Invertebrate Orders Research Articles

Trophic niche ofOecobius maculatus(Araneae: Oecobiidae): evidence based on natural diet, prey capture success, and prey handling

Abstract Field and laboratory observations of the feeding ecology (natural diet, prey capture success, and prey handling) of Oecobius maculatus Simon 1870 were combined in this study to reveal the level of trophic specialization by this species. Natural prey were investigated on the Croatian island of Brac. Field observations revealed that although spiders captured prey belonging to five invertebrate orders, the most frequently captured prey were ants, which were also the most abundant available prey in the locality. In laboratory experiments, O. maculatus spiders accepted three other prey types with a higher probability than ants and were significantly more efficient at capturing and handling flies than ants. These results suggest that this species is a stenophagous generalist with a narrow prey range due to ecological circumstances.

Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods.

Artificial lighting allows humans to be active at night, but has many unintended consequences, including interference with ecological processes, disruption of circadian rhythms and increased exposure to insect vectors of diseases. Although ultraviolet and blue light are usually most attractive to arthropods, degree of attraction varies among orders. With a focus on future indoor lighting applications, we manipulated the spectrum of white lamps to investigate the influence of spectral composition on number of arthropods attracted. We compared numbers of arthropods captured at three customizable light-emitting diode (LED) lamps (3510, 2704 and 2728 K), two commercial LED lamps (2700 K), two commercial compact fluorescent lamps (CFLs; 2700 K) and a control. We configured the three custom LEDs to minimize invertebrate attraction based on published attraction curves for honeybees and moths. Lamps were placed with pan traps at an urban and two rural study sites in Los Angeles, California. For all invertebrate orders combined, our custom LED configurations were less attractive than the commercial LED lamps or CFLs of similar colour temperatures. Thus, adjusting spectral composition of white light to minimize attracting nocturnal arthropods is feasible; not all lights with the same colour temperature are equally attractive to arthropods.

Prey of the silver-headed antechinus (Antechinus argentus), a new species of Australian dasyurid marsupial

The silver-headed antechinus (Antechinus argentus) is one of Australia’s most recently described mammals, and the single known population at Kroombit Tops in south-east Queensland is threatened. Nothing is known of the species’ ecology, so during 2014 we collected faecal pellets each month (March–September) from a population at the type locality to gather baseline data on diet composition. A total of 38 faecal pellets were collected from 12 individuals (eight females, four males) and microscopic analysis of pellets identified seven invertebrate orders, with 70% combined mean composition of beetles (Coleoptera: 38%) and cockroaches (Blattodea: 32%). Other orders that featured as prey were ants, crickets/grasshoppers, butterflies/moths, spiders, and true bugs. Given that faecal pellets could only be collected from a single habitat type (Eucalyptus montivaga high-altitude open forest) and location, this is best described as a generalist insectivorous diet that is characteristic of other previously studied congeners.

Do Field Margins Enrich the Diet of the Eurasian SkylarkAlauda arvensison Intensive Farmland?

To help restore food availability for birds, arable field margins (extensively managed strips of land sown with grasses and forbs) have been established on European farmland. In this study we describe the effect of field margins on the diet of Eurasian Skylark nestlings and adults living on intensively managed Dutch farmland. We tested the hypotheses that field margins offer a higher diversity of invertebrate prey than intensively managed crops, and that the diet of nestlings receiving food from field margins will therefore be more diverse than that of other nestlings. Field margins had a greater variety of invertebrate prey groups to offer than the intensively managed crops. Coleoptera were the most frequently and most abundantly eaten prey group by both adults and nestlings. Together, Coleoptera, Diptera, Lepidoptera, Hymenoptera and Araneae accounted for 91% of the nestling diet. Nestlings ate larger prey items and a larger proportion of larvae than adults. Almost 75% of both adults and nestlings consumed plant material, perhaps indicating a scarcity of invertebrate resources. When provided with food from field margins, the mean number of invertebrate orders in the nestling diet increased significantly from 4.7 to 5.5 and the number of families from 4.2 to 5.8 per sample. Thus, birds that used field margins for foraging could indeed provide their young with more invertebrate prey groups than birds only foraging in crops and grassland.

