus, and Saimiri) and Cacajao species had similar small intestine quotients, which is expected due to their high rates of animal matter consumed. We show that diverse adaptations in digestive structure exist among frugivorous primates, which in turn reflect different dietary patterns within this group that may enable the geographic coexistence of different primate species.

Effects of Anthropogenic Disturbance of Natural Habitats on the Feeding Ecology of Moorish Geckos.

Urbanization and anthropic influences can drastically modify a natural habitat and transform it into an easily recognizable "urban habitat". Human activities can also induce less severe modifications of what apparently might still look like natural habitats. Therefore, these subtle alterations may be hidden but can still cause important negative effects on plant and animals. In contrast, some species seem able to take advantage of these anthropic alterations. Here, we examined the possible effects of the anthropogenic disturbance of an apparent natural habitat on the feeding ecology and body condition of Moorish geckos, Tarentola mauritanica. For this, we compared microhabitat structure, invertebrate availability, the diet composition (estimated from fecal contents), diet selection patterns and body condition of the two populations of geckos inhabiting two contiguous small islands. These islands have similar environmental characteristics, but highly contrasting differences in urbanization and anthropogenic influence. We found that, although the abundance of potential invertebrate prey was similar on both habitats, the diversity of invertebrate prey was lower in the altered habitat. As a consequence, although composition of the diet of geckos was similar on both islands, the diversity of prey and food niche breadth were lower in the altered habitat, and patterns of diet selection changed. However, these inter-habitat differences did not seem to affect the body size and body condition of geckos. We discuss how flexibility in feeding ecology may allow some species to cope with small anthropic disturbances of the habitat.

Trophic niche overlap among Neotropical carnivores in a silvicultural landscape

Abstract To enable long-term coexistence, species need to differentiate at least one of the three main dimensions of the ecological niche (temporal, spatial, or trophic dimension). Here, we investigated whether mammalian predators (Chrysocyon brachyurus, Cerdocyon thous, Lycalopex vetulus, and Puma concolor) follow the prediction of trophic niche partitioning, which is expected when partitioning of food resources represents an important mechanism for coexistence. We predicted low niche overlap in general and low between P. concolor and the other species. We analyzed 207 fecal samples collected at a landscape composed of forest remnants immersed in Eucalyptus plantations. Food items (animals and plants) were identified using exoskeletons, feathers, scales, teeth, hair, and seeds. We calculated the frequency and percentage of occurrence of food items, niche breadth, and niche overlap between pairs of species. Prey size was similar among all predators, consuming mainly small-sized prey (<1 kg). However, niche breadth was larger for smaller carnivores compared to larger ones. No species pair showed significantly lower niche overlap than expected by chance. Our study provided detailed information on trophic resource use of sympatric carnivores, showing that trophic niche partitioning seems not to be crucial for the coexistence of carnivores in the study area.

Numerical Response of Owls to the Dampening of Small Mammal Population Cycles in Latvia.

Strong numerical and functional responses of owls to voles in cyclic environments are well known. However, there is insufficient knowledge from the boreonemoral region in particular, with depleted populations of small mammals. In this study, we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings, and population trends to lay out the numerical response of six owl species to dampened small mammal population cycles. We found temporarily increasing food niche breadth in tawny and Ural owls. There were no other responses in the tawny owl, whereas the breeding performance of three forest specialist species-pygmy, Tengmalm's, and Ural owls-corresponded to the vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls decreased, and the change in the Ural owl population can be attributed to the depletion of small mammal populations. We found evidence of a carry-over effect in the eagle owl arising from a strong correlation of declining breeding performance with the small mammal abundance indices in the previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate of the likely effects of habitat destruction that needs to be investigated further, with stronger responses in more specialized (to prey or habitat) species.

