Low Dietary Overlap Research Articles

Stomach content and stable isotope analyses provide complementary insights into the trophic ecology of coastal temperate bentho-demersal assemblages under environmental and anthropogenic pressures

Assessing organic matter fluxes and species interactions in food webs is of main interest to understand the ecological functioning in bays and estuaries characterised by a wide diversity of primary producers and consumers. Demersal fish and cephalopod assemblages were studied across a network of 24 shallow subtidal stations in the bay of Saint-Brieuc for their diversity, stable isotope compositions and stomach contents. The community was composed of 21 taxa, eight species accounting for 94.4% of the total abundance. Three different assemblages were identified along bathymetric gradient and spatial patterns in fish dredging. Marine POM and SOM were the most likely bases of food webs regarding δ13C range displayed by fish and cephalopod without differences among assemblages. Amphipoda was the main prey item in stomachs leading to significant diet overlaps among fish species, with some variations in additional items. Sepia officinalis was characterised by a singular diet and very low dietary overlap with other species. Contrasted stable isotope values and niche overlaps among species were evidenced in the δ13C/δ15N space. Callionymus lyra and Buglossidium luteum, characterised by the widest isotopic niches, encompassed those of other species, except the singular 13C-depleted Spondyliosoma cantharus. Coupling taxonomic assemblages, stomach contents and stable isotope analyses help disentangling the resources uses and evidencing trophic pathways. Contrasts in fish and cephalopod demersal assemblages occurring at different depths not necessarily imply differences in the trophic resources uses in such complex shallow coastal ecosystems under anthropogenic influences.

Native and no-native herbivorous relationships have mutual benefit: Lepus flavigularis case

Lepus flavigularis is an endemic leporid from southeastern Oaxaca, México, listed as “endangered” under Mexican law and the IUCN Red List. The main threat to the species is severe habitat fragmentation due to human activities. The jackrabbit shares the grasslands with cattle (Bos taurus), but the trophic interaction between these herbivores is unknown. This study aimed to determine the seasonal diet of Lepus flavigularis and cattle, to identify the possible dietary overlap between these mammals. The study zone covers an area around the locality of Santa María del Mar in Oaxaca, southern México. Plant species were identified using linear transects, and vegetation cover was also estimated using circular plots. Throughout the study fresh L. flavigularis and B. taurus fecal samples were collected, which were processed using the microhistological technique to determine the seasonal botanical composition of diets from the two species. Twenty-three plant species were recorded in the diet of L. flavigularis and 29 species in the diet of B. taurus. Both herbivores fed primarily on Poaceae species throughout the year (L. flavigularis: dry season (ds) = 79.79 %, wet season (ws) = 91.54 %; B. taurus: ds = 78.02 %, ws = 84.63 %) despite the significant difference in the availability of plant species between seasons. No significant differences were found in the seasonal composition of the diet between the two species. Twelve plant species were consumed by both herbivores during the two seasons. The dietary overlap between the two species was high for both seasons (ds Ojk = 0.7311, ws Ojk = 0.8459). Trophic niche breadth was low for both species, with a high dietary overlap. We recorded low seasonal use values for L. flavigularis and B. taurus when compared to forage availability. Low trophic niche breadth and high dietary overlap between the two herbivores suggest forage resources competition. However, we expect that jackrabbits benefit from cattle presence, as long as the stocking rate does not increase. Furthermore, B. taurus grazing reduces height, cover, and density of vegetation, which could help L. flavigularis to avoid predators.

Mandible shape variation and feeding biomechanics in minks

European and American minks are very similar in ecology, behavior and morphology. Both species hunt terrestrial vertebrates and aquatic prey, but the American mink is a more generalist predator which, among other factors, allows it to outcompete the European mink in areas where it has been introduced. We used 3D geometric morphometrics and estimates of muscle mechanical advantage to assess the degree of variation in mandibular morphology, and to determine whether such variation reflects dietary differences between the two species. The three main axes of variation represented interspecific differences, a common allometric trajectory between species and sexes, and the interspecific effect of sexual size dimorphism, with males having overall stronger bites than females. Differences in mandible shape and biomechanical parameters suggest that American minks are better equipped for preying on terrestrial vertebrates, while the features seen in European mink could be related to tougher prey, fish capture, or both. Additionally, within each species, the larger specimens of each sex present indicators of a higher percentage of terrestrial prey in their diet. These results indicate a low potential dietary overlap between both species, suggesting that factors other than prey competition may have a role in the decline of the European mink.

