Identification Of Predators Research Articles

Nest site vegetation structure influences nest predators and nesting success of understory birds in a dry evergreen forest in northeastern Thailand

Abstract Nest predation is typically the main cause of nest failure in forest understory birds; thus, identification of primary nest predators is key to understanding nest predation patterns. Furthermore, responses of predators are likely affected by vegetation structure, but predator responses to micro-scale habitat characteristics are largely unknown, especially in tropical forests. We used a long-term study with one of the largest datasets of its kind to investigate the extent to which micro-habitat structure (5-m radius surrounding a nest) can predict the likelihood of predation and by which predator. In a secondary evergreen forest in northeastern Thailand, 2013–2021, we found 1,016 active nests of 13 species and 24-hr video-monitored 500 of them. We recorded 336 predation events from 16 nest predator species. From this and previous studies at our site, we identified the top 4 predator species/species-groups accounting for ~83% of predation events: Macaca leonina (northern pig-tailed macaque, 36% of predation events), cat snakes (Boiga cyanea [green cat snake] and Boiga siamensis [grey cat snake]) (20%), Lycodon cf. davisonii (Blandford’s bridle snake, 18%), and accipiters (A. trivirgatus [Crested Goshawk] and A. badius [Shikra]) (9%). These 4 predator species differed in their responses to vegetation structure likely reflecting differences in foraging behaviors. Macaque and accipiters, both diurnal and visually-oriented, tended to depredate more visible/open nests, but macaques depredated nests surrounded by more trees and short woody stems (<3 m tall) compared to raptors. For snakes, both nocturnal, cat snakes depredated nests with higher numbers of both short woody stems and woody climbers, whereas bridle snakes depredated nests with more trees and fewer climbers. As noted previously, nest predator identity is critical to understanding habitat-predation patterns. Our data suggest that nest site vegetation characteristics influence the likelihood of a given species of predator locating a nest and that even small changes in vegetation structure could significantly alter predation patterns.

Identification of mammals based on hair microstructure: Methodological adaptations and new morphological patterns

The characterization of patterns of hair microstructure is an important instrument for studying the diet and ecology of mammals, representing an accessible method for identifying predators and their prey. The present study aimed to: (1) describe methodological adaptations developed to optimize traditional guard hair analysis protocols; (2) propose adjustments in the classification of morphological patterns of medulla and cuticle; and (3) establish the microstructural pattern of Brazilian mammals’ hair to assist in the identification of prey and predators in studies based on fecal samples. Hairs from 53 mammal species, including small (n = 16), medium (n = 28) and large size (n = 9), distributed in 24 families and nine orders were analyzed. The orders with the most species analyzed were Carnivora (n = 14), Rodentia (n = 13) and Didelphimorphia (n = 8), while the most representative families were Didelphidae (n = 8), Cricetidae (n = 7) and Felidae (n = 6). Among the species, 13 (24.5% of the total) did not have the microstructural patterns described in studies developed previously in Brazilian territory: Alouatta guariba, Blarinomys breviceps, Bradypus torquatus, Callicebus personatus, Callithrix geoffroyi, Dasyprocta leporina, Hylaeamys seuanezi, Potos flavus, Priodontes maximus, Rhipidomys mastacalis, Sapajus robustus, Sylvilagus minensis and Tayassu pecari. More descriptive nomenclatures were proposed regarding the observed patterns and new patterns were described for species evaluated in previous studies. Our results contribute to the diagnosis of species to be more accurate, contributing to the development of future studies.

Identification of soil-dwelling predators of tick nymphs (Acari: Ixodidae) by stable isotope labeling.