Increased availability of preferred food and decreased foraging costs from degraded grasslands lead to rodent pests in the Qinghai-Tibet Plateau

The increased population density of rodent species during ongoing grassland degradation further deteriorates its conditions. Understanding the effects of grassland degradation on rodent feeding habits is of great value for optimizing grassland management strategies. In this study, lightly degraded (LD), moderately degraded (MD), severely degraded (SD), and reseeded grassland (RG) were selected and their plant resources and soil physical properties were investigated. In addition, the study usedITS2barcode combined with the Illumina MiSeq sequencing method to analyze the food composition and proportion of plateau zokors in different grassland conditions. The results showed that, with grassland degradation, plant biomass decreased, but the relative proportion of forbs increased (LD: 32.05 ± 3.89%; MD: 28.97 ± 2.78%; SD: 49.16 ± 4.67% and RG: 10.93 ± 1.53%). Forbs were the main food of the plateau zokor, accounting for more than 90% of their diet, and the animal had a clear preference forPotentillaspecies; the soil compaction of feeding habits showed a decreasing trend in the 10–25 cm soil layer, suggesting a decreased foraging cost. Nutritional analysis showed that the stomach content of crude protein in zokors feeding on MD grassland was significantly higher than that of animals feeding on the other grassland types. Structural equation modeling showed that soil physical properties and the relative biomass of forbs had significant (P< 0.05) and extremely significant (P< 0.001) impacts on the population density of plateau zokors, with direct impact contribution rates of 0.20 and 0.63. As the severity of grassland degradation increased, although the aboveground and underground biomass of the plants decreased, the proportion of food preferred by the plateau zokor increased, and the corresponding changes in the feeding environment resulted in decreased foraging energy expenditure, thereby increasing the suitability of the degraded grassland for the plateau zokor. Compared with degraded grassland, the food diversity and evenness of zokors increased, the food niche width enlarged, and the proportion of weeds decreased in RG, which increased the difficulty of obtaining food. Reseeding in grassland management is therefore an effective way to control plateau zokors.

Diet shifting of tortoise-eating Golden Eagles (Aquila chrysaetos) in southeastern Bulgaria

Top predators may adapt their diets to changes in prey availability where human-induced environmental changes are intense. This long-term study of the breeding-season diet of Golden Eagle (Aquila chrysaetos) in the Strandzha Mountains analyzed shifts in diet caused by the population decline in principal prey species, the tortoises (Testudo hermanni and T. graeca). Tortoises comprised 50.0% of the eagle diet by prey number in the 1990s, but that share collapsed to 5.8% in 2014–2021. During this later interval, Golden Eagles preyed more intensively on lighter-weight prey such as Northern White-breasted Hedgehog (Erinaceus roumanicus, an increrase of 28.2% by number) and Edible Dormouse (Glis glis, an increase of 14.9% by number). Hedgehogs predominated in the diet of an individual eagle nest site for the first time in 1998 and became the principal prey in 2014–2021. Differences in food niche breadth and proportions of mesopredators between tortoise- and hedgehog-dominated individual annual diets were not significant, corresponding to a low level of food stress. The only eagle with an annual diet dominated by Squamata (snakes and lizards) was an exception, having the widest food niche. Young domestic ungulates have almost completely disappeared from eagle diets at the same as the reduction of tortoises, corresponding to a concurrent decline of livestock farming. The results obtained here have relevance to conservation management of both predator and prey populations.

06. Diet of the recently introduced white-lipped frog Leptodactylus fragilis from a suburban ecosystem in western Cuba

ABSTRACT - Diet and trophic interactions are essential for understanding aspects of the natural history of a species and evaluating its role within the ecosystem. A successful coloniser often has the ability to exploit a wide variety of prey during its establishment and may generate negative impacts due to competition with the local fauna. During both the dry and rainy seasons of 2019, in a suburban ecosystem in western Cuba, we analysed the diet of the recently introduced white-lipped frog Leptodactylus fragilis. Captured frogs were measured and stomach-flushed and released 24 h after analysis at the site of capture. Ninety-one L. fragilis were captured, 73 of them (80.2 %) had prey in the stomach. The most consumed prey were beetles, followed by spiders, and crickets. No difference was observed in prey consumption between seasons. This frog may change its foraging strategy according to the habitat it occupies. In this study, we observed high values of food niche breadth, which may imply a greater competition of L. fragilis for food resources with the native syntopic anurans in Cuba. Studies on temporal and spatial dynamics are needed to understand the possible competitive interaction with native amphibians in this area.

