Food habits of the sympatric insectivorous bats Rhinolophus rouxi and Hipposideros lankadiva from Sri Lanka

The diets of Rhinolophus rouxi and Hipposideros lankadiva were studied during October 1984 in Sri Lanka, by analysing the faeces collected from individuals. As a comparison, insects were collected with a light trap at different sites in the study area.
Rhinolophus rouxi showed no specialization for any particular insect prey. The diet composition in this species shows a good correspondence to the composition in dry weight of insects collected by light traps. Dipterans were under-represented in the faeces compared to the numbers trapped. This suggests that R. rouxi forages unselectively on prey larger than the generally very small dipterans. After the first monsoon showers, the remains of beetles, especially scarabaeids, and termites were more common in the faeces of R. rouxi. Bats caught at hourly intervals during one night showed an increase in the proportion of moths consumed.
In contrast, H. lankadiva was found to feed mainly on beetles, particularly scarabaeids, together with large, slow-flying insects such as bugs or nuptial ants. The proportion of beetles (79%-100%) in the faeces of this species was about three times higher than their representation in the insect collections. This suggests that H. lankudiuu forages selectively.     

Evaluation of Trail-Cameras for Analyzing the Diet of Nesting Raptors Using the Northern Goshawk as a Model

Diet studies present numerous methodological challenges. We evaluated the usefulness of commercially available trail-cameras for analyzing the diet of Northern Goshawks (Accipiter gentilis) as a model for nesting raptors during the period 2007–2011. We compared diet estimates obtained by direct camera monitoring of 80 nests with four indirect analyses of prey remains collected from the nests and surroundings (pellets, bones, feather-and-hair remains, and feather-hair-and-bone remains combined). In addition, we evaluated the performance of the trail-cameras and whether camera monitoring affected Goshawk behavior. The sensitivity of each diet-analysis method depended on prey size and taxonomic group, with no method providing unbiased estimates for all prey sizes and types. The cameras registered the greatest number of prey items and were probably the least biased method for estimating diet composition. Nevertheless this direct method yielded the largest proportion of prey unidentified to species level, and it underestimated small prey. Our trail-camera system was able to operate without maintenance for longer periods than what has been reported in previous studies with other types of cameras. Initially Goshawks showed distrust toward the cameras but they usually became habituated to its presence within 1–2 days. The habituation period was shorter for breeding pairs that had previous experience with cameras. Using trail-cameras to monitor prey provisioning to nests is an effective tool for studying the diet of nesting raptors. However, the technique is limited by technical failures and difficulties in identifying certain prey types. Our study also shows that cameras can alter adult Goshawk behavior, an aspect that must be controlled to minimize potential negative impacts.     

Molecular identification of prey in predator diets

In many situations prey choice by predators in the field cannot be established or quantified using direct observation. The remains of some prey may be visually identified in the guts and faeces of predators but not all predators ingest such hard remains and even those that do consume them may also ingest soft-bodies prey that leave no recognizable remnants. The result is, at best, a biased picture of prey choice. A range of molecular techniques and applications are reviewed that allow prey remains to be identified, often to the species and even stage level. These techniques, all of which are still in use, include enzyme electrophoresis, a range of immunological approaches using polyclonal and monoclonal antibodies to detect protein epitopes, and recently developed polymerase chain reaction (PCR)-based methods for detecting prey DNA. Analyses may be postmortem, on invertebrate and vertebrate predators collected from the field, or noninvasive assays of the remains in regurgitated bird pellets or vertebrate faeces. It was concluded that although monoclonal antibodies are currently the most effective method in use today, PCR-based techniques have proved to be highly effective and versatile in recent laboratory trials and are likely to rapidly displace all other approaches.     

Food of the serotine bat, Eptesicus serotinus—is faecal analysis a valid qualitative and quantitative technique?