Ticks (Family Ixodidae) spend most of their life cycle as immature stages in the soil and litter, and as any other soil invertebrates, are likely to be controlled top-down by soil-dwelling predators. To date, the ability of soil invertebrate predators to control ixodid tick population remains little known, partly due to methodological difficulties. In the current study, we developed and successfully tested a novel method of labeling live Ixodes ricinus (L., 1758) (Ixodida: Ixodidae) nymphs with a 15N isotope label. Labeled ticks were used in a small-scale 8-day-long microcosm experiment to reveal soil predators attacking nymphs. Only a small fraction (4.1% of all samples) of soil generalist predators preyed upon nymphs. A strong 15N label was found in 5 predator species, namely 2 spiders (Pachygnatha listeri Sundevall, 1830, Tetragnathidae and Ozyptila sp., Theridiidae), 2 gamasid mites (Pergamasus beklemischevi Sellnick, 1929 and Pergamasus quisquiliarum [Canestrini, 1882], Parasitidae), and 1 staphylinid beetle (Geostiba circellaris [Gravenhorst, 1806], Staphylinidae). The isotopic labeling can be a useful tool in revealing a range of invertebrate predators that can control tick populations in soil.

Wildlife whodunnit: forensic identification of predators to inform wildlife management and conservation

AbstractGenetic evidence at predation sites is rapidly improving predator‐prey interaction studies and can provide information beyond field‐based investigations. However, factors contributing to the retention of genetic evidence have received limited investigation in a field setting, and researchers have yet to leverage genetic evidence to improve traditional field investigations. Using data from 61 mortality investigations of mule deer (Odocoileus hemionus), white‐tailed deer (O. virginianus), and elk (Cervus canadensis), we evaluated factors influencing predator DNA amplification success and misidentification of predators in field investigations. We found that predator DNA was detected more for prey with higher body mass (18.5% increase per standard deviation [23.1 kg] in carcass body mass above the mean [32.8 kg]). Predator DNA was also 27.0% more likely to amplify when collected from kill sites that had not undergone a freeze‐thaw cycle between the mortality and the investigation. The delay between the kill and the investigation, the swabbing surface, and the amount of precipitation did not influence amplification of predator DNA. Misidentifications of the predator based on the field ID were not influenced by the investigation delay or investigator confidence level, suggesting that investigators should collect genetic evidence even when they feel certain about the predator. Errors in identifying the predator during the field investigation increased for prey with smaller body mass, and the predator was actually more likely to be misidentified than correctly identified for fawns and calves < ~21 kg. Black bears (Ursus americanus), bobcats (Lynx rufus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) were equally likely to be missed in a field investigation, but bobcats tended to be falsely assigned more than expected and cougars were falsely assigned as the predator less than expected. Using genetic evidence as validation, we showed how patterns of predation and the field signs left by predators differed for some species depending on the size of the prey. Our findings should help researchers and managers to optimize their use of genetics to enhance field investigations.

Ants (Hymenoptera: Formicidae) increase predation of Belenois solilucis (Lepidoptera: Pieridae) eggs in organic agriculture production systems: a multiple-site field study at Rashad, Sudan

Organic farming is becoming more popular as there is a greater demand for pesticide-free food. Pest control in organic agricultural production requires a set of skills, including the identification of effective predators and land-use practices. Predation by selected Coleopteran, Dipteran, and Hemipteran insects and Araneae is well established, whereas the predatory role of ants (Hymenoptera: Formicidae) has received little attention in the Rashad district, Sudan. This study was carried out to assess the predation rates of Belenois solilucis eggs and the impact of the land use type around the properties on these rates. An experimente involving predation tests on Belenois solilucis eggs and fauna sampling were conducted in 18 areas of organic agriculture in the Rashad district. The study showed that ants can reduce the eggs population by 26.8% per day. At the same time, other predator taxa, primarily Coleoptera, from Coccinellidae and Staphylinidae families, removed only 13% of the eggs. Ant species with the most significant recruiting power were Axinidris acholli, Tapinoma carininotum, and Technomyrmex moerens. Ant genera such as Linepithema, Dorymyrmex, and Camponotus ants were also frequently observed. The proportion of the planted area within a 500-meter radius, in addition to the interaction of other landscape categories, had a minor influence on predation, but only when the predators were not ants. The landscape does not affect predation by predators in general, including ants, or on ant predation in particular.

