Natural prey of the crab spider Thomisus onustus (Araneae: Thomisidae), an extremely powerful predator of insects

The natural prey of the crab spider Thomisus onustus inhabiting Eryngium plants was studied in the Absheron Peninsula, Azerbaijan. The total percentage of specimens of T. onustus found while feeding was low (9.1%). However, solitary late instar and adult females exhibited a very high feeding percentage (29.9%). Other sex–age groups of T. onustus, including small juveniles, adult males, and females guarding egg sacs, were found feeding significantly less frequently. Investigation has shown that T. onustus is a polyphagous predator, with representatives of four arthropod orders found in its diet. The primary food of T. onustus was Diptera and Hymenoptera, which collectively accounted for 94.2% of total prey. Worker ants constituted about one‐fifth of the prey, suggesting that T. onustus is a myrmecophagic spider. The length of prey killed by T. onustus ranged between 1.25 and 16.00 mm (mean 6.21 mm) and constituted from 34.4 to 587.9% (mean 194.9%) of length of their captors. The most frequently captured were large arthropods, exceeding the size of the spiders (83.1%). Small and medium‐sized juveniles captured considerably larger prey (in terms of prey–predator length ratio) than late instar and adult females. Over half of their prey constituted arthropods more than two‐fold larger than the spiders.     

Feeding ecology of the common sun skink,Eutropis multifasciata (Reptilia: Squamata: Scincidae), in the plains of central Vietnam

We studied the feeding ecology of Eutropis multifasciata in the tropical plains of central Vietnam to understand better the foraging mode, spatiotemporal and sexual variation in dietary composition, and rarefaction curves of prey-taxon richness for males and females. Stomach contents (n = 161) were collected from October 2013 to May 2014 using a nonlethal stomach-flushing technique. A total of 680 food items (624 animal items and 56 plant items) was found in 161 stomachs of skinks, representing 19 unique animal categories. We found that the diet of E. multifasciata is composed mainly of small, sedentary and clumped prey and that this skink specialises on spiders, insect larvae, snails, grasshoppers and crickets (with a combined importance index of 60%). Dietary composition, prey size and total prey volume in E. multifasciata changed between dry and rainy seasons and among regions. The total volume of food items consumed by males was larger than that of females, and the diversity and evenness index of prey categories were larger in males than in females. However, using rarefaction curves revealed that females have the higher prey-taxon richness after points between 130 and 140 prey items for frequency, and between 160 and 170 prey items for number of items, and the differences were not statistically significant. The foraging behaviour of E. multifasciata best fits a ‘widely foraging’ model.     

Diet of tropical insectivorous birds in lowland Malaysian rainforest

ABSTRACT

Despite the importance of diet in avian ecology, knowledge of bird diet in tropical regions, particularly South-East Asia, is limited. Assessing predator–prey relationships of how energy flows across ecosystems provides insight into niche segregation of sympatric species. We examined induced-regurgitation samples from 15 species of insectivorous birds – 12 babblers and three flycatcher-like species – from the Krau Wildlife Reserve, central Peninsular Malaysia. The main objective of this study was to compare and characterise the diet of similar trophically insectivorous birds so as to examine the occurrence of dietary overlap or segregation. The majority of identified prey items belong to the following arthropod taxa: Coleoptera (53%), Hymenoptera (19%), Blattodea (11%), and Araneae (11%). The diet of all bird species slightly overlapped (p = 0.070) but network analysis yielded a relatively low value (R_o = 0.53), indicating dietary divergence may have occurred among the studied bird species, possibly reflected by the variation in proportion of arthropod groups. A high proportion of Coleoptera and three other arthropod groups (i.e. Hymenoptera, Blattodea and Araneae) in the diet of studied birds could be related to their richness and abundance in aerial leaf-litter, the substrate preferred by most babblers. Dietary differences may further be explained by variations in bill shapes and sizes, likely corresponding to prey size. Unique foraging strategies (utilising different vertical strata, microhabitats, and attack manoeuvres) could also lead to dietary separation among sympatric species. Flycatcher-like species were expected to flycatch different prey items (families or lower taxa) versus the gleaning birds (most babblers). This study successfully discerned more details on the diets of insectivorous birds inhabiting Malaysian forests, providing a foundation for future studies on the ecology and biology of understorey birds.     