Mechanisms of coexistence in a diverse Neotropical mammalian carnivore community

Abstract Mammalian carnivore diversity within the Reserva Natural del Bosque Mbaracayú in eastern Paraguay is represented by five families (Canidae, Mephitidae, Mustelidae, Procyonidae, and Felidae) and includes large-bodied, apex predators, several omnivores, and numerous mesocarnivores. The competitive exclusion principle argues that sustained spatial and temporal coexistence of two or more species with identical ecological requirements is unsustainable. The Reserve is a mosaic of habitats that has become isolated due to extensive deforestation of the surrounding Upper Paraná Atlantic Forest. Nevertheless, it is remarkable in that 16 mammalian carnivore species are documented as coexisting within the Reserve. We sought to determine the extent to which this diverse community is mitigating competition through the partitioning of available niche space by assessing dietary ecology of mammalian carnivores present, including diet breadths and dietary overlap, and by examining spatial patterns within the reserve. Feces were collected from all 16 mammalian carnivore species from seven areas within the reserve and specific identifications were confirmed by molecular analyses. Diet breadth, B^, standardized diet breadth, B^A, and Pianka’s Index for dietary overlap, O^, were calculated. A Chi-square goodness-of-fit test was performed to test for randomness of samples associated with survey areas. Diet analyses indicated a spectrum from dietary generalists to specialists. Species segregated into six dietary guilds, defined as groups of species with O^ > 0.5. Four guilds included only one species each (Neotropical otter, crab-eating fox, jaguar, and puma). The low dietary overlap between jaguar and puma contrasts with studies conducted elsewhere. One guild consisted of four highly omnivorous species (maned wolf, Molina’s hog-nosed skunk, crab-eating raccoon, and South American coati). The sixth guild included eight species which mostly consumed small vertebrates, primarily mammals as well as birds and reptiles (bush dog, two mustelines, five small felids). The mustelines (tayra and lesser grison) had extremely high dietary overlap. Although they did not segregate spatially, they are known to occupy distinct niches in vertically stratified forests. The five small felids also showed extremely high dietary overlap. Three of them were found to segregate spatially within the Reserve and two did not, although one (jaguarundi) is known to segregate temporally, being more active diurnally. The exceptionally rich community of mammalian carnivore species at the Reserva Natural del Bosque Mbaracayú appeared to avoid unsustainable competition by a variety of mechanisms, some utilizing different food items, or, in the case of high dietary overlap, utilizing spatial or temporal resources differently.

Do the evolutionary interactions between moths and bats promote niche partitioning between bats and birds?

Ecological theory suggests that the coexistence of species is promoted by the partitioning of available resources, as in dietary niche partitioning where predators partition prey. Yet, the mechanisms underlying dietary niche partitioning are not always clear. We used fecal DNA metabarcoding to investigate the diets of seven nocturnal insectivorous bird and bat species. Low diet overlap (2%–22%) supported resource partitioning among all species. Differences in diet corresponded with species identity, prey detection method, and foraging behavior of predators. Insects with ultrasonic hearing capabilities were consumed significantly more often by birds than bats, consistent with an evolved avoidance of echolocating strategies. In turn, bats consumed a greater proportion of noneared insects such as spruce budworms. Overall, our results suggest that evolutionary interactions among bats and moths translate to dietary niche partitioning and coexistence among bats and nocturnal birds.