Cats were Responsible for the Headless Carcasses of Shearwaters: Evidence from Genetic Predator Identification

オオミズナギドリの首なし死骸はネコの捕食によるものだった：遺伝学的捕 食者検出によるエビデンス．イエネコ Felis silvestris catus は，最も有名な侵略的外来捕食者の一つとして知 られている．海鳥は，島嶼においてイエネコの影響を受けてきた典型的な分類群であり，首のない死骸が頻 繁に観察されることがある．本研究では，御蔵島において，イエネコによって近年個体数が減少していると 言われているオオミズナギドリ Calonectris leucomelas の死骸を対象に，遺伝的捕食者検出を行い，さらに死 骸の特徴を明らかにした．今回の調査では，オオミズナギドリの死骸を 8 個体分発見した．死骸の傷口から 採取したスワブサンプルの遺伝子分析により，8 つの死骸のうち 6 つでイエネコの DNA が検出され，イエ ネコの捕食が確認された．これら 6 つの死骸はすべて頭がないか，頭がかろうじて食道や器官で胴体部とつ ながったほぼ首なしという状態で，そのうちのいくつかは消化管も消失していた．本研究では，この首なし という死骸の状態について，イエネコの捕食を疑うことができる主な特徴として提示する．我々の知る限り， 本研究は海鳥を対象とした初めての遺伝的捕食者検出の事例であり，これにより世界的なイエネコの捕食の 実態が，より多くの関係者に認識されるようになるであろう．さらに，この遺伝学的エビデンスが御蔵島に おける本格的なイエネコ対策の展開に貢献することも期待される

Multilocus DNA metabarcoding diet analyses of small cetaceans: a case study on highly vulnerable humpback dolphins and finless porpoises from the Pearl River Estuary, China.

Accurate diet identification of top predators is crucial to fully understand their ecological roles. Compared to terrestrial animals, gathering dietary information from cetaceans is notoriously difficult. Here, we applied a multilocus metabarcoding approach to investigate the diet of vulnerable Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises from the Pearl River Estuary (PRE), China. Our analyses identified 21 prey fish species from the 42 humpback dolphin stomachs, as well as 10 species of fish and 1 species of cephalopod from the 13 finless porpoise stomachs. All of the taxa were assigned to the species level, highlighting that the multimarker approach could facilitate species identification. Most of the prey species were small- and medium-sized fishes that primarily fed on zooplankton. The calculated similarity index revealed a moderated dietary overlap between the 2 cetaceans, presumably due to the feeding of the 2 predators in association with fishing vessels in the PRE. A more diverse diet was observed in humpback dolphins in the closed fishing season compared to the fishing season, implying the influence on the dolphin diet due to the availability of commercial fishery resources. However, according to the results of species rarefaction curves, our findings on the feeding habits of the 2 cetaceans are still limited by insufficient sample size and therefore should be interpreted with caution. This study represents a first attempt to apply the multilocus DNA metabarcoding technique in the diet analysis of small cetaceans, although more efforts are needed to improve this type of analysis.

Uncertain foraging opportunities and predation risk exert additive effects on induced neophobia in cichlids

Neophobia is defined as the avoidance of novel or unknown stimuli, including unknown predators, and can be induced by exposure to uncertain ecological conditions. In addition to uncertainty related to predation risk, uncertainty may also arise from increased foraging competition. Prey forced to spend time and energy competing for limited resources may not have enough time available to devote to predator identification and hence benefit from increased neophobia. Here, we tested the potential interaction of reduced foraging opportunities and elevated predation risk on the strength of neophobia (the antipredator response towards a novel chemical cue). In our first experiment, shoals of juvenile convict cichlids, Amatitlania nigrofasciata , were exposed to high (10% total body weight/day) or low (1% total body weight/day) relative food abundance for 7 days. During the final 3 days, we exposed the shoals to high versus low background predation risk, resulting in a 2 × 2 design. We found that while low food abundance alone and risk alone induced a weak neophobic response to a novel cue (versus water control), cichlids pre-exposed to high risk and low food abundance exhibited significantly a stronger neophobic response, in an additive pattern. In our second experiment, we exposed shoals of cichlids to a fixed amount of food distributed on a single (high competition) patch or across five (low competition) patches for 7 days, with the same risk manipulation as above for the final 3 days. As in experiment 1, we found that high competition alone and risk alone elicited a weak neophobic response to novel cues and that high risk and high competition had additive effects on the strength of induced neophobia among juvenile cichlids. Together, our results indicate that uncertainty of risk and of foraging opportunities exert additive effects on the phenotypically plastic neophobia among prey populations. • Neophobia should reduce costs of bad decisions under uncertain conditions. • Increased competition should increase uncertainty of foraging opportunities. • We exposed cichlids to high vs low predation risk under high vs low competition. • Neophobic responses were stronger under high competition. • Uncertain risk and foraging opportunities exert additive effects on neophobia.

