Search

Predation is a crucial ecosystem function, transferring nutrients and shaping the abundance and diversity of animals within communities. On coral reefs, fish-fish predation (i.e., piscivory) is arguably one of the best known ecosystem functions, yet is also one of the least well quantified. Recent work has suggested that the prey capture performance of piscivorous fishes may differ when feeding on actively swimming vs. cryptobenthic fish prey. However, the extent of this difference remains unquantified. Our goal, therefore, was to conduct performance-based experiments comparing piscivorous fishes feeding on two different fish prey types, namely, actively swimming vs. cryptobenthic prey (i.e., prey sitting on the benthos). While predators were able to immediately detect actively swimming prey, when feeding on cryptobenthic prey, predators were generally unable to detect the prey until it moved. Both focal predators, the grabber Pseudochromis fuscus and the engulfer Pterois volitans were less successful at capturing cryptobenthic prey (mean 28% probability of capture), compared to actively swimming prey (85%). Overall, our study demonstrates the heterogeneous nature of fish predation on coral reefs, and the challenges of feeding on different prey functional groups. [ABSTRACT FROM AUTHOR]

The ability of echolocating toothed whales to detect and classify prey at long ranges enables efficient searching and stalking of sparse prey in these time-limited dives. However, nonecholocating deep-diving seals such as elephant seals appear to have much less sensory advantage over their prey. Both elephant seals and their prey rely on visual and hydrodynamic cues that may be detectable only at short ranges in the deep ocean, leading us to hypothesize that elephant seals must adopt a less efficient reactive mode of hunting that requires high prey densities. To test that hypothesis, we deployed high-resolution sonar and movement tags on 25 females to record simultaneous predator and prey behavior during foraging interactions. We demonstrate that elephant seals have a sensory advantage over their prey that allows them to potentially detect prey 5 to 10 s before striking. The corresponding prey detection ranges of 7 to 17 m enable stealthy approaches and prey-specific capture tactics. In comparison, prey react at a median range of 0.7 m, close to the neck extension range of striking elephant seals. Estimated search swathes of 150 to 900 m² explain how elephant seals can locate up to 2,000 prey while swimming more than 100 km per day. This efficient search capability allows elephant seals to subsist on prey densities that are consonant with the deep scattering layer resources estimated by hydroacoustic surveys but which are two orders of magnitude lower than the prey densities needed by a reactive hunter. [ABSTRACT FROM AUTHOR]

Within the predator–prey relationship, predator behavior is less studied. Even in natural populations, it shows great diversity, and the factors influencing this are even less known. Among these factors, the personality type of the individual, (including exploration, and neophilia) and the practice significantly influence the success of adapting to a changing environment and switching to new prey types. In the present study, we investigated the first five consecutive foraging trials on live fish prey in naïve pikeperch individuals, which previously consumed or refused pelleted food. We hypothesized that individuals which were willing to consume alternative (pelleted) food would also show higher foraging success on living prey and that the practice would influence the learning process. Our results show that the timing of prey detection is influenced by exploratory behavior, the latency of the first attack by the aptitude for consuming pellets, and both traits by the individual's practice. However, neither of the factor affects the latency and success rate of capturing the prey, suggesting that predation is an independent behavioral trait. [ABSTRACT FROM AUTHOR]

Understanding the sensory ecology of species is vital if we are to predict how they will function in a changing environment. Visual cues are fundamentally important for many predators when detecting and capturing prey. However, many marine areas have become more turbid through processes influenced by climate change, potentially affecting the ability of marine predators to detect prey. We performed the first study that directly relates a pelagic seabird species's foraging behaviour to oceanic turbidity. We collected biologging data from 79 foraging trips and 5472 dives of a visually dependent, pursuit-diving seabird, the Manx shearwater (Puffinus puffinus). Foraging behaviour was modelled against environmental variables affecting underwater visibility, including water turbidity, cloud cover and solar angle. Shearwaters were more likely to initiate area-restricted search and foraging dives in clearer waters. Underwater visibility also strongly predicted dive rate and depth, suggesting that fine-scale prey capture was constrained by the detectability of prey underwater. Our novel use of dynamic descriptors of underwater visibility suggests that visual cues are vital for underwater foraging. Our data indicate that climate change could negatively impact seabird populations by making prey more difficult to detect, compounded by the widely reported effects of reduced prey populations. [ABSTRACT FROM AUTHOR]

Wood mouse Apodemus sylvaticus and striped field mouse A. agrarius are the most abundant mouse species in Central Europe coexisting in several habitats not only such as in forests but also in rural and urban areas. Their basic colours are similar, but the striped field mouse has a pronounced black stripe on its back. The biological function of this phenotypic difference is unexplored; therefore, our goal was to study the impact of fur pattern as well as the scent on the survival of these species. In our study, we used plasticine models mimicking wood mouse and striped field mouse. For imitating mouse scent, cotton pads saturated with mouse urine were placed under the models. In spring 2016, 200 plasticine mice divided into four types (non‐striped with scent, non‐striped without scent, striped with scent, striped without scent) were placed randomly in four sampling sites in the mid‐sized city, Pécs, Hungary. During 4 weeks of exposure, we recorded predation on 71 plasticine models. Birds (51%) and large mammals (25%) were the most common predators, and in 24% of the cases, the models disappeared. Considering predation only by large mammals, we found that the daily survival rate of both striped and non‐striped models with scent decreased in comparison to models without scent. Thus, large mammalian predators could discover plasticine models sooner than avian predators, which suggests a strong impact of scent. Despite the high rate of bird predation, we did not detect an effect of fur pattern suggesting that it may not be related to survival but might have other functional roles. With the dummy mouse experiment, we showed that fur pattern may play a minor role in mice detection by predators, thus further studies are needed to discover its ecological function. [ABSTRACT FROM AUTHOR]

Arachnids are the most abundant land predators. Despite the importance of their functional roles as predators and the necessity to understand their diet for conservation, the trophic ecology of many arachnid species has not been sufficiently studied. In the case of the wandering spider, Phoneutria boliviensis F. O. Pickard‐Cambridge, 1897, only field and laboratory observational studies on their diet exist. By using a DNA metabarcoding approach, we compared the prey found in the gut content of males and females from three distant Colombian populations of P. boliviensis. By DNA metabarcoding of the cytochrome c oxidase subunit I (COI), we detected and identified 234 prey items (individual captured by the spider) belonging to 96 operational taxonomic units (OTUs), as prey for this wandering predator. Our results broaden the known diet of P. boliviensis with at least 75 prey taxa not previously registered in fieldwork or laboratory experimental trials. These results suggest that P. boliviensis feeds predominantly on invertebrates (Diptera, Lepidoptera, Coleoptera, and Orthoptera) and opportunistically on small squamates. Intersex and interpopulation differences were also observed. Assuming that prey preference does not vary between populations, these differences are likely associated with a higher local prey availability. Finally, we suggest that DNA metabarcoding can be used for evaluating subtle differences in the diet of distinct populations of P. boliviensis, particularly when predation records in the field cannot be established or quantified using direct observation. [ABSTRACT FROM AUTHOR]

