Numerous Prey Research Articles

An Assessment of Spatial and Temporal Variation in the Diet of Cape Clawless Otters (Aonyx capensis) in Marine Environments

We studied the diet of Cape clawless otters (Aonyx capensis) at three sites along the eastern and southern coast of South Africa to assess possible spatial variation along a community species richness and biomass gradient associated with rocky shores. A total of 309 spraints representing two seasons (summer 2013/2014 and winter 2014) were collected and subsequently analysed. The percentage occurrence and percentage dry mass of numerous prey categories were compared between sites and seasons. Variation in the importance of prey items was found between sites, whilst no variation was found between seasons within the same site. Crab was the most important prey item in the southernmost study area (Tsitsikamma National Park) and at the northernmost study site (KwaZulu-Natal Coast), whilst lobster was the most important prey item in the central area (Mkambati Nature Reserve). Fish was the second most important prey item at all three sites. Our results suggest that otters are opportunistic feeders that are likely able to adapt to potential prey species and abundance changes associated with current and future anthropogenically driven changes. Furthermore, long-term, site-specific stability in diet suggests that monitoring the diet of otters could provide some useful information on the status of shoreline communities.

Behavioral responses of predator-naïve dwarf hamsters (Phodopus campbelli) to odor cues of the European ferret fed with different prey species

Many mammalian predators are able to identify their prey by odors and, vice versa, numerous prey species recognize predator odors as well. The present paper reports on the behavioral responses of predator-naïve dwarf hamsters (Phodopus campbelli) towards the urine odors of carnivorous ferrets, which were raised on either a chicken, mouse or hamster diet. Chemical composition from ferret urines of the different diet groups was analyzed, while quantitative differences in urinary volatile constituents were observed through capillary gas chromatography–mass spectrometry. In a Y-maze arrangement, hamsters were offered several two-choice odor discrimination tasks and their behavior was quantified. Hamsters were easily able to discriminate the urine odor of ferrets fed with mice against ferrets fed with hamsters. This is probably the first report indicating that a prey species can distinguish urine odors of even an unknown predator species that has been fed different prey species. The analytical data complemented behavioral assays.

Feeding Potential of Adult Dragonflies, <I>Pantala flavescens</I> (Fabricius), <I>Brachythemis contaminata</I> <I>Fabricius</I> and <I>Bradinopyga geminata</I> Rambur (Anisoptera: Libellulidae) on Insect Pests under Laboratory Condition

Feeding potential of three dragonfly species was worked out on the basis of numerical value and fresh prey weight under laboratory condition at Anand (Gujarat) during 2013. Adult dragonflies , viz., Pantala flavescens , Brachythemis contaminata and Bradinopyga geminata were used as predator and Nilaparvata lugens , Aphis craccivora and Aedes sp. were used as prey. Daily biomass consumption of P. flavescens, B. contaminata and B. geminata were 224.51 mg, 149.35 mg and 169.34 mg respectively. The prey numbers consumed by each dragonfly species were significantly different. However, irrespective of prey species biomass consumption was the same. Feeding potential of the dragonflies was positively correlated with their body weight. Feeding potential of females of P. flavescens and B. contaminata was slightly higher than their respective males.

Food habits and resource partitioning in a guild of Neotropical swifts

ABSTRACT The Coastal Cordillera of Venezuela has a rich avifauna including swifts. The aerial arthropod prey of three species found there, Gray-rumped Swift (Chaetura cinereiventris), Vaux’s Swift (Chaetura vauxi), and White-tipped Swift (Aeronautes montivagus), included spiders plus nine orders and 110 families of insects. Diptera and Hymenoptera were the most numerous prey taxa (>60%) taken by all three swifts. Prey size ranged from 0.5–17.9 mm body length, and averaged 2.69 mm for Gray-rumped Swifts, 2.91 mm for Vaux’s Swifts, and 5.52 mm for White-tipped Swifts. Niche breadth was similar in Gray-rumped and Vaux’s Swifts (2.4 and 3.13), and niche overlap was also high (0.98). Niche breadth was higher in White-tipped Swifts (8.49) and niche overlap was <60 with both Gray-rumped and Vaux’s swifts. Observed elevational differences in foraging habitat and altitudinal foraging zones are proposed as resource partitioning mechanisms for this guild of sympatric aerial insectivores.

