Prey Capture Behavior Research Articles

An adaptive bio-inspired optimisation model based on the foraging behaviour of a social spider

AbstractExisting bio-inspired models are challenged with premature convergence among others. In this paper, an adaptive social spider colony optimisation model based on the foraging behaviour of social spider was proposed as an optimisation problem. The algorithm mimics the prey capture behaviour of the social spider in which, the spider senses the presence of the prey through vibrations transmitted along the web thread. Spiders are the search agents while the web is the search space of the optimisation problem. The natural or biological phenomenon of vibration was modeled using wave theory while optimisation theory was considered in optimizing the objective function of the optimisation problem. This objective function was considered to be the frequency of vibration of the spiders and the prey as this is the function that enables the spider differentiates the vibration of the prey from that of neighbouring spiders and therefore forages maximally. To address the parameter tuning problem, the search pattern...

Neuromuscular organization of the Ctenophore Pleurobrachia bachei.

Ctenophores are descendants of one of the earliest branching metazoan lineage with enigmatic nervous systems. The lack of convenient neurogenic molecules and neurotransmitters suggests an extensive parallel evolution and independent origins of neurons and synapses. However, the field lags due to the lack of microanatomical data about the neuro-muscular systems in this group of animals. Here, using immunohistochemistry and scanning electron microscopy, we describe the organization of both muscular and nervous systems in the sea gooseberry, Pleurobrachia bachei, from North Pacific. The diffuse neural system of Pleurobrachia consists of two subsystems: the subepithelial neural network and the mesogleal net with about 5,000-7,000 neurons combined. Our data revealed the unexpected complexity of neuromuscular organization in this basal metazoan lineage. The anatomical diversity of cell types includes at least nine broad categories of neurons, five families of surface receptors and more than two dozen types of muscle cells as well as regional concentrations of neuronal elements to support ctenophore feeding, complex swimming, escape, and prey capture behaviors. In summary, we recognize more than 80 total morphological cell types. Thus, in terms of cell-type specification and diversity, ctenophores significantly exceed what we currently know about other prebilaterian groups (placozoan, sponges, and cnidarians), and some basal bilaterians.

A method for accurately estimating social spider numbers without colony damage

Ecologists are often required to accurately estimate the number of individuals residing in groups of variable sizes inside opaque shelters. Here, we have used x-rays as a non-destructive solution to this problem in social spiders which reside within collectively built opaque, silken, nest-like retreats. Social spiders are model systems for understanding social organization, collective behaviours and population genetics of inbred populations. Such studies often require an accurate determination of the number of individuals, developmental stages and orientation of individuals within the colony which is difficult without compromising the integrity of their retreat or affecting colony behaviour. We demonstrate the effectiveness of x-rays in accurately estimating colony size in the social spider Stegodyphus sarasinorum Karsch, 1892 (Eresidae). This method can also be applied to evaluate body sizes, developmental stages and individual orientation within the colony. We show that this technique does not alter spider prey-capture behaviour or short-term survival compared to control colonies.

Cooperative foraging in neotropical pseudoscorpions: effects of prey changes on behavioral adjustments of colonies

The pseudoscorpion Paratemnoides nidificator is a generalist predator that captures large arthropods that live on tree trunks. Few pseudoscorpions species show some degree of sociality. We investigated how colonies of the pseudoscorpion P. nidificator adjust their cooperative capture behavior under a situation of changing prey types as a simulation of variation in prey availability. We hypothesized that colonies would be more efficient at prey capture under repeated exposure to the same prey, and that the change in the availability of prey would be followed by new behavioral adjustments to adequately exploit the new prey. Eight experimental colonies housed in the laboratory received repetitions of three different ant species as prey. The number of pseudoscorpions attacking the prey, the number of behavioral acts, and the time expended subduing prey were evaluated as measures of prey capture performance, in relation to repetitive exposure to the same prey and also in relation to prey type changes. However, only individuals’ recruitment significantly responded to prey type exposure. Prey capture behavior was heterogeneous among colonies, resulting in highly variable behavioral responses. Colonies showed a tendency toward increasing capture success through repeated prey type exposure. However, 50% of the colonies were unable to capture the new prey type and died of starvation. Although it is a generalist predator, prey capture behavior could depend on different coordination components for subduing and handling large prey. Therefore, changes in prey availability could cause the attenuation of a cooperative relationship in some colonies, making them more prone to failure during capture.

