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PubMed2000

Experimental evidence for innate predator recognition in the Seychelles warbler.

Nest predation is a major determinant of fitness in birds and costly nest defence behaviours have evolved in order to reduce nest predation. Some avian studies have suggested that predator recognition is innate whereas others have stressed the importance of learning. However, none of these studies controlled for the genetic origin of the populations investigated and the effect of unfamiliarity with the predator. Here we determined whether experience with a nest predator is a prerequisite for nest defence by comparing predator recognition responses between two isolated but genetically similar Seychelles warbler (Acrocephalus sechellensis) populations, only one of which had experience of the egg predating Seychelles fody (Foudia sechellarum). Individuals in the predator-free population significantly reduced nest guarding compared to individuals in the population with the predator, which indicates that this behaviour was adjusted to the presence of nest predators. However, recognition responses (measured as both alarm call and attack rates) towards a mounted model of the fody were equally strong in both populations and significantly higher than the responses towards either a mounted familiar non-predator and a mounted, novel, non-predator bird species. Responses did not differ with a warbler's age and experience with the egg predator, indicating that predator recognition is innate.

Animals↗

PubMed2001

Pyrazine odour makes visually conspicuous prey aversive.

Unpalatable insects frequently adopt multimodal signals to ward off predators, incorporating sounds and odours into their colourful displays. Pyrazine is an odour commonly used in insect warning displays, and has previously been shown to elicit unlearned biases against common warning colours, e.g. yellow and red in naive predators. We designed two experiments to test for similar effects of pyrazine on the conspicuousness of prey, perhaps the most ubiquitous aspect of aposematic coloration. In the first experiment, we offered predators (Gallus gallus domesticus) a choice between conspicuous crumbs and cryptic crumbs in the presence or absence of pyrazine. In the second experiment, we manipulated the birds' experience of conspicuous prey during an initial training phase. Only in the presence of pyrazine did birds show a bias against conspicuously coloured food, and this occurred whether or not they had previously experienced food that contrasted with the background. This emergent behaviour relied upon the visual and odorous signal components being presented together. These unlearned, yet hidden, responses against conspicuousness demonstrate that there are initial benefits to prey being conspicuous when the multimodal nature of warning signals is accounted for.

Animals↗

PubMed2001

Fat reserves and perceived predation risk in the great tit, Parus major.

The fat reserves of small birds are built up daily as insurance against starvation. They are believed to reflect a trade-off between the risks of starvation and predation such that in situations of high predation risk birds are expected either to reduce their fat reserves in response to mass-dependent predation risk or to increase them in response to foraging interruptions. We assessed the effect on fat reserves of experimentally altering the perceived (but not the actual) risk of predation of wild great tits at a winter feeding site. The perceived predation risk was alternated between 'safe' and 'risky'. Increasing the perceived risk of predation involved 'swooping' a model sparrowhawk over the feeder at four unpredictable times each day using a remote mechanism We produce evidence that the experiment was suceessfull in altering the perceived risk of predation. As predicted from the hypothesis of mass-dependent predation risk, great tits (Parus major) carried significantly reduced fat reserves during the 'risky' treatment. Furthermore, dominant individuals were able to reduce their reserves more than subordinates. As birds returned to feeders within seconds after a predator 'attack', the reduction in fat reserves cannot be attributed to an interruption in feeding.

Adipose Tissue↗

PubMed2002

The consequences of crowned eagle central-place foraging on predation risk in monkeys.

The African crowned eagle (Stepahnoaetus coronatus) is the primary predator for arboreal primates throughout sub-Saharan forests. Monkeys typically respond with alarm calls when they are aware of the presence of crowned eagles and such calls can be considered a corollary of predation risk within primate groups. Alarm calls from six species of monkeys were recorded across the home range of an eagle pair in Taï National Park, Côte d'Ivoire. Spatial and temporal variation in primate alarm calling was found to be related to eagle ranging behaviour according to the predictions of central-place foraging models. Radio-tracking data indicate that eagle activity is higher in the centre of their home range and monkey alarm-calling rates are correspondingly elevated near eagle nests as opposed to farther away. Alarm-calling rates are also temporally coupled with measures of eagle activity. There were considerable differences between the species in both rates and spatial patterns of alarm calling. The variation we measure in predation risk is expected to have consequences at the behavioural and population level.