In the presence of I Moina i juice, the free neuromast-intact fish ingested significantly higher ( I p i < 0.05) proportion of live I Moina i (11.9 ± 9.3%) than frozen I Moina i (1.9 ± 2.7%), indicating that the mechanoreception facilitated prey detection. The I Moina i remaining in the beaker were detected using the naked eye, counted and the ingestion of I Moina i was calculated as [(number of I Moina i eaten/total number of I Moina i given) × 100]. Vision-mediated feeding behaviour of early juvenile Sultan fish, Leptobarbus hoevenii Keywords: ingestion rates; Jelawat; prey detection; sensory organs EN ingestion rates Jelawat prey detection sensory organs 1784 1787 4 03/13/21 20210401 NES 210401 The Sultan fish, or "Jelawat", I Leptobarbus hoevenii i is a cyprinid with a natural distribution in streams, rivers and lakes of some Southeast Asian countries, including Malaysia and Thailand (Mohsin & Ambak, 1983; Vidthayanon et al., 1997). [Extracted from the article]

Tardigrade behavioural studies have focused on responses to abiotic environmental conditions. Predator–prey interactions have received some attention, but not how predators and prey might detect one another. Here, we investigate whether a predatory tardigrade species is attracted to, and a potential prey tardigrade avoids, areas previously occupied by the other. In our experiments, Milnesium lagniappe was the predator and Macrobiotus acadianus the prey. Petri dishes with non-nutrient agar were used as experimental arenas. In one treatment, we allowed Macrobiotus to roam over half of the agar for 20 h, while leaving the other half free of Macrobiotus. We then removed the prey and introduced the predator. In the control treatment, no prey were added. Results indicated that Milnesium individuals were significantly concentrated in the area previously occupied by Macrobiotus , whereas no such concentration was evident when Macrobiotus had not been present. A similar protocol was used to test whether Macrobiotus avoided areas previously occupied by the predator. As expected, Macrobiotus were significantly concentrated in the area never occupied by Milnesium , unlike the control treatment. These results suggest that both species can detect the other without physical contact and react accordingly. Given that the experiments were conducted in darkness, detection is probably olfactory. [ABSTRACT FROM AUTHOR]

In the evolutionary arms race between predators and their prey, prey often evolve to be as cryptic as they can, while predators in turn hone their sensory strategies to detect prey. Examinations of the sensory strategies implemented by predators to detect their prey, as well as the ecological consequences of these interactions, are at the crux of understanding and predicting predator–prey dynamics.We review the sensory strategies used by predators that rely on private information (attending directly to cues and signals generated by their prey) and those that gather social information (attending to the signals and behaviours of others). We focus our enquiry on bats, an ideal group to shed light on these questions given their ecological diversity, varied foraging strategies and wide range of social behaviours.We discuss the costs and benefits of using private and social information for foraging. We investigate diverse strategies of information use and examine the effects different predatory strategies have on predator sensory systems.We provide an overview of the sensory ecology of information use in hunting in bats and, by identifying current gaps in knowledge, highlight fruitful directions for future research. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the senses that facilitate prey detection in the marble goby (Oxyeleotris marmorata) larvae. The ingestion ratios of live (generate chemical and mechanical stimuli) or frozen Artemia nauplii (generate chemical but no mechanical stimuli) by the intact or free neuromast (mechanoreceptor)-ablated O. marmorata larvae (11 mg/L streptomycin treatment before feeding) under the light or dark (fish vision was obstructed) condition were examined. Vision, mechano-, and chemoreceptions were all found to be essential in prey detection of the O. marmorata larvae. Prey movement has a significant influence as a visual stimuli on the O. marmorata larval feeding as the Artemia nauplii ingestion ratio was approximately 40% higher with significant (p = 0.001, d = 3.0), when the intact larvae were fed with the live (78.1 ± 1.5%), rather than the frozen (40.9 ± 2.8%) Artemia nauplii, under the light condition. This result was assured when no significant difference (p = 0.572, d = 0.2) was found between the ingestion ratios of frozen Artemia nauplii by the intact O. marmorata larvae under light and dark conditions. These findings demonstrate that prey detection in the O. marmorata larvae was facilitated by multi-modal senses, allowing O. marmorata larvae to survive in their natural habitats. • Vision is essential in prey detection of O. marmorata larvae. • Mechano- and chemoreceptions are also involved in prey detection of O. marmorata larvae. • O. marmorata larvae are attracted to prey movement. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems many biotic and abiotic factors influence predator–prey interactions directly or indirectly. In ephemeral pools the water level can change drastically, which may have a significant impact on predator–prey interactions, especially where ecological niches of predator(s) and prey comprise different layers of the water column. We tested the ability of benthic predatory Hoplobatrachus crassus tadpoles to detect their prey, tadpoles of the bottom-dweller Fejervarya syhadrensis and column-feeder Microhyla nilphamariensis, using visual and chemical cues, and the effect of a change in water level on the survival of the prey when exposed to H. crassus tadpoles. H. crassus tadpoles detected their prey using visual cues but not chemical ones (kairomones). Under the high-water-level condition, more M. nilphamariensis tadpoles survived than F. syhadrensis tadpoles. Under the low-water-level condition, predation levels did not differ for the two prey species. These results imply that H. crassus tadpoles hunt bottom-dwelling prey tadpoles using visual signals. M. nilphamariensis tadpoles escape the risk of predation from the bottom-dwelling predator mainly due to their ecological niche (the water column). These results showed that a change in water level can shift predation pressure between tadpoles residing in the different layers of a water column and determine the outcome of predator–prey interactions. [ABSTRACT FROM AUTHOR]

Next‐generation sequencing (NGS) is increasingly used for diet analyses; however, it may not always describe diet samples well. A reason for this is that diet samples contain mixtures of food DNA in different amounts as well as consumer DNA which can reduce the food DNA characterized. Because of this, detections will depend on the relative amount and identity of each type of DNA. For such samples, diagnostic PCR will most likely give more reliable results, as detection probability is only marginally dependent on other copresent DNA. We investigated the reliability of each method to test (a) whether predatory beetle regurgitates, supposed to be low in consumer DNA, allow to retrieve prey sequences using general barcoding primers that co‐amplify the consumer DNA, and (b) to assess the sequencing depth or replication needed for NGS and diagnostic PCR to give stable results. When consumer DNA is co‐amplified, NGS is better suited to discover the range of possible prey, than for comparing co‐occurrences of diet species between samples, as retested samples were repeatedly different in prey detections with this approach. This shows that samples were incompletely described, as prey detected by diagnostic PCR frequently were missed by NGS. As the sequencing depth needed to reliably describe the diet in such samples becomes very high, the cost‐efficiency and reliability of diagnostic PCR make diagnostic PCR better suited for testing large sample‐sets. Especially if the targeted prey taxa are thought to be of ecological importance, as diagnostic PCR gave more nested and consistent results in repeated testing of the same sample. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Chemical communication in aquatic species can affect many key life history traits, such as prey and predator detection and mate searching. However, changes in the environment can disrupt the effectiveness of signals and the ability of individuals to detect these signals. Many studies have examined the effect of secondary compounds from exotic plants on the ecology and physiology of a range of taxa, but whether the replacement of natural forests with exotic trees influences the behavioural responses of animals by disrupting chemical communication has rarely been investigated. We experimentally tested how eucalypt tree chemicals influenced three key aspects of chemical communication in adult male palmate newts. We tested for effects of both exposure to eucalypt water (i.e. extracts obtained by soaking leaves in mineral water) and the origin of newts (eucalypt plantations and natural oak forests). We examined whether exposure to eucalypt water altered the chemosensory ability of males to detect pools containing females or conspecific alarm cues and to find food. We found that eucalypt leachates had different effects on each behavioural trait. Fewer males detected female chemicals when exposed to the eucalypt than the oak water treatment, independent of the males' habitat of origin. Newts from oak forest were less able to detect conspecific alarm cues signalling predatory events when exposed to eucalypt water than when exposed to oak water, or than newts from eucalypt plantations for either water treatment. The ability of males to find food using chemical cues was similar in oak and eucalypt treatments. Our results suggest that chemical compounds not previously encountered during the evolutionary history of the species can influence the ability to respond to predators and locate mates. Future studies should explore the fitness costs associated with a reduced ability to respond to predators or detect mates. [ABSTRACT FROM AUTHOR]