The diet of Epfesicus serotinus was investigated by faecal analysis and the validity of this technique as a means of obtaining reliable quantitative results was assessed. Knowledge of what the bats eat will allow predictions of which habitats contribute most prey. Three male serotines were kept in captivity during the months of July and August 1991 and fed known quantities of identified insects. With captive E. serotinus the remains of prey appeared within 33 min of first bite and continued to appear for up to 32 h after consumption. Scales from two Noctua pronuba moths consumed were contained in 59 subsequent droppings. Similarly, fragments of three beetles, Geotrupes stercorarius , were contained in 28 subsequent faeces.
Analysis of the faeces of free-living bats revealed insects from seven orders. Coleoptera were found to be present in 96.1% of the droppings examined; the next most frequently found order was Lepidoptera, occurring in 14.7%. The beetles were mostly associated with hay meadows ( Aphodius spp. and Melolontha spp.), or grazed pasture ( Aphodius spp. and Geotrupes spp.). Quantitative determination of prey eaten is not possible owing to the large number of the droppings shown to contain the remains of marker insects and the long period over which they are produced.     

The influence of meal size on prey DNA detectability in piscivorous birds

Molecular methods allow noninvasive assessment of vertebrate predator–prey systems at high taxonomic resolution by examining dietary samples such as faeces and pellets. To facilitate the interpretation of field‐derived data, feeding trials, investigating the impacts of biological, methodological and environmental factors on prey DNA detection, have been conducted. The effect of meal size, however, has not yet been explicitly considered for vertebrate consumers. Moreover, different noninvasively obtained sample types remain to be compared in such experiments. Here, we present a feeding trial on abundant piscivorous birds, Great Cormorants (Phalacrocorax carbo), to assess meal size effects on postfeeding prey DNA detection success. Faeces and pellets were sampled twice a day after the feed of large (350–540 g), medium (190–345 g) and small (15–170 g) fish meals contributing either a large (>79%) or small (<38%) share to the daily consumption. Samples were examined for prey DNA and fish hard parts. Molecular analysis of faeces revealed that both large meal size and share had a significantly positive effect on prey DNA detection rate postfeeding. Furthermore, large meals were detectable for a significantly longer time span with a detection limit at ~76 hr and a 50% detection probability at ~32 hr postfeeding. In pellets, molecular methods reliably identified the meal consumed the previous day, which was not possible via morphological analysis or when examining individual faeces. The less reliable prey DNA detection of small meals or meal shares in faeces signifies the importance of large numbers of dietary samples to obtain reliable trophic data.     

Diet choice of large carnivores in northern Cameroon

The diet of African wild dogs, lions and spotted hyenas was studied in the woodland savannah of Faro National Park and surrounding hunting zones in northern Cameroon during the dry season. Faecal analysis revealed that the diet of the three large carnivores overlaps considerably. Frequencies of prey remains of large and medium‐sized antelopes were highest, with Buffon's kob being by far the most common prey species. Carnivores seem to consume most abundant prey species. No prey item of domestic livestock was found in the faeces. Faecal analysis has proved to be a useful method to reveal diet choice for large carnivores in northern Cameroon. Detailed information on the distribution and density of large carnivores and their prey is needed to give a better picture of the status of carnivores in northern Cameroon and to help resolve conflicts with livestock. Further investigations into the seasonal variation of predation and other factors structuring the large carnivore community in northern Cameroon are recommended.     

Diet choice of large carnivores in northern Cameroon

The diet of African wild dogs, lions and spotted hyenas was studied in the woodland savannah of Faro National Park and surrounding hunting zones in northern Cameroon during the dry season. Faecal analysis revealed that the diet of the three large carnivores overlaps considerably. Frequencies of prey remains of large and medium‐sized antelopes were highest, with Buffon's kob being by far the most common prey species. Carnivores seem to consume the most abundant prey species. No prey item of domestic livestock was found in the faeces. Faecal analysis has proved to be a useful method to reveal diet choice for large carnivores in northern Cameroon. Detailed information on the distribution and density of large carnivores and their prey is needed to give a better picture of the status of carnivores in northern Cameroon and to help resolve conflicts with livestock. Further investigations into the seasonal variation of predation and other factors structuring the large carnivore community in northern Cameroon are recommended.     

