Range Of Prey Items Research Articles

Food items and feeding habits of two Nothobranchiidae, Epiplatys chaperi sheljuzhkoi (poll, 1953) and Nimbapanchax petersi (sauvage, 1882) in Banco river, Côte d’ivoire

Food and feeding habits of two Nothobranchiidae species, Epiplatys chaperi sheljuzhkoi (Poll, 1953) and Nimbapanchax petersi (Sauvage, 1882) from Banco River were investigated between January and December 2016. Stomach contents of 119 and 397 individuals of E. sheljuzhkoi and N. petersi were respectively analyzed, ranging in size from 13 and 55 mm, 11 and 48 mm standard Length, respectively. Formicidae being terrestrial insects, constituted the main prey (RI>50) of both species, and aquatic insect larvae (Hydrophilidae and Chironomidae) were secondary or accessory preys. The food items in stomach showed a small spectrum in E. sheljuzhkoi than N. petersi but differences were not significant (Chi-square, p>0.05). Diet composition of both species showed little variation according to seasons, sampling zones and size groups (Anova, p>0.05). However, a decreasing trend in terrestrial insects and an increase of other preys in stomach contents has been observed from upstream to downstream. For ontogenic variation, large specimens group fed much more on aquatic insect larvae, fish scales and macrophytes than small size group. This work indicated that both species fed on a small range of prey items dominated by insects in Banco River and could be considered strict insectivorous predators. This work concludes that both species have similar diets and the canopy cover of Banco forest plays an important role in the feeding and conservation of these species.
 Key words: Epiplatys, Nimbapanchax, canopy cover, diet, terrestrial insects, Formicidae, predator.

Individual specialists within a generalist niche: variable diet of stoats and implications for conservation

Conservation programmes aiming to suppress or remove invasive small mammal populations that threaten endemic fauna assume that eliminating an individual predator has the same effect as eliminating a conspecific in terms of decreasing risk to the prey species. However, marked between-individual variation in prey take could, at times, lead to uneven predation pressure. Such variation in the diets of introduced predators has long been hypothesised in New Zealand, suggesting that some observed rates of predation are not typical of the prey population as a whole. We used stable isotope analysis to estimate the isotopic dietary niches of stoats Mustela erminea (n = 51) caught in three New Zealand National Parks. We modelled δ13C and δ15N ratios from five tissue types to estimate the isotopic niche for each individual stoat, and for each population. The isotopic niche used by the population of stoats in Nelson Lakes National Park was substantially larger (5.3 ‰2) than for those at either Mt Aspiring National Park (3.1 ‰2) or Fiordland National Park (2.8 ‰2). Despite this, a measure of individual specialisation (proportional niche use) in stoats at Nelson Lakes National Park (0.4 ± 0.3) was similar to the other two sites. Collectively these data suggest a comparable degree of individual specialisation even within a more generalist population niche. This variability in the range of prey items taken by small carnivores, between populations and individuals of the same species, has consequences for how we design and monitor small mammal control programmes; for example, the threatened species outcomes observed in one area or time period may not be applicable to another.

Feeding preferences and functional responses of Calathus granatensis and Pterostichus globosus (Coleoptera: Carabidae) on pupae of Bactrocera oleae (Diptera: Tephritidae).

Carabid beetles are important predators in agricultural landscapes feeding on a range of prey items. However, their role as predators of the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), one of the most serious pests of olives, is unknown. In this context, the feeding preferences and the functional responses of two carabid beetle species, Calathus granatensis (Vuillefroy) and Pterostichus globosus (Fabricius), were studied under laboratory conditions. Feeding preference assays involved exposing carabid beetles to different ratios of B. oleae pupae and an alternative prey, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Both species fed on B. oleae pupae however, C. granatensis always showed a significant preference for that prey whereas P. globosus switched to C. capitata pupae when the offered ratio was below 0.5. The total prey biomass consumed was significantly higher for P. globosus than for C. granatensis. Functional response curves were estimated based on different densities of B. oleae pupae and both carabid beetle species exhibited a type II functional response using Rogers' random-predator equation. P. globosus showed shorter handling time (1.223 ± 0.118 h) on B. oleae pupae than C. granatensis (3.230 ± 0.627 h). Our results suggest that both species can be important in reducing the densities of B. oleae in olive groves, although P. globosus was more efficient than C. granatensis.