During the breeding season, males often produce costly and extravagant displays or physical ornaments to attract females. Numerous studies have established that testosterone could directly influence the expression of certain sexual signals. However, few of these studies have focused on the indirect role that testosterone could play in modulating prey detection and visual performance to improve the foraging ability of males and hence their acquisition of nutritional resource. In the present study, we experimentally modified the testosterone levels of European tree frog males ( Hyla arborea ), staying in the natural range previously measured in the field, and we investigated the effect of testosterone on the foraging ability of individuals. Foraging capacities were measured on males placed in an arena with a virtual cricket moving on a computer screen. Our results demonstrated a significant effect of testosterone on the hunting behavior of H. arborea . We observed that testosterone reduced the orientation latency to virtual prey for supplemented males compared to controls. In addition, testosterone significantly increased the attack promptness of male frogs. Finally, our experiment did not demonstrate any impact of testosterone on male attack success. [ABSTRACT FROM AUTHOR]

In trophic studies on piscivorous birds, it is vital to know which kind of dietary sample provides the information of interest and how the prey can be identified reliably and efficiently. Often, noninvasively obtained dietary samples such as regurgitated pellets, feces, and regurgitated fish samples are the preferred source of information. Fish prey has usually been identified via morphological analysis of undigested hard parts, but molecular approaches are being increasingly used for this purpose. What remains unknown, however, is which dietary sample type is best suited for molecular diet analysis and how the molecular results compare to those obtained by morphological analysis. Pellets, feces, and regurgitated fish samples of Great Cormorants ( Phalacrocorax carbo sinensis) were examined for prey using both morphological hard part analysis and molecular prey identification. The sample types and methods were compared regarding number of species detected (overall and per sample) as well as the prey species composition and its variability among individual samples. Via molecular analysis, significantly higher numbers of prey species were detected in pellets, feces, and fish samples. Of the three sample types, pellets contained the most comprehensive trophic information and could be obtained with the lowest sampling effort. Contrastingly, dietary information obtained from feces was least informative and most variable. For all sample types, the molecular approach outperformed morphological hard part identification regarding the detectable prey spectrum and prey species composition. We recommend the use of pellets in combination with molecular prey identification to study the diet of piscivorous birds. [ABSTRACT FROM AUTHOR]

In the absence of direct sunlight, nocturnal animals face sensory challenges different to those affecting their diurnal counterparts whilst foraging. Anecdotal observations have led to the general prediction that the auditory sensory mode is the most prominent for the bat-eared fox (Otocyon megalotis), a nocturnal, insectivorous canid. The present study aimed to clarify the relative importance of different sensory modes to foraging bat-eared foxes by conducting sensory trials with individuals belonging to a habituated population in the Kuruman River Reserve in South Africa. Foxes were tested in repeated trials controlling for particular sensory stimuli using live or pre-killed prey. Auditory cues proved significant (p ≤0.01) predictors of fox foraging success with olfactory and visual cues indicated as being of secondary importance. This study thus provides empirical confirmation for anecdotal reports that the bat-eared fox is predominantly reliant on auditory cues to determine hunting success. [ABSTRACT FROM AUTHOR]

Pulse fishing may pose a promising alternative for diminishing the ecosystem effects of beam trawling. However, concerns about the impact on both target and non-target species still remain, amongst others the possible damage to the electro-receptor organs, the Ampullae of Lorenzini, of elasmobranchs. The current study aimed to examine the role of pulsed direct current (PDC) used in pulse trawls on the electro-detection ability of the small-spotted catshark, Scyliorhinus canicula . The electroresponse of the sharks to an artificially created prey-simulating electrical field was tested before and after exposure to the pulsed electrical field used to catch flatfish and shrimp. No statistically significant differences were noted between control and exposed animals, both in terms of the number of sharks exhibiting an electroresponse prior to and following exposure as well as regarding the timing between onset of searching behaviour and biting at the prey simulating dipole. These results indicate that, under the laboratory circumstances as adopted in this study, the small-spotted catshark are still able to detect the bioelectrical field of a prey following exposure to PDC used in pulse trawls. However, to fully grasp the impact of PDC on elasmobranchs, further studies are imperative, including examining the effect on reproduction and young life stages, the longer-term and indirect influences and experiments under field conditions. [ABSTRACT FROM AUTHOR]

World experiences involve multisensory stimulation that arises simultaneously from multiple sources. Yet, we experience a coherent and unified world. Many studies have focused on how sensory information from distinct modalities are integrated and showed that numerous behavioural and cognitive benefits are provided by multisensory processes. Much work has been done with mammalian models but research on avian species also expands our knowledge on multisensory processes. Avian species exhibit a great diversity of behaviours and these species have provided evidence that multisensory processes benefit by the learning that occurs in natural situations. Cross-modal influences on the control of sensorimotor processes occur in circumstances of sensory loss. Also, studies suggest pervasive multisensory influences throughout the avian brain. This review summarizes research done on the imprinting behaviour of precocial bird species, on the ability of barn owls to detect prey and on the vocal communication of songbirds. • Avian groups exhibit a large range of natural behaviours that rely on multisensory processing. • Multisensory exposure fosters different kinds of learning. • Social interactions through multisensory information benefit to learning processes. • Line of evidence for a role of information from different modalities in circumstances of sensory loss. • Multisensory interactions in the avian brain challenge the view that each modality processes information independently. [ABSTRACT FROM AUTHOR]

Predators have evolved many different ways to detect hidden prey by using advanced sensory organs. However, in some environmental contexts sensory information may be obscured. The relation between sensory organs, obstruction and searching efficiency remains little explored. In this study we experimentally examined the ways in which a sensory system (‘remote detection’), which enables red knots, Calidris canutus , to detect hard objects buried in wet soft sediments, is obstructed by plants. At an important coastal nonbreeding site of this species, the Banc d'Arguin (Mauritania, West Africa), most of the intertidal foraging area is covered by sea grass. The structurally complex networks of belowground roots and rhizomes and aboveground sea grass may obstruct information on the presence of buried bivalves and thus affect searching efficiency. Under aviary conditions we offered red knots buried bivalves in either bare soft sediments or in sea grass patches and measured prey encounter rates. Red knots detected prey by direct touch in sea grass but remotely in bare sediment. Physical modelling of the pressure field build-up around a probing bill showed that within a layer of sea grass rhizomes, permeability is reduced to the extent that the pressure field no longer reveals the presence of an object. In bare sediment, where searching efficiency is constant, red knot intake rate levelled off with increasing prey density (described by a so-called type II functional response). In the sea grass beds, however, prey density increases with sea grass density and simultaneously decreases searching efficiency, which will at some point lead to a decrease in intake rate when prey densities increase (i.e. a type IV functional response). Clearly, prey detection mechanisms dictate that the combined effects of prey density and habitat complexity should be taken into account when predicting forager distributions and habitat preference. [ABSTRACT FROM AUTHOR]

