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PubMed1998

Phototaxic foraging of the archaepaddler, a hypothetical deep-sea species.

An autonomous agent (animat, hypothetical animal), called the (archae) paddler, is simulated in sufficient detail to regard its simulated aquatic locomotion (paddling) as physically possible. The paddler is supposed to be a model of an animal that might exist, although it is perfectly possible to view it as a model of a robot that might be built. The agent is assumed to navigate in a simulated deep-sea environment, where it forages for autoluminescent prey. It uses a biologically inspired phototaxic foraging strategy, while paddling in a layer just above the bottom. The advantage of this living space is that the navigation problem--and hence our model--is essentially two-dimensional. Moreover, the deep-sea environment is physically simple (and hence easy to simulate): no significant currents, constant temperature, completely dark. A foraging performance metric is developed that circumvents the necessity to solve the traveling salesman problem. A parametric simulation study then quantifies the influence of habitat factors, such as the density of prey, and body geometry (e.g., placement, direction and directional selectivity of the eyes) on foraging success. Adequate performance proves to require a specific body geometry adapted to the habitat characteristics. In general, performance degrades gracefully for modest changes of the geometric and habitat parameters, indicating that we work in a stable region of "design space." The parameters have to strike a compromise between, on the one hand, to "see" as many targets at the same time as possible. One important conclusion is that simple reflex-based navigation can be surprisingly efficient. Additionally, performance in a global task (foraging) depends strongly on local parameters such as visual direction tuning, position of the eyes and paddles, and so forth. Behavior and habitat "mold" the body, and the body geometry strongly influences performance. The resulting platform enables further testing of foraging strategies or vision and locomotion theories stemming either from biology or from robotics.

Animals↗

PubMed2003

Mercury effects on predator avoidance behavior of a forage fish, golden shiner (Notemigonus crysoleucas).

Mercury contamination of fish is widespread in North America and has resulted in the establishment of fish consumption advisories to protect human health. However, the effects of mercury exposure to fish have seldom been investigated. We examined the effects of dietary mercury exposure at environmental levels in a common forage species, golden shiner (Notemigonus crysoleucas). Fish were fed either an unaltered diet (12 ng/g wet wt methylmercury [MeHg] as Hg), a low-Hg diet (455 ng/g Hg), or a high-Hg diet (959 ng/g Hg). After 90 d mean fish whole-body total Hg concentrations were 41, 230, and 518 ng/g wet wt, respectively, which were within the range of concentrations found in this species in northern U.S. lakes. There were no mortalities or differences in growth rate among groups. Groups of fish from each treatment were exposed to a model avian predator and their behavioral response videotaped for analysis. Brain acetylcholinesterase (AChE) activity was determined in fish after behavioral testing. Fish fed the high-Hg diet had significantly greater shoal vertical dispersal following predator exposure, took longer to return to pre-exposure activity level, and had greater shoal area after return to pre-exposure activity than did the other treatments, all of which would increase vulnerability of the fish to predation. There were no differences in brain AChE among treatments. We conclude that mercury exposure at levels currently occurring in northern United States lakes alters fish predator-avoidance behavior in a manner that may increase vulnerability to predation. This finding has significant implications for food chain transfer of Hg and Hg exposure of fish predators.

Acetylcholinesterase↗

PubMed2002

Neuropeptides and amphibian prey-catching behavior.

In mammals, a number of hypothalamic neuropeptides have been implicated in stress-induced feeding disorders. Recent studies in anurans suggest that stress-related neuropeptides may act on elemental aspects of visuomotor control to regulate feeding. Corticotropin-releasing hormone (CRH) and alpha-melanocyte-stimulating hormone, potent an orexic peptides in mammals, inhibit visually-guided prey-catching in toads. Neuropeptide Y (NPY), an orexic peptide in mammals, may be an important neuromodulator in inhibitory pre-tectal-tectal pathways involved in distinguishing predator and prey. Melanocortin, NPY and CRH neurons project onto key visuomotor structures within the amphibian brain, suggesting physiological roles in the modulation of prey-catching. Thus, neuropeptides involved in feeding behavior in mammals influence the efficacy of a visual stimulus in releasing prey-catching behavior. These neuropeptides may play an important role in how frogs and toads gather and process visual information, particularly during stress.