Generalist, selective or ‘mixed’ foragers? Feeding strategies of two tropical toads across suburban habitats

AbstractSuitable habitats for anurans can be found in the ever‐growing tropical urban environments but anurans' adaptations to urban conditions, including their trophic ecology remain largely unknown. We studied the food habits of two generalist, widespread West African Sclerophrys adult toads: African common (Sclerophrys regularis) and Hallowell's toad (Sclerophrys maculata). The first was studied in Lomé (Togo), Cotonou (Benin) and Ikeja (Nigeria), and the second in Port Harcourt and Ikeja (both Nigeria); the latter city represents the only studied sympatric occurrence. Mean dietary overlap between population pairs was relatively high, and diet composition of the two species when sympatric did not differ significantly. Food niche width was significantly positively correlated with local rainfall in both species, and diet composition changed significantly between the dry and wet seasons. Diversity metrics revealed that females had a more diversified diet, with higher evenness and lower dominance index values than males. The diet of both species was not correlated to prey type availability, in both the wet and dry season. Both toad species targeted specific food items rather than opportunistically consume prey as observed in most anurans which may be a response to high anuran diversity typically found in the tropics or an adjustment to urban habitats.

Seasonal Variation in Gut Microbiota Related to Diet in Fejervarya limnocharis.

Simple SummaryGut microbiota, such as Proteobacteria, Firmicutes, and Bacteroidetes, show chitin-degrading and/or antibiotic biosynthesis ability. To evaluate whether ecological factors (diet) and host conditions (body size, body mass, and body condition) affect the gut microbiota diversity, we analysed the diet composition and host condition in Fejervarya limnocharis among different seasons and/or sexes. The dietary difference was not significant among seasons and between males and females, but host condition seasonally changed. Using bioinformatics analysis, we observed that food variations and body mass were significantly correlated with gut microbial composition. Our findings suggest that gut microbiomes of F. limnocharis vary seasonally in response to diet variations when facing environmental changes.Organisms adapt to environmental fluctuations by varying their morphology and structural, physiological, and biochemical characteristics. Gut microbiome, varying rapidly in response to environmental shifts, has been proposed as a strategy for adapting to the fluctuating environment (e.g., new dietary niches). Here, we explored the adaptive mechanism of frog intestinal microbes in response to environmental changes. We collected 170 Fejervarya limnocharis during different seasons (spring, summer, autumn, and pre-hibernation) to study the compositional and functional divergence of gut microbiota and analysed the effects of seasonal feeding habits and body condition on intestinal microorganisms using 16S rRNA high-throughput sequencing, Tax4Fun function prediction analysis, and bioinformatics analysis. The results showed no significant dietary difference in various seasons and between males and females. However, a significantly positive correlation was detected between dietary diversity and food niche width. Host condition (body size, body mass, and body condition) also revealed seasonal changes. The frogs were colonised by 71 bacterial phyla and dominated by Proteobacteria, Firmicutes, and Bacteroidetes. Stenotrophomonas was the most abundant genus in the Proteobacteria. The composition, diversity, and function of intestinal microorganisms in different seasons were significantly different. Significant differences were observed in composition and function but not in the microbial diversity between sexes. Furthermore, seasonal foods and body mass were significantly correlated with gut microbial composition. Our results suggest that gut microbiomes of F. limnocharis vary seasonally in response to diet under fluctuating environments.

Food habits, ecomorphological patterns and niche breadth of the squeaker, Synodontis schall (Pisces: Siluriformes: Mochokidae) from Niger River in Northern Benin

The squeaker, Synodontis schall dominates the Mochokid fish sub-community in Niger River in Northern Benin and shows a great economic and commercial importance. The diet of S. schall has been analysed to evaluate the food habit and resource utilization in this regional River. Fish samplings were made monthly from February 2015 to July 2016 using unbaited longlines and traps, seines and experimental gillnets. The results indicated that S. schall is an omnivore foraging in benthic and pelagic habitats with diet dominated by aquatic insects (34.32%), sand particles (18.768%), macrophytes (13.415%), seeds (8.549%), roots (8.319%), detritus (5.344%), mollusks (1.204%) and phytoplankton (0.6255%). The omnivore food habit depicted was also shown by the ecomorphological analysis mainly the relative gut length (GL/SL) varying between 0.8 and 5. The species showed high diet flexibility with high niche breadth ranging between 1.86 and 5.74. Synodontis schall exhibited an ontogenetic diet shift that was also confirmed by Pianka’s diet overlap indexes ranging between O jk =0.54-0.93. The conservation and the sustainable fisheries exploitation of S. schall require the reinforcement of fishing regulation, habitat protection and ecosystem follow-up.