A method of obtaining dietary data for slow worms (Anguis fragilis) by means of non‐harmful cooling and results from a Danish population

Diet composition of slow worms (Anguis fragilis) from a Danish population was recorded from May to September 2006. Slow worms were maintained in cool conditions (at 8°C) for a maximum of 126 h, which made approximately half of the animals regurgitate. The method worked equally well on juveniles and adults. The regurgitations revealed that the slow worms preyed on small snails, slugs, pill millipedes (Glomeris marginata), earthworms and Lepidoptera larvae. There were seasonal changes in taxon composition of the diet but no ontogenetic or sex‐related differences. The food quality of selected prey types was tested on juveniles in a laboratory experiment. Mealworms gave a significantly lower gain in mass and snout–vent length than slugs, earthworms and a mix of all three prey types. A supplementary experiment revealed that slow worms from the present population completely rejected mealworms as prey. Earthworms seemed to be nutritionally inferior to molluscs.     

An unusual ecology among whiptails: the case of Cnemidophorus lacertoides from a restinga habitat in southern Brazil

We studied the ecology of Cnemidophorus lacertoides at a restinga habitat in southern Brazil. Peak activity occurred between 12.00 and 15.00. The mean body temperature of active lizards (35.0 ± 2.9°C) was relatively low compared with other whiptails and was significantly influenced by environmental temperatures. Mean snout–vent length and mean body mass of individuals were 56.5 mm and 4.4 g, respectively. Male and female C. lacertoides were not significantly different in body size. Cnemidophorus lacertoides consumed 12 types of prey, with ants and spiders being the most important items. Unexpectedly, lizards did not consume termites, which tend to be very important items in the diets of most whiptails. We conclude that the population of Cnemidophorus lacertoides we studied deviates from the typical whiptail ecology because many of its ecological features differ from those of most other cnemidophorines of similar size.     

The diet of the Eleonora’s falcon (Falco eleonorae) in the Aegean archipelago (Greece)

ABSTRACT

In the present study we investigated the diet of Eleonora’s falcons in Greece and assessed the regional dietary pattern of 16 breeding colonies of the Aegean. Overall 224 nests were visited and a total of 8067 prey items were collected which contained two mollusca classes, seven insect orders, one reptile family, two mammalian taxa and at least 54 avian species. Cicadas were the most common insects found in pellets (45.1%) followed by flying ants (34.8%) and beetles (15.8%) while just 20 species (33.3%) accounted for over 90% of the avian prey items identified in bird remains dominated (>50%) by the Willow Warbler (Phylloscopus trochilus), the Red-backed Shrike (Lanius collurio) and the Whitethroat (Sylvia communis). Insect feeding peaked in late August (39.8%) and late September (20.8%), whereas bird remains built up in falcon nests from mid-August onwards, culminating in late September (57.2%) and declined abruptly afterwards. Overall the falcons’ diet diversity increased as the breeding season progressed and from the north towards the south Aegean. The avian prey species richness was negatively influenced by the distance of the colonies from the mainland and the weather conditions during September which coincides with the fledgling period of the young and the autumn peak of passerine migration.     

Predatory habits of the grasshopper-hunting wasp Stizus continuus (Hymenoptera: Crabronidae): diet preference,predator–prey size relationships and foraging capacity

In a coastal salt-marsh of Spain, the digger wasp Stizus continuus primarily hunted for grasshoppers of the genus Heteracris, revealing (at least in the period of the study and in this area) this wasp to be almost monophagous. In contrast, grasshoppers of the genus Acrotylus were ignored by the wasps in spite of their high abundance in the environment. We hypothesize that this bias occurred because Acrotylus is found more often on the soil and on grasses, while Heteracris is nearly only found on Sarcocornia bushes, which probably represent the habitat mostly exploited by the wasps for hunting. The greater variance in size of the prey collected by larger females produced weak wasp–prey size correlations. Some wasps were observed to carry in flight prey weighing close to or more than the maximum theoretically possible, suggesting that they have to descend with prey to the nest from the above-soil hunting sites.     

The prey and predators of Homalopsine snakes

The diets of all South-East Asian water snakes of the subfamily Homalopsinae are reviewed. New diet observations for 10 species of homalopsine snakes are presented. The data on four of these, Cantoria violacea, Enhydris doriea, E. longicauda and Gerarda prevostina represent the first published diet records for these species. The observations for Fordonia leucobalia, Myron richardsonii andEnhydris enhydris represent the first taxonomically detailed diet records for these three species. The records provided for Cerberus rynchops, Enhydris plumbea and Homalopsis buccata add new taxonomic categories to previous records. The records provided for Cerberus rynchops, E. plumbea and Homalopsis buccata add new taxonomic categories to previous records. Four generalities emerge from our findings: (1) freshwater homalopsines feed primarily on fish and the adults and larvae of amphibians; (2) at least four of the eight estuarial species specialize on crustaceans while two primarily prey on fish; (3) feeding on crustaceans appears to have evolved independently at least twice; (4) prey are usually less than 10% of the predator's mass. The known predators of homalopsines are summarized and include both invertebrates and vertebrates. The microhabitats of the estuarial species are discussed and related to prey and habitat preferences.     