Intra-specific plasticity in parental investment in a long-lived single-prey loader

Seabirds exhibit considerable behavioural flexibility in foraging investment in order to meet the nutritional needs of their chicks during variable environmental conditions. Although regulation of offspring provisioning is generally thought to be related to species-specific constraints imposed by central place foraging, some studies suggest different responses within the same species linked to local differences in foraging conditions. Under adverse conditions, seabirds are expected to be less flexible because they must secure their own survival chances first before investing in current reproduction. Short-ranging single-prey loaders are expected to show large intra-specific variation in time spent on foraging because their mode of foraging is energetically expensive, and because they face restricted possibilities to increase the numerical prey input to the colony compared to multiple prey loaders. In this study, we examined if and how the single-prey loading Sandwich Tern Thalasseus sandvicensis varies colony attendance based on the nutritional status of their chick as well as parental body condition in two study colonies. The proportion of time that a chick was left unattended at the colony negatively correlated with chick body condition, suggesting that the parents tried to counterbalance poor feeding conditions by investing more time in foraging. Energy transport rates to the chicks (corrected for time spent away from the colony) and body condition of the chicks were similar in both colonies. However, at Zeebrugge, where adults were in poor body condition, parental non-attendance was much lower than on Griend, even when chicks were in poor condition. Still, our results suggest that parental nest non-attendance in Sandwich Terns is merely a corrective response to food loss to kleptoparasitic gulls in order to meet the nutritional status of the chick, although an effect of adult body condition could not be excluded.

Diet composition of an invasive population of Lithobates catesbeianus (American Bullfrog) from Argentina

The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.

Diet of Barn Owl Tyto alba in Central South Bulgaria as influenced by landscape structure

This study of the diet of Barn Owl Tyto alba analyzed pellets containing 18,810 prey specimens. Small mammals (98.2% by number, 97.5% by biomass) dominated, while birds, reptiles, amphibians, and insects constituted a negligible portion of the diet (1.8% by number, 2.5% by biomass). Voles (Microtus spp.) were the most numerous prey (35.3 ± 14.4%, range 14.6%-67.1%) in 9 localities (69.2%, n = 13 individually studied localities) and dominated the biomass in all diets (51.4 ± 14.1%, range 27.4%-78.2%). The lesser white-toothed shrew (Crocidura suaveolens) (20.8 ± 7.6%, range 7.3%-32.8%) was the most frequent prey in the other 4 localities (30.8%). The breeding localities with more similar proportions of habitats in their hunting territories had significantly higher diet overlaps (r = 0.336, P < 0.01). The amount of wetlands and the indices of habitat heterogeneity and topographic relief among the landscape characteristics of the hunting territories significantly influenced diet composition according to redundancy analysis. Larger areas of wetlands correlated with higher predation on wetland mammal species, as well as the European pine vole (Microtus subterraneus) and white-toothed shrews, and thus with broader food niche breadth.

Diet of a Cryptic but Widespread Invader, the Oriental Weatherfish (Misgurnus anguillicaudatus) in Idaho, USA

Abstract The oriental weatherfish (Misgurnus anguillicaudatus) is invasive to 13 U.S. states and at least 9 other countries. Although this cryptic fish species is widespread, very little is known regarding its ecology. We used baited minnow traps to collect 237 individuals from water bodies connected to the Boise River, Idaho. To determine the diet of the fish within this invasive population, we dissected and examined stomach contents of the sampled fish. Most of the stomachs (158 of 237) were empty, and 42 contained only the trap bait. However, 37 contained natural food items. Gravimetric analysis, frequency of occurrence, and mean percent by number all indicated macroinvertebrates as the primary diet component, with chironomid larvae as the most numerous prey eaten. Graphical analysis of prey-specific abundance also indicated that oriental weatherfish fed on a generalized diet, of which detritus is likely an important part. An omnivorous diet may, in part, explain the species' ability to expand its inva...