Invertebrate diet of the Houbara Bustard Chlamydotis [undulata] macqueenii in Abu Dhabi from calibrated faecal analysis

The ecology of the Houbara Bustard Chlamydotis [undulata] macqueenii is poorly known and populations are declining due to hunting and habitat loss. As wintering populations in Abu Dhabi may be limited by habitat and food, we studied the diet using calibrated faecal analysis. Prey were categorized into 16 groups and fed to captive birds under controlled conditions. We calculated the recovery rates of prey following digestion and identified consistent fragments for each group. Wild Houbara Bustard faeces were collected and examined for key fragments, and initial prey intake was calibrated. Plant remains were identified and their contribution was estimated. Fewer than 28% faeces contained >50% plant material by volume and only 12% contained 95% or more. Numerically, the most important prey were: ants (64%), large nocturnal tenebrionids (14.5%), small climbing tenebrionids (12%) and diurnal tenebrionids. However, the Tenebrionidae contributed 97% of the animal biomass. The relative proportions of prey in the diet were similar to relative abundance as assessed by pitfall trapping. Estimates of the energetic value of the prey suggested that on average Houbara Bustards must consume around 670 desert invertebrates/day to meet energy needs. The effort required to catch these prey may vary at least ten-fold seasonally. On average plants could provide a further 6.4–14% energy but more work is needed on this. Whether Houbara Bustards wintering in Abu Dhabi are prey-limited depends on prey densities and renewal rates which remain unknown.     

The foraging ecology of the mountain long-eared bat Plecotus macrobullaris revealed with DNA mini-barcodes

Molecular analysis of diet overcomes the considerable limitations of traditional techniques for identifying prey remains in bat faeces. We collected faeces from individual Mountain Long-eared Bats Plecotus macrobullaris trapped using mist nets during the summers of 2009 and 2010 in the Pyrenees. We analysed their diet using DNA mini-barcodes to identify prey species. In addition, we inferred some basic features of the bat's foraging ecology that had not yet been addressed. P. macrobullaris fed almost exclusively on moths (97.8%). As prey we detected one dipteran genus (Tipulidae) and 29 moth taxa: 28 were identified at species level (23 Noctuidae, 1 Crambidae, 1 Geometridae, 1 Pyralidae, 1 Sphingidae, 1 Tortricidae), and one at genus level (Rhyacia sp., Noctuidae). Known ecological information about the prey species allowed us to determine that bats had foraged at elevations between 1,500 and 2,500 m amsl (above mean sea level), mostly in subalpine meadows, followed by other open habitats such as orophilous grasslands and alpine meadows. No forest prey species were identified in the diet. As 96.4% of identified prey species were tympanate moths and no evidence of gleaning behaviour was revealed, we suggest P. macrobullaris probably forages by aerial hawking using faint echolocation pulses to avoid detection by hearing moths. As we could identify 87.8% of the analysed sequences (64.1% of the MOTUs, Molecular Operational Taxonomic Units) at species level, we conclude that DNA mini-barcodes are a very useful tool to analyse the diet of moth-specialist bats.     

Why do eastern curlews Numenius madagascariensis feed on prey that lowers intake rate before migration?

Eastern curlews Numenius madagascariensis spending the nonbreeding season in eastern Australia foraged on three intertidal decapods: soldier crab Mictyris longicarpus, sentinel crab Macrophthalmus crassipes and ghost‐shrimp Trypaea australiensis. Due to their ecology, these crustaceans were spatially segregated (=distributed in ‘patches’) and the curlews intermittently consumed more than one prey type. It was predicted that if the curlews behaved as intake rate maximizers, the time spent foraging on a particular prey (patch) would reflect relative availabilities of the prey types and thus prey‐specific intake rates would be equal. During the mid‐nonbreeding period (November–December), Mictyris and Macrophthalmus were primarily consumed and prey‐specific intake rates were statistically indistinguishable (8.8 versus 10.1 kJ×min^?1). Prior to migration (February), Mictyris and Trypaea were hunted and the respective intake rates were significantly different (8.9 versus 2.3 kJ×min^?1). Time allocation to Trypaea‐hunting was independent of the availability of Mictyris. Thus, consumption of Trypaea depressed the overall intake rate. Six hypotheses for consuming Trypaea before migration were examined. Five hypotheses: the possible error by the predator, prey specialization, observer overestimation of time spent hunting Trypaea, supplementary prey and the choice of higher quality prey due to a digestive bottleneck, were deemed unsatisfactory. The explanation for consumption of a low intake‐rate but high quality prey (Trypaea) deemed plausible was diet optimisation by the curlews in response to the pre‐migratory modulation (decrease in size/processing capacity) of their digestive system. With a seasonal decrease in the average intake rate, the estimated intake per low tide increased from 1233 to 1508 kJ between the mid‐nonbreeding and pre‐migratory periods by increasing the overall time spent on the sandflats and the proportion of time spent foraging.     