Digging with ‘hands’: observations of food capture in the flying gurnard Dactylopterus volitans (Linnaeus, 1758)

ABSTRACT

Videofilms of a foraging flying gurnard (Dactylopterus volitans) were collected at Itaipu, Niterói, RJ, Brazil. Analysis revealed details of the use of anterior parts of the pectoral fins which act as digging ‘hands’ to access infaunal prey items that are subsequently captured by oral suction feeding. Each pectoral fin has two distinct sections articulated separately on the pectoral girdle. The digging ‘anterior pectoral fin’ mainly consists of segmented and flexible fin rays but has an anterior robust unsegmented ray that provides an edge to the ‘hand’, allowing penetration of the substratum. The huge ‘posterior pectoral fins’ are supported by unsegmented rays. Most digging episodes involved one ‘hand’ and consisted of 1–7 cycles of movement with frequencies 1.15–3.74 cycles s^?1. During a cycle, the ‘hand’ is moved forwards and medially above the substratum, then is twisted medially and simultaneously depressed so that the anterior unsegmented ray impacts and enters the substratum. The hand is then drawn backwards and laterally to disturb the substratum. To prevent upward pitching of the head during digging, the ‘posterior pectoral fins’ are both moved anteriorly and laterally to shift the centre of gravity forwards while the caudal and ?second dorsal fins continue to provide propulsive force.     

Foraminiferan (Protozoa) epizoites on the anthuridean (Crustacea,Isopoda) Calathura brachiata (Stimpson)

Foraminiferan epizoites were studied on the isopod Calathura brachiata (Stimpson). Most individuals found belonged to the genus Cibicides. The foraminiferans were either rare or quite frequent on Calathura brachiata, indicating patchy occurrence of living foraminiferans. They were most frequent on the anterior part of the body (head, first pereonites) and the first two pairs of legs (pereopods). This pattern, which is unusual among foraminiferan epizoites on isopods, is explained by habitat selection of the foraminiferans and the behaviour of the isopod, which presumably rests between feeding with the anterior part of the body held in an upward position, allowing foraminiferans to settle on mouthparts and on the legs (first two pereopods) used in grasping prey. The size range of the foraminiferans indicates that settling of foraminiferans from the water column is more important for the development of foraminiferan epibiosis on Calathura than migration of individuals from the bottom and this may be the general pattern for most isopod species.     

Aspects of natural history in a sand boa,Eryx muelleri (Erycidae) from arid savannahs in Burkina Faso,Togo, and Nigeria (West Africa)

The ecology of West African arid savannah snakes is still poorly known, especially in regard to the fossorial species. Here, field data on distribution, morphometrics, habitat use and diet are reported for the sand boa Eryx muelleri (Erycidae) from three different countries, i.e. Burkina Faso, Togo and Nigeria. This snake was observed in 21 distinct localities, and a total of 39 individuals was recorded. The species is likely fairly common and locally abundant. Mean body length of snakes was similar among countries and between sexes, but males had proportionately longer tails than females. Body length was significantly positively correlated with both tail length and head length. Adult sex ratio was close to parity. Most of the specimens were found in well-vegetated spots with low percentage of bare soil. There were apparently both ontogenetic and intersexual dietary variations: (1) a single analysed juvenile fed upon a small-sized lizard, whereas adults fed considerably upon young rodents; and (2) females fed exclusively upon young rodents and males upon both lizards and young rodents. In conservation terms, the species is actively exported from Togo for the pet trade, and additional individuals may also be illegally collected in other countries.     

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.     

