Spatial vision in the praying mantis: is distance implicated in size detection?

Summary The catching behaviour of the praying mantis Sphodromantis viridis is investigated in order to see whether or not the detection of prey size depends on the detection of prey distance. A first experiment demonstrates the mantid's ability to discriminate small differences in prey distance. Next, the preferred prey size is determined for a number of distances with the preference being indicated by the strike rates. The results demonstrate that the mantid's judgements of size are based on a relative (angular) scale rather than on an absolute (millimetre) scale. This is a strong piece of evidence that a relation between size and distance does not exist. Finally, the attack behaviour is analysed in detail, but it turns out that prey size has no effect on the organization of both the lunge of the body and the strike of the raptorial forelegs. Taken together, the findings of this study suggest that mantids localize prey with precision, but they do so without any knowledge of the absolute size of prey.     

Predatory success in the water stick insect: The role of visual and mechanical stimulations after moulting

The more foreleg femur and claw movements that a water stick insect, Ranatra linearis, performs during the 4-h period following a moult, the higher will be its subsequent strike efficiency. The amount of movement is influenced by external factors such as the presence of prey or light. The experiments reported here show that the absence of visual cues during the post-moult periods impairs subsequent performance, but not as much as the absence of both visual and mechanical cues. Perception of mechanical stimuli only during that period subsequently influences the accuracy of simple type strikes elicited when prey is near the forelegs; whereas perception of visual stimuli subsequently improves the accuracy of more complex predatory movements.     

Intrinsic Mechanics and Control of Fast Cranio-Cervical Movements in Aquatic Feeding Turtles

Aquatic feeding strikes on agile prey in snake-necked turtlesinvolve fast neck extension, bucco-pharyngo-oesophageal expansion,and head retraction. The ultimate, rectilinear accelerationof the head towards the prey requires complex vertebral rotations,that vary widely from strike to strike. This poses complex motorcontrol issues for the numerous intrinsic neck-muscles, whichare the sole neck extensors. Mathematical modelling revealsthat extensor activity might be superfluous for this phase ofthe strike. The ultimate acceleration of the head at the endof the strike always coincides with forceful oropharyngeal expansion.The momentum of the induced flow of water is sufficient to pullthe head (and the neck) straight towards the prey. This buccalexpansion proceeds identically to that observed in primary aquaticfeeders: a rostro-caudal expansion sequence characterized byan optimal timing of the functional components supporting theexpansion wave. Yet distinct structural solutions, both at theskeletal, and muscular level, are involved. This points towardsprominent hydrodynamic constraints. Head and neck are retractedby extrinsic neck muscles. Given the high number of degreesof freedom, this musculo-skeletal system is obviously under-determined,which compromises control. We propose that erroneous foldingof the neck (i.e., diverging from the highly persistent retractedconfiguration) might be avoided through the presence of a subtleclick system at the level of the joint between cervical vertebrae5 and 6.     

Trap‐jaws revisited: the mandible mechanism of the ant Acanthognathus

Abstract.Ants of the genus Acanthognathus stalk small insects and catch their prey by a strike with their long, thin mandibles. The mandibles close in less than 2.5 ms and this movement is controlled by a specialized closer muscle. In Acanthognathus , unlike other insects, the mandible closer muscle is subdivided into two distinct parts: as in a catapult, a large slow closer muscle contracts in advance and provides the power for the strike while the mandibles are locked open. When the prey touches specialized trigger hairs, a small fast closer muscle rapidly unlocks the mandibles and thus releases the strike. The fast movement is steadied by large specialized surfaces in the mandible joint and the sensory‐motor reflex is controlled by neurones with particularly large, and thus fast‐conducting, axons.     