Bacillus thuringiensis in caterpillars and associated materials collected from protected tropical forests in northwestern Costa Rica

Bacillus thuringiensis (Bt) synthesizes crystalline inclusions that are toxic to caterpillars (Lepidoptera) and other orders of invertebrates. Materials associated with 37 caterpillars from 16 species, collected while feeding on 15 different species of host plants in dry, cloud and rain forests located in the Area de Conservación Guanacaste in northwestern Costa Rica, were examined for the presence of Bt. From a total of 101 derived samples, 25 Bt isolates were cultured: 56% from host plant leaves, 8% from caterpillar guts and 36% from caterpillar fecal pellets. Bt was isolated from at least one sample in 38% of the systems constituted by the food plant, gut and fecal pellets corresponding to a single caterpillar. Four different morphologies of crystalline inclusions were observed, with bipyramidal and irregular crystal morphologies being the most prevalent.

Are nesting seabirds important determinants of invertebrate community composition on subantarctic Adams Island?

Nesting seabirds import marine-derived nutrients into terrestrial food webs, affecting invertebrate abundance and community composition directly, through provision of decaying animal matter as a food source, and indirectly through effects on vegetation and prey abundance. Invertebrates have shown strong responses to seabird presence in some, but not all, ecosystems previously studied. In contrast to mainland range contractions, New Zealand’s subantarctic islands retain abundant seabird populations. We sampled ground invertebrates on mammal-free Adams Island, using pitfall traps. We surveyed sites in two vegetation types (tussock and forest) with either no nesting seabirds or nesting colonies of Gibson’s wandering albatross, sooty shearwaters or white-headed petrels. We collected 11 invertebrate orders and identified 20 Coleoptera species or higher taxa. The carrion beetle, Paracatops antipoda comprised over 50 % of Coleoptera individuals collected. P. antipoda was more abundant in forest than tussock and was positively associated with sooty shearwaters and negatively associated with white-headed petrels when compared with bird-free sites using a Poisson generalized linear model. Sooty shearwaters were also associated with elevated abundance of several herbivorous and invertebrate decomposer taxa. Nesting seabirds do appear to influence invertebrate community composition on Adams Island, but the direction of this effect appears to be taxa-specific. Further sampling with spatial replication of colonies is required to determine the extent to which these apparent taxa-specific responses are consistent across colonies and habitats.

Seasonal variation in the diet of juvenile lake sturgeon,Acipenser fulvescens, Rafinesque, 1817, in the Winnipeg River, Manitoba, Canada

The lake sturgeon, Acipenser fulvescens, is a threatened species across most of its range. To understand any potential shifts in diet across season or habitat, stomach contents were examined from juvenile lake sturgeon caught in the Winnipeg River, Manitoba, Canada. This information will aid in assessment of environmental impacts and conservation initiatives for this threatened species. From 2006 to 2008 gut contents were collected from juvenile lake sturgeon using a non-lethal gastric lavage methodology. Juvenile lake sturgeon were sampled from four discrete deep water habitat types (13.7–27.4 m depths), during the months of May, June, July and October. In total, 13 066 prey items belonging to 14 prey groups were collected from 345 juvenile lake sturgeon (251–835 mm TL). Overall, juvenile lake sturgeon consumed a low diversity of organisms; insect larvae from three invertebrate orders, Trichoptera, Diptera and Ephemeroptera, accounted for 97.4% of the total numeric abundance of prey items recovered. A relationship between size of juvenile lake sturgeon and prey quantity or type was not observed. Diet of juvenile lake sturgeon varied in relation to season, with Diptera (77.6%) being the most abundant prey in May, Trichoptera the most abundant in June (n = 3,056, 60.4%) and July (n = 2,055, 52.6%). During October, 96% of stomachs examined were empty. In terms of habitat type, the standardized abundance of invertebrate prey items was highest in deep water habitats characterized by medium water velocity (depths > 13.7 m) and coarse substrate (particle sizes > 0.063 mm) in May and June when compared to deep water habitats characterized by low water velocity (<0.2 m.s−1) and fine substrate (particle sizes < 0.063 mm). However, in July, the opposite was observed and prey abundance in juvenile lake sturgeon stomachs decreased with increasing particle size. Results suggest a high degree of dietary overlap among juvenile lake sturgeon from multiple size/age classes occupying deep-water habitats of the Winnipeg River.