The mechanosensory lateral line system of fishes detects water motions within a few body lengths of the source. Several types of artificial stimuli have been used to probe lateral line function in the laboratory, but few studies have investigated the role of flow sensing in benthic feeding teleosts. In this study, we used artificial flows emerging from a sandy substrate to assess the contribution of flow sensing to prey detection in the peacock cichlid, Aulonocara stuartgranti, which feeds on benthic invertebrates in Lake Malawi. Using a positive reinforcement protocol, we trained fish to respond to flows lacking the visual and chemical cues generated by tethered prey in prior studies with A. stuartgranti. Fish successfully responded to artificial flows at all five rates presented (characterized using digital particle image velocimetry), and showed a range of flow-sensing behaviors, including an unconditioned bite response. Immediately after lateral line inactivation, fish rarely responded to flows and the loss of vital fluorescent staining of hair cells (with 4-di-2-ASP) verified lateral line inactivation. With in 2 days post-treatment, some aspects of flow-sensing behavior returned and after 7 days, flow-sensing behavior and hair cell fluorescence both returned to pre-treatment levels, which is consistent with the reported timing of hair cell regeneration in other vertebrates. The presentation of ecologically relevant water flows to assess flow-sensing behaviors and the use of a positive reinforcement protocol are methods that present new opportunities to study the role of flow sensing in the feeding ecology of benthic feeding fishes. [ABSTRACT FROM AUTHOR]

Bats broadcast rapid sequences of echolocation calls, named 'drinking buzzes', when they approach water to drink on the wing. So far this phenomenon has received little attention. We recorded echolocation sequences of drinking bats for 12 species, for 11 of which we also recorded feeding buzzes. Based on the different sensorial tasks faced by feeding and drinking bats, we hypothesize that the drinking buzz structure will differ from that of feeding buzzes since unlike the latter drinking buzzes are not designed to detect and track mobile prey. We demonstrated that drinking buzzes are structurally different from feeding buzzes. We show that the buzz- II phase common in feeding buzzes is absent in drinking buzzes; that is, call frequency is not lowered to broaden sonar beam since the task of drinking does not imply tracking fast-moving targets. This finding indirectly confirms the role of buzz II in feeding buzzes. Pulse rate in drinking buzzes is also lower than in feeding buzzes, as predicted since the high pulse rate typical of feeding buzzes is important to update rapidly the relative location of moving targets. The most likely function of drinking buzzes is to guide a safe drinking manoeuvre, similar to 'landing buzzes' broadcast when bats land on the ground. [ABSTRACT FROM AUTHOR]

Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species due to the relatively stable conditions in deep waters for most parameters (e.g. temperature, salinity, oxygen, and pH). To explore the potential for deep-sea hermit crabs (Pagurus tanneri) to acclimate to future ocean acidification, we compared their olfactory and metabolic performance under ambient (pH ~7.6) and expected future (pH ~7.1) conditions. After exposure to reduced pH waters, metabolic rates of hermit crabs increased transiently and olfactory behaviour was impaired, including antennular flicking and prey detection. Crabs exposed to low pH treatments exhibited higher individual variation for both the speed of antennular flicking and speed of prey detection, than observed in the control pH treatment, suggesting that phenotypic diversity could promote adaptation to future ocean acidification. [ABSTRACT FROM AUTHOR]

The 'evolutionary arms race' between predator and prey is responsible for many physiological, morphological, and behavioural adaptations and some of the most compelling examples relate to the generation and detection of visual signals. Better understanding of adaptations can arise from approaching predator-prey dynamics from the point of view of the animals themselves, such as through animal-borne cameras. As we learn more about an animal's visual system, we can take this further and analyse visual scenes through their eyes. In this study video cameras mounted on tiger sharks were used to analyse motion cues of sea turtles using two-dimensional motion detector (2DMD) models. Sharks were also equipped with tri-axial motion-sensors to compare visual motion cues to behaviour, using the behavioural metrics of overall dynamic body acceleration (ODBA), path tortuosity, tailbeat frequency and tailbeat acceleration signal amplitude. When comparing the behaviours of sharks in the minute before and after interactions with sea turtles, we found lower ODBA of sharks associated with sea turtles that produced greater visual motion cues. These turtles also invoked swimming by sharks that was more tortuous than when no turtle was encountered. Together, these behaviours suggest that tiger sharks may potentially stalking turtles that produced greater motion cues. Many sea turtles did not stand out from the background motion suggesting they remain motionless as a form of camouflage. This study provides insights into the use of visual cues in prey identification by tiger sharks and the camouflage strategies used by sea turtles to avoid predation. • Tiger shark swimming behaviour is altered after interacting with visible sea turtles. • Reduced movement helps to camouflage sea turtles from approaching tiger sharks. • Combining visual perception and animal-borne cameras helps to understand behaviour. [ABSTRACT FROM AUTHOR]

Measuring the strength of trophic interactions in marine systems has been central to our understanding of community structuring. Sea urchin tethering has been the method of choice to evaluate rates of predation in marine benthic ecosystems. As standardly practiced, this method involves piercing the urchin test, potentially introducing significant methodological artifacts that may influence survival or detection by predators. Here we assess possible artifacts of tethering comparing invasive (pierced) and non-invasive tethering techniques using the sea urchin Paracentrotus lividus . Specifically, we looked at how degree of confinement and high water temperature (first order artifacts) and predator guild and size of the prey (second order artifacts) affect the survival and/or detectability of pierced urchins. Our results show that first order artifacts only arise when pierced sea urchins are placed in sheltered bays with confined waters, especially when water temperature reaches extremely high levels. Prey detectability did not increase in pierced sea urchins for the most common predators. Also, test piercing did not alter the preferences of predators for given prey sizes. We conclude that the standard tethering technique is a robust method to test relative rates of sea urchin predation. However, local conditions could increase mortality of the tethered urchin in sheltered bays or in very high temperature regimes. Under these conditions, adequate pierced controls (within predator exclusions) need to be included in assays to evaluate artifactual sources of mortality. [ABSTRACT FROM AUTHOR]

In a predator-prey interaction, the fitnesses of the predator and the prey depend on their abilities to recognize each other, a process that may involve different sensory modalities. Squamate reptiles are highly dependent on chemical senses for such recognition, and here we explored the ability of a generalist saurophagous snake, Philodryas chamissonis, to discriminate scents of two congeneric and sympatric lizard prey species, Liolaemus nitidus and L. chiliensis. A generalist saurophagous snake might just be sensitive to lizard scents in general, and if so, no discrimination between prey species is expected. However, these lizards use different substrates; L. nitidus basks on rocks, whereas L. chiliensis mainly basks on bushes and rarely on ground. The snake P. chamissonis basks on ground and rocks, and rarely on bushes. Therefore, if the rate of encounter affects the ability to recognize prey, we predict that P. chamissonis would show prey discrimination because scents of L. chiliensis may be encountered less frequently in its habitat. Results showed that the snake had a refined discrimination of lizard prey, reducing tongue flick rate and movements in response to scents from the common prey scents, L. nitidus. We also studied the ability of L. chiliensis to detect the snake and found that snake scents triggered a reduction in activity. The potential infrequent encounter between predator and prey may explain the asymmetric predator-prey recognition, as can be predicted from the 'life-dinner' principle. [ABSTRACT FROM AUTHOR]