Amphibians↗

PubMed2004

The role of semiochemicals in the avoidance of the seven-spot ladybird, Coccinella septempunctata, by the aphid parasitoid, Aphidius ervi.

The role of semiochemicals in mediating intraguild interactions between the seven-spot ladybird, Coccinella septempunctata, and the aphid parasitoid, Aphidius ervi, was investigated. Female parasitoids avoided leaves visited by C. septempunctata adults and larvae during the previous 24 hr. Ethanol extracts of C. septempuntata adults and larvae also induced avoidance responses by A. ervi. Two of the hydrocarbons identified by gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS), n-tricosane (C23H48), and n-pentacosane (C25H52), when tested individually at levels found in the adult extract, induced avoidance by A. ervi. Further investigation of the larvae extract, and footprint chemicals deposited by adults in glass Petri dishes, confirmed the presence of the hydrocarbons. Parasitism rates of the pea aphid, Acyrthosiphon pisum, on broad bean plants, Vicia faba, which had been sprayed with a mixture of the chemicals, were lower than those on control plants. The effect, however, was no longer evident if parasitoid foraging was delayed by 24 hr after the plants were treated. The ecological significance of intraguild avoidance behavior and implications for possible use of the semiochemicals involved in future biological control programs are discussed.

Alkanes↗

PubMed2002

Modeling an electrosensory landscape: behavioral and morphological optimization in elasmobranch prey capture.

Most biological sensory systems benefit from multiple sensors. Elasmobranchs (sharks, skates and rays) possess an array of electroreceptive organs that facilitate prey location, mate location and navigation. Here, the perceived electrosensory landscape for an elasmobranch approaching prey is mathematically modeled. The voltages that develop simultaneously in dozens of separate sensing organs are calculated using electrodynamics. These voltages lead directly to firing rate modifications in the primary afferent nerves. The canals connecting the sense organs to an elasmobranch's surface exhibit great variation of location and orientation. Here, the voltages arising in the sense organs are found to depend strongly on the geometrical distribution of the corresponding canals. Two applications for the modeling technique are explored: an analysis of observed elasmobranch prey-capture behavior and an analysis of morphological optimization. For the former, results in specific predator-prey scenarios are compared with behavioral observations, supporting the approach algorithm suggested by A. Kalmijn. For the latter, electrosensory performance is contrasted for two geometrical models of multiple sense organs, a rounded head and a hammer-shaped head.

Algorithms↗

PubMed2001

Object segmentation model: analytical results and biological implications.

A simple, biologically motivated neural network for segmentation of a moving object from a visual scene is presented. The model consists of two parts: an object selection model which employs a scaling approach for receptive field sizes, and a subsequent network implementing a spotlight by means of multiplicative synapses. The network selects one object out of several, segments the rough contour of the object, and encodes the winner object's position with high accuracy. Analytical equations for the performance level of the network, e.g., for the critical distance of two objects above which they are perceived as separate, are derived. The network preferentially chooses the object with the largest angular velocity and the largest angular width. An equation for the velocity and width preferences is presented. Additionally it is shown that for certain neurons of the model, flat receptive fields are more favourable than Gaussian ones. The network exhibits performances similar to those known from amphibians. Various electrophysiological and behavioral results--e.g., the distribution of the diameters of the receptive fields of tectal neurons, of the tongue-projecting salamander Hydromantes italicus and the range of optimal prey velocities for prey catching--can be understood on the basis of the model.

Animals↗

PubMed1998

Predation on Aedes aegypti (Diptera: Culicidae) by Theridion rufipes (Araneae: Theridiidae) in Puerto Rico.

Theridion rufipes Lucas was found in rearing cages of Aedes aegypti (L.) in the School of Medicine, San Juan, PR. From the 1970s to the 1990s, the spiders had a continuous existence in the cages and in the room outside the cages. A single spider eventually could eliminate all the mosquitoes in a cage. The behavior of the mosquitoes in the web was observed by isolating spiders individually in glass or plastic flasks. When a mosquito comes in contact with the beads of sticky silk on the web, it is immediately paralyzed before the spider approaches it. The instant immobilization without a struggle as well as other aspects of prey behavior suggest that there is a compound in the sticky webs that causes the paralysis. Analysis of this material might lead to the discovery of a new insecticide. Efforts to control dengue in Puerto Rico should not interfere with the natural enemies of the vector.

Aedes↗

PubMed2004

Stochastic analysis of the Lotka-Volterra model for ecosystems.