Modulation in the feeding prey capture of the ant-lion, Myrmeleon crudelis

Ant-lions are pit-building larvae (Neuroptera: Myrmeleontidae), which possess relatively large mandibles used for catching and consuming prey. Few studies involving terrestrial arthropod larva have investigated prey capture behavior and kinematics and no study has shown modulation of strike kinematics. We examined feeding kinematics of the ant-lion, Myrmeleon crudelis, using high-speed video to investigate whether larvae modulate strike behavior based on prey location relative to the mandible. Based on seven capture events from five M. crudelis, the strike took 17.60 ± 2.92?msec and was characterized by near-simultaneous contact of both mandibles with the prey. Modulation of the angular velocity of the mandibles based on prey location was clearly demonstrated. M. crudelis larvae attempted to simultaneously contact prey with both mandibles by increasing mean angular velocity of the far mandible (65 ± 21?rad?sec(-1) ) compared with the near mandible (35 ± 14?rad?sec(-1) ). Furthermore, kinematic results showed a significant difference for mean angular velocity between the two mandibles (P<0.005). Given the lengthy strike duration compared with other fast-striking arthropods, these data suggest that there is a tradeoff between the ability to modulate strike behavior for accurate simultaneous mandible contact and the overall velocity of the strike. The ability to modulate prey capture behavior may increase dietary breadth and capture success rate in these predatory larvae by allowing responsive adjustment to small-scale variations in prey size, presentation, and escape response.     

Effects of force detecting sense organs on muscle synergies are correlated with their response properties

Sense organs that monitor forces in legs can contribute to activation of muscles as synergist groups. Previous studies in cockroaches and stick insects showed that campaniform sensilla, receptors that encode forces via exoskeletal strains, enhance muscle synergies in substrate grip. However synergist activation was mediated by different groups of receptors in cockroaches (trochanteral sensilla) and stick insects (femoral sensilla). The factors underlying the differential effects are unclear as the responses of femoral campaniform sensilla have not previously been characterized. The present study characterized the structure and response properties (via extracellular recording) of the femoral sensilla in both insects. The cockroach trochantero-femoral (TrF) joint is mobile and the joint membrane acts as an elastic antagonist to the reductor muscle. Cockroach femoral campaniform sensilla show weak discharges to forces in the coxo-trochanteral (CTr) joint plane (in which forces are generated by coxal muscles) but instead encode forces directed posteriorly (TrF joint plane). In stick insects, the TrF joint is fused and femoral campaniform sensilla discharge both to forces directed posteriorly and forces in the CTr joint plane. These findings support the idea that receptors that enhance synergies encode forces in the plane of action of leg muscles used in support and propulsion.     

Evolution of hyperflexible joints in sticky prey capture appendages of harvestmen (Arachnida,Opiliones)

The rigid leg segments of arthropods are flexibly connected by joints, which usually consist of two ball-and-bowl hinges, permitting a uniaxial pivoting up to 140°. Here, we report the occurrence of hyperflexible joints (range of movements?=?160–200°) in the pedipalps (second pair of appendages) of some harvestmen (Sabaconidae and Nemastomatidae), representing some of the most flexible leg joints among arthropods. Hyperflexion is achieved by a reduction of hinges and a strong constriction of the joint region. We demonstrate that hyperflexion occurs during prey capture and is used to clamp appendages of the prey, in addition to attachment by glue secreted by specialized setae. By means of high-speed video recordings, we found that in the Sabaconidae the tibiotarsal joint of the pedipalp can flex extremely rapidly (<5 ms), limiting prey escape. This is the fastest reported predatory strike in arachnids and caused both by leverage and a click mechanism. By comparative analysis of different related taxa, we retraced joint evolution and found that hyperflexion has independently evolved in Sabaconidae and Nemastomatidae, with totally different joint kinematics. We hypothesize that (rapid) hyperflexion evolved to enhance the efficiency of the pedipalp as a means of prey capture, because in springtails detachable scales limit the action of the sticky secretion of pedipalpal setae.     

Predatory behavior of the snake Bothrops jararaca and its adaptation to captivity

Habituation to captivity is difficult for some species. Understanding the motivational elements involved in predation may ease this habituation. Seventy‐one Brazilian jararaca snakes (Bothrops jararaca [Wied, 1824], Viperidae, Crotalinae) recently captured and never fed in captivity were tested for predatory behavior on rodents. Lighting was adapted to allow predatory sessions to occur during the first hours of the night when these animals are more active. Up to three prey subjects were presented in a session. In the first experiment, the preference for prey size and color was assessed using albino and dark‐colored rodents. In a second experiment, a group of snakes was submitted to 12 sessions during a period of almost 2 years. The strike strategy was classified in one of two categories: envenomation (E) or seizing (S). Envenomation involved a bite delivered by the snake with prompt retrieval of the head; holding the rodent in the snake’s jaws since the first strike, without retrieving the fangs and holding the prey during venom action, characterized S strike. Trailing and swallowing the dead prey always followed E strike. Results suggest that snakes fed more often on larger subjects. The color of the prey was not a relevant factor. E strike was predominant in the first predatory event in captivity. After habituation, S strike was predominant. Snakes may have a poor perception of the prey objects in captivity and adopt a strike strategy that assures the control of the prey. Also, the use of small prey subjects to ease feeding during adaptation to captivity may be less effective. Zoo Biol 20:399–406, 2001. © 2001 Wiley‐Liss, Inc.     