Orb‐web spiders (Araneae: Araneomorphae; Orbiculariae) captured by hunting‐wasps (Hymenoptera: Sphecidae) in an area of Atlantic Forest in south‐eastern Brazil

Members of two hunting‐wasp families, Pompilidae and Sphecidae, are among the major predators of orb‐web spiders. In this study, we collected paralysed spiders from natural nests and trap‐nests provisioned by sphecids in an area of Brazilian Atlantic Forest, and compared these data with the composition of species collected by visual searching during one year. Prey preferences were analysed based on the relative abundance of spider species, their size and web characteristics. We also compiled a list of orb‐weavers captured by four sphecid genera reported in 40 other studies. A large number of prey was obtained from natural nests of Trypoxylon (Trypargilum) albonigrum in Parque Estadual Intervales, especially species of Eustala, Parawixia, and Araneus (Araneidae). Other prey, stored in trap‐nests by T. lactitarse and unidentified hunting‐wasp species, included Nephila (Tetragnathidae), Parawixia, Ocrepeira, Mecynogea, Acacesia (Araneidae), and other spider species that were less abundant. All the species that were heavily preyed upon had a relatively lower abundance in our samples of prey availability. The range of body sizes of spiders captured by Trypoxylon in our study area include the size of some abundant orb‐weavers always absent in their nests. These results indicate that factors other than abundance in the field and the spider's size influence prey selection or susceptibility to attack.     

Sexual dimorphism,reproduction and diet of the casque-headed treefrog Itapotihyla langsdorffii (Hylidae: Lophiohylini)

Itapotihyla langsdorffii is a large “casque-headed” treefrog (Hylidae: Lophiohylini) found along most of the Brazilian Atlantic Forest biome. We studied some aspects of the ecology of a population of I. langsdorffii from the Estação Biológica de Santa Lúcia, in Espírito Santo State, southeastern Brazil. Itapotihyla langsdorffii shows considerable sexual size dimorphism, with females (mean snout-vent length 103 mm) being significantly larger than males (mean snout-vent length 81 mm). This species is an explosive breeder with a generalized reproductive mode and has a mean brood size of over 6000 eggs. It feeds on few, large prey, with orthopterans being the dominant items in the diet, though even smaller frogs may occasionally be preyed upon. We discuss our data, making comparisons with other Neotropical hylids, with emphasis on other species in the Tribe Lophiohylini.     

An investigation of predator‐induced defence responses in ciliated protozoa

Predator‐induced defence responses have been reported in 15 species of ciliates representing three subclasses: Hypotrichia, Stichotrichia and Hymenostomia. However, the discovery of this phenomenon in such distantly related groups suggests that it could be more widespread within the Ciliophora. In laboratory experiments, we tested 23 potential prey species with a range of potential predators including other ciliates (12 spp.), amoebae (two spp.), rotifers (two spp.), a turbellarian worm (Stenostomum sphagnetorum), and an oligochaete worm (Chaetogaster sp.). In each experiment, one predator species was incubated for 24?h with one potential prey species and the latter was examined for evidence of a defence response. One new example of predator‐induced morphological change was recorded (Euplotes viridis) and detailed observations were made for one poorly known example (E. eurystomus). Both species significantly increased their width (by about 35% and 23%, respectively) in the presence of the turbellarian worm S. sphagnetorum. An induced life cycle change was recorded for the first time among hypotrichs with E. muscorum exhibiting significantly increased rates of encystation in the presence of the ciliate predators Dileptus anser and Spathidium sp. Finally, Euplotes patella, Euplotes sp. and Stylonychia pustulata, which are usually regarded as omnivorous rather than predatory ciliates, all induced morphological change in Colpidium kleini, the C. kleini cells becoming significantly shorter and wider. No examples of induced defence response were found among groups other than hypotrichs and hymenostomes.     

A behavioural inventory of adult Stenus species (Coleoptera: Staphylinidae)

According to focal animal sampling, the genus-specific behaviour of Stenus beetles (Coleoptera, Staphylinidae) can be presented in the form of a comprehensive ethogram including 73 distinct behavioural patterns. Most observed behavioural patterns can be assigned to five functional systems: ‘feeding’, ‘reproduction’, ‘grooming’, ‘resting’ and ‘protection’. In addition to grooming behaviour, searching behaviour takes a large amount of time (50–90% of the total observation time), which is indicative of the broad prey spectrum of Stenus species. The biological significance of selected behavioural aspects concerning ‘searching for prey’, ‘prey capture’, ‘mating’, ‘self-grooming’ and ‘locomotion on the water surface’ is addressed in the discussion.     

