Seasonal Variation in Diet and Feeding Strategy of Three Mayfly Species

Understanding the feeding habits of aquatic invertebrates under reference conditions can contribute to our understanding of community assemblages in freshwaters. Here, seasonal changes in the diet of three species of Ephemeroptera from Irish high status rivers were investigated. A fluorescent dye, 4'6 diamidino-2-phenylindole, was used to differentiate the various types of gut contents and to allow bacteria and biofilm matrix to be visualised. Through interpretation of gut contents and feeding strategy plots, Baetis rhodani was found to have a generalist diet with detritus, algae and biofilm—the main food types. Two congeneric species, Ecdyonurus venosus and E. insignis, were found to be detritus specialists. Seasonal sampling indicated that biofilm can provide a valuable food source to E. venosus at times of high flow when detritus is not readily available. There was evidence of niche separation in summer when E. insignis and E. venosus co-existed. E. insignis fed on coccoid algae while E. venosus consumed no coccoid algae. B. rhodani consistently ingested a similar broad diet throughout the year. A detritus-based diet is likely nutrient poor leading to lower growth rates. These findings are discussed in the context of the behaviour of these species and sensitivity to nutrient enrichment.

Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima, southwestern Japan, were studied for 2 years by means of fecal analysis. The altitudinal range of fecal samples collected was 30 m to 1,203 m above sea level, and it was divided into three zones: low-zone forest (0-399 m), middle-zone forest (400-799 m), and high-zone forest (800 m-1,230 m). There was a considerable altitudinal and seasonal variation in the macaques' diet. Seed/fruit and animal matter were eaten more in the lower zones, whereas more fiber and fungi were consumed in the higher zones. In all of the zones, they ate seed/fruits the most in autumn (September-November) and the least in spring (March-April). They ate fibrous food the most in spring and the least in autumn. Macaques relied on seed/fruits heavily in the lower zone for a longer period than in the higher zones. Macaques in the high-zone forest ate almost no seed/fruit foods from March to May. Altitudinal variations in availability of seed/fruit foods seem to have influenced the altitudinal variations in diet. Total basal area of seed/fruit-food trees, species richness of seed/fruit-foods, main seed/fruit-food types available, and annual fleshy-fruit production all decreased with increasing altitude. Both interannual variation and annual cyclicity of diet were found in all zones.

Capsule Redshank diet from southern Europe during migration shows spatial and seasonal variations. Aims To assess seasonal variation in Redshank diet at a major passage site, and to compare data derived from analysing pellets or faeces. Methods At the Odiel Marshes in 2001, pellets from spring migration (39), autumn migration (121) and midwinter (15) were analysed, together with faecal samples from autumn (84). Results The abundance of different invertebrate groups in pellets varied between seasons. In spring, Chironomus salinarius pupae and larvae dominated by volume, followed by Ephydridae larvae and the beetle Paracymus aenus. Polychaetes and molluscs dominated in autumn, and isopods in midwinter. In autumn, chironomid larvae, Mesembryanthemum nodiflorum seeds and Artemia cysts were relatively more abundant in faeces, whereas polychaetes, isopods, molluscs and cestode cysticercoids were more abundant in pellets. Harder and/or larger items were thus relatively more abundant in pellets than faeces. Pellet analysis gave more emphasis to mudflat prey, and faeces to saltpan prey. Conclusion Pellet and faecal analysis give different results for wader diet, and it is useful to combine the two methods. However, they show significant correlations both in diet range and rank abundance of prey items. Redshank diet shows much seasonal and spatial variation in southern Europe.