Nest remains are insufficient to identify predators of waterfowl nests

Context Nest predation is a leading cause of nest failure for most ground-nesting birds. Methods that allow for accurate classification of fate and identification of predators are important for understanding productivity and conservation strategies. Past studies have used a visual inspection of nest remains to determine nest fate and predict predator identity. Most formal assessments of these methods have addressed small-bodied birds nesting in trees or shrubs, and have revealed that use of evidence at nests can be relatively accurate for determining nest fate but may lead to incorrect conclusions regarding predator identity. However, few have tested the latter hypothesis for larger ground-nesting birds with precocial young. Aim We aimed to evaluate a classification system developed for determining nest fate and identifying predators of waterfowl nests, at both the scale of individual nests and across the study area. Methods From 2016 to 2020, we located 989 blue-winged teal (Spatula discors), mallard (Anas platyrhynchos) and gadwall (Mareca strepera) nests in central North Dakota. We placed cameras at a subset of 249 nests and recorded evidence of nest remains at depredated nests. Key results The most common predators were American badgers (Taxidea taxus), followed by striped skunks (Mephitis mephitis), raccoons (Procyon lotor) and red foxes (Vulpes vulpes). Using evidence of nest remains, we determined nest fates with high accuracy (98.0%). However, evidence of nest remains was only sufficient for identifying predators at 50% of nests, and the classification system was correct only 69.7% of the time. The predicted proportion of predators across the study area differed between the classification system and our video evidence as well. Conclusions The accuracy of predator identifications based upon the classification system that we evaluated was not supported at any scale. Implications Our results suggest that evidence of nest remains can be used to determine nest fate for large-bodied precocial, ground-nesting birds, but accurate identification of nest predators will require alternative methods such as nest cameras.

No evidence that cameras affect shorebird nest survival on the coastal plain of Arctic National Wildlife Refuge, AK

Cameras are important tools used to determine nest fate, identify predators and evaluate behaviour; however, they may impact the parameters they are used to measure, thereby biasing results. We evaluated the impact of cameras ˜ 10 m from the nest on shorebird nest survival at the Canning River Delta, Alaska, 2017–2018 (ncontrol = 122, ncamera = 109) using a much larger sample size than in previous studies conducted in the Arctic and random assignments at nest discovery. We found no effect of camera presence at the nest on daily nest survival (model‐averaged daily survival rate (DSR) 85% confidence interval (CI); control: 0.971–0.983, camera: 0.969–0.982). We suggest that nest survival studies of tundra‐nesting birds should consider the use of cameras to minimize researcher disturbance, increase the accuracy of fate assignments, and broaden the ecological data collected (e.g. incubation behaviour, predator identification and non‐anthropogenic non‐predation disruption such as by caribou).

The influence of egg presence and eggshell colour in the attraction of visually oriented predators to nests of a tropical forest bird

Several hypotheses have been proposed to account for the function of eggshell pigmentation. One predicts that patterns of colour and markings provide camouflage against visually oriented nest predators. However, the effectiveness of any anti‐predatory function of eggshell colour may be reduced if predators can use the nests per se as foraging cues (nest‐crypsis hypothesis). Here, we tested whether eggshell pigmentation, and a set of concurrent variables, could explain nest predation in natural nests of the Atlantic Forest endemic Blue Manakin Chiroxiphia caudata containing plasticine eggs. Nests were continuously monitored for predator identification using infra‐red camera traps, and we considered the nest‐crypsis hypothesis by testing the premise that if predators can use nests as visual cues, they would be recorded checking empty nests at rates similar to those containing eggs. Six bird species were identified as visually oriented predators of nest contents, and predation frequencies were low and not influenced by eggshell colour. Empty nests and nests containing eggs were visited by predators at similar frequencies, independently of eggshell colour, which provided the first direct support for the nest‐crypsis hypothesis. It suggests that for this tropical forest, open‐nesting passerine, selective forces driving nest concealment and nest camouflage may be stronger than selection for eggshell colour variation.