Structure and interactions in a cave guano–soil continuum community

Bat guano represents an important food resource for cave-dwelling organisms, hosting up to entire communities in a single deposit. Sampling conducted in guano and its interface with the adjacent soil revealed a wide variation in physicochemical parameters (nitrogen, phosphorus, organic matter, pH and moisture) along that continuum. The invertebrate orders that showed the greatest abundance and species richness were: Mesostigmata, Sarcoptiformes and Trombidiformes, all belonging to subclass Acari. The results clearly showed that mite species are the most abundant group in guano deposits. Such species can directly or indirectly feed on this food resource. The abiotic factors of the guano significantly explained some community parameters. Furthermore, moisture was the parameter that best explained the abundance distribution for the most common mite species. Lastly, a trophic web of the most abundant species in the guano was devised based on literature data, interspecies correlation, preferences for microhabitats and abundance rates of the populations. It was possible to observe that the temporal changes in the guano deposit determine a successional process in the community, including the trophic web structure.

The Diet of Western Burrowing Owls in an Urban Landscape

While we know much about the diet of Western Burrowing Owls (Athene cunicularia hypugaea) in many of their more natural habitats, little is known about their diets in urban environments. We analyzed pellets and prey remains collected at burrows used by Burrowing Owls living in urban grasslands in Santa Clara County, California. We hypothesized that the composition of prey species in the diet of these urban owls would differ from that of owls living in agricultural and more-natural western habitats and, in particular, that rodents would be a smaller component of the diet, We found the invertebrate-to-vertebrate ratio to be approximately 94:6 by number. Orthoptera, Dermaptera, and Coleoptera were the most abundant invertebrate orders, while rodents accounted for 70% of the estimated biomass per burrow of all orders. This overall composition and these taxa are typical for Burrowing Owls in western habitats. However, Botta's pocket gopher (Thomomys bottae) was an important prey species by biomass, a species not often recorded as a dominant prey item of owls living in western habitats. The California vole (Microtus californicus) and house mouse (Mus musculus) were also dominant prey items by biomass. We recommend managing Western Burrowing Owl habitat for species, especially rodents such as pocket gophers and voles, that do well in urban habitats.

Diet of the Introduced Greenhouse Frog in Hawaii

To determine the potential impacts of the Cuban terrestrial Greenhouse Frog, Eleutherodactylus planirostris, on native invertebrates in Hawaii, we conducted a stomach content analysis of 427 frogs from ten study sites on the island of Hawaii. At each site, we also collected invertebrates with two sampling methods, leaf litter collection and sticky traps, to determine if diets were representative of the available resources. Dominant prey items consisted of Hymenoptera: Formicidae (32.4% of total diets), Acari (19.2%), and Collembola (17.4%). Non-native invertebrate categories comprised 43.2% of their diet (Amphipoda, Isopoda, and Hymenoptera: Formicidae). Invertebrate orders that contain native species in Hawaii found most often in the stomachs included Acari (mites; 19.2%), Araneae (spiders; 3.1%), Collembola (springtails; 17.4%), and Psocoptera (booklice; 2.3%), although it is unknown whether native species of these groups were present in the stomach samples. Eleutherodactylus planirostris predominantly consumed leaf litter invertebrates and selected proportionately more Formicidae than was available in the environment. A total population density of 12,500 frogs ha−1 was estimated at one study site. With this density estimate and number of prey consumed, E. planirostris may consume 129,000 invertebrates ha−1 night−1 at some sites. This research highlights the need to understand the direct and indirect effects of predation by E. planirostris on invertebrates in Hawaii.

How good are carabid beetles (Coleoptera, Carabidae) as indicators of invertebrate abundance and order richness?

Ground invertebrates were sampled by pitfall trapping on Brentmoor Heath, Surrey, UK during the summers of 2009 and 2010 to determine whether the abundance and species richness of carabids on bare ground patches are representative of invertebrate abundance and order richness on the same patches. Four patch sizes were investigated as well as the adjacent mown and unmown areas, and a range of environmental parameters were measured at each patch. Results show that increasing abundance and richness of carabids can give a broad indication of whether invertebrate abundance and order richness are increasing. Invertebrates in general are sensitive to a greater number of environmental variables and complex interactions than carabids are, due to the vast array of biological requirements of the large range of invertebrate species. All else being equal, smaller patches appear to benefit both carabid abundance and invertebrate abundance. Converse to the results of carabid species richness, larger patches appear to benefit invertebrate order richness. This study highlights the importance of testing the effect of habitat management strategies on a range of taxa rather than assuming the results for a bioindicator will suffice for management decisions. Whilst bioindicators may give a broad indication of effects on similar taxa, the precise nature of those effects will be determined by a number of species- and site-specific variables.