Breeding diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax in the Australian Capital Territory in 2011–2019

The diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax breeding sympatrically in the Australian Capital Territory during 2011–2019 were compared by analysis of pellets and prey remains (six Little Eagle territories and 13 Wedge-tailed Eagle territories; 69 and 49 collections for a total of 232 and 256 prey items, respectively). Little Eagles took 33% mammals (29% European Rabbits Oryctolagus cuniculus), 44% birds, 6% reptiles and 17% insects by number, and 65% mammals (62% Rabbits), 27% birds, 8% reptiles and <1% insects by biomass. Wedge-tailed Eagles took 59% mammals (23% Rabbits and 19% macropods), 38% birds, 1% reptiles, <1% fish and 1% insects by number, and 89% mammals (20% Rabbits, 38% macropods), 10% birds, and <1% reptiles, fish and insects by biomass. Indices of dietary diversity (Shannon Index and Standardised Food Niche Breadth) were 2.57 vs 3.07 and 0.19 vs 0.24, respectively; Geometric Mean Prey Weights (GMPW) were 164 vs 1392 g, but discounting a biased sample of insects in many pellets from two fledglings, Little Eagle GMPW was more like 340 g. Dietary proportions and some metrics for both species appear to have changed little since the preceding decade, although Wedge-tailed Eagle dietary diversity increased slightly and dietary overlap (80%) increased greatly, concomitantly with some pairs of Wedge-tailed Eagles replacing pairs of Little Eagles. Intraguild predation occurred, including Wedge-tailed Eagle predation on Little Eagles.

Diet Selection of Heteracris littoralis in a Cultivated Environment, Mzab Valley, Septentrional Sahara, Algeria

This paper presents the results of a study on the diet of Heteracris littoralis in an agro-ecosystem at Mzab valley, Ghardaïa Province, Northern Sahara, Algeria. The diet was determined by the analysis of plant fragments in the feces of H. littoralis sampled in the field. The studied grasshopper consumed 12 of the 30 plant species found in the cultivated environment. The results showed that the locust predominantly fed on a few plants, such as Lagenaria siceraria and Solanum lycopersicum, although their diet includes over 12 plant species. Its food niche breadth was narrow (0.51), with a selectivity index of 0.61 for females, 0.52 for males and 0.42 for larvae. The plants consumed by the two sexes and larvae were not significantly different. This study suggests that Eyprepocnemidinae is a polyphagous grasshopper species, in spite of pronounced preference towards Cucurbitaceae and Solanaceae. This property results in a low Berger-Parker index value (0.24). Results are of great significance, increasing the understanding of insect herbivore feeding behavior and how to control the damage caused by this Orthoptera.

Bioenergy landscapes drive trophic shifts in generalist ants

Changes in trophic niche-the pathways through which an organism obtains energy and nutrients-are a fundamental way in which organisms respond to environmental conditions. But the capacity for species to alter their trophic niches in response to global change, and the ways they do so when able, remain largely unknown. Here we examine food webs in three long-term and large-scale experiments to test how resource availability and nutritional requirements interact to determine an organism's trophic niche in the context of one of the largest global trends in land use-the rise in bioenergy production. We use carbon and nitrogen stable isotope analyses to characterize arthropod food webs across three biofuel crops representing a gradient in plant resource richness (corn monocultures, fields dominated by native switchgrass and restored prairie), and to quantify changes in the trophic niche of a widespread generalist ant species across habitats. In doing so, we measure the effects of basal resource richness on food chain length, niche breadth and trophic position. We frame our results in the context of two hypotheses that explain variation in trophic niche-the niche variation hypothesis which emphasizes the importance of resource diversity and ecological opportunity, and the optimal diet hypothesis which emphasizes dietary constraints and the availability of optimal resources. Increasing plant richness lengthened food chains by 10%-20% compared to monocultures. Niche breadths of generalist ants did not vary with resource richness, suggesting they were limited by optimal diet requirements and constraints rather than by ecological opportunity. The ants instead responded to changes in plant richness by shifting their estimated trophic position. In resource-poor monocultures, the ants were top predators, sharing a trophic position with predatory spiders. In resource-rich environments, in contrast, the ants were omnivores, relying on a mix of animal prey and plant-based resources. In addition to highlighting novel ecosystem impacts of alternate bioenergy landscapes, our results suggest that niche breadth and trophic diversification depend more on the presence of optimal resources than on ecological opportunity alone.