Prey selection by nesting House Martins Delichon urbica Linné, 1758 (Aves: Hirundinidae) in Algiers suburbs (Algeria)

The diet of the House Martin Delichon urbica was analyzed in a suburban area in Pins maritimes, northeast of Algiers (Algeria). The diet was determined by analyzing 120 faecal samples collected from a breeding colony between April and September 2007. Insects were the most numerous prey types (99.86%). Hymenopterans were the dominant preys (56.99%), followed by Coleopterans (20.14%), Homopterans (14.22%), Heteropterans (5.45%), and Dipterans (3.10%). Division of the prey items into families demonstrated that the highest relative frequency was large Hymenopterans in the family Formicidae (54.0%). The dominant species in the diet was Tetramorium biskrensis, which comprised 32.6% of the diet. It was followed by Camponotus barbaricus (6.9%) and Monomorium salomonis (5.6%). Comparison between diet and availability of preys using the Savage index showed that T. biskrensis, Crematogaster scutelaris, Pheidole pallidula, Diptera sp. unident. and Aphidae sp. unident. were positively selected by D. urbica.

Abundance, size, and diel feeding ecology of Blackfordia virginica (Mayer, 1910), a non-native hydrozoan in the lower Napa and Petaluma Rivers, California (USA)

Blackfordia virginica (Mayer, 1910) is a small hydrozoan that has invaded estuaries around the world. In the lower Napa and Petaluma rivers, located within the San Francisco Estuary, B. virginica populations followed a classic pulsed bloom event. Medusae monthly bell diameter measurements showed an initial increasing trend with a wide range of sizes, followed by a decreasing average size and narrower size range towards bloom culmination. Biomass was generally greatest in June. Medusae were pelagic feeders, consuming both invertebrates and fish larvae. Copepod nauplii were by far most numerous prey in the guts, followed by cyclopoid copepods and mysids. Further studies of B. virginica are needed to understand its potential impacts on estuarine ecosystems, which may be great where it is abundant.

Diet and foraging habitats of non-breeding white storks (Ciconia ciconia) in Bulgaria

The diet of non-breeding White Storks was studied by pellet analysis and included mainly insects (99.9%, n=28947) with a predominance of grasshoppers (Orthoptera, 76.1%), and beetles (Coleoptera, 26.1%). The bush crickets Decticus albifrons/verrucivorus were the most numerous prey (29.9% by items), occurring in almost all pellets (98% occurrence in pellets, n=147) and predominating in half of them (49.7%). The grasshopper associations in the pellets specify foraging mainly in mesophytic grasslands that usually replace abandoned fields and overgrown pastures with a low level of grazing. The xerophytic grass-shrubby habitats, not rare on stony terrains, were of less importance, providing around 20% by prey. The typical aquatic inhabitants and the use of carrion around villages were exceptions in the study diet. The number of innutritious materials in the pellets rose when the White Storks hunted on nippy and agile grasshoppers and decreased when the main pray was slower beetles taken from the ground. The roosting of non-breeding White Storks disappeared when their preferred feeding habitats were ploughed up in the following years.

Notes on feeding ecology of macrourid fishes from the mid-Atlantic Ridge, North Atlantic

At least 16 macrourid fishes (Gadiformes, Macrouridae) inhabit the mid-Atlantic Ridge of the North Atlantic. To investigate the roles of macrourids in the food-web and compare feeding patterns of the most frequent co-occurring species, diet information on five of the species were described and compared. Pelagic and benthopelagic copepods were the most numerous prey but did not contribute much on a weight basis. Cephalopods were by far the most important prey of the small grenadiers, while shrimps and fish became increasingly significant with increasing size. Previous studies from other areas have also found pelagic prey to be important, but in contrast to this study, cephalopods were more important on the mid-Atlantic Ridge than in continental margin locations.