Field trials to evaluate effects of continuously planted transgenic insect-resistant cottons on soil invertebrates

Impacts on soil invertebrates are an important aspect of environmental risk assessment and post-release monitoring of transgenic insect-resistant plants. The purpose of this study was to research and survey the effects of transgenic insect-resistant cottons that had been planted over 10 years on the abundance and community structure of soil invertebrates under field conditions. During 3 consecutive years (2006-2008), eight common taxa (orders) of soil invertebrates belonging to the phylum Arthropoda were investigated in two different transgenic cotton fields and one non-transgenic cotton field (control). Each year, soil samples were taken at four different growth stages of cotton (seedling, budding, boll forming and boll opening). Animals were extracted from the samples using the improved Tullgren method, counted and determined to the order level. The diversity of the soil fauna communities in the different fields was compared using the Simpson's, Shannon's diversity indices and evenness index. The results showed a significant sampling time variation in the abundance of soil invertebrates monitored in the different fields. However, no difference in soil invertebrate abundance was found between the transgenic cotton fields and the control field. Both sampling time and cotton treatment had a significant effect on the Simpson's, Shannon's diversity indices and evenness index. They were higher in the transgenic fields than the control field at the growth stages of cotton. Long-term cultivation of transgenic insect-resistant cottons had no significant effect on the abundance of soil invertebrates. Collembola, Acarina and Araneae could act as the indicators of soil invertebrate in this region to monitor the environmental impacts of transgenic plants in the future.

Molecular and functional characterisation of resilin across three insect orders

Resilin is an important elastomeric protein of insects, with roles in the storage and release of energy during a variety of different functional categories including flight and jumping. To date, resilin genes and protein function have been characterised only in a small number of flying insects, despite their importance in fleas and other jumping insects. Microscopy and immunostaining studies of resilin in flea demonstrate the presence of resilin pads in the pleural arch at the top of the hind legs, a region responsible for the flea’s jumping ability. A degenerate primer approach was used to amplify resilin gene transcripts from total RNA isolated from flea ( Ctenocephalides felis), buffalo fly ( Haematobia irritans exigua) and dragonfly ( Aeshna sp.) pharate adults, and full-length transcripts were successfully isolated. Two isoforms (A and B) were amplified from each of flea and buffalo fly, and isoform B only in dragonfly. Flea and buffalo fly isoform B transcripts were expressed in an Escherichia coli expression system, yielding soluble recombinant proteins Cf-resB and Hi-resB respectively. Protein structure and mechanical properties of each protein before and after crosslinking were assessed. This study shows that resilin gene and protein sequences are broadly conserved and that crosslinked recombinant resilin proteins share similar mechanical properties from flying to jumping insects. A combined use of degenerate primers and polyclonal sera will likely facilitate characterisation of resilin genes from other insect and invertebrate orders.

Aboveground Macroinvertebrate Diversity and Abundance in Sand Sagebrush Prairie Managed With the Use of Pyric Herbivory

Through pyric herbivory (i.e., fire-induced grazing patterns), native grasslands were historically a spatially heterogeneous environment. It is hypothesized that the mosaic of habitats created by pyric herbivory supports a more diverse invertebrate community compared to modern range management. Patch-burn management, a pyric herbivory technique, is an application of prescribed fire and grazing whereby the timing and location of the burned and grazed patches is varied, creating a diversity of habitat conditions. Although disturbance in sandsage (Artemisia filifolium Torr.) prairie historically included fire and grazing, fire disturbance has been nearly eradicated from this ecosystem in western Oklahoma. We compared patch-burn management to traditional management (i.e., moderate grazing with no fire) in sandsage prairie to evaluate the impact of these two management regimes on aboveground invertebrates. We sampled invertebrates at 44 points in each of 3 mo (May, June, and July) with the use of Dietrick vacuum sampling. Diversity, total abundance, and abundance of seven invertebrate orders (Araneae, Diptera, Hemiptera, Homoptera, Hymenoptera, Lepidoptera, and Orthoptera) were similar between patch-burn and traditional pastures. When examined on a patch level, five invertebrate orders were also similar between their respective time since burn patch and the traditional patches. Araneae and Coleoptera abundance were higher in traditional patches, and Hemiptera abundance was higher in current-year burn patches. Our results suggest a heterogeneity-based management scheme based on pyric herbivory does not negatively impact the overall invertebrate community and may benefit a wider variety of invertebrates by providing areas of varying levels of disturbance. In comparison, homogeneous landscapes such as those created by traditional management may only benefit segments of the invertebrate community that have habitat associations with moderately disturbed or undisturbed areas. Therefore, a disturbance regime involving the interaction of fire and grazing may be valuable for maintaining biodiversity and productivity within sandsage prairie ecosystems.