Different food particle sources in the pearl oyster Pinctada margaritifera and its epibionts

Suspended bivalve culture (e.g. longlines) transfers benthic biomass - including bivalves and various epibionts - toward the water column, creating strong trophic interactions with the planktonic compartment. Trophic interactions are of central interest for ecologists, yet not well understood in coastal lagoon food webs, especially in tropical areas. Using stable isotope (SI) analyses, this study explored the trophic relationships between marine particulate organic matter (POM), pearl oysters and epibionts, in two contrasted production areas in French Polynesia. Different size classes of POM (0.7–2 µm, 2–20 µm, 20–80 µm, 80–250 µm and >250 µm) were well discriminated both by their δ13C and δ15N signature and results showed a low dietary overlap between pearl oysters and epibionts, likely due to assimilation of large particles in greater proportion by pearl oysters. Pearl oyster diet may vary in time in relation with variations of the basal trophic resource and selective feeding, such that their isotopic signature is more variable compared with that of epibionts. Pearl oysters and epibionts might alter nutrient cycling in a different way as reflected by their different tissue C:N.

Diet Diversity and Dietary Overlap of Two Sympatric Vulture Species in Hirpora Wildlife Sanctuary, Kashmir

Bird species that use similar resources are expected to use variant foraging approaches and segregate in order to minimize a possible competition among them. However, if they fail to attain this exclusion, competition results. We studied the diet composition and dietary overlap between two sympatric vulture species: Himalayan vulture (Gyps himalayensis) and Bearded vulture (Gypaetus barbatus), the two important avian scavengers of Hirpora Wildlife Sanctuary of Kashmir Himalaya. Analysis of pellets collected from feeding and roosting sites of these vulture species revealed a significant variation in their food consumption with Himalayan species consuming mostly larger dead mammalian species with higher frequency occurrence of 66.66% of Bubalus bubalus and bearded species the smaller dead mammalian ones with highest frequency occurrence of Ovis aries (83.82%). Diet spectrum of Himalayan vulture was more diverse (H’=1.97) than that of Bearded vulture (H’=1.64). The values of Berger-Parker index (Pimax) follows the reverse order of diversity with Pimax=36.2% for Himalayan vulture and Pimax =48.7% for Bearded vulture. There was very low dietary overlap between the two species (Ojk=0.466; C=0.457) which may favor their co-existence. The management of carrions of livestock and setting up of vulture restaurants is the need of the hour for the conservation of these scavenging birds which are facing high risk of extinction in Hirpora Wildlife Sanctuary.

Resource partitioning between fisheries and endangered sharks in a tropical marine food web

AbstractFisheries can act as top predators and affect marine biodiversity and ecosystem functioning via their target species. We studied a coastal food web in the Pacific Ocean that is modular and encompasses 360 species and small- and large-scale fisheries. Small-scale fisheries (SSF), two hammerhead sharks, one stingray, and one flatfish species are network hubs, interacting with multiple species among and within trophic levels (TLs) and modules. SSF and endangered hammerhead sharks act as hyper-hubs, which are network hubs preying on other network hubs and likely imposing widespread top-down effects. Hyper-hubs have two consequences to network structure. First, they show low dietary overlap, connecting the network in complementary ways. Second, they have overlapping indirect interactions, suggesting they can strongly affect each other. Simulations assuming distinct fishery regulations and species extinctions of different TLs and topological roles did not change network structure but redefined hub identity. We hypothesize that competition shapes resource partitioning between fisheries and hammerhead sharks. Our findings suggest that ecosystem-level strategies informed by network approaches can optimize investments to conserve marine ecosystems and ensure food security over coastal areas in the developing world.

Trophic ecology of syntopic anurans of tropical stream communities

AbstractWe investigated trophic resource partitioning in seven syntopic anurans from low- and mid-elevation stream habitats of a tropical riparian ecosystem by utilising stomach content analysis (SCA) and stable isotope analysis (SIA). Our SCA data revealed dietary similarities, narrow trophic niche breadth, and low dietary niche overlap inAnsonia muelleri, Limnonectes magnus, Occidozyga laevis, Megophrys stejnegeri, Pulchrana grandocula, Sanguirana mearnsi, andStaurois natatorwhich could be attributed to these anurans’ selection of available local prey items. We confirmed ant-specialisation (myrmecophagy) of the Mindanao island endemic bufonidA. muelleribased on our temporal SCA dietary data. Our SIA estimates of assimilation of potential prey sources confirmed thatL. magnus,P. grandocula, andO. laevisare generalist predators, opportunistically feeding on locally abundant insect prey items. This study on trophic resource partitioning in syntopic anurans provides the first picture of trophic interactions, i.e., predation and competition in stream communities in tropical riparian zones of a watershed ecosystem in northeast Mindanao of the southern Philippines.