Feeding habits of small-spotted catshark (Scyliorhinus canicula Linnaeus, 1758) from the eastern central Adriatic Sea

The feeding habits of small-spotted catshark, Scyliorhinus canicula, from the central Adriatic Sea, were investigated with respect to fish size, season and sampling location. Stomach contents of 1200 specimens, collected at monthly intervals (January to December 2010), were analysed. The prey items identified in the stomachs belonged to eight major groups: Cephalopoda, Polychaeta, Stomatopoda, Decapoda, Mysidacea, Euphausiacea, Amphipoda and Teleostei. Decapods were the most important ingested prey in all seasons, for medium sized fish (22–38 cm TL). Euphausiids and mysids constituted the main prey items of small fish (<22 cm TL) while teleosts dominated the stomach contents of larger specimens (>38 cm TL). Two decapods, Alpheus glaber (%IRI = 5.1) and Solenocera membranacea (%IRI = 3.0), were the most numerous prey items identified to species level. The mean weight of stomach contents (relative to predator size) increased significantly for fish larger than 30 cm TL, while the mean number of prey items did not differ significantly among size-classes. The percentage of empty stomachs showed a monthly variation with a maximal occurrence in February (48.0%) and a minimal in August (9.0%). The lowest feeding frequency could be related to low sea temperatures during the winter. The small-spotted catshark could be considered a generalistic predator.

Food Habits of Two Fork-tailed Swifts in Venezuela

The aerial arthropod prey of Neotropical Palm Swifts (Tachornis squamata) and Lesser Swallow-tailed Swifts (Panyptila cayennensis) in Venezuela included seven Orders and 60 families of insects plus spiders and mites. Diptera were the most numerous prey (>50%) taken by both swifts. Prey size ranged from 0.5 to 7.9 mm and averaged 2.43 and 2.77 mm, respectively. Both prey type and foraging habitat differences of these swifts could be interpreted as mechanisms for resource partitioning.

Feeding strategy and cannibalism of the Argentine hake Merluccius hubbsi

The diet composition and feeding strategy of the Argentine hake Merluccius hubbsi in the San Matías Gulf were analysed in order to use this information for the sustainable management of the fishery. Merluccius hubbsi behaved as an opportunistic predator. Small M. hubbsi consumed planktonic crustaceans, whereas medium and large fish ate numerous prey taxa with low frequency of occurrence and variable specific abundance. Intra- and intercohort cannibalism were detected in all size groups and were particularly significant in large M. hubbsi. Medium-sized M. hubbsi consumed small conspecifics and large-sized M. hubbsi consumed both small and medium M. hubbsi. These results indicate that the removal of large M. hubbsi by fishing may increase the risk of overfishing by two combined effects: a direct effect of recruitment-overfishing and an indirect effect of growth-overfishing through an enhanced cannibalism of medium M. hubbsi on small M. hubbsi. Intra- and intercohort cannibalism and other trophic relationships in the M. hubbsi should therefore be considered explicitly in stock assessment models.

Food Habitats of the Breeding Long-Legged Buzzard (&lt;i&gt;Buteo rufinus&lt;/i&gt;) in Northwestern China

During breeding season, the diets of the Long-legged Buzzards (Buteo rufinus) were studied through pellet and prey remains analysis in arid habitat of northwestern China from 2005 to 2006. By number, mammals 60.00% constituted of the diet, birds 18.00%, reptiles 22.00%. In term of biomass, mammals comprised 87.19% of the diet, birds 6.18%, reptiles 6.63%. The most numerous prey of the Long-legged Buzzards was Rhombomys opimus (48.00%), but Gazella subgutturosa (57.97%) dominated the diet by biomass. Special findings included homing pigeon and a number of nestling and fledging Passerines in the diet. Our results showed that mammals and birds were major prey of breeding Long-legged Buzzard, and results suggest that this Buzzard is an opportunistic hunter and feeds on a wide range of food habitat.

Ecological determinants of recruitment to populations of a temperate reef fish, Trachinops caudimaculatus (Plesiopidae)