The food habits of a Malagasy Giant: Hipposideros commersoni (E. Geoffroy, 1813)

Hipposideros commersoni is a large microchiropteran bat endemic to Madagascar. We analysed fragments of its prey from faeces and from underneath feeding perches to describe its diet from four sites. Diet was similar across sites and Coleoptera was the main prey item by percentage volume (75%), followed by Hemiptera (13%). Carabidae and Scarabidae were the most frequent coleopterans found in the diet. Direct observations (n = 3) were made of bats flying short distances from perches along forest trails to prey on Cicadidae ( c. 20 mm in length) located on tree trunks. There were differences in the composition of faecal samples collected form netted bats and pellets collected under feeding perches, with the latter consisting of more Blattoptera (Blattellidae 'cockroaches'). Hipposideros commersoni appears to have a unique foraging behaviour and diet among Malagasy microchiropterans and its preference for certain Coleoptera and other large invertebrates may account for reported seasonal variation in body fattening and activity.     

Comparing three types of dietary samples for prey DNA decay in an insect generalist predator

The rapidly growing field of molecular diet analysis is becoming increasingly popular among ecologists, especially when investigating methodologically challenging groups, such as invertebrate generalist predators. Prey DNA detection success is known to be affected by multiple factors; however, the type of dietary sample has rarely been considered. Here, we address this knowledge gap by comparing prey DNA detection success from three types of dietary samples. In a controlled feeding experiment, using the carabid beetle Pterostichus melanarius as a model predator, we collected regurgitates, faeces and whole consumers (including their gut contents) at different time points postfeeding. All dietary samples were analysed using multiplex PCR, targeting three different length DNA fragments (128, 332 and 612 bp). Our results show that both the type of dietary sample and the size of the DNA fragment contribute to a significant part of the variation found in the detectability of prey DNA. Specifically, we observed that in both regurgitates and whole consumers, prey DNA was detectable significantly longer for all fragment sizes than for faeces. Based on these observations, we conclude that prey DNA detected from regurgitates and whole consumers DNA extracts are comparable, whereas prey DNA detected from faeces, though still sufficiently reliable for ecological studies, will not be directly comparable to the former. Therefore, regurgitates and faeces constitute a useful, nonlethal source for dietary information that could be applied to field studies in situations when invertebrate predators should not be killed.     

Interspecific coprophagia by wild red foxes: DNA metabarcoding reveals a potentially widespread form of commensalism among animals

Vertebrate animals are known to consume other species'' faeces, yet the role of such coprophagy in species dynamics remains unknown, not least due to the methodological challenges of documenting it. In a large‐scale metabarcoding study of red fox and pine marten scats, we document a high occurrence of domestic dog DNA in red fox scats and investigate if it can be attributed to interspecific coprophagia. We tested whether experimental artifacts or other sources of DNA could account for dog DNA, regressed dog occurrence in the diet of fox against that of the fox’s main prey, short‐tailed field voles, and consider whether predation or scavenging could explain the presence of dog DNA. Additionally, we determined the calorific value of dog faeces through calorimetric explosion. The high occurrence of dog DNA in the diet of fox, the timing of its increase, and the negative relationship between dog and the fox''s main prey, point to dog faeces as the source of DNA in fox scats. Dog faeces being highly calorific, we found that foxes, but not pine martens, regularly exploit them, seemingly as an alternative resource to fluctuating prey. Scattered accounts from the literature may suggest that interspecific coprophagia is a potentially frequent and widespread form of interaction among vertebrates. However, further work should address its prevalence in other systems and the implications for ecological communities. Tools such as metabarcoding offer a way forward.     