Smaller and Isolated Grassland Fragments Are Exposed to Stronger Seed and Insect Predation in Habitat Edges

Habitat fragmentation threatens terrestrial arthropod biodiversity, and thereby also leads to alterations of ecosystem functioning and stability. Predation on insects and seeds by arthropods are two very important ecological functions because of their community-structuring effects. We addressed the effect of fragment connectivity, fragment size, and edge effect on insect and seed predation of arthropods. We studied 60 natural fragments of two grassland ecosystems in the same region (Hungarian Great Plain), 30 forest-steppes, and 30 burial mounds (kurgans). The size of fragments were in the range of 0.16–6.88 ha for forest-steppe and 0.01–0.44 ha for kurgan. We used 2400 sentinel arthropod preys (dummy caterpillars) and 4800 seeds in trays for the measurements. Attack marks on dummy caterpillars were used for predator identification and calculation of insect predation rates. In the case of seeds, predation rates were calculated as the number of missing or damaged seeds per total number of exposed seeds. Increasing connectivity played a role only in generally small kurgans, with a negative effect on insect and seed predation rates in the edges. In contrast, fragment size moderated edge effects on insect and seed predation rates in generally large forest-steppes. The difference between edges and centres was more pronounced in small than in large fragments. Our study emphasizes the important role of landscape and fragment-scale factors interacting with edge effect in shaping ecosystem functions in natural grassland fragments of modified landscapes. Managing functional landscapes to optimize the assessment of ecosystem functions and services needs a multispatial scale approach.

Hair as a tool for identification of predators and prey: a study based on scats of jaguars (Panthera onca) and pumas (Puma concolor)

Abstract: Microscopic hair identification is a non-invasive, simple, and economical method applied in scientific studies to identify mammal species. In ecology, this method is used mainly in mastofaunistic inventories and dietary studies. In the last decade, the number of dietary studies using the microscopic identification of hairs has grown substantially, but the application of this technique as a tool for the identification of both predators and prey species is still scant. Thus, the aim of this study was to identify predator and prey hairs in scat samples from the two largest species of carnivores in the Neotropical region, the jaguar (Panthera onca Linnaeus, 1758) and the puma (Puma concolor Linnaeus, 1771). We examined a total of 100 scat samples being 50 from the Pantanal of Mato Grosso do Sul and 50 from the Atlantic Forest of Paraná. We used different identification categories that included the hair microscopic and macroscopic identification, as well as the use of hooves and nails present in the scats associated with tracks and kills found in the field. We identified 57 prey items in the Pantanal samples and 61 in the Atlantic Forest samples. Predator´s hairs were identified in 34% of Pantanal samples and in 46% of Atlantic Forest samples. The combination of hair microscopic and macroscopic characteristics was efficient in the identification of different taxonomic levels, with most identifications reaching the level of the species. However, the methodological protocol for microscopic hair identification was not fully effective in obtaining all the microstructural patterns of the studied mammals. Adjustments in the technique are necessary to differentiate microstructural characteristics of species belonging to the same family. We recommend macroscopic identification of scat content items (hairs, hooves or nails) of both prey and predators to be used to complete the microscopic hair identification technique in dietary ecological studies.

Diagnosing nest predators and anti-predator response of red wattled lapwing, Vanellus indicus (Boddaert, 1783)

Identification of nest predators and anti-predator behavior of Vanellus indicus (red wattled lapwings) were studied during two constitutive breeding periods (March-August) of 2018 and 2019. The study was performed along the river Ganges, Raebareli (Uttar Pradesh), India. The number of nesting pairs was counted by the line transect method and anti-predator responses were recorded by the focal sampling method. The nesting pairs varied significantly within and between study sites and years. A variety of predators (avian, mammalian and reptilian) were identified while some predators were designated in the unknown category. Sitting tight response was significantly different during the incubation period. The mobbing response, flying away and running away responses were significantly different during the post-incubation period. Circle noisily over the nests and alarm call were not significant between the two reproductive stages. We conclude that red wattled lapwings can differentiate among diverse predator species and adopt various anti-predator responses against them at different stages of their breeding cycle.