Relationship between Diet and Microhabitat Use of Red-legged Salamanders (Plethodon shermani) in Southwestern North Carolina

The selection of a foraging habitat may be driven by food availability or by the cost associated with the use of that habitat. This basic tradeoff can lead individuals in the same population to occupy different habitats in response to perceived risk levels. In the southeastern United States, plethodontid salamanders are often observed climbing vegetation, which represents a potential foraging habitat. We examined whether diet composition of the Red-legged Salamander, Plethodon shermani, differed between salamanders found on vegetation and on the ground surface. Contrary to the results of a previous study, we found that the overall number and mass of prey items did not differ between salamanders in these two microhabitats. Furthermore, we found no evidence that the relative use of different prey categories varied in relation to a salamander's selected microhabitat. Although salamanders of all body sizes had consumed a diverse range of prey items, we found evidence of an ontogenetic shift in prey utilizatio...

Effect of Rhabdias pseudosphaerocephala on prey consumption of free-ranging cane toads (Rhinella marina) during Australian tropical wet seasons

The development of biological control measures to reduce the impact of invasive species is a desired goal. Rhabdias species have recently been advocated as biological control agents for invasive anurans. This study describes a field-based approach to support laboratory results on the potential impact of the lung nematode Rhabdias pseudosphaerocephala on the prey consumption of its host, the invasive cane toad (Rhinella marina, Bufonidae). Toads were sampled from various populations in the Wet Tropics of Australia during the wet seasons of 2010 and 2012. Consumed prey items were counted in 212 cane toads and identified to class and order levels and the number of lung nematodes was counted for each toad. The number of R. pseudosphaerocephala in free-ranging cane toads affected negatively the diversity of prey items consumed, but was not related to the number of prey items or the number of ants consumed. The results suggest that infection of free-ranging cane toads by the lung nematode reduces their range of prey items. Possible reasons could be a reduced locomotor activity resulting in changes of foraging modes of infected toads which was reported from some laboratory trials. Infection of cane toads by R. pseudosphaerocephala may therefore have the potential to alter the impact of cane toads on invertebrate communities and their competition for food resources with native Australian anurans.

Diet composition of juveniles of rough ray Raja radula (Chondrichthyes: Rajidae) from the Ionian Sea

The diet of juvenile specimens of Raja radula from the Ionian Sea was investigated. The stomach contents of 43 specimens were analysed in order to evaluate composite index (IRI Index of Relative Importance). To assess feeding strategy and trophic niche width, prey-specific biomass plotted against frequency of occurrence and Levins index were used, respectively. The diet of juvenile specimens of R. radula consisted mainly of crustacean decapods followed by algae, polychaetes and molluscs. Among crustaceans, Liocarcinus spp. were the most important prey items, with four species with relatively high IRI values. Most specimens had been feeding on L. pusillus, L. depurator and polychaetes, but the variation of prey-specific biomass indicates that there is not a clear dominance of any prey and the value of niche width indicates a high variability in R. radula diet. Differences between sexes exists only in % IRI values related to Liocarcinus spp. The results indicate that R. radula feeds on a wide range of prey items, although crustaceans were the favoured food source.

Abundance and biology of warty oreo (Allocyttus verrucosus) and spiky oreo (Neocyttus rhomboidalis) (Oreosomatidae) off south-eastern Australia

The distribution, abundance, size structure, reproductive biology and diet of warty oreo, Allocyttus verrucosus (Gilchrist), and spiky oreo, Neocyttus rhomboidalis (Gilchrist), from the continental slope region (400-1200 m depth) of south-eastern Australia are described. The depth distributions of the two species overlap, with spiky oreo being more abundant in intermediate depths (600-800 m) and warty oreo abundance peaking at greater depths (900-1200 m). There was evidence of size structuring with depth. Warty oreo juveniles and subadults were comparatively more abundant in depths of less than 1000 m and adults dominated at greater depths. In spiky oreo, juveniles were largely restricted to the depth range of 700-900 m. Size at 50% maturity in females was 28 and 35 cm for warty and spiky oreos, respectively. Males mature at slightly smaller sizes. Spawning occurs in May–June for warty oreo and between August and October for spiky oreo. Just prior to spawning in warty oreo the sexes appear to segregate by depth, with females becoming progressively more dominant with depth. Both species are benthopelagic feeders, consuming a range of prey items including crustaceans, fish and squid. Salps were also an important component of the diet of spiky oreo.