The diet of the diadem leaf-nosed bat Hipposideros diadema: confirmation of a morphologically-based prediction of carnivory

The diet of Hipposideros diadema was investigated over three seasons at two sites on Cape York Peninsula, Australia using faecal analysis (at both sites) and prey remains identification (at one site). The possibility that this species feeds on terrestrial vertebrates, a behaviour here referred to as carnivory, was suggested by the similarity of three of its morphological features with those of eight of the 10 species of bats known to exhibit carnivory.
The study confirmed that H. diadema is at least occasionally carnivorous. Bird feathers were found in faeces at both sites; however, their occurrence was limited to a collection of faecal pellets from the early dry season at Iron Range and a single pellet from the wet season at Chillagoe. The birds taken could not be identified to family or species. Coleoptera, Lepidoptera and various orthopteroid orders were the main insect taxa in faecal pellets. The frequency of these taxa in the diet varied significantly among the three seasons at both sites. Analysis of prey remains indicated that large, hard-bodied insects, mainly cerambycid and scarabaeid beetles and acridid grasshoppers, particularly the locust Gastrimargus musicus , were taken frequently. The mean length of intact beetle elytra collected below roosts was 18.0 mm. No vertebrate material was found in prey remains. Hipposideros diadema is similar to several other bats which exhibit carnivory in preying infrequently on vertebrates. The term 'partial carnivore' or 'occasional carnivore' is suggested for these species.     

Feeding ecology of the armored shrew, from the north-eastern Democratic Republic of Congo

The diet of Scutisorex somereni (Soricomorpha: Soricidae) from forests in the Democratic Republic of Congo was investigated to elucidate its feeding ecology in the context of its unique spinal modifications. It ate a wide range of small and large invertebrates, including representatives of Coleoptera, Formicidae, Lepidoptera and Diptera larvae, Chilopoda, Diplopoda and Araneae, but the principal prey was Oligochaeta. All diet samples contained Oligochaeta and these contributed 38–45% of prey volume. While 64% of prey occurrences were <10 mm in length, 56% of prey volume comprised invertebrates >26 mm, mostly large Oligochaeta (some of >50 mm). Soil-dwelling prey comprised 46% by composition (59% by volume) of the diet. Besides its peculiar skeletal modifications, it has an exceptionally long intestine relative to its body size. It was concluded that S. somereni is primarily an earthworm-eating shrew and partially subterranean rather than truly fossorial in foraging mode. Its diet and foraging mode cannot explain the unique vertebral modifications of this zoological curiosity.     

Detecting frogs as prey in the diets of introduced mammals: a comparison between morphological and DNA‐based diet analyses

Amphibians are currently the most threatened group of vertebrates worldwide, and introduced fauna play a major role in their decline. The control of introduced predators to protect endangered species is often based on predation rates derived from diet studies of predators, but prey detection probabilities using different techniques are variable. We measured the detectability of frogs as prey, using morphological and DNA‐based diet analyses, in the stomachs and faeces of four mammal species that have been introduced to many areas of the world. Frogs (Litoria raniformis) were fed to rats (Rattus norvegicus and R. rattus), mice (Mus musculus) and hedgehogs (Erinaceus europaeus). DNA‐based analysis outperformed morphological analysis, increasing the prey detection rate from 2% to 70% in stomachs and from 0% to 53% in faeces. In most cases, utilizing either stomachs or faeces did not affect the success of prey DNA detection; however, using faeces extended the detectability half‐life from 7 to 21 h. This study is the first to measure prey DNA detection periods in mammalian stomachs, and the first to compare prey DNA detection periods in the stomachs and faeces of vertebrates. The results indicate that DNA‐based diet analysis provides a more reliable approach for detecting amphibians as prey and has the potential to be used to estimate the rate of predation by introduced mammals on endangered amphibians.     

Effect of Diet History on Prey and Pollen Food Choice by Two Lady Beetle Species

Mixed diets of prey and plant-provided foods, such as pollen, have been shown to benefit a wide range of arthropods. However, diet shifting between these two very different food sources remains poorly understood. We hypothesized that previous diet should influence subsequent time allocation between prey and plant food types; to reach a balanced diet, consumers are expected to allocate more time to resources previously lacking in their diet. We tested this hypothesis by observing the foraging choices of larvae of two omnivorous coccinellid species: Coccinella septempunctata L. and Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), following a diet history of prey, pollen or a mixed diet of both food types. Results showed an asymmetrical tendency of C. septempunctata larvae to complement their previous diet with unfamiliar food: larvae allocated more time to pollen feeding, but not to prey, when each of the foods was previously absent from their diet. Study results have important implications for the use of plant-provided food supplements to enhance biological control by these omnivorous consumers.     