Documenting the terrestrial invertebrate fauna of Barrow Island, Western Australia

An intensive survey of terrestrial invertebrates was undertaken on Barrow Island, off the north-west coast of Western Australia, over a 5-year period from 2005 to 2009. The study was conducted as part of an environmental impact assessment for a liquefied natural gas (LNG) development on the island, with the aim of providing baseline information on invertebrates as a component of a future detection program in support of the island's quarantine system. The study used a standardised methodology for sampling a variety of undisturbed native vegetation communities, in addition to disturbed sites (vegetated and non-vegetated sites) across the island. Pre-eminent invertebrate taxonomists from Australia and overseas were engaged to assist with the identification of the various invertebrate orders collected. A total of 1873 species and morphospecies from 27 invertebrate orders were collected, 292 of which represented named species. A total of 321 families of invertebrates were represented in the collections. Samples taken during the same month in two consecutive years exhibited almost the same degree of difference as samples taken during the same year in the wet and the dry season. For ants, the fauna had greater affinity with the adjacent Pilbara than the Carnarvon basin Bioregion. In terms of sampling rigour and taxonomic coverage, this work represents one of the most intensive and comprehensive terrestrial invertebrate surveys presently undertaken in Australia.

Feeding habits of Molina's hog-nosed skunk, Conepatus chinga (Carnivora: Mephitidae) in the extreme south of Brazil

Feeding habits of the Molina's hog-nosed skunk, Conepatus chinga (Molina, 1782) in the extreme south of Brazil. We analyzed 60 stomachs of road-kills of C. chinga in the extreme south of Brazil. The contents revealed 808 prey parts, including invertebrates (frequency of occurrence - FO = 96.7% and relative abundance - RA = 94.7%), vertebrates (FO = 18.3% and RA = 2.8%) and plants (FO = 31.7% and RA = 2.3%). We identified 18 kinds of food, including the invertebrate order Coleoptera which showed the highest FO (86.7%) and RA (75.2%). Other important orders were Orthoptera (FO = 35% and RA = 10.4%) and Araneae (FO = 41.7% and RA = 4%). The combination of occurrence and abundance of the preys consumed allowed classifying C. chinga as an omnivorous with a predominance of insects, especially Coleoptera, consuming other invertebrates, vertebrates and plants in smaller numbers. Behavioral and morphological adaptations of C. chinga favor the predation of insects, which are preys that offer low physical resistance and are available in all terrestrial environments.

Foraging Range and Habitat use by Aquatic WarblersAcrocephalus paludicolaDuring a Fall Migration Stopover

Stopover sites of migratory songbirds are of great importance in the context of the maintenance of a species migration strategy. Here we studied the spatial needs and habitat selection of the endangered Aquatic Warbler at a major migration stopover site in France, the nature reserve of the Seine estuary. We radio-tracked 15 migrant birds in August 2008 to study habitat use and selection at that stopover site, and analysed faeces and blow trap samples to determine the local diet of the species and to compare food availability among the different available habitats in the reserve. Range size was estimated with fixed kernels and was on average 9 ha (90% isopleths), with daily core ranges (50% isopleths) of just over 1 ha. There was no variation in range size or habitat use during the survey period (August) or during an individual stopover stay. Studying habitat selection within the modelled ranges, we found that the species displayed a preference for wet grassland habitats. Larger daily ranges included more reedbed and fewer grassland areas. This matches the habitat preferences known from breeding and wintering grounds. The main identified prey belonged to a few invertebrate orders, with Odonata, Lepidoptera, Coleoptera and Araneida making the largest contributions to the biomass consumed. There was no significant difference in invertebrate availability between grassland and reedbed habitats in the study area. The availability of grassland habitats close to the reedbeds appears to be a key parameter to ensure the rapid and efficient refuelling of migrant Aquatic Warblers during their autumn migration.