There is no conclusive evidence of any nonhuman animal using the sun as part of its predation strategy. Here, we show that the world's largest predatory fish-the white shark (Carcharodon carcharias)-exploits the sun when approaching baits by positioning the sun directly behind them. On sunny days, sharks reversed their direction of approach along an east-west axis from morning to afternoon but had uniformly distributed approach directions during overcast conditions. These results show that white sharks have sufficient behavioral flexibility to exploit fluctuating environmental features when predating. This sun-tracking predation strategy has a number of potential functional roles, including improvement of prey detection, avoidance of retinal overstimulation, and predator concealment. [ABSTRACT FROM AUTHOR]

Two sand-dwelling cichlids from Lake Malawi ( Aulonocara stuartgranti, Tramitichromis sp.) that feed on benthic invertebrates, but have different lateral line phenotypes, use lateral line and/or visual cues to detect prey under light versus dark conditions. The current study examined how ecologically relevant variation in light intensity [0-800 lux (lx)] influences detection of prey (mobile, immobile) in each species by analyzing six behavioral parameters. Both species fed at light intensities ≥1 lx and trends in behavior among light intensities were informative. However, prey type and/or time of day (but not light intensity) predicted all four parameters analyzed with generalized linear mixed models in A. stuartgranti, whereas the interaction of light intensity and time of day predicted three of these parameters in Tramitichromis sp. Data suggest that the critical light intensity is 1-12 lx for both species, that the integration of visual and lateral line input explains differences in detection of mobile and immobile prey and behavioral changes at the transition from 1 to 0 lx in A. stuartgranti, and that Tramitichromis sp. likely uses binocular vision to locate prey. Differences in the sensory biology of species that exploit similar prey will have important implications for the trophic ecology of African cichlid fishes. [ABSTRACT FROM AUTHOR]

Mechanistic insights and predictive understanding of the spatial distributions of foragers are typically derived by fitting either field measurements on intake rates and food abundance, or observations from controlled experiments, to functional response models. It has remained unclear, however, whether and why one approach should be favoured above the other, as direct comparative studies are rare., The field measurements required to parameterize either single or multi-species functional response models are relatively easy to obtain, except at sites with low food densities and at places with high food densities, as the former will be avoided and the second will be rare. Also, in foragers facing a digestive bottleneck, intake rates (calculated over total time) will be constant over a wide range of food densities. In addition, interference effects may depress intake rates further. All of this hinders the appropriate estimation of parameters such as the 'instantaneous area of discovery' and the handling time, using a type II functional response model also known as 'Holling's disc equation'., Here we compare field- and controlled experimental measurements of intake rate as a function of food abundance in female bar-tailed godwits Limosa lapponica feeding on lugworms Arenicola marina., We show that a fit of the type II functional response model to field measurements predicts lower intake rates (about 2·5 times), longer handling times (about 4 times) and lower 'instantaneous areas of discovery' (about 30-70 times), compared with measurements from controlled experimental conditions., In agreement with the assumptions of Holling's disc equation, under controlled experimental settings both the instantaneous area of discovery and the handling time remained constant with an increase in food density. The field data, however, would lead us to conclude that although handling time remains constant, the instantaneous area of discovery decreased with increasing prey densities. This will result into highly underestimated sensory capacities when using field data., Our results demonstrate that the elucidation of the fundamental mechanisms behind prey detection and prey processing capacities of a species necessitates measurements of functional response functions under the whole range of prey densities on solitary feeding individuals, which is only possible under controlled conditions. Field measurements yield 'consistency tests' of the distributional patterns in a specific ecological context. [ABSTRACT FROM AUTHOR]

Seabirds foraging on pelagic fish develop behavioral strategies specifically adapted to locate inconspicuous prey that are aggregated in spatially dynamic patches. In the marine environment, they may use various mechanisms to detect cues of prey availability. The aggregation of predators at a patch of food is a particularly obvious cue to locate prey, a mechanism known as local enhancement. Pioneering studies described the formation of foraging groups at sea, showing that seabirds are attracted to feeding conspecifics. Improved foraging success due to local enhancement has been suggested from modeling studies, but no direct validation of these results exists. We deployed video cameras concomitantly with GPS loggers on Cape gannets to study the behavioral responses of equipped birds to the aggregation of predators at food patches. We showed that the reaction distances of equipped birds increased with the size of an aggregation, demonstrating that predator aggregations enhance food detectability for foragers. For small aggregations (<50 gannets), reaction distances were mostly less than 10 km, and they increased up to almost 40 km for larger aggregations (100–150 gannets). In addition, we showed that the number and frequency of dives increased with the number of conspecifics aggregated, up to a threshold. The predator aggregations on a patch of food could, therefore, not only inform about the presence of prey but also entail information about foraging conditions. From direct observations on the various components involved, our study provides justification of the use and advantages of local enhancement in foraging seabirds.To locate inconspicuous and ephemeral fish schools in the ocean, seabirds may use indirect cues such as feeding conspecifics. Based on video cameras and GPS loggers concomitantly attached to Cape gannets, we showed that predator aggregations on a patch of food enhanced prey detectability. Gannets reacted to join a group of 50 feeding conspecifics from ~10 km, whereas a group of 100–150 gannets triggered a reaction from up to 40 km. [ABSTRACT FROM PUBLISHER]

Cone snails, predatory marine gastropods, have developed a specialized prey capture method in which a long, distensible proboscis is used to identify prey and inject venom via a hydraulically propelled hollow radular tooth. Using brightfield, epifluorescence, confocal, and transmission and scanning electron microscopy, we describe the morphology of ciliated sensory structures concentrated on the tip of the proboscis. The number and morphology of these sensory papillae are linked to the type of preferred prey: cone snails feeding on worms and mollusks have short, cone or finger-shaped papillae, whereas fish-hunting cone snails have long tubular papillae in addition to short conical papillae. Sensory papillae are well positioned to provide information necessary to locate, identify, and dispatch prey. Proboscis tips and their sensory papillae regenerated within 10 d following experimental ablation, and snails with regenerated proboscis tips were able to locate and envenomate prey. The remarkable intrageneric variation found in the morphology of these sensory structures is probably linked to the specialized prey that cone snail species have evolved to hunt. [ABSTRACT FROM AUTHOR]

Abstract: The adaptive radiations of African cichlids resulted in a diversity of feeding morphologies and strategies, but the role of sensory biology in prey detection and feeding ecology remains largely unexplored. Two endemic Lake Malawi cichlid genera, Tramitichromis and Aulonocara, feed on benthic invertebrates, but differ in lateral line morphology (narrow and widened lateral line canals, respectively) and foraging strategy. The hypothesis that they use their lateral line systems differently was tested by looking at the relative contribution of the lateral line system and vision in prey detection by Tramitichromis sp. and comparing results to those from a complementary study using Aulonocara stuartgranti (Schwalbe et al., 2012). First, behavioral trials were used to assess the ability of Tramitichromis sp. to detect live (mobile) and dead (immobile) benthic prey under light and dark conditions. Second, trials were run before, immediately after, and several weeks after chemical ablation of the lateral line system to determine its role in feeding behavior. Results show that Tramitichromis sp. is a visual predator that neither locates prey in the dark nor depends on lateral line input for prey detection and is thus distinct from A. stuartgranti, which uses its lateral line or a combination of vision and lateral line to detect prey depending on light condition. Investigating how functionally distinctive differences in sensory morphology are correlated with feeding behavior in the laboratory and determining the role of sensory systems in feeding ecology will provide insights into how sensory capabilities may contribute to trophic niche segregation. [Copyright &y& Elsevier]