Ablation of a Neuronal Population Using a Two-photon Laser and Its Assessment Using Calcium Imaging and Behavioral Recording in Zebrafish Larvae

To identify the role of a subpopulation of neurons in behavior, it is essential to test the consequences of blocking its activity in living animals. Laser ablation of neurons is an effective method for this purpose when neurons are selectively labeled with fluorescent probes. In the present study, protocols for laser ablating a subpopulation of neurons using a two-photon microscope and testing of its functional and behavioral consequences are described. In this study, prey capture behavior in zebrafish larvae is used as a study model. The pretecto-hypothalamic circuit is known to underlie this visually-driven prey catching behavior. Zebrafish pretectum were laser-ablated, and neuronal activity in the inferior lobe of the hypothalamus (ILH; the target of the pretectal projection) was examined. Prey capture behavior after pretectal ablation was also tested.

Evolutionary shift towards lateral line dependent prey capture behavior in the blind Mexican cavefish

Feeding strategies are dependent on multi-modal sensory processing, that integrates visual, chemosensory, and mechanoreceptive cues. In many fish species, local environments and food availability dramatically influence the evolution of sensory and morphological traits that underlie feeding. The Mexican cavefish, Astyanax mexicanus, have developed robust changes in sensory-dependent behaviors, but the impact on prey detection and feeding behavior is not known. In the absence of eyes, cavefish have evolved enhanced sensitivity of the lateral line, comprised of mechanosensory organs that sense water flow and detect prey. Here, we identify evolved differences in prey capture behavior of larval cavefish that are dependent on lateral line sensitivity. Under lighted conditions, cavefish strike Artemia prey at a wider angle than surface fish; however, this difference is diminished under dark conditions. In addition, the strike distance is greater in cavefish than surface fish, revealing an ability to capture, and likely detect, prey at greater distances. Experimental ablation of the lateral line disrupts prey capture in cavefish under both light and dark conditions, while it only impacts surface fish under dark conditions. Together, these findings identify an evolutionary shift towards a dependence on the lateral line for prey capture in cavefish, providing a model for investigating how loss of visual cues impacts multi-modal sensory behaviors.

Stereotyped feeding behaviors of polyphenic bluegill sunfish

AbstractPolymorphic populations are often considered as intermediate stages of speciation. Bluegill sunfish (Lepomis macrochirus) from Lake Waban, Wellesley, MA have diverged into two ecomorphs based on their diet, occupied habitat and morphology. Littoral bluegills are generalist feeders that consume a variety of aquatic invertebrates. Pelagic bluegills feed primarily on Daphnia. We aimed to understand if suction pressure generation, prey capture behaviors and pharyngeal jaw morphology differed between the littoral and pelagic ecomorphs feeding on three prey types. Littoral and pelagic bluegills showed similar feeding kinematics and peak pressure, however, significant differences were observed among prey types within an ecomorph. Feeding events on brine shrimp were slower and accompanied by less negative pressure for both ecomorphs. Littoral bluegills varied their use of ram among prey types, however, pelagic bluegills (zooplankton specialists) did not. Similar to previous studies, when presented with different prey items both dietary generalists and specialists varied equally in most aspects of their feeding behaviors. However, pelagic bluegills (dietary specialists) did not vary in their approach behaviors. Despite the lack of differences in trophic morphology among the individuals sampled here, the prey approach behaviors of dietary specialists appears to be fixed in pelagic bluegills. This result deemphasizes the importance of suction during feeding and places more importance on prey approach behaviors.

Almost like a whale - first evidence of suction feeding in a seabird.