Seasonal variations in the plant diet of the Chinese Monal revealed by fecal DNA metabarcoding analysis

The stomach contents of 1,047 harbour porpoises (Phocoena phocoena) bycaught in gillnets off Iceland were analysed. Most of the samples were obtained southwest (SW) and southeast (SE) of Iceland and the majority were taken in March and April. The sex ratio was biased towards males (63% males), particularly in the SE area (76%). The proportion of sexually mature porpoises was 35% and was higher in the northern part of the study area. Most examined stomachs contained identifiable food remains (97%). More than 40 fish and invertebrate prey taxa were identified.Overall capelin (Mallotus villosus) comprised the predominant prey, followed by sandeel (Ammodytidae sp.), then gadids, cephalopods and redfish (Sebastes marinus), while other taxa were of less importance. Differences were detected in diet composition among 5 areas around Iceland with redfish and gadids more prominent in the northern areas. Off SW Iceland there was considerable seasonal variation in the porpoise diet, where capelin appeared to be dominant in late winter and spring and sandeel in the summer through early winter. Predominance of capelin in the diet coincided with the spawning migration of capelin from northern waters along the east, south and west coasts of Iceland. Mature females appeared to have a more diverse diet than other reproductive classes. The length distributions of fish consumed by the porpoises ranged from 1 to 51 cm although most fish prey were less than 30 cm.

Strengthening of the East Asian summer monsoon revealed by a shift in seasonal patterns in diet and climate after 2–3 Ma in northwest China

Temporal and spatial variation in Hg accumulation in zebra mussels (Dreissena polymorpha): Possible influences of DOC and diet

Feeding habits and habitat use of the colubrid snakes Philodryas olfersii and P. patagoniensis in southern Brazil are presented here. Philodryas olfersii and P. patagoniensis are sympatric in the study area and both dwell in open and forested areas. Specimens preserved in collections and observations of snakes in the field yielded the data. Both species are diet generalists, feeding on small vertebrates, mainly frogs. Philodryas patagoniensis has a broader diet, a less variable frequency of food items, and fed on heavier prey than P. olfersii. Seasonal variation in diet occurs in both species. The semiarboreal Philodryas olfersii is more slender and has a longer tail than the terrestrial P. patagoniensis, characters that may reflect differences in microhabitat use. There are a strong relationship between habitat use and frequency of a given food type. Differences in the use of food resources between P. olfersii and P. patagoniensis seem to reflect differences in foraging microhabitats used by each species.