Hymenoptera. Chapter 12

We present the first review of Hymenoptera alien to Europe. Our study revealed that nearly 300 species of Hymenoptera belonging to 30 families have been introduced to Europe. In terms of alien species diversity within invertebrate orders, this result ranks Hymenoptera third following Coleoptera and Hemiptera. Two third of alien Hymenoptera are parasitoids or hyperparasitoids that were mostly introduced for biological control purposes. Only 35 phytophagous species, 47 predator species and 3 species of pollinators have been introduced. Six families of wasps (Aphelinidae, Encyrtidae, Eulophidae, Braconidae, Torymidae, Pteromalidae) represent together with ants (Formicidae) about 80% of the alien Hymenoptera introduced to Europe. The three most diverse families are Aphelinidae (60 species representing 32% of the Aphelinid European fauna), Encyrtidae (55) and Formicidae (42) while the Chalcidoidea together represents 2/3 of the total Hymenoptera species introduced to Europe. The first two families are associated with mealybugs, a group that also included numerous aliens to Europe. In addition, they are numerous cases of Hymenoptera introduced from one part of Europe to another, especially from continental Europe to British Islands. These introductions mostly concerned phytophagous or gall-maker species (76 %), less frequently parasitoids. The number of new records of alien Hymenoptera per year has shown an exponential increase during the last 200 years. The number of alien species introduced by year reached a maximum of 5 species per year between 1975 and 2000. North America provided the greatest part of the hymenopteran species alien to Europe (96 species, 35.3%), followed by Asia (84 species, 30.9%) and Africa (49 species, 18%). Three Mediterranean countries (only continental parts) hosted the largest number of alien Hymenoptera: Italy (144 spp.), France (111 spp.) and Spain (90 spp.) but no correlation was found with the area of countries. Intentional introduction, mostly for biological control, has been the main pathway of introduction for Hymenoptera. Consequently, the most invaded habitats are agricultural and horticultural as well as greenhouses. To the contrary, Hymenoptera alien in Europe are mostly associated with woodland and forest habitats. Ecological and economic impacts of alien Hymenoptera have been poorly studied. Ants have probably displaced native species and this is also true for introduced parasitoids that are suspected to displace native parasitoids by competition, but reliable examples are still scarce. The cost of these impacts has never been estimated.

First report of predation on floral visitors by crab spiders on Croton selowii Baill. (Euphorbiaceae)

In the literature it has been extensively mentioned that crab spiders (Araneae: Thomisidae) prey on floral visitors of several plant species. Here we present observations of Croton selowii Baill. (Euphorbiaceae), a monoecious species harboring individuals of crab spiders in an area of coastal vegetation of Pernambuco state, Brazil. The species is visited by several invertebrate orders, and some of them were preyed upon by the spiders, mainly Diptera species. The spiders rubbed the forelimbs within the flowers, which may constitute a strategy to camouflage these structures. Croton selowii seems to represent a suitable foraging site for the spiders, because it has a generalist pollination system (thus being visited by a wide range of invertebrate species) and blooms in a period of low flower resource availability in the area.

Diet composition ofXenopus borealisin Taita Hills: effects of habitat and predator size

AbstractFrogs in the genusXenopusare ubiquitous in sub‐Saharan Africa, yet very little is recorded on their ecology. They are commonly found in anthropogenically disturbed habitats, but how do these compare to conspecifics from natural habitats? The diet ofXenopus borealisfrom three different sites in Taita Hills, Kenya was established based on a sample of 77 (54 females and 23 males) specimens from two disturbed and one pristine sites.Xenopus borealisfrom all the sites was found to be a dietary generalist, feeding predominantly on invertebrates. A total of twelve invertebrate orders both terrestrial and aquatic were recorded in addition to amphibian eggs, tadpoles and fish. Frogs from the pristine forest were smaller and had ingested more terrestrial prey items than frogs in the disturbed open habitat ponds. The stomach content (both by mass and quantity) was independent of body size. The results suggest thatX. borealisis an opportunistic generalist predator which may be constrained by food availability in its natural habitat. However, disturbed habitats provide abundant food items which are enough to significantly increase the mean size of the population.