In nature, animals must contend with the presence of noise, which may limit their ability to detect prey, attract mates and escape predators. Sources of noise vary and may originate from natural (e.g. animal sounds, water) or anthropogenic (e.g. traffic, construction) sources. The vibratory sensory modality has long been overlooked in the study of anthropogenic effects on wildlife. Human-induced environmental changes may introduce noise sources as well as artificial substrates that alter vibratory noise profiles, leading to maladaptive behavioural responses. We conducted field measurements of vibratory noise on various substrate types (natural and artificial) used by animals in human-developed habitats. Next, we conducted laboratory experiments on how vibratory noise affects the prey detection ability of the European garden spider, Araneus diadematus. We tested whether changes in vibratory noise profiles consistent with anthropogenic alterations of vibratory habitats are sufficient to alter the spider's sensitivity to prey cues. We found that overall noise amplitude on artificial substrates was lower and less variable across contexts compared with natural substrates. In experiments with different noise levels, we observed that garden spiders showed noise-dependent changes in sensitivity to prey-mimicking cues, with response thresholds lowest at intermediate noise levels. Experimental levels of intermediate noise consistent with field measurements on natural substrates suggest that spiders' predatory performance is higher when webs are constructed on natural substrates. This suggests that human-introduced substrates may interfere with spiders' predatory performance. As human activities and habitat alteration are widespread, our findings highlight the need to consider the vibratory sensory channel in assessing anthropogenic impacts on wildlife. [Copyright &y& Elsevier]

The relative importance of visual and chemical cues of prey in their detection by the juveniles ofCalotes versicolorwas studied using laboratory-born, 2-month-old individuals starved for 48 hrs. Grasshoppers served as the prey in all experiments. In trials with deionized water and cologne water (pungency control), the lizards showed no tongue flicking. Presentation of prey-body chemical cues on cotton swabs also did not evoke tongue flicking in test lizards indicating a lack of response to different odors through the vomeronasal olfactory system. The same test lizards lunged at the transparent glass beaker housing an active prey, with their mouth open as if to catch it. They showed no tongue flicking. In contrast, when an immobile prey was presented similarly the test lizards ignored it. Apparently, chemical cues are of little value in prey detection inC. versicolor. The study shows thatC. versicolorjuveniles use visual cues and prey movements in detection and capture of prey. [ABSTRACT FROM PUBLISHER]

Polarization sensitivity is a characteristic of the visual system of cephalopods. It has been well documented in adult cuttlefish, which use polarization sensitivity in a large range of tasks such as communication, orientation and prédation. Because cuttlefish do not benefit from parental care, their visual system (including the ability to detect motion) must be efficient from hatching to enable them to detect prey or predators. We studied the maturation and functionality of polarization sensitivity in newly hatched cuttlefish. In a first experiment, we examined the response of juvenile cuttlefish from hatching to the age of 1 month towards a moving, vertically oriented grating (contrasting and polarized stripes) using an optomotor response apparatus. Cuttlefish showed differences in maturation of polarization versus luminance contrast motion detection. In a second experiment, we examined the involvement of polarization information in prey preference and detection in cuttlefish of the same age. Cuttlefish preferentially chose not to attack transparent prey whose polarization contrast had been removed with a depolarizing filter. Performances of prey detection based on luminance contrast improved with age. Polarization contrast can help cuttlefish detect transparent prey. Our results suggest that polarization is not a simple modulation of luminance information, but rather that it is processed as a distinct channel of visual information. Both luminance and polarization sensitivity are functional, though not fully matured, in newly hatched cuttlefish and seem to help in prey detection. [ABSTRACT FROM AUTHOR]

Jumping spiders are known to rely on visual information when making predatory decisions, but the relative roles of global and local motion, shape and interior spatial detail in eliciting attack remain poorly resolved. We manipulated videos of crickets and presented jumping spiders, Phidippus audax, with choice tests. Consistent with previous studies, spiders more often approached videos depicting moving prey versus motionless prey. Spiders attended to local motion characteristics, preferring videos of natural cricket motion over videos of a snapshot of a cricket that moved across the screen with the same start-and-stop global motion pattern as the natural cricket. However, spiders showed no evidence of preference between moving images that differed in shape and interior spatial detail: a cricket snapshot and a rectangle of the same size and colour. These results indicate that spiders either cannot detect differences between the stimuli, or can detect differences but show no preference. To distinguish between these possibilities, we used an aversive conditioning protocol. Conditioning was effective, as we could train spiders to choose a moving snapshot over a natural cricket. However, we were unable to induce discrimination between cricket snapshots and rectangles, suggesting that spiders were unable to distinguish these images even when motivated to do so. There was no significant difference in the spiders'' propensity to choose cricket videos with natural stop-and-start motion versus those without pauses, so we found no evidence that the commonly observed pausing behaviour of walking prey influences the propensity of spiders to attack. Taken together, our results support the hypothesis that movement is more important than image shape for predatory decisions of this jumping spider. [Copyright &y& Elsevier]

DNA-based gut content analysis has become an important tool for unravelling feeding interactions in invertebrate communities under natural conditions. It usually implies killing of the consumer and extracting the DNA from its food, using either the whole animal or its dissected gut. This post-mortem approach, however, is not suitable for investigating the diet of rare or protected species and also prohibits tracking individual dietary preferences as each consumer can provide trophic information only once. Moreover, removing large numbers of consumers from a habitat for analysis might critically change population densities and affect species interactions. Here, we present DNA-based analysis of invertebrate regurgitates, a novel approach to overcome these limitations. Conducting feeding experiments where adult Poecilus cupreus (Coleoptera: Carabidae) were fed with larvae of Amphimallon solstitiale (Coleoptera: Scarabaeidae), we show that detection success in regurgitates compared to samples prepared from whole beetles was similar or significantly enhanced for small/medium and large prey DNA fragments, respectively. Prey DNA detection success remained high in regurgitates stored in ethanol for 21 months at room temperature prior to DNA extraction. We conclude that in those invertebrates where regurgitates can be obtained, examination of food DNA in regurgitates offers many advantages over conventional post-mortem gut content analysis. [ABSTRACT FROM AUTHOR]

The cranial lateral line canal system of teleost fishes is morphologically diverse and is characterized by four patterns. One of these, widened lateral line canals, has evolved convergently in a wide range of teleosts, including the Lake Malawi peacock cichlids (Aulonocara), and has been attributed to its role in prey detection. The ability to study Aulonocara in the laboratory provides an opportunity to test the hypothesis that their reported ability to feed on invertebrate prey living in sandy substrates in their natural habitat is the result of lateral-line-mediated prey detection. The goal of this study was to determine whether Aulonocara stuartgranti could detect hydrodynamic stimuli generated by tethered brine shrimp (visualized using digital particle image velocimetry) under light and dark conditions, with and without treatment with cobalt chloride, which is known to temporarily inactivate the lateral line system. Fish were presented with six pairs of tethered live and dead adult brine shrimp and feeding behavior was recorded with HD digital video. Results demonstrate that A. stuartgranti: (1) uses the same swimming/feeding strategy as they do in the field; (2) detects and consumes invertebrate prey in the dark using its lateral line system; (3) alters prey detection behavior when feeding on the same prey under light and dark conditions, suggesting the involvement of multiple sensory modalities; and (4) after treatment with cobalt chloride, exhibits a reduction in their ability to detect hydrodynamic stimuli produced by prey, especially in the dark, thus demonstrating the role of the lateral line system in prey detection. [ABSTRACT FROM AUTHOR]