Stone martens (Martes foina) are documented as generalist throughout their distributional range whose diet composition is affected by food availability. We tested if this occurs and what feeding strategies it follows in a typical Mediterranean ecosystem in Central Greece by analysing contents from 106 stomachs, seasonally collected from three different habitats during 2003–2006. Seasonal variation in diet and feeding strategies was evident and linked to seasonal nutritional requirements, but possibly imposed by strong interference competition and intraguild predation. Fleshy fruits and arthropods predominated in the diet, but also mammals and birds were frequently consumed. An overall low dietary niche breadth (B A = 0.128) indicated a fruit specialization tendency. A generalised diet occurred in spring with high individual specialisation, whereas more animal-type prey was consumed than fruits. A population specialization towards fruits was indicated during summer and autumn, whereas insects were consumed occasionally by males. In those seasons it switched to more clumped food types such as fruits and insects. In winter it selectively exploited both adult and larvae insects and partially fruits overwinter on plants. The tendency to consume particular prey items seasonally reflected both the population specialist behaviour and the individual flexibility preyed on different food resources.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 481:249-268 (2013) - DOI: https://doi.org/10.3354/meps10233 Long-term variation in common dolphin diet in relation to prey abundance M. Begoña Santos1,*, Imogen German1,2, Diana Correia1,3, Fiona L. Read1,2, Jose Martinez Cedeira4, Mara Caldas5, Alfredo López4, Francisco Velasco6, Graham J. Pierce2 1Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, PO Box 1552, 36200 Vigo, Spain 2Oceanlab, University of Aberdeen, Aberdeenshire AB41 6AA, UK 3University of Algarve, 8005-139 Faro, Portugal 4CEMMA, PO Box 15, 36380 Gondomar, Spain 5Investigación Planificación y Dessarrollo S.A., Paseo Imperial 10-12, Bajo, 28005 Madrid, Spain 6Instituto Español de Oceanografía, Centro Oceanográfico de Santander, Promontorio San Martín, s/n. PO Box 240, 39080 Santander, Spain *Email: m.b.santos@vi.ieo.es ABSTRACT: Understanding the effects of changes in prey abundance on predators is essential to predict responses of marine ecosystems to perturbation and ensure sustainable fishing. As abundant top predators feeding largely on commercially exploited fish, common dolphins Delphinus delphis are expected to be affected by fluctuations in fish abundance. Previous studies variously suggest that common dolphins show a preference for energy-rich species or that they are opportunistic predators. In the latter case, the intensity of predation on all prey species would be expected to vary in proportion to their abundances. If such relationships are seen for only a few prey species, and the importance of other species varies inversely with the abundance of these ‘preferred’ prey, this would indicate selective feeding. We suggest that studies on diet at the population level can provide insights into such individual-level foraging decisions. We analysed stomach contents from 514 stranded and by-caught common dolphins in Galicia (NW Spain), collected over 2 decades. The most important prey were sardine, blue whiting and hake. Using zero-inflated generalised additive models to deal with non-linear relationships and the high number of zeros in prey count data, we tested for evidence of ‘preference’ for the main prey species, as well as confirming the existence of ontogenetic, spatial and seasonal variation in diet. Relationships between diet and annual prey abundance do not conclusively confirm either opportunistic or selective predation, but there is more evidence for the former. Lack of evidence for selective predation on energy-rich sardine could be due to current low stock levels. KEY WORDS: Diet selection · Sardine · Hake · Blue whiting · Feeding ecology · Zero-inflated models Full text in pdf format PreviousNextCite this article as: Santos MB, German I, Correia D, Read FL and others (2013) Long-term variation in common dolphin diet in relation to prey abundance. Mar Ecol Prog Ser 481:249-268. https://doi.org/10.3354/meps10233 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 481. Online publication date: May 07, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Seasonal variation in diet of golden jackal in Serbia was assessed by stomach content analysis. During the period 2004–2013, 339 samples were collected at two localities—Surcin (central Serbia, 15 km west of Belgrade, along river Sava) and Veliko Gradiste (northeastern Serbia, 85 km east of Belgrade, along Danube River). Jackals consumed a broad range (15) of different food categories. Seasonal differences in diet are related with the availability of certain food categories. Small mammals are the most important food category when they are most abundant—in summer and autumn regarding both frequency of occurrence and frequency of biomass consumed (32.1 %O and 36.5 %B, and 29.0 %O and 37.0 %B, respectively). Moreover, high percentage of plant material is recorded during summer (23.8 %O, 20.8 %B), consisting mainly of fruit that ripen at this time of the year. Due to presence of domestic ungulate leftovers on illegal dumps year-round, this food category is representing its staple diet. High overlap between summer and autumn as well as between winter and spring is recorded (C = 0.97 and C = 0.94, respectively). These findings confirm golden jackal’s opportunistic nature, foraging behaviour and high dependence on human-provided food resources.

Ontogenetic and seasonal variation in diet was examined for 11 species of insectivorous forest-floor frogs and lizards from a lowland wet forest in north-eastern Costa Rica. Specimens were collected systematically over an entire seasonal cycle and represented individuals of all sizes. Individual prey items were removed from stomachs of preserved specimens, measured and identified. Ontogenetic shifts in prey size were pervasive. Ontogenetic shifts in prey composition were limited to four species; these were not the species with greatest range in body size, nor the species with the broadest diets. Small prey types (ants, mites, collembolans) decreased in representation and large prey types (roaches, orthopterans, millipedes) increased in importance over ontogeny; this could be because prey selection is based primarily on prey size or because of different prey preferences among age classes. There is little evidence for size-structure in this assemblage. There is no evidence that total availability of arthropod prey varies among seasons, but some evidence that preferred prey are less common in the wet season. Diet was similar between lizards and frogs. Lizards were more likely to have empty stomachs, but also greater stomach volume, than frogs; this indicates a difference in food-gathering strategies. Our study indicates strong similarity between frogs and lizards in diet despite enormous differences in physiology and behaviour.