Feeding interactions between Atlantic salmon (Salmo salar) postsmolts and other planktivorous fish in the Northeast Atlantic

In recent decades, there has been a decline in the marine growth of Atlantic salmon (Salmo salar) over large parts of the distribution range. One hypothesis for this reduced growth is increased interspecific competition with other planktivorous pelagic fish in the ocean. Here, interactions between salmon postsmolts and other pelagic fish (mackerel (Scomber scombrus) and herring (Clupea harengus)) in the Northeast Atlantic were investigated. There was a low diet overlap between postsmolts and the two other planktivorous pelagic species. Both mackerel and herring were feeding predominantly on copepods and other small zooplankton, while salmon were feeding mostly on fish larvae. All three species feed on euphausiids and amphipods. Furthermore, postsmolts geographically overlapped with mackerel but had a low geographic overlap with herring. There was no correlation between the abundance or survival of salmon from key index rivers and the abundance of pelagic fish. This study did not find evidence to support the hypothesis that observed temporal changes in marine growth and survival of salmon can be explained by feeding interactions with pelagic fish.

Trophic status and diversity of fish species in selected tributaries of Bentota River

Present study was carried out to investigate the, abundance and trophic status of fishes inhabiting tributaries of the Bentota River. Fish were sampled using gill nets, seine nets, cast nets and some were also collected from fishermen’s catches harvested at the tributaries of the Benthota River in Katapola, Ganegoda, Avitthawa, Yagirala and Galatara. To investigate the trophic status, stomach contents were analyzed and quantified using the Point method based on the percentage of bio volume per food category. Ten species of fish were recorded from all five sites, including two endemic species, Clarias brachysoma, Channa orientalis and one invasive alien fish Chitala ornata. Some indigenous species such as Puntius vittatus (n=400), Rasbora daniconius (n=134), Puntius dorsalis (n = 42) and Trichogaster pectoralis (n=71) were also caught in reasonable number. Parts of fish (scales, fins and flesh), mollusks, adult insects, insects larvae, macrophytes and digested/detritus matters were identified as main food categories in the stomach. Based on the gut content analysis, three feeding guilds i.e. piscivorous, herbivorous and zooplanktivorous, were identified. High diet overlap values were recorded in species pairs belonged to the same feeding guild i.e. Chitala.ornata- Channa orientalis while low diet overlap values were recorded in species belonged to different feeding guilds. Remains of fins of Channa orientalis, and Rasbora daniconius and some invertebrates observed in stomach contents of C. ornata, indicated its negative impacts on biodiversity in study sites. Therefore urgent attention should be paid to population control of C.ornata and to prevent its further invasion into new habitats.

Exotic Prey Facilitate Coexistence between Pumas and Culpeo Foxes in the Andes of Central Chile

Coexistence between species with similar ecological niches implies species must segregate along one or more niche axes to survive. Space, time, and trophic resources are regarded as the principal axes upon which species segregate. We examined segregation along these niche axes to determine mechanisms underlying coexistence between the two main predators, puma (Puma concolor) and culpeo foxes (Lycalopex culpaeus) in the Andes of Central Chile. We used occupancy modeling to examine space use and overlap, Kernel Density Estimation to determine temporal activity patterns and overlap, and analysis of prey remains in feces to assess diet breadth and similarity. We found high spatial overlap and positive associations between detection of the carnivores lending little support for spatial segregation. Similarly, we found high nocturnal, temporal overlap between pumas and foxes that matched peaks in activity of prey. In contrast, we found relatively low dietary overlap indicating niche segregation likely occurs along the dietary axis. The Puma diet was dominated by introduced, exotic hares and foxes appeared to shift away from hares to rabbits, small mammals, and seeds. Given that lagomorphs are the main dietary resource for pumas in particular, management decisions regarding the control or eradication of such exotic species could negatively affected puma survival.