The analysis of prey DNA in faeces is a non-invasive approach to examine the diet of birds. However, it is poorly known how gut transition time, environmental factors and laboratory treatments such as storage conditions or DNA extraction procedures affect the detection success of prey DNA. Here, we examined several of these factors using faeces from carrion crows fed with insect larvae. Faeces produced between 30 min and 4 h post-feeding tested positive for insect DNA, representing the gut transition time. Prey detection was not only possible in fresh but also in 5-day-old faeces. The type of surface the faeces were placed on for these 5 days, however, affected prey DNA detection success: samples placed on soil provided the lowest rate of positives compared to faeces left on leaves, on branches and within plastic tubes. Exposing faeces to sunlight and rain significantly lowered prey DNA detection rates (17% and 68% positives in exposed and protected samples, respectively). Storing faeces in ethanol or in the freezer did not affect molecular prey detection. Extracting DNA directly from larger pieces of faecal pellets resulted in significantly higher prey detection rates than when using small amounts of homogenized faeces. A cetyltrimethyl ammonium bromide-based DNA extraction protocol yielded significantly higher DNA detection rates (60%) than three commercial kits, however, for small amounts of homogenized faeces only. Our results suggest that collecting faeces from smooth, clean and non-absorbing surfaces, protected from sunlight and rain, improves DNA detection success in avian faeces. [ABSTRACT FROM AUTHOR]

There are two very different approaches to laryngeal echolocation in bats. Although most bats separate pulse and echo in time by signalling at low duty cycles (LDCs), almost 20% of species produce calls at high duty cycles (HDCs) and separate pulse and echo in frequency. HDC echolocators are sensitive to Doppler shifts. HDC echolocation is well suited to detecting fluttering targets such as flying insects against a cluttered background. We used two complementary experiments to evaluate the relative effectiveness of LDC and HDC echolocation for detecting fluttering prey. We measured echoes from fluttering targets by broadcasting artificial bat calls, and found that echo amplitude was greatest for sounds similar to those used in HDC echolocation. We also collected field recordings of syntopic LDC and HDC bats approaching an insect-like fluttering target and found that HDC bats approached the target more often (18.6% of passes) than LDC bats (1.2% of passes). Our results suggest that some echolocation call characteristics, particularly duty cycle and pulse duration, translate into improved ability to detect fluttering targets in clutter, and that HDC echolocation confers a superior ability to detect fluttering prey in the forest understory compared with LDC echolocation. The prevalence of moths in the diets of HDC bats, which is often used, as support for the allotonic frequency hypothesis, can therefore be partly explained by the better flutter detection ability of HOC bats. [ABSTRACT FROM AUTHOR]

Elasmobranch fishes (sharks, skates and rays) possess highly sensitive electrosensory systems, which enable them to detect weak electric fields such as those produced by potential prey organisms. Different species have unique electrosensory pore numbers, densities and distributions. Functional differences in detection capabilities resulting from these structural differences are largely unknown. Stingrays and other batoid fishes have eyes positioned on the opposite side of the body from the mouth. Furthermore, they often feed on buried prey, which can be located non-visually using the electrosensory system. In the present study we test functional predictions based on structural differences in three stingray species (Urobatis halleri, Pteropiatytrygon violacea and Myliobatis californica) with differing electrosensory system morphology. We compare detection capabilities based upon behavioral responses to dipole electric signals (5.3-9.6μA). Species with greater ventral pore numbers and densities were predicted to demonstrate enhanced electrosensory capabilities. Electric field intensities at orientation were similar among these species, although they differed in response type and orientation pathway. Minimum voltage gradients eliciting feeding responses were well below 1 nV cm-1 for all species regardless of pore number and density. [ABSTRACT FROM AUTHOR]

Short range hydrodynamic and electrosensory signals are important during final stages of prey capture in elasmobranchs (sharks, skates and rays), and may be particularly useful for dorso-ventrally flattened batoids with mouths hidden from their eyes. In stingrays, both the lateral line canal and electrosensory systems are highly modified and complex with significant differences on ventral surfaces that relate to feeding ecology. This study tests functional hypotheses based on quantified differences in sensory system morphology of three stingray species, Urobatis hailer!, Myliobatis californica and Pteroplatytrygon violacea. Part I investigates the mechanosensory lateral line canal system whereas part II focuses on the electrosensory system. Stingray lateral line canals include both pored and non-pored sections and differ in branching complexity and distribution. A greater proportion of pored canals and high pore numbers were predicted to correspond to increased response to water flow. Behavioral experiments were performed to compare responses of stingrays to weak water jets mimicking signals produced by potential prey at velocities of 10-20cm s-1. Bat rays, M. californica, have the most complex and broadly distributed pored canal network and demonstrated both the highest response rate and greater response intensity to water jet signals. Results suggest that U. hailer! and P. violacea may rely on additional sensory input, including tactile and visual cues, respectively, to initiate stronger feeding responses. These results suggest that stingray lateral line canal morphology can indicate detection capabilities through responsiveness to weak water jets. [ABSTRACT FROM AUTHOR]

Birds that forage by probing in sand, soil or mud substrates must often use senses other than vision to find their prey. Kiwis (Apterygidae) are nocturnal probing birds inhabiting forested areas in New Zealand. Their visual sense is reduced, but they have a highly developed sense of smell, a bill tip organ similar to that found in Scolopacidae shorebirds, which may be used to detect vibrotactile cues produced by burrowing prey (remote touch), and prominent ear openings. We designed a foraging experiment presenting mealworm prey to eight captive North Island brown kiwis, Apteryx mantelli, under a variety of trial conditions to discover whether they were using hearing, olfaction, remote touch or direct touch (chance alone), singly or together, to find prey. Kiwis were most efficient at finding prey using olfaction alone or in combination with other cues, but switched to locating prey with lower efficiency using remote touch, in the absence of olfactory cues. They did not appear to use auditory cues for foraging. The ability to switch between sensory modalities depending on the quality of the cues available has been documented before in other groups of birds (including thrushes (Turdidae) and sandpipers (Scolopacidae)) and would be of great advantage to wild kiwis foraging under a wide range of environmental conditions. [Copyright &y& Elsevier]

Abstract: It has been suggested that birds prefer to use a particular eye while learning to detect cryptic prey and that this eye preference enhances foraging performance. European starlings (Sturnus vulgaris) with the left, right, or both eyes available learned to detect inconspicuous cues associated with the presence of hidden prey. Acquisition scores were not significantly different between left and right-eyed birds; however, performance in the binocular condition was significantly higher than in the two monocular conditions. When binocular birds were tested with familiar and unfamiliar cues present simultaneously, the familiar cue was selected significantly more often than the unfamiliar cue, suggesting that the birds were searching for specific cue features. When monocular birds were tested using only the naïve eye, performance dropped significantly. In right-eyed birds using the naïve left eye, performance remained at chance levels over transfer trials. However, left-eyed birds using the naïve right eye had a superior performance compared to the initial acquisition scores of right-eyed birds and also showed a significant improvement in performance over transfer trials. Thus, although there was no direct evidence of lateralization during acquisition, there was unilateral transfer of the prey detection skill from the right to the left hemisphere. [Copyright &y& Elsevier]