A stochastic Lotka-Volterra-type model for the interaction between the preys and the predators in a random environment is investigated. A self-competition mechanism within the prey population itself is also included. The effect of a random environment is modeled as random variations in the birth rate of the preys and the death rate of the predators. The stochastic averaging procedure of Stratonovich and Khasminskii is applied to obtain the probability distributions of the system state variables at the state of statistical stationarity. Asymptotic behaviors of the system variables are discussed, and the mean transition time from an initial state to a critical state is obtained. Effects on the ecosystem behaviors of the self-competition term, of the random variation in the prey birth rate, and of the random variation in the predator death rate are investigated.

Animals↗

PubMed1999

Demographic influences on the hunting behavior of chimpanzees.

We investigated hunting in an unusually large community of wild chimpanzees at Ngogo in the Kibale National Park, Uganda. Aspects of predation were recorded with respect to the prey, the predators, and hunting episodes. During 23 months of observation, the Ngogo chimpanzees caught 128 prey items from four primate and three ungulate species. Chimpanzees preyed selectively on immature red colobus primarily during group hunts, with adult males making the majority of kills. Party size and composition were significant predictors of the probability that chimpanzees would hunt and of their success during attempts. Chimpanzees were more likely to hunt red colobus if party size and the number of male hunters were large; party size and the number of male hunters were also significantly larger in successful compared with unsuccessful hunts. The Ngogo chimpanzees did not appear to hunt cooperatively, but reciprocal meat-sharing typically took place after kills. Hunts occurred throughout the year, though there was some seasonality as displayed by periodic hunting binges. The extremely high success rate and large number of kills made per successful hunt are the two most striking aspects of predation by the Ngogo chimpanzees. We compare currently available observations of chimpanzee hunting behavior across study sites and conclude that the large size of the Ngogo community contributes to their extraordinary hunting success. Demographic differences between groups are likely to contribute to other patterns of interpopulation variation in chimpanzee predation.

Animals↗

PubMed2005

The effects of ants on the entomophagous butterfly caterpillar Feniseca tarquinius, and the putative role of chemical camouflage in the Feniseca-ant interaction.

Butterfly caterpillars in the lycaenid subfamily Miletinae are predators of ant-tended Homoptera, yet they lack specialized secretory and call-production organs crucial to ant association in other lycaenids. Here, we address the question of how miletine caterpillars have invaded the ant-Homoptera symbiosis through a study of the only New World miletine, Feniseca tarquinius, a predator of the wooly aphid Prociphilus tesselatus. Previous interpretations have suggested that F. tarquinius and other miletine caterpillars avoid ant aggression by concealing themselves under silken webs. In contrast, our field data indicate that F. tarquinius caterpillars are less likely to be concealed in the presence of the ants Camponotus pennsylvanicus and Formica obscuriventris than in the absence of ants, although caterpillar and ant behaviors vary between years. Chemical analysis and behavioral assays suggest that chemical camouflage, not physical concealment, is responsible for the ants' failure to detect and remove F. tarquinius caterpillars from aphid colonies. Analyses by gas chromatography indicate that the cuticular lipid composition of caterpillars are similar to that of their aphid prey, although it varies with prey species. Behavioral assays confirm that solvent extracts of F. tarquinius caterpillars and P. tesselatus aphids evoke similar behavioral responses in C. pennsylvanicus ants. Chemical camouflage is well known in social parasites of ants, but the present study represents one of a few documented cases where chemical deceit is important to interactions with ants outside the nest.

Animals↗

PubMed2003

Phosphorylated cyclic AMP response element binding protein expression induced in the periaqueductal gray by predator stress: its relationship to the stress experience, behavior and limbic neural plasticity.