Trophic ecology of tadpoles in floodplain wetlands: combining gut contents, selectivity, and stable isotopes to study feeding segregation of syntopic species

Little consensus exists on the role of food partitioning in the organization of tadpole assemblages. We studied trophic ecology of syntopic tadpoles through the analysis of gut contents, selectivity, and stable isotopes to assess the occurrence of food partitioning in tadpole assemblages. Tadpoles (n = 194) were collected in three wetlands and corresponded to four species: Elachistocleis bicolor (Eb), Scinax nasicus (Sn), Physalaemus albonotatus (Pa), and Dendropsophus sp. (D); and belonged to four ecomorphological groups (EMGs): suspension feeders (Eb), nektonic (Sn), benthic (Pa) and macrophagous (D). Sn, and Pa showed low selective diet and a wider trophic spectrum than Eb and D, which mainly consumed one or two food categories. Diet overlap was higher between Sn and Pa. Still, Sn and Pa presented some differences in the food resources consumed. Stable isotopes analysis showed that Eb, Sn, and Pa had a lower trophic position than D, explained by the high contribution of animal food oligochaete in D diet, in contrast to the importance of algae in the diet of Eb, Sn, and Pa. Diet specialization of some species, combined with the low dietary and isotopic overlap among the ecomorphological groups, suggests that trophic partitioning facilitates coexistence of syntopic tadpoles.

Temporal and ontogenetic variation in the diet of three small pelagic fish in the Black Sea of Turkey

In the South Eastern Black Sea, anchovy (Engraulis encrasicolus), sprat (Sprattus sprattus), and horse mackerel (Trachurus mediterraneus) are the most important small pelagic fish both ecologically and economically. The stomach contents of 1485 fish, including anchovy, sprat, and horse mackerel, were examined. Fish fed on 35 prey taxa, and there were dietary differences among predators. Anchovies predominantly consumed calanoid copepods and bivalves; sprats had a diet dominated by calanoid copepods and Chaetognatha (Parasagitta setosa); horse mackerel consumed mainly decapods and calanoid copepods. Copepods in the stomachs of sprat were more abundant and more frequent than in the stomachs of anchovy or horse mackerel during all year. As the anchovies and horse mackerel grew, their copepod consumption increased, but despite their size, sprats consumed a similar amount of copepods. Seasonal shifts in diet were observed in all three species. In winter and autumn months, all small pelagic fish consumed copepod species. The bivalve larvae were mostly consumed in summer by anchovies (N%: 72.98) and in spring by sprats and horse mackerel (N%: 88.59 and 81.08, respectively). Decapod species were preferred in spring months by horse mackerel. P. setosa was mostly consumed in autumn and winter by sprat. Anchovy showed a low dietary overlap with sprat but had a high dietary overlap with horse mackerel. The feeding strategy of anchovy seems to be mixed, while horse mackerel is a generalist at the individual level, and sprat is a specialist at the population level.

Diets of Two Nonnative Freshwater Turtle Species (Trachemys scriptaandPelodiscus sinensis) in Kawai Nui Marsh, Hawaii