We studied the foraging ecology of a tropical seabird community in 2 islands of the Seychelles from 2005 to 2007. Chick dietary samples were used to compare feeding habits among species and assess inter-annual and seasonal variations in diet. Fish prey dominated the diet of the community (68 to 100%, of prey consumed), although cephalopods were present in 61.3, 40.0, 27.1 and 32.9% of the food samples from white-tailed tropicbirds, sooty terns, brown noddies and wedge-tailed shearwaters, respectively. We found high diet overlap between species (Mullidae fish being the first prey consumed [30 to 90%] for all species except for the white-tailed tropicbird [\textless2%]) but some segregation in prey length. Other important prey were Exocoetidae, Carangidae, Scombridae and Clupeidae mainly for white-tailed tropicbirds, sooty terns and brown noddies, Hemiramphidae and Coryphaenidae for white-tailed tropicbirds, and Engraulidae and fish larvae for lesser noddies and Audubon's shearwaters. Despise some inter-annual and seasonal variations in diet, these were not consistent within the community. Responses of the seabird community to an environmental perturbation that negatively affected chick growth and breeding success of lesser noddies emphasised the higher vulnerability of species with smaller foraging ranges and/or with lower ability to switch diet (lesser noddy, roseate tern) compared to less range-restricted and/or more opportunistic ones (white-tailed tropicbird, brown noddy, sooty tern, white tern). Although situated in a tropical region, the food availability in the Seychelles seems to be predictable at a large (annual) temporal scale, but highly unpredictable at a small (intra-seasonal or daily) temporal scale.

Herbivorous fishes can be sensitive to environmental fluctuations, which influence both availability of food resources and metabolic rate, and thus nutritional requirements. Impacts on herbivore nutritional ecology may result from seasonal variations in temperature and meteoceanographic shifts such as wind-induced upwelling events. We evaluated the effects of seasonal changes on the nutritional ecology of 3 nominally herbivorous fishes (Acanthurus chirurgus, Sparisoma axillare and Kyphosus vaigiensis) in a subtropical rocky reef on the southeastern Brazilian coast using a combination of gut content analysis (at 2 scales of magnification) and stable isotope analysis. Sampling of in situ water temperature covered both patterns of seasonal variation in sea surface temperature, and seasonal occurrence of upwelling. Local upwelling occurred throughout the year but less frequently in winter. Diet and isotopic niche displayed little seasonal variation. Species-specific patterns of seasonal variation indicated distinct responses to environmental fluctuations. Temperature alone cannot explain the locality-specific variation in the nutritional ecology of herbivorous reef fish, and contrary to predictions that digestion in herbivorous fishes is impaired by cooler temperatures, no significant shifts in species’ nutritional ecology were detected.

The stomachs of 130 sandpaper skates, Bathyraja kincaidii (Garman, 1908), were sampled from off central California to determine their diet composition. The overall diet was dominated by euphausiids, but shrimps, polychaetes and squids were also important secondary prey. A three-factor MANOVA demonstrated significant differences in the diet by sex, maturity status and oceanographic season using numeric and gravimetric measures of importance for the major prey categories. These three main factors explained more variation in diet than interactions between the factors, and season explained the most variance overall. A detailed analysis of the seasonal variation among the prey categories indicated that abundance changes in the most important prey, euphausiids, were coupled with seasonal changes in the importance of other prey. When upwelling occurred and productivity was great (Upwelling and Oceanic seasons), euphausiids were likely highly abundant in the study area and were the most important prey for B. kincaidii. As productivity declined (Davidson Current season), euphausiids appeared to decrease in abundance and B. kincaidii switched to secondary prey. At that time, gammarid amphipods and shrimps became the most important prey items and polychaetes, mysids and euphausiids were secondary.