Little auks (Alle alle) are one of the most numerous seabird species in the world and feed primarily on copepods in arctic waters. Their high daily energy requirements leave them vulnerable to current changes in the arctic plankton community, where a smaller, less-profitable copepod species (Calanus finmarchicus) becomes increasingly abundant. Little auks have been estimated to require ∼60,000 copepods per day, necessitating prey capture rates of ∼6 copepods per second underwater. To achieve such performance, it has been suggested that little auks capture their prey by (non-visual) filter feeding. We tested this hypothesis by exposing little auks to varying copepod densities within a shallow experimental pool and filming their prey capture behaviour. At none of the copepod densities tested did birds filter feed. Instead, all birds captured copepods by what we identified as visually guided suction feeding, achieved through an extension of their sub-lingual pouch. Suction feeding is very common in fish and marine mammals, but to the best of our knowledge, this is the first time that it has been specifically identified in a seabird species. While presumably less efficient than filter feeding, this behaviour may allow little auks to foster higher resilience when facing the consequences of arctic climate change.

Search and foraging behaviors from movement data: A comparison of methods.

Search behavior is often used as a proxy for foraging effort within studies of animal movement, despite it being only one part of the foraging process, which also includes prey capture. While methods for validating prey capture exist, many studies rely solely on behavioral annotation of animal movement data to identify search and infer prey capture attempts. However, the degree to which search correlates with prey capture is largely untested. This study applied seven behavioral annotation methods to identify search behavior from GPS tracks of northern gannets (Morus bassanus), and compared outputs to the occurrence of dives recorded by simultaneously deployed time–depth recorders. We tested how behavioral annotation methods vary in their ability to identify search behavior leading to dive events. There was considerable variation in the number of dives occurring within search areas across methods. Hidden Markov models proved to be the most successful, with 81% of all dives occurring within areas identified as search. k‐Means clustering and first passage time had the highest rates of dives occurring outside identified search behavior. First passage time and hidden Markov models had the lowest rates of false positives, identifying fewer search areas with no dives. All behavioral annotation methods had advantages and drawbacks in terms of the complexity of analysis and ability to reflect prey capture events while minimizing the number of false positives and false negatives. We used these results, with consideration of analytical difficulty, to provide advice on the most appropriate methods for use where prey capture behavior is not available. This study highlights a need to critically assess and carefully choose a behavioral annotation method suitable for the research question being addressed, or resulting species management frameworks established.

Rapid whole brain imaging of neural activity in freely behaving larval zebrafish (Danio rerio).

The internal brain dynamics that link sensation and action are arguably better studied during natural animal behaviors. Here, we report on a novel volume imaging and 3D tracking technique that monitors whole brain neural activity in freely swimming larval zebrafish (Danio rerio). We demonstrated the capability of our system through functional imaging of neural activity during visually evoked and prey capture behaviors in larval zebrafish.

Burrowing with a kinetic snout in a snake (Elapidae: Aspidelaps scutatus).

Of the few elongate, fossorial vertebrates that have been examined for their burrowing mechanics, all were found to use an akinetic, reinforced skull to push into the soil, powered mostly by trunk muscles. Reinforced skulls were considered essential for head-first burrowing. In contrast, I found that the skull of the fossorial shield-nosed cobra (Aspidelaps scutatus) is not reinforced and retains the kinetic potential typical of many non-fossorial snakes. Aspidelaps scutatus burrows using a greatly enlarged rostral scale that is attached to a kinetic snout that is independently mobile with respect to the rest of the skull. Two mechanisms of burrowing are used: (1) anteriorly directed head thrusts from a loosely bent body that is anchored against the walls of the tunnel by friction, and (2) side-to-side shovelling using the head and rostral scale. The premaxilla, to which the rostral scale is attached, lacks any direct muscle attachments. Rostral scale movements are powered by, first, retractions of the palato-pterygoid bar, mediated by a ligament that connects the anterior end of the palatine to the transverse process of the premaxilla and, second, by contraction of a previously undescribed muscle slip of the m. retractor pterygoidei that inserts on the skin at the edge of the rostral scale. In derived snakes, palatomaxillary movements are highly conserved and power prey capture and transport behaviors. Aspidelaps scutatus has co-opted those mechanisms for the unrelated function of burrowing without compromising the original feeding functions, showing the potential for evolution of functional innovations in highly conserved systems.