Although recruitment is often influenced by microhabitat characteristics that affect larval settlement and post-settlement growth and survival, the influence of some habitat features, such as the presence of conspecifics and the accessibility of food, are poorly understood, particularly on temperate reefs. We investigated the ecological determinants of recruitment in the southern hulafish (Trachinops caudimaculatus; McCoy, 1890), a small zooplanktivorous reef fish in Port Phillip Bay, Australia. We hypothesised that T. caudimaculatus would show positive relationships with microhabitat characteristics that provide greater access to food and shelter for newly settled recruits. To test this hypothesis, we surveyed T. caudimaculatus populations and associated microhabitat characteristics on shallow reefs. Overall, habitat characteristics explained 65% of the variation in recruitment, with recruitment greatest to reefs with abundant (1) adults, suggesting positive settlement cues and benefits to survival through shoaling, (2) accessible food (numerous prey), suggesting enhanced survival because of faster growth, and (3) shelter, suggesting enhanced survival through greater availability of refuges from predation. As T. caudimaculatus is an important prey species and sensitive to changes in pelagic productivity, mobile predators and water quality, we suggest it may be a suitable bioindicator of changes to temperate reef ecosystems.

Field evidence for pervasive indirect effects of fishing on prey foraging behavior

The indirect, ecosystem-level consequences of ocean fishing, and particularly the mechanisms driving them, are poorly understood. Most studies focus on density-mediated trophic cascades, where removal of predators alternately causes increases and decreases in abundances of lower trophic levels. However, cascades could also be driven by where and when prey forage rather than solely by prey abundance. Over a large gradient of fishing intensity in the central Pacific's remote northern Line Islands, including a nearly pristine, baseline coral reef system, we found that changes in predation risk elicit strong behavioral responses in foraging patterns across multiple prey fish species. These responses were observed as a function of both short-term ("acute") risk and longer-term ("chronic") risk, as well as when prey were exposed to model predators to isolate the effect of perceived predation risk from other potentially confounding factors. Compared to numerical prey responses, antipredator behavioral responses such as these can potentially have far greater net impacts (by occurring over entire assemblages) and operate over shorter temporal scales (with potentially instantaneous response times) in transmitting top-down effects. A rich body of literature exists on both the direct effects of human removal of predators from ecosystems and predators' effects on prey behavior. Our results draw together these lines of research and provide the first empirical evidence that large-scale human removal of predators from a natural ecosystem indirectly alters prey behavior. These behavioral changes may, in turn, drive previously unsuspected alterations in reef food webs.

Dietary composition, plasticity, and prey selection of Pallas's cats

Dietary plasticity and diet composition of Pallas’s cat (Otocolobus manul) was quantified in central Mongolia. Diet of Pallas’s cat was assessed by scat analyses, and prey surveys were used to estimate prey availability. Prey selection was calculated using multinomial likelihood ratio tests. Analysis of 146 scats identified 249 prey items. Pallas’s cats ate a broad range of small mammals, insects, birds, reptiles, and carrion, but Daurian pikas (Ochotona dauurica) were the most frequently consumed prey. Multinomial likelihood ratio tests indicated nonrandom selection of prey species. Pikas were selected disproportionately to their availability, and other more numerous prey items were used less than expected, indicating feeding specialization. Specialization on pikas appears to optimize energy intake per unit foraging by Pallas’s cats, because pikas are 2–4 times larger than other small mammal prey. We argue that pika control programs in China and Mongolia potentially threaten Pallas’s cat populations, because no other prey species could fill the niche occupied by the pika in terms of size and year-round availability. DOI: 10.1644/09-MAMM-A-342.1.

Feeding Ecology of Coryphaenoides rupestris from the Mid-Atlantic Ridge

The Macrourid fish roundnose grenadier, Coryphaenoides rupestris, is one of the most common benthopelagic fishes on the northern mid-Atlantic Ridge. The ecology of the species is comparatively well studied in continental slope waters of the North Atlantic, but not on the mid-Atlantic Ridge, which is a central mid-ocean area of its distribution. In total, 166 specimens from the RV G.O. Sars cruise in July 2004 were examined. The diet mainly comprised cephalopods, pelagic shrimps and fish. Pelagic and benthopelagic copepods were the most numerous prey, but did not contribute much on a weight basis. Cephalopods were by far the most important prey of the small grenadiers, while shrimps and fish became increasingly significant with increasing size. Previous studies from other areas have also found pelagic prey to be important, but in contrast to this study, cephalopods were generally of less importance. The study was an element of more wide-ranging food-web studies of the mid-Atlantic Ridge macro- and megafauna communities within the international MAR-ECO project.