A large range of aquatic vertebrates employs passive electroreception to detect the weak bioelectric fields that surround their prey. Bioelectric fields are dynamic in strength and frequency composition, but typically consist of a direct current (DC) and an alternating current (AC) component. We examined the biological relevance of these components for prey detection behaviour in the brown bullhead by means of a preference test. We gave each fish the choice between two small dipoles emitting a DC step or AC stimulus of variable strength, respectively. We used AC stimuli that were either representative for ventilatory movements by prey (1 Hz sine wave) or optimal for the ampullary electroreceptor cells (10 Hz sine wave). In an attempt to present a more complex stimulus, we also used slightly modified recordings of bioelectric prey fields, but this yielded no results. Brown bullheads prefer DC stimuli to 10 Hz sine waves if the stimulus intensity of either component is much larger. When the stimulus presentation consists of DC versus 1 Hz, most fish will choose randomly unless the stimulus intensities differ greatly. Then, they favour the component that had a higher amplitude during training. Our results suggest an intrinsic behavioural preference for very low frequency signals (<10 Hz) as well as plasticity in prey detection behaviour. [ABSTRACT FROM AUTHOR]

When insects walk, they generally produce sounds. These can reveal the walkers' presence and location to potential predators such as owls, bats and nocturnal primates. Additionally, predators might extract information on taxon, palatability, size or profitability from the rustling sounds. In contrast to ear morphology, hearing physiology and psychoacoustics of acoustically oriented predators, little attention has hitherto been paid to the acoustic structure and information content of prey sounds. An important element in the ecology of acoustic prey detection remained virtually unexplored: the influence of the substrate type on rustling sounds. In this study, we analysed amplitude and frequency parameters from insects walking on various natural substrates, in both Germany (Carabus beetles) and Madagascar (various beetles and cockroaches). The data show that rustling sound amplitude and frequency content depend on substrate type. On moist substrates arthropods produced less intense and less broadband rustling sounds than on dry substrates. Sound pressure level was reduced by about 6dB, halving the detection range for the predator. For a given insect, rustling sound amplitude increased with walking speed. Finally, we found that the previously established correlation of arthropod size and rustling amplitude holds across multiple substrates. Based on these data, we provide for the first time estimates of realistic detection distances in the field. These distances range from below 1 m to over 13m, depending on the substrate, insect mass, walking speed and background noise level. These estimates are crucial for an understanding of the foraging ecology, foraging efficiency and sensory ecology of acoustic predators. [ABSTRACT FROM AUTHOR]

1. There is considerable debate over the impact of seal predation on salmonid populations in both the Atlantic and Pacific oceans. Conventional hard-part analysis of scats has suggested that salmonids represent a minor component of the diet of grey seals ( Halichoerus grypus) and harbour seals ( Phoca vitulina) in the UK. However, it is unclear whether this is an accurate reflection of the diet or due to methodological problems. To investigate this issue, we applied quantitative PCR (qPCR) to examine the presence of salmonids in the diet of seals in the Moray Firth, UK, during the summers of 2003 and 2005. 2. Two qPCR assays were designed to detect Atlantic salmon Salmo salar and sea trout Salmo trutta DNA in field samples and experimentally spiked scats. The proportion of scats sampled in the field that were positive for salmonid DNA was low (ª10%). However, the DNA technique consistently resulted in more positive scats than when hard-part analysis was used. 3. An experimental study using spiked scat material revealed a highly significant negative relationship between Ct values obtained from the Atlantic salmon qPCR assay and the proportion of Atlantic salmon material added to scats. The Ct value denotes the cycle number at which the increasing fluorescence signal of target DNA crosses a threshold value. Ct values from field-collected seal scats suggested they contained a very low concentration of salmonid remains (1–5%) based on an approximate calibration curve constructed from the experimental data. 4. Synthesis and applications. The qPCR assay approach was shown to be highly efficient and consistent in detection of salmonids from seal scats, and to be more sensitive than conventional hard-parts analysis. Nevertheless, our results confirm previous studies indicating that salmonids are not common prey for seals in these Scottish estuaries. These studies support current management practice, which focuses on control of the small number of seals that move into key salmonid rivers, rather than targeting the larger groups of animals that haul-out in nearby estuaries. [ABSTRACT FROM AUTHOR]

The sensory bases of food detection, food location and food choice in nocturnal primates are poorly understood. Grey mouse lemurs, Microcebus murinus, are omnivorous nocturnal strepsirhines and generally regarded a good model for the most ancestral primate condition. We set up a series of choice experiments in a controlled laboratory environment to investigate the roles of acoustic, olfactory and visual cues and the importance of unimodal versus multimodal cues for prey perception in this species. Subjects in our study were able to find hidden prey better than expected by chance using any of the three sensory modalities tested; that is, any of the cues provided was sufficient and none was indispensably necessary to trigger prey detection. Availability of visual cues alone enabled successful prey detection in >90% of trials. Detection performance increased with the number of modalities available. Taken together, our data identify vision as a key modality for prey detection in captive-born grey mouse lemurs and at the same time stress the role of multimodal information for successful foraging in this nocturnal primate. [Copyright &y& Elsevier]

Chemical communication may play a major role in aquatic environments because of visibility limitations, but when turbidity is reduced do chemical and visual stimuli interact to elicit food-search behaviour by Procambarus clarkii? Does P. clarkii use visual cues to detect its prey? We conducted behavioural experiments in a Y maze, under non-turbid conditions. In the experiments P. clarkii was exposed to chemical plus visual (CV) and visual only (V) stimuli transmitted by Chironomus riparius. The results revealed that P. clarkii detected CV and V cues associated with the presence of C. riparius. In controls, with no prey, crayfish displayed only searching behaviour, whereas in treatments they exhibited searching, detection and attack behaviours. Further, there were no significant differences between CV and V stimuli in the mean number of attacks performed by crayfish. Thus, our findings indicate that under low turbidity, visual cues are sufficient to mediate prey detection by P. clarkii. [ABSTRACT FROM AUTHOR]

Very little is known about how nocturnal primates find their food. Here we studied the sensory basis of food perception in wild-caught gray mouse lemurs (Microcebus murinus) in Madagascar. Mouse lemurs feed primarily on fruit and arthropods. We established a set of behavioral experiments to assess food detection in wild-born, field-experienced mouse lemurs in short-term captivity. Specifically, we investigated whether they use visual, auditory, and motion cues to find and to localize prey arthropods and further whether olfactory cues are sufficient for finding fruit. Visual cues from motionless arthropod dummies were not sufficient to allow reliable detection of prey in choice experiments, nor did they trigger prey capture behavior when presented on the feeding platform. In contrast, visual motion cues from moving prey dummies attracted their attention. Behavioral observations and experiments with live and recorded insect rustling sounds indicated that the lemurs make use of prey-generated acoustic cues for foraging. Both visual motion cues and acoustic prey stimuli on their own were sufficient to trigger approach and capture behavior in the mouse lemurs. For the detection of fruit, choice experiments showed that olfactory information was sufficient for mouse lemurs to find a piece of banana. Our study provides the first experimental data on the sensory ecology of food detection in mouse lemurs. Further research is necessary to address the role of sensory ecology for food selection and possibly for niche differentiation between sympatric Microcebus species. [ABSTRACT FROM AUTHOR]