The Feeding Behaviour of a Sit-and-Wait Predator,Ranatra dispar (Heteroptera: Nepidae): The Combined Effect of Food Deprivation and Prey Size on the Behavioural Components of Prey Capture

Previous work has shown a significant effect of hunger on the predatory behaviour in a sit-and-wait predator Ranatra dispar, the water stick insect (Bailey 1986 a). The experiments reported here were designed to investigate the combined effect of prey size and hunger on the predatory behaviour in order to identify which behavioural components are effected. It was found that the hunger level determines whether R. dispar will initially be aroused or not but the distance at which the arousal takes place is influenced by the size of the prey. This is believed to reflect the capacity and interrelation between visual and mechanoreceptor, sensory organs. The decision to strike at a prey is, although again influenced by hunger, significantly affected by prey size. The distance of the prey when the strike takes place is affected by hunger not the size of the prey. The outcome of the strike is determined by the size of the prey, not the hunger level of the predator. This is believed to reflect the relationship between strike trajectory, leg morphology and prey size. Food deprivation affects all components of predatory behaviour of R. dispar leading up to prey capture, by increasing not only distance of response but also the number of strikes, hits, and captures per unit presentation of prey. It does not affect capture efficiency which remains at about 70 to 80 %. Food deprivation also increases the range of prey sizes that R. dispar responds to and attempts to capture. The effect of food deprivation is considered to reflect a motivational change in responsiveness to particular prey stimuli usually described as a sensitization of particular stimulus-response relations rather than the food deprivation affecting the sensory mechanisms. The predatory success in relation to size of model prey suggested a hypothetical size that could be captured, irrespective of predator motivational level, which is based primarily on the relationship between the shape of the grasping leg and size of prey.     

Post-Strike Behavior of Timber Rattlesnakes (Crotalus horridus) During Natural Predation Events

The complexity of natural environments is an important component of animal behavior, and laboratory environments often cannot reproduce that complexity. Strike‐induced chemosensory searching (SICS) is a robust phenomenon among venomous snakes that has been studied extensively in the laboratory. To date, observations of this behavior in the field have been limited largely to anecdotes; the extent to which post‐strike behaviors in the laboratory accurately reflect what occurs in nature has not been examined. In this study, I use time‐lapse video equipment in the field to record the predatory behavior of timber rattlesnakes (Crotalus horridus). This represents the first quantitative analysis of post‐strike predatory behaviors associated with natural feeding events. As in the laboratory, stereotyped post‐strike behaviors were only observed after successful strikes, and not after missed strikes. Snakes in the field were observed to proceed through the same basic behavioral stages that have been documented in the laboratory: striking prey, releasing prey immediately after strike, post‐strike immobility, location of the chemosensory trail, trail following, and prey swallowing. However, the duration of post‐strike immobility, trail location, and prey swallowing was substantially longer in field than in laboratory studies. Additionally, post‐strike immobility was significantly longer when snakes struck large prey (prey over 100 g) than when they struck small prey. Overall, these results indicate that the behavioral challenges associated with SICS may be more robust than laboratory studies have indicated.     

Prey capture in mantids: A non-stereotyped component of lunge

The praying mantis Tenodora aridifolia sinensis strikes at prey with the pincer-like motion of its prothoracic legs. During strike the mantis moves its body forward toward the prey in a lunge which is propelled by its four walking legs. Using a tethered mantis preparation we have studied the lunge produced by the movement of the walking legs. We have found that lunge is correctly oriented toward prey no matter where it moves in three-dimensional space. This demonstrates that the lunge that accompanies the strike is in this species aimed and not invariant in distance and direction as suggested for other mantids.     