Food spectrum analysis of the Asian toad,Duttaphrynus melanostictus (Schneider, 1799) (Anura: Bufonidae), from Timor Island,Wallacea

The Asian toad, Duttaphrynus melanostictus (Schneider, 1799), is widespread throughout tropical Asia and very abundant where it occurs. It was relatively recently introduced to Timor, the second largest island in the biogeographic region called Wallacea. Timor Island shows an exceptionally high level of endemism in a wide range of faunal groups and there are concerns that D. melanostictus may have a negative impact on this diversity, including vertebrates, through direct predation. To evaluate the impact the diet of D. melanostictus might have on the local fauna, gut contents of 83 preserved toad specimens from five habitat types in Timor-Leste, a country occupying the eastern half of Timor Island, were examined. We identified 5581 prey items, comprising the following animal groups: annelids; snails and slugs; spiders and harvestmen; woodlice; millipedes and centipedes; grasshoppers, crickets and earwigs; termites; thrips and true bugs; beetles; ants; hymenopterans other than ants; true flies; butterflies; unidentified insects; and insect larvae. Small eusocial insects (ants and termites) constituted the major part of the diet (61.6% and 23.4%, respectively). No vertebrate prey was recorded. Prey item composition did not differ between habitats. The wide prey spectrum well indicates that D. melanostictus is a generalist invertebrate feeder, as other studies, from regions where this species occurs naturally, have already shown. Although the Asian toad seems to not generally prey on vertebrates, vertebrate species that are morphologically similar to invertebrates in their overall appearance may be consumed. Hence, a negative effect on some taxa (e.g. blindsnakes) may be possible. We also present some limited data on intestinal parasites occurring in D. melanostictus.     

Diet of Enyalius bilineatus (Leiosauridae: Squamata) at a site in southeastern Brazil: effects of phylogeny and prey availability

We studied the diet of Enyalius bilineatus (Leiosauridae: Squamata) at the Inhotim Institute, southeastern Brazil, through induced regurgitation. We obtained 27 individuals using pitfall traps with drift-fence, active search, opportunistic encounters and capture by persons not directly involved in the study. We quantified prey availability at the site using pitfall traps and used electivity indices to identify preferred prey items based on ingested and available prey. Preferred prey included Lepidoptera larvae considering number of prey ingested and Orthoptera considering volume ingested. We obtained the available data on diet of Enyalius species from the literature and compared a phylogenetic distance matrix with a diet dissimilarity matrix, showing that phylogenetically closer species tended to have less dissimilar diets. We used independent contrasts to show that environmental impact did not reduce Enyalius population trophic niches, excluding the effects of phylogeny on niche breadth. Species of Enyalius may adapt to some disturbance in their habitats.     

Autumn and winter food habits of bobcats in Washington state

The stomach contents were examined from 324 western Washington bobcats ( Felis rufus ) and 123 from eastern Washington taken by hunters from 1976 through 1980, for major prey items as well as sex- and age-related differences in diet. Western Washington bobcats ate primarily mountain beavers ( Aplodontia rufa ) (42% occurrence) and snowshoe hares ( Lepus americanus ) (26%). Within that population females ate larger quantities of smaller prey such as douglas squirrels ( Tamiasciurus douglasi ) and lesser amounts of deer ( Odocoileus sp.) than males. Bobcat diets in eastern Washington were more diverse; main foods consisted of lagomorphs ( Sylvilagus nuttallii, Lepus sp.) (20%), red squirrels ( Tamiasciurus hudsonicus ) (15%), deer (11%), and voles ( Microtus sp.) (11%). Age-related differences were most prevalent in this population, with adults consuming larger quantities of deer and larger prey than did kittens.     

Diet and feeding behaviour of the leaf-litter frog Ischnocnema henselii (Anura: Brachycephalidae) in Araucaria rain forests on the Serra Geral of Rio Grande do Sul,Brazil†

Abstract

We analysed the diet of Ischnocnema henselii from a subtropical Araucaria forest through stomach flushing. The identified prey items comprised arthropods such as spiders, ants, orthopterans, collembolans and homopterans. We consider I. henselii to be a nocturnal and opportunistic sit-and-wait predator. Small animals are preferred. Because this species lives permanently on the forest floor, we also determined the composition of the habitat's leaf-litter mesofauna. By using Winkler sieve extraction, we obtained a spectrum of small invertebrates that reflected the prey in the stomach contents well. The only exceptions were mites, the most abundant leaf-litter inhabitants, which frogs either avoided or ignored. Our results represent the first information on the diet of I. henselii and are discussed in comparison with data on related species and in relation to the relevance of this predator within the food web of subtropical montane rain forests in southern Brazil.