Identification of keystone predators in Haizhou Bay food web based on the revised SURF index

Keystone predator species play an important role in regulating the number, richness and distribution of prey species. Based on the bottom trawl surveys in Haizhou Bay, keystone predator species in fish communities were identified by the revised SURF (supportive role to fishery ecosystems) index. Conger myriaster, Saurida elongata, Hexagrammos otakii, Chelidonichthys spinosus, and Larimichthys polyactis were the keystone predators in the fish community. They had high number of nodes degree, and were also the main predators of many species. Further, they had strong ability of clustering. The fluctuations of their density would have great impacts on ecosystem energy flow and food web structure. The method not only considered the feeding ratio between species, but also took the amount of catch and abundance of species as important factors in the identification of keystone predators. Compared with the traditional method, this method had great improvement and provided a new one for the identification of key predators. Our results showed that the strong inter-specific interactions played an important role in maintaining the structure and function of food webs. Protection of key predators would benefit the stability of biological communities and species diversity. Therefore, ecosystem-based fisheries management (EBFM) should give priority to the protection of key species. The important economic fish species, C. myriaster and L. polyactis, should be protected with high priority as they suffered from higher fishing pressure.

Impact of introduced nest predators on insular endemic birds: the case of the Azores Woodpigeon (Columba palumbus azorica)

Nest predation is the main cause of reproductive failure in many bird species. Identification of predators is crucial to understand and interpret the factors that affect nest predation. Although nest predation is a natural top-down regulator of bird populations, its effect is usually more dramatic when introduced predators are involved, particularly in oceanic islands. In the Azores archipelago, the endemic Azores Woodpigeon (Columba palumbus azorica) is believed to be under high predation pressure. We used motion-triggered cameras to monitor nests of the Azores Woodpigeon on two islands of the archipelago (Pico and Terceira) in order to identify nest predators, quantify their impact on this bird and better understand the determinants of predation rates. We sampled 56 nests, during 569 camera trap days, obtaining around 125,000 photographic records. Two introduced predators were identified, black rat (on both islands) and feral cat (only on Terceira), both depredating eggs and chicks. Breeding success, calculated using the Mayfield method, was estimated at 19% on Pico and only 9% on Terceira. Overall, predation was the main cause of breeding failure. General linear models showed that predation rates are positively correlated to fruit availability and negatively correlated to elevation, human population density and adult Woodpigeon attendance at the nest. Edge distance, nest height or cover of trees did not affect predation. Camera traps also provided additional and useful information on predator behaviour when approaching a nest and on daily activity patterns of both adult Woodpigeon and nest predators.

Acetylcholinesterase Enzyme (AChE) as a Biosensor and Biomarker for Pesticides: A Mini Review

Due to the increase in pesticide usage the cost of food production has been drastically reduced worldwide. There are dangers related to the ever-increasing pesticide application especially to the non-target biota and to also to the environment at large. Pesticides bind with the active site of acetylcholinesterase (AChE) and inhibit the breakdown of acetylcholine and causes the blockage of synaptic transmission in cholinergic nerves. When AChE is inhibited, ChE accumulates and the nerve impulse cannot be stopped, leading to muscle contraction, paralysis and sometimes dead may occur. Pesticides and other chemicals that inhibit AChE activity can be able to cause abnormal behavioural patterns of the affected animals. The effects of AChE inhibition in vertebrate include vasodilation of blood vessels, slower heart rate, constriction of bronchioles and reduced secretion of mucus in the respiratory tract, intestinal cramps, secretion of saliva, sweat and tears, and constriction of eye pupil. The inhibition of the AChE activity will also definitely affect the optomotor behaviour of a fish which in turn will affect feeding capability, identification and avoidance of predators, and spatial orientation of the species. Carbamates, organophosphate and eserine are the major pesticides that inhibit the AChE activity of many animals. Cholinesterases including AChE have been considered as interesting biomarkers and biosensor for many years in the monitoring of environmental contamination. This is sensitive to selected organophosphate and carbamate pesticides and may be responding to low levels of contaminants in the environment, putatively by compounds other than or in addition to pesticides. In respect to the above AChE is regarded as a good Biosensor and biomarker in assessing pesticides and other chemical pollutants in the environment.