Dietary separation of sympatric carnivores identified by molecular analysis of scats

We studied the diets of four sympatric carnivores in the flooding savannas of western Venezuela by analysing predator DNA and prey remains in faeces. DNA was isolated and a portion of the cytochrome b gene of the mitochondrial genome amplified and sequenced from 20 of 34 scats. Species were diagnosed by comparing the resulting sequences to reference sequences generated from the blood of puma (Puma concolor), jaguar (Panthera onca), ocelot (Leopardus pardalus) and crab-eating fox (Cerdocyon thous). Scat size has previously been used to identify predators, but DNA data show that puma and jaguar scats overlap in size, as do those of puma, ocelot and fox. Prey-content analysis suggests minimal prey partitioning between pumas and jaguars. In field testing this technique for large carnivores, two potential limitations emerged: locating intact faecal samples and recovering DNA sequences from samples obtained in the wet season. Nonetheless, this study illustrates the tremendous potential of DNA faecal studies. The presence of domestic dog (Canis familiaris) in one puma scat and of wild pig (Sus scrofa), set as bait, in one jaguar sample exemplifies the forensic possibilities of this noninvasive analysis. In addition to defining the dietary habits of similar size sympatric mammals, DNA identifications from faeces allow wildlife managers to detect the presence of endangered taxa and manage prey for their conservation.     

A PCR-based method for diet analysis in freshwater organisms using 18S rDNA barcoding on faeces

The development of DNA barcoding from faeces represents a promising method for animal diet analysis. However, current studies mainly rely on prior knowledge of prey diversity for a specific predator rather than on a range of its potential prey species. Considering that the feeding behaviour of teleosts may evolve with their environment, it could prove difficult to establish an exhaustive listing of their prey. In this article, we extend the DNA barcoding approach to diet analysis to allow the inclusion of a wide taxonomic range of potential prey items. Thirty-four ecological clade-specific primer sets were designed to cover a large proportion of prey species found in European river ecosystems. Selected primers sets were tested on isolated animal, algal or plant tissues and thereafter on fish faeces using nested PCR to increase DNA detection sensitivity. The PCR products were sequenced and analysed to confirm the identity of the taxa and to validate the method. The methodology developed here was applied to a diet analysis of three freshwater cyprinid species that are assumed to have similar feeding behaviour [Chondrostoma toxostoma toxostoma (Vallot 1837), Chondrostoma nasus nasus (Linnaeus, 1758) and Barbus barbus, (Linneaus 1758)]. These three species were sampled in four different hydrographic basins. Principal Component Analysis based on prey proportions identified distinct perilithon grazer and benthophagous behaviours. Furthermore, our results were consistent with the available literature on feeding behaviour in these fish. The simplicity of the PCR-based method and its potential generalization to other freshwater organisms may open new perspectives in food web ecology.     

Nutritional quality of fish faeces is enhanced by highly unsaturated fatty acid-producing heterotrophic protozoa

Highly unsaturated fatty acids such as 20:5n3 (EPA) are both hormone precursors and cell membrane components, making them important nutrients for aquatic animals. Many animals must obtain EPA from their diets because they cannot synthesize enough EPA to meet their requirements, and algae are the main source of EPA in aquatic ecosystems. In a previous study, we detected EPA in the faeces of Danio rerio, a freshwater fish, even though the fish consumed a green algae diet that did not contain EPA. The objective of this study was to determine why EPA was detected in fish faeces. A significant positive relationship was detected between the number of heterotrophic protozoa and the concentration of EPA in the faeces, which suggests that this EPA was of protozoan origin. In addition, another experiment showed that protozoa adhered to faeces far more than the green algal diet remnants, which indicates that protozoa preferred to swarm on faeces. Furthermore, we cultured protozoa in an EPA-free medium and fed them a bacterial diet also lacking EPA, and found that Cyclidium sp. synthesized EPA de novo. The results demonstrate that protozoa produce essential fatty acids and enhance the nutritional quality of animal faeces in detritus-based food webs in freshwater ecosystems.