Morphology and function of the feeding apparatus of the lungfish, Lepidosiren paradoxa (Dipnoi)

The feeding mechanism of the South American lungfish, Lepidosiren paradoxa retains many primitive teleostome characteristics. In particular, the process of initial prey capture shares four salient functional features with other primitive vertebrates: 1) prey capture by suction feeding, 2) cranial elevation at the cranio-vertebral joint during the mouth opening phase of the strike, 3) the hyoid apparatus plays a major role in mediating expansion of the oral cavity and is one biomechanical pathway involved in depressing the mandible, and 4) peak hyoid excursion occurs after maximum gape is achieved. Lepidosiren also possesses four key morphological and functional specializations of the feeding mechanism: 1) tooth plates, 2) an enlarged cranial rib serving as a site for the origin of muscles depressing the hyoid apparatus, 3) a depressor mandibulae muscle, apparently not homologous to that of amphibians, and 4) a complex sequence of manipulation and chewing of prey in the oral cavity prior to swallowing. The depressor mandibulae is always active during mouth opening, in contrast to some previous suggestions. Chewing cycles include alternating adduction and transport phases. Between each adduction, food may be transported in or out of the buccal cavity to position it between the tooth plates. The depressor mandibulae muscle is active in a double-burst pattern during chewing, with the larger second burst serving to open the mouth during prey transport. Swallowing is characterized by prolonged activity in the hyoid constrictor musculature and the geniothoracicus. Lepidosiren uses hydraulic transport achieved by movements of the hyoid apparatus to position prey within the oral cavity. This function is analogous to that of the tongue in many tetrapods.     

Laboratory studies of predation by the Antarctic mite Gamasellus racovitzai (Acarina: Mesostigmata)

Summary Laboratory investigations of predation by Gamasellus racovitzai (Acarina: Mesostigmata) on Cryptopygus antarcticus (Insecta: Collembola) are described. The predator appeared to search at random, but, when contact with prey had been made, a rapid attack involved looping the forelegs over the prey to hold it whilst the chelicerae moved forward horizontally to puncture the side of the prey. The mean predation rate by deutonymphs, approximately one prey per predator per 12 days, was independent of prey density, but with adults this rate increased to about one prey per predator per 3 days. A study of leg geometry predicted a maximum prey size that could be captured: some experimental evidence suggested that mites selected prey near to this predicted size. The contribution of the laboratory results towards understanding the dynamics of field populations is discussed.     

Response of the Praying Mantis,Sphodromantis Viridis,to Target Change in Size and to Target Visual Occlusion

Mantises (Mantodea, Mantidae) visually detect insect prey and capture it by a ballistic strike of their specialized forelegs. We tested predatory responses of female mantis, Sphodromantis viridis, to computer generated visual stimuli, to determine the effects of (i) target size and velocity (ii) discrete changes in target size and (iii) visual occlusion. Maximal predatory responses were elicited by stimuli that (i) subtended ~20°–23° horizontally and ~16°–19° vertically, at the eye, and moved across the screen at angular velocities of ~46°–119°/s, (ii) increased in size in a stepwise manner, with step duration ≥0.8 s, while stimuli decreasing in size elicited only peering movements, (iii) Stimuli disappearing gradually behind a virtual occlusion elicited one or more head saccades but not actual interception.     

Functional groups in piscivorous fishes

Piscivory is a key ecological function in aquatic ecosystems, mediating energy flow within trophic networks. However, our understanding of the nature of piscivory is limited; we currently lack an empirical assessment of the dynamics of prey capture and how this differs between piscivores. We therefore conducted aquarium‐based performance experiments, to test the feeding abilities of 19 piscivorous fish species. We quantified their feeding morphology, striking, capturing, and processing behavior. We identify two major functional groups: grabbers and engulfers. Grabbers are characterized by horizontal, long‐distance strikes, capturing their prey tailfirst and subsequently processing their prey using their oral jaw teeth. Engulfers strike from short distances, from high angles above or below their prey, engulfing their prey and swallowing their prey whole. Based on a meta‐analysis of 2,209 published in situ predator–prey relationships in marine and freshwater aquatic environments, we show resource partitioning between grabbers and engulfers. Our results provide a functional classification for piscivorous fishes delineating patterns, which transcend habitats, that may help explain size structures in fish communities.     

The fast mandible strike in the trap-jaw ant Odontomachus

Ants of the ponerine genus Odontomachus employ a trap-jaw mechanism that allows them to instantaneously close their long, sturdy mandibles to catch prey or to defend themselves. Photoelectric scanning has revealed that these trap-jaws can be closed in less than 0.5 ms and that they decelerate before they collide with each other. The mandible strike is released in a reflexlike action when particular trigger hairs are touched. This reflex takes 4 to 10 ms and is probably the fastest reflex yet described for any animal. This speed is based on a catch mechanism in the mandible joint that keeps the extended mandibles open during contraction of the powerful closer muscle and allows the potential energy it produces to be stored within cuticular elements, apodemes, and the closer muscle itself. During a strike a relatively small specialized trigger muscle unlocks the catch, instantaneously releasing the stored energy to accelerate the mandible.     