Electrophysiological studies in cats and recently in rats implicate neuroplasticity in the periaqueductal gray (PAG) and its afferents in stressor-induced increases in fearful behavior and anxiety-like behavior (ALB). Such increases may model aspects of affective changes following traumatic stress in humans. The present study explored the role of neuroplasticity in PAG and its connection with the central nucleus of the amygdala (ACE) in male rodent anxiety-like response to predator stress. In the first of two studies, the effects of predator stress on the induction of phosphorylated cyclic AMP response element binding protein (pCREB) were investigated. pCREB expression in the PAG and ventromedial hypothalamus (VMH) was examined immunohistochemically. Predator stress increased the degree of pCREB expression in PAG cells (measured densitometrically) but did not increase the number of cells expressing pCREB (measured stereologically). Moreover, predator stress-specific increase in pCREB-like immunoreactivity (lir) was restricted to the right lateral column of the PAG. In addition, pCREB lir in the right lateral column likely reflects aspects of the stress experience because the stressor (cat behavior) and the response to the stressor (rat defensive behavior) are highly predictive of degree of pCREB expression. There was no effect of predator stress on pCREB lir in the VMH. Because pCREB expression has been associated with long-lasting potentiation (LLP) of neural transmission, we examined the effects of predator stress on transmission in the ACE-PAG pathway in a second study. Predator stress elevated evoked potential measures of ACE-PAG transmission in the right hemisphere but not in the left hemisphere 11-12 days after predator stress. This finding is consistent with the longer-lived effects of pharmacological stress on amygdalo-PAG transmission in the right hemisphere but not in the left hemisphere in cats. Of interest is the fact that the same aspects of the stressor experience and reaction to it, which are predictive of the degree of pCREB expression, are also highly predictive of the degree of potentiation of measures of ACE-PAG transmission. Behavioral analyses revealed that the most consistent effects of predator stress are on behavior in the plus maze (open arm exploration and risk assessment) and on startle. In addition, covariance analysis suggests that ACE-PAG potentiation mediates some but not all of the changes in ALB produced by predator stress. Because pCREB expression may be a precursor to neuroplastic changes in certain forms of memory and LLP, the present findings complement studies in the cat, showing that neuroplastic changes in the PAG underlie changes in affect following stress. Furthermore, these findings suggest that neuroplastic changes in PAG may be important mediators of predator stress-induced changes in affective behavior in rodents. Finally, consistent with cat and human studies, the right hemisphere appears particularly important in long-term response to stress.

Animals↗

PubMed2005

Hunting increases adaptive auditory map plasticity in adult barn owls.

The optic tectum (OT) of barn owls contains topographic maps of auditory and visual space. Barn owls reared with horizontally displacing prismatic spectacles (prisms) acquire a novel auditory space map in the OT that restores alignment with the prismatically displaced visual map. Although juvenile owls readily acquire alternative maps of auditory space as a result of experience, this plasticity is reduced greatly in adults. We tested whether hunting live prey, a natural and critically important behavior for barn owls, increases auditory map plasticity in adult owls. Two groups of naive adult owls were fit with prisms. The first group was fed dead mice during 10 weeks of prism experience, while the second group was required to hunt live prey for an identical period of time. When the owls hunted live prey, auditory maps shifted substantially farther (five times farther, on average) and the consistency of tuning curve shifts within each map increased. Only a short period of time in each day, during which the two groups experienced different conditions, accounts for this effect. In addition, increased map plasticity correlated with behavioral improvements in the owls' ability to strike and capture prey. These results indicate that the experience of hunting dramatically increases adult adaptive plasticity in this pathway.

Acoustic Stimulation↗

PubMed2001

Global dynamics of a ratio-dependent predator-prey system.

Recently, ratio-dependent predator-prey systems have been regarded by some researchers to be more appropriate for predator-prey interactions where predation involves serious searching processes. However, such models have set up a challenging issue regarding their dynamics near the origin since these models are not well-defined there. In this paper, the qualitative behavior of a class of ratio-dependent predator-prey system at the origin in the interior of the first quadrant is studied. It is shown that the origin is indeed a critical point of higher order. There can exist numerous kinds of topological structures in a neighborhood of the origin including the parabolic orbits, the elliptic orbits, the hyperbolic orbits, and any combination of them. These structures have important implications for the global behavior of the model. Global qualitative analysis of the model depending on all parameters is carried out, and conditions of existence and non-existence of limit cycles for the model are given. Computer simulations are presented to illustrate the conclusions.

Animals↗

PubMed2004

Social behavior: how do fish find their shoal mate?

Fish form social aggregations called shoals which often consist of fish with similar morphologies. Experiments using zebrafish pigment variants demonstrate that fish can select shoal mates solely on the basis of their color patterns, and that early experience plays a key role in determining these shoaling preferences.

Animals↗

PubMed2002

Memory for animal tracks: a possible cognitive artifact of human evolution.