Sexual Dimorphism and Breeding Success in Tree Swallows and Collared Flycatchers

The common pattern of small differences in body size between the sexes of many bird species has been related to a number of ecological factors, including functional differences in niche utilization (Selander 1966, Wallace 1974, Hogstad 1978), sexual differences in nest defense requirements (e.g., Wiklund and Stigh 1983, Safina 1984), and to differential migration strategies (Ketterson and Nolan 1983). While a number of these studies assume that a small degree of sexual dimorphism in body size leads to differential flight performance (see Andersson and Norberg 1981), the possible consequences of such differences have rarely been investigated empirically. Gosler (1987a, 1987b) suggested that sexual differences in the bill length of Great Tits (Parus major) may enhance the ability of pair members to aquire food, through decreased intrapair competition. This same argument has been made for the evolution of reversed sexual size dimorphism in raptors (Newton 1979), typically in reference to differences in wing size/shape and flight performance. This argument rests on the premise that pair members that differ in body size/shape are able to exploit a wider range of prey items. Gosler's (1987a, 1987b) studies of Great Tits provided such evidence and also drew a direct link between the degree of within-pair sexual dimorphism and breeding success. However, more recent work by Matthysen et al. (1991) found no such link among Blue (P. caeruleus) and Great Tits in Belgium. Previous studies have demonstrated significant effects of small differences in wing length and shape on the foraging behavior of several species of birds (e.g., Andersson and Norberg 1981, Lifjeld and Slagsvold 1988). In this paper, we assess the relationship between reproductive success and intra-pair differences in wing length. This study differs from previous efforts by focusing on an aerial insectivore, the Tree Swallow (Tachycineta bicolor), and on a species that feeds by gleaning and flycatching, the Collared Flycatcher (Ficedula albicollis).

Diet ofDinocras cephalotesandperla bipunctata(Plecoptera, Perlidae) in a South‐West Irish stream

This study provides the first, although limited, examination of the diets of the only two Irish perlids, Dinocras cephalotes (Curtis) and Perla bipunctata (Pictet). D. cephalotes was found to include a wide range of prey items in its diet (including plant matter) but the major components (Baetis rhodani and chironomids) varied little despite considerable variation in benthic invertebrate taxa at different sites. Marked positive selection of certain prey taxa was also apparent. The diet of P. bipunctata appeared narrower but relatively low numbers of individuals were available. Although there were some differences in the composition of the diet (prey types and size) amongst three age classes of D. cephalotes there was still considerable overlap between them. An expansion in the size range of mayfly prey was also evident with increase in predator age.

The diet of the eastern short-horned lizard (Phrynosoma douglassi brevirostre) in Alberta and its relationship to sexual size dimorphism

The diet of Phrynosoma douglassi brevirostre in Alberta was investigated and potential prey abundance was examined. The Alberta populations are less strongly myrmecophagous than the average for the species, when the diet is broken down by prey item counts. Breakdown of the diet by prey dry weight shows that ants, nonsilphid Coleoptera, and Orthoptera are the major components of the diet. The range of prey sizes taken is large, but the species concentrates on a small range of prey sizes, from 2.1 to 6.0 mm in length. Arthropod abundances are significantly different between all three study sites, and there is always a significant difference in distribution between the pooled pitfall samples and the pooled gut samples of any one study site. The general dissimilarity in distribution between the pooled gut samples of any two study sites suggests some dietary flexibility. The size range of prey items taken by the large lizards includes and slightly exceeds the size range of prey items taken by medium-sized lizards, and there is a significant positive correlation of average prey size with lizard snout–vent length. There are significant differences in the prey sizes, prey dry weights, and prey item counts between large lizards and medium-sized lizards, indicating intersexual dietary partitioning.

THE DIET OF THE CURLEW SANDPIPER AT LANGEBAAN LAGOON, SOUTH AFRICA

Summary Puttick, G. M. 1978. The diet of the Curlew Sandpiper at Langebaan Lagoon, South Africa. Ostrich 49:158-167. Nereid worms (mainly Ceratonereis erythraensis) and the hydrobiid gastropod Assiminea globulus were the most important prey items throughout the year for Curlew Sandpipers Calidris ferruginea feeding at Langebaan Lagoon. Other important items were the amphipod Urothoe grimaldi, the crabs Hymenosoma orbiculare and Cleistostoma edwardsii and dipteran larvae (Stratiomyidae). Immature Curlew Sandpipers took smaller prey items than adult birds. The diet of male and female birds differed in the proportion, sue and range of prey items taken.