Hydrodynamic image formation by the peripheral lateral line system of the Lake Michigan mottled sculpin, Cottus bairdi

Lake Michigan mottled sculpin (Cottus bairdi) have a lateral-line-mediated prey-capture behaviour that consists of an initial orientation towards the prey, a sequence of approach movements, and a final strike at the prey. This unconditioned behaviour can be elicited from blinded sculpin in the laboratory by both real and artificial (vibrating sphere) prey. In order to visualize what Lake Michigan mottled sculpin might perceive through their lateral line when approaching prey, we have combined anatomical, neurophysiological, behavioural and computational modelling techniques to produce three-dimensional maps of how excitation patterns along the lateral line sensory surface change as sculpin approach a vibrating sphere. Changes in the excitation patterns and the information they contain about source location are consistent with behavioural performance, including the approach pathways taken by sculpin to the sphere, the maximum distances at which approaches can be elicited, distances from which strikes are launched, and strike success. Information content is generally higher for laterally located sources than for frontally located sources and this may explain exceptional performance (e.g. successful strikes from unusually long distances) in response to lateral sources and poor performance (e.g. unsuccessful strikes) to frontal sources.     

Evolution and ecology of feeding in elasmobranchs

Paleozoic chondrichthyans had a large gape, numerous spike-liketeeth, limited cranial kinesis, and a non-suspensory hyoid,suggesting a feeding mechanism dominated by bite and ram. Modernsharks are characterized by a mobile upper jaw braced by a suspensoryhyoid arch that is highly kinetic. In batoids, the upper jawis dissociated from the cranium permitting extensive protrusionof the jaws. Similar to actinopterygians, the evolution of highlymobile mandibular and hyoid elements has been correlated withextensive radiation of feeding modes in elasmobranchs, particularlythat of suction. Modern elasmobranchs possess a remarkable varietyof feeding modes for a group containing so few species. Biting,suction or filter-feeding may be used in conjunction with ramto capture prey, with most species able to use a combinationof behaviors during a strike. Suction-feeding has repeatedlyarisen within all recent major elasmobranch clades and is associatedwith a suite of morphological and behavioral specializations.Prey capture in a diverse assemblage of purported suction-feedingelasmobranchs is investigated in this study. Drop in water pressuremeasured in the mouth and at the location of the prey showsthat suction inflow drops off rapidly with distance from thepredator's mouth. Elasmobranchs specializing in suction-feedingmay be limited to bottom associated prey and because of theirsmall gape may have a diet restricted to relatively small prey.Behavior can affect performance and overcome constraints imposedby the fluid medium. Suction performance can be enhanced byproximity to a substrate or by decreasing distance from predatorto prey using various morphological and/or behavioral characteristics.Benthic suction-feeders benefit by the increased strike radiusdue to deflection of water flow when feeding close to a substrate,and perhaps require less accuracy when capturing prey. Suctionand ram-suction-feeding elasmobranchs can also use suction inflowto draw prey to them from a short distance, while ram-feedingsharks must accelerate and overtake the prey. The relationshipbetween feeding strategy and ecology may depend in part on ecological,mechanistic or evolutionary specialization. Mechanistic suction-feedingspecialist elasmobranchs are primarily benthic, while most epibenthicand pelagic elasmobranchs are generalists and use ram, suction,and biting to catch a diversity of prey in various habitats.Some shark species are considered to be ecological specialistsin choosing certain kinds of prey over others. Batoids are evolutionaryspecialists in having a flattened morphology and most are generalistfeeders. Filter-feeding elasmobranchs are ecological, mechanistic,and evolutionary specialists.     

A stochastic approach to predator-prey models

A deterministic investigation of a linear differential equation system which describes predator vs prey behavior as a function of equilibrium densities and reproductive rates is given. A more realistic structure of this model in a stochastic framework is presented. The reproductive rates and initial population sizes are considered to be random variables and their probabilistic behavior characterized by various joint probability distributions. The deterministic behaviors of the prey and predator species as functions of time are compared with the mean behaviors in the stochastic model.