Island ecosystems provide habitat for many endemic species that may be threatened by nonnative species introductions. We examined nonnative freshwater turtle occurrences and diets to examine potential predation effects on native species in Kawai Nui Marsh, Oahu, Hawaii. No freshwater turtles are native to the Hawaiian Archipelago. The Pond Slider (Trachemys scripta) and Chinese Softshell (Pelodiscus sinensis) were the only turtles found in the marsh after 767 trap days. Trachemys scripta stomachs (n = 50) contained mostly the nonnative plant Commelina diffusa and nonnative snails (Pomacea sp.), whereas Pelodiscus sinensis stomachs (n = 5) contained mostly snails. Interspecific dietary overlap was low and intersexual dietary overlap in the sliders was high, with more diverse female diets. Small, medium, and large size classes of T. scripta stomachs contained different proportions of plant and animal matter, with the small size class containing less plant matter than the medium size class, and the large size class containing a greater volume of animal than plant matter. No native species were found in the stomach contents of the turtles sampled except a freshwater sponge (Heteromyenia baileyi). This lack of native species in their diets may have more to do with the degraded state of the marsh and lack of native taxa than with a preference for nonnative taxa. A potential concern could be nonnative freshwater turtle presence in pristine wetland habitats in Hawaii, because of the higher abundances of native species in those areas.

Subtle foodscape displacement of a native ungulate by free‐ranging livestock in a forest agroecosystem

AbstractThe prevalence of livestock grazing in wildlife areas is increasing. This transformation of ecosystems into agroecosystems is concerning because the introduction of new species may cause niche displacement of the functionally related native species. We used a large‐scale fence scheme and fecal analyses to study the influence of free‐ranging livestock on moose diet on three boreal forest ranges. We found low interspecific diet overlap between moose and livestock (mean Pianka's O across ranges = 0.21, SD = 0.104), and the diet overlap with livestock did not differ between moose in areas with livestock and in adjacent control areas without livestock. Still, moose sympatric with livestock had less fecal nitrogen (a proxy for diet quality) than moose in the control areas. Our findings suggest that interspecific interactions other than direct food competition contributed to reduce the moose’ foraging opportunities, such as altered forage abundance and composition, or behavioral avoidance of livestock. We caution that displacement in the foodscape (i.e., spatiotemporal use of food) can occur through pathways not evident in niche indices based on composition of plant species in the diet.

Selecting Piscivorous Bird Species for Monitoring Environmental Change in the Banc d'Arguin, Mauritania

This study aims to select piscivorous bird species to be used as indicators to monitor changes in fish diversity at the Banc d'Arguin, Mauritania. Such species should have a high diet diversity, low dietary overlap and data should be easy to collect. We compared the diets of five colony nesting bird species at the Banc d'Arguin: the Slender-billed Gull Chroicocephalus genei, Caspian Tern Hydroprognecaspia and Royal Tern Thalasseus maximus albididorsalis, which are part of an ongoing monitoring program, and the White-breasted Cormorant Phalacrocorax carbo lucidus and Mauritanian Spoonbill Platalea leucorodiabalsaci as potential new additions. All species considerably differed in prey species composition, prey species diversity and prey size. Diet overlap indices varied between 0.05 and 0.69 with the highest overlap values between Mauritanian Spoonbill and Slender-billed Gull. There are major differences between the species in ecological and behavioural mechanisms promoting diet segregation, such as foraging habitat use, foraging ranges and prey-catching techniques. We conclude that the species investigated serve our monitoring goal well. Practical recommendations for the implementation of a monitoring program are given.

Boreal forest titans do not clash: low overlap in winter habitat selection by moose (Alces americanus) and reintroduced bison (Bison bison)

Despite moose (Alces americanus) likely being both an ecological and cultural keystone species in the North American boreal forest, few studies have examined niche overlap between moose and other ungulates. In response to concerns from local people about the potential for competition for habitat between moose and reintroduced bison (Bison bison), and the potential for disturbance to moose by bison and bison hunters, we investigated overlap in winter habitat selection by these species in southwestern Yukon, Canada. We used available geo-referenced data of animal locations, and associated environmental covariates, to develop resource selection probability function (RSPF) models of early-winter and late-winter habitat selection by moose and bison. In early-winter, moose selected sub-alpine shrub-dominated habitats, whereas bison extensively selected wet sedge meadows in lowland valleys. Both species used a greater variety of habitats in late-winter, with moose selecting drainages above tree line or river valleys with deciduous forest cover, while bison selected either south-facing grassy slopes or wet sedge meadows. Given observed differences in seasonal habitat selection between moose and bison, these species are predicted to overlap on only 0.5 and 6.6% of our 12,818-km2 study area during early-winter and late-winter, respectively. The lack of demonstrated winter habitat overlap between moose and reintroduced bison, coupled with low diet overlap, points to an overall low potential for competition for winter habitat between these species, or for disturbance to moose attributable to bison or bison hunters. Resource partitioning that facilitates coexistence on a shared landscape suggests that concern over the impact of reintroduced bison on resident populations of moose is likely unwarranted.