Humpback whales feed on hatchery-released juvenile salmon.

Humpback whales are remarkable for the behavioural plasticity of their feeding tactics and the diversity of their diets. Within the last decade at hatchery release sites in Southeast Alaska, humpback whales have begun exploiting juvenile salmon, a previously undocumented prey. The anthropogenic source of these salmon and their important contribution to local fisheries makes the emergence of humpback whale predation a concern for the Southeast Alaska economy. Here, we describe the frequency of observing humpback whales, examine the role of temporal and spatial variables affecting the probability of sighting humpback whales and describe prey capture behaviours at five hatchery release sites. We coordinated twice-daily 15 min observations during the spring release seasons 2010–2015. Using logistic regression, we determined that the probability of occurrence of humpback whales increased after releases began and decreased after releases concluded. The probability of whale occurrence varied among release sites but did not increase significantly over the 6 year study period. Whales were reported to be feeding on juvenile chum, Chinook and coho salmon, with photographic and video records of whales feeding on coho salmon. The ability to adapt to new prey sources may be key to sustaining their population in a changing ocean.

Variation in Echolocation and Prey-capture Behavior of Rhinolophus ferrumequinum during Foraging Flight

Variation in Echolocation and Prey-capture Behavior of Rhinolophus ferrumequinum during Foraging Flight

The nutritional physiology of sharks

Sharks compose one of the most diverse and abundant groups of consumers in the ocean. Consumption and digestion are essential processes for obtaining nutrients and energy necessary to meet a broad and variable range of metabolic demands. Despite years of studying prey capture behavior and feeding habits of sharks, there has been little exploration into the nutritional physiology of these animals. To fully understand the physiology of the digestive tract, it is critical to consider multiple facets, including the evolution of the system, feeding mechanisms, digestive morphology, digestive strategies, digestive biochemistry, and gastrointestinal microbiomes. In each of these categories, we make comparisons to what is currently known about teleost nutritional physiology, as well as what methodology is used, and describe how similar techniques can be used in shark research. We also identify knowledge gaps and provide suggestions to continue the progression of the field, ending with a summary of new directions that should be addressed in future studies regarding the nutritional physiology of sharks.

Activation of the hypothalamic feeding centre upon visual prey detection

The visual system plays a major role in food/prey recognition in diurnal animals, and food intake is regulated by the hypothalamus. However, whether and how visual information about prey is conveyed to the hypothalamic feeding centre is largely unknown. Here we perform real-time imaging of neuronal activity in freely behaving or constrained zebrafish larvae and demonstrate that prey or prey-like visual stimuli activate the hypothalamic feeding centre. Furthermore, we identify prey detector neurons in the pretectal area that project to the hypothalamic feeding centre. Ablation of the pretectum completely abolishes prey capture behaviour and neurotoxin expression in the hypothalamic area also reduces feeding. Taken together, these results suggest that the pretecto-hypothalamic pathway plays a crucial role in conveying visual information to the feeding centre. Thus, this pathway possibly converts visual food detection into feeding motivation in zebrafish.

Cannibalism: Do risks of fighting and reprisal reduce predatory rates?

Cannibalism is a common phenomenon among insects. It has raised considerable interest both from a theoretical perspective and because of its importance in population dynamics in natural ecosystems. It could also play an important role from an applied perspective, especially when using predatory species in biological control programmes. The present paper aims to study the cannibalistic behaviour of Nabis pseudoferus Remane and the functional response of adult females. In a non-choice experiment, adult females showed clear acceptance of immature conspecifics as prey, with relatively high mortality values (51.89 ± 2.69%). These values were lower than those occurring for heterospecific prey, Spodoptera exigua Hübner, under the same conditions (80.00 ± 2.82%). However, the main result was that the rate of predation on heterospecific prey was reduced to 59.09 ± 7.08% in the presence of conspecific prey. The prey-capture behaviour of adult females differed when they hunted conspecific versus heterospecific prey. This was shown in the average handling time, which was 23.3 ± 3.3 min in the first case (conspecific) versus 16.6 ± 2.5 min in the second (heterospecific). Furthermore, the values increased in the former case and declined in the latter according to the order in which the prey were captured. The difference in handling time was not significant when adjusting the adult female functional response to conspecific nymphs. We argue that these results likely indicate risk aversion and a fear of reprisal among conspecifics.