In silico and empirical evaluation of twelve metabarcoding primer sets for insectivorous diet analyses.

During the most recent decade, environmental DNA metabarcoding approaches have been both developed and improved to minimize the biological and technical biases in these protocols. However, challenges remain, notably those relating to primer design. In the current study, we comprehensively assessed the performance of ten COI and two 16S primer pairs for eDNA metabarcoding, including novel and previously published primers. We used a combined approach of in silico, in vivo‐mock community (33 arthropod taxa from 16 orders), and guano‐based analyses to identify primer sets that would maximize arthropod detection and taxonomic identification, successfully identify the predator (bat) species, and minimize the time and financial costs of the experiment. We focused on two insectivorous bat species that live together in mixed colonies: the greater horseshoe bat (Rhinolophus ferrumequinum) and Geoffroy's bat (Myotis emarginatus). We found that primer degeneracy is the main factor that influences arthropod detection in silico and mock community analyses, while amplicon length is critical for the detection of arthropods from degraded DNA samples. Our guano‐based results highlight the importance of detecting and identifying both predator and prey, as guano samples can be contaminated by other insectivorous species. Moreover, we demonstrate that amplifying bat DNA does not reduce the primers' capacity to detect arthropods. We therefore recommend the simultaneous identification of predator and prey. Finally, our results suggest that up to one‐third of prey occurrences may be unreliable and are probably not of primary interest in diet studies, which may decrease the relevance of combining several primer sets instead of using a single efficient one. In conclusion, this study provides a pragmatic framework for eDNA primer selection with respect to scientific and methodological constraints.

DNA-based identification of predators of the corallivorous Crown-of-Thorns Starfish (Acanthaster cf. solaris) from fish faeces and gut contents

The corallivorous Crown-of-Thorns Starfish (CoTS, Acanthaster spp.) has been linked with the widespread loss of scleractinian coral cover on Indo-Pacific reefs during periodic population outbreaks. Here, we re-examine CoTS consumption by coral reef fish species by using new DNA technologies to detect Pacific Crown-of-Thorns Starfish (Acanthaster cf. solaris) in fish faecal and gut content samples. CoTS DNA was detected in samples from 18 different coral reef fish species collected on reefs at various stages of CoTS outbreaks in the Great Barrier Reef Marine Park, nine of which had not been previously reported to feed on CoTS. A comprehensive set of negative and positive control samples confirmed that our collection, processing and analysis procedures were robust, although food web transfer of CoTS DNA cannot be ruled out for some fish species. Our results, combined with the (i) presence of CoTS spines in some samples, (ii) reported predation on CoTS gametes, larvae and settled individuals, and (iii) known diet information for fish species examined, strongly indicate that direct fish predation on CoTS may well be more common than is currently appreciated. We provide recommendations for specific management approaches to enhance predation on CoTS by coral reef fishes, and to support the mitigation of CoTS outbreaks and reverse declines in hard coral cover.

Investigating the influence of groups of variables on the task of predicting the age of an author in blog posts

The identification of the profile of users from texts on the Internet is a relevant task in the context of today's society. This activity is known in the literature as Author Profiling. Among the essential characteristics to be deduced in this task is the age. This feature is paramount, for example, for the identification of potential sexual predators in environments targeted for children. However, one of the issues faced in resolving this problem is the identification of which variables should be taken into account to address this problem. Thus, this article aims to identify which variables are relevant in building a data mining solution to infer a user's age from a text on the Internet. An experimental study was carried out in a database of a prestigious international competition, considered a benchmarking of the area, to validate this work. The results showed that there is a difference between the possibilities of variables that can be constructed to solve this problem and justifies the importance of each variable group for this purpose. The main contribution of this study was to find different relevance among groups of variables previously mentioned in the literature.