Although many human behaviors are held to have adaptive significance, specific examples of behaviors that represent direct holdovers from the ancient world have been few, particularly in the cognitive realm. In the present research, the authors tested the hypothesis that such cognitive examples might in fact exist and be experimentally verifiable. They suggested that human predispositions to learn basic aspects of hunting with relative ease might be "left over" from human evolution in the pre-agricultural past. This hypothesis was tested in 3 experiments with reference to the learning and recall of animal tracks, an activity of probable high adaptive significance within the area of visual memory. Undergraduate students selected at random learned and recalled animal tracks with significantly greater ease than they recalled other animate and inanimate items. A single exception lay in relatively unfamiliar kitchen implements, which were recalled with greater facility than were animal tracks, consistent with current theoretical considerations. Results indicate that direct behavioral holdovers from the ancient world may exist in the cognitive realm and that these may be accessed experimentally and predictably under appropriate conditions.

Adult↗

PubMed2003

Nitrogen oxides elicit antipredator responses in juvenile channel catfish, but not in convict cichlids or rainbow trout: conservation of the ostariophysan alarm pheromone.

Recent studies with cyprinid and characin (superorder Ostariophysi) fishes suggest that purine-N-oxides function as chemical alarm cues (alarm pheromones) and that the nitrogen oxide functional group acts as the chief molecular trigger. To further test the hypothesis that the nitrogen-oxide functional group is evolutionarily conserved as an active component of the Ostariophysan alarm pheromone system, we exposed juvenile channel catfish (Ictalurus punctatus, Siluriformes) to conspecific skin extract, hypoxanthine-3-N-oxide (the putative alarm pheromone) and a suite of structurally and functionally similar compounds. Conspecific skin extract and hypoxanthine-3-N-oxide elicited significant increases in species typical antipredator behaviors. A structurally dissimilar compound possessing a nitrogen oxide functional group (pyridine-N-oxide) elicited a significant, but less intense alarm response. Compounds lacking a nitrogen oxide functional group were not significantly different from control stimuli. In addition, two non-Ostariophysan species known to possess chemical alarm cues (convict cichlids, Acrchocentrus nigrofasciatus, Cichlidae, Acanthopterygii and rainbow trout, Oncorhynchus mykiss, Salmonidae, Protacanthopterygii) did not show any increase in antipredator behavior in response to hypoxanthine-3-N-oxide. These data demonstrate the conservation of chemical alarm cues within at least three orders of the superorder Ostariophysi.

Animals↗

PubMed1983

Partial kindling and emotional bias in the cat: lasting aftereffects of partial kindling of the ventral hippocampus. II. Physiological changes.

The first study revealed that evocation of repeated afterdischarges (ADs) in the perforant path-dentate system of the ventral hippocampus of cats induced a lasting increase in defensive sensitivity to species-characteristic threats. This study examined interictally maintained changes in physiological properties of two limbic pathways which covaried with the behavioral changes. It was found that ADs which spread to the amygdala and ventromedial hypothalamus induced a lasting (30-60 days) increase in evoked transmission of excitatory activity from the amygdala to the ventromedial hypothalamus. This change is consistent with the role of the amygdalo-hypothalamic pathway in defensive behavior in the cat. Lasting increases in the EPSP component of the dentate field potential induced by perforant path stimulation were found, as well. Countering this increase in hippocampal excitability were long-lasting increases in recurrent inhibition. The increase in recurrent inhibition in the hippocampus was interpreted to mean that the ability of the hippocampus to transmit neural activity at high rates was lastingly impaired. This finding is also consistent with the proposed role of the ventral hippocampus in modulating predatory aggression and defense. It was concluded that interictally maintained changes in defensiveness were dependent on a form of lasting synaptic potentiation of excitatory activity from the amygdala to the ventromedial hypothalamus, and an equally lasting attenuation of function due to increased recurrent inhibition in the ventral hippocampus.

Aggression↗

PubMed2002

[From wild horse to riding horse].

Over 45 million years of evolution the horse developed to a highly specialized animal in anatomy, physiology and behavior. No other animal had influenced the economic and cultural history of men to such extent. Hunting prey since the ice age, domesticated 4000 B.C. and used for thousands of years as unique animal all over the world has attained a new role today as partner in sport, as companion animal and even as cotherapeutic. The well known behavioral demands in use and keeping are still often not fulfilled.

Animal Husbandry↗