Sticky trap predation in the Neotropical resin bug Heniartes stali (Wygodzinsky) (Hemiptera: Reduviidae: Harpactorinae)

Certain species of assassin bugs have evolved the sticky trap strategy to capture prey using adhesive substances on their legs. The resin bug Heniartes stali collects a sticky exudate from the trichomes of a blackberry plant and smears its legs with it through an intriguing gathering process. We report laboratory experiments aimed at understanding the capture behavior of H. stali when it encountered three insect prey species with different mobility: the coleopteran larvae of Tribolium castaneum, a slow-moving organism; workers of the aggressive and highly mobile ant Camponotus rufipes; and winged prey, the fly Drosophila sp. Bugs stalked prey approaching within reach of their forelegs. After the bug threw forwards its forelegs, the prey became stuck and was subsequently held firmly by clutching with the aid of the middle legs, also smeared with trichome exudate. The bugs took longer to catch ants and immobilize them than larvae. Attacks on flies were unsuccessful because of flight escape before contact with H. stali occurred. A clear association between exudate harvesting and prey-capture behavior was unequivocally demonstrated. This is the first detailed description of a sticky leg trap from harvested plant exudate in Heniartes and related prey-capture behavior.

Trade-offs in an ant-plant-fungus mutualism.

Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host-plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.

Thermal Resilience of Feeding Kinematics May Contribute to the Spread of Invasive Fishes in Light of Climate Change.

As a consequence of global warming, tropical invasive species are expected to expand their range pole-ward, extending their negative impacts to previously undisturbed, high-latitude ecosystems. Investigating the physiological responses of invasive species to environmental temperature is important because the coupled effects of climate change and species invasion on ecosystems could be more alarming than the effects of each phenomenon independently. Especially in poikilotherms, the rate of motion in muscle-driven biomechanical systems is expected to double for every 10 °C increase in temperature. In this study, we address the question, “How does temperature affect the speed of jaw-movement during prey-capture in invasive fishes?” Kinematic analysis of invasive-fish prey-capture behavior revealed that (1) movement velocities of key components of the feeding mechanism did not double as water temperature increased from 20 °C to 30 °C; and (2) thermal sensitivity (Q10 values) for gape, hyoid, lower-jaw rotation, and cranial rotation velocities at 20 °C and 30 °C ranged from 0.56 to 1.44 in all three species. With the exception of lower-jaw rotation, Q10 values were significantly less than the expected Q10 = 2.0, indicating that feeding kinematics remains consistent despite the change in environmental temperature. It is conceivable that the ability to maintain peak performance at different temperatures helps facilitate the spread of invasive fishes globally.

A kinematic investigation into the feeding behavior of the Goliath grouper Epinephelus itajara

Goliath grouper Epinephelus itajara suffered significant overfishing in the United States until they were protected from harvest in 1990. As the population recovers, interactions between Goliath grouper and anglers have increased, and are often reported to management agencies as complaints after grouper predation upon hooked fish. Goliath grouper are generally characterized as opportunistic predators capable of consuming a wide variety of prey types; however, minimal data are available regarding the prey capture behavior of this species. Kinematic analyses of adult Goliath grouper feeding events demonstrated the capacity of individuals to modulate feeding behavior based upon the mobility and position of ‘prey’ items. Mobile epibenthic food (tethered swimming fish) elicited larger maximum gapes, faster times to food capture, shorter times to mouth closing, and more rapid total bite durations than food items that were not moving (cut dead bait). Feeding sequences involving mobile food items were characterized by a significantly higher degree of ram feeding behavior, while immobile food elicited primarily suction feeding and were preceded by a slower and closer approach to the food item prior to the onset of mouth opening. The findings are discussed in light of predation upon angled species and demonstrate the ability of Goliath grouper to adjust their feeding strategy based upon prey type and condition. This behavior likely allows for the exploitation of a wide variety of prey and provides an expansive dietary breadth for these opportunistic predators.