Interannual Variation in Diet, Dietary Diversity, and Dietary Overlap in Three Sympatric Strepsirrhine Species in Southeastern Madagascar

Dietary data are used to categorize species diets, but these categorizations do not take into account the mutability of food resources in time or space, the level of interspecific competition in various communities as these resources change, nor the dietary flexibility of species. In this study, we assess the diets of three sympatric species, Eulemur rufifrons, Propithecus edwardsi, and Varecia variegata, in the Vatoharanana site in Ranomafana National Park, Madagascar. We determine dietary diversity, overlap, and interannual variation with data collected from 2001 to 2003. We then compare results on food preference and time feeding with data collected on each species in the late 1980s and early 1990s to determine whether these findings are consistent over the long term. We found little interannual variation in the proportion of time spent eating particular plant parts for each of the lemur species during the three study years (2001–2003), and between the earlier and current study. Food items were not always consumed based solely on availability. Dietary diversity was lower in the two frugivorous species (V. variegata and E. rufifrons) compared with the folivorous species (P. edwardsi), and V. variegata and E. rufifrons were more likely to focus their feeding time on one particular genus and plant part in each year. The study species used different strategies to deal with food, particularly fruit, shortages such as a plastic social structure (V. variegata), habitat shifting (E. rufifrons), and dietary switching (P. edwardsi). Although there was low dietary overlap between the study species, they depended on a small number of shared fruits in each of the study years (Chrysophyllum, Syzygium, Ocotea, Plagioscyphus), which may indicate some potential for interspecific competition. Because these lemur species, like all primates, lead relatively long lives (avg. >30 years) and have slow rates of aging, longitudinal studies are needed to test hypotheses reliant on basic dietary information.

Trophic dynamics of few selected nearshore coastal finfishes with emphasis on prawns as prey item

A trophic dynamic study of marine finfishes was undertaken based on stomach content analysis of twenty four species (N = 1742) collected from the nearshore coastal waters off Goa, west coast of India (15°29′07.6″ N to 15°34′44.3″ N, and 73°38′10.5″ E to 73°46′03.1″ E) during November 2010 to May 2013. This study aimed to thoroughly understand the feeding attributes of finfishes, and comprehend the possible effects of bycatch-related loss of biomass on trophic ecology. The study assessed diet preferences of the finfishes, their feeding guilds, significance of prawns as prey items, and the influence of mouth parts in prey selection. Altogether 84 prey taxa were identified from the stomach contents. Percentage Index of Relative Importance (IRI) values revealed that zooplankton (34.74), prawns (21.71), phytoplankton (19.80), and teleosts (18.62) were the major prey categories, and, among prawns, Metapenaeus dobsoni (%IRI = 19.34) was the single-most important prey item. Cluster analysis revealed three major trophic guilds namely ‘teleost feeders’ (mean Trophic Level (TrL) = 4.06 ± 0.42; mean B = 0.46 ± 0.24), ‘zooplankton feeders’ (mean TrL = 3.43 ± 0.29; mean B = 0.23 ± 0.13), and ‘prawn feeders' (mean TrL = 3.86 ± 0.25; mean B = 0.48 ± 0.32), with low diet overlap among them. Principal Component Analysis of prey categories and mouth parts of finfishes suggested that zooplanktivory is associated with gill raker density as well as number of gill arches bearing rakers, whereas gape height determined the size of large-sized prey (fish and invertebrates). The study identified M. dobsoni, mysis and teleosts as highly influential prey for predatory finfishes. The present results could be useful to resolve broader issues in fisheries management.