Animals↗

PubMed2000

Parental care and clutch sizes in North and South American birds.

The evolutionary causes of small clutch sizes in tropical and Southern Hemisphere regions are poorly understood. Alexander Skutch proposed 50 years ago that higher nest predation in the south constrains the rate at which parent birds can deliver food to young and thereby constrains clutch size by limiting the number of young that parents can feed. This hypothesis for explaining differences in clutch size and parental behaviors between latitudes has remained untested. Here, a detailed study of bird species in Arizona and Argentina shows that Skutch's hypothesis explains clutch size variation within North and South America. However, neither Skutch's hypothesis nor two major alternatives explain differences between latitudes.

Animals↗

PubMed1993

Chemosensory orientation behavior in juvenile sea turtles.

It has been widely believed for several decades that hatchling sea turtles imprint to chemical cues characteristic of their natal beach and use this information as part of a repertoire of mechanisms enabling their return to the same beach for mating and nesting. This has proven very difficult to test. Although the imprinting theory is conceptually simple, functionally it is quite complex. This involves not only chemical imprinting of nestlings but growth and migration to habitats where the adults are found, long-term memory of their earlier chemical exposure, reproductive maturation, and homing. A few studies have been conducted to examine these elements of the imprinting theory. Experiments involving the exposure of embryos and hatchlings to chemicals suggest that juvenile turtles 'imprint' to the chemical environment of their nest. This can be termed chemical imprinting. Loggerhead turtles, Caretta caretta, and ridley turtles, Lepidochelys kempi, appear to be attracted to chemicals (morpholine and natural seawater, respectively) to which they were exposed as embryos. The strongest support for chemical imprinting is that six-month-old green turtles, Chelonia mydas, exposed to either morpholine or 2-phenylethanol in the nest and for a period of time after hatching, respond similarly to the chemical to which they were exposed as nestlings. Although chemical imprinting does not 'prove' the imprinting theory of turtle homing, it is a necessary component of the theory not previously examined.

Animals↗

PubMed2001

Paddlefish strike at artificial dipoles simulating the weak electric fields of planktonic prey.

The freshwater paddlefish Polyodon spathula (Polyodontidae) feeds primarily on the water flea (Daphnia sp.), and previous studies suggest that these fish detect their planktonic prey using their rostral electrosensory system. Zooplankton produce direct-current and oscillating alternating-current electric fields containing multiple frequencies and amplitudes. We asked whether an inanimate electric field is sufficient to elicit paddlefish strikes equivalent to their feeding behavior. Juvenile paddlefish respond to artificial dipole stimuli by investigating the electric field and striking at the dipole electrode tips. These behavioral responses, scored as strikes, exhibit a bandpass characteristic with a maximum response between 5 and 15 Hz. Responses were less frequent at higher (20, 30, 40, 50 Hz) and lower (0.1, 0.5, 1 Hz) test frequencies, with a steep drop-off below 5 Hz. Strike rates also varied with stimulus intensity. Response frequency was greatest at 0.25 microA peak-to-peak amplitude, with reduced responses at lower and higher amplitudes (0.125 and 1.25 microA). Striking behavior was also influenced by water conductivity: strike rate was reduced at higher water conductivity. Dipole-elicited strikes exhibit behavioral plasticity. Fish habituate to repetitive dipole stimuli that are not reinforced by prey capture, and they dishabituate after food reinforcement. These experiments characterize paddlefish feeding strikes towards dipole electrodes at signal frequencies and intensities simulating the electric fields of zooplankton, their natural prey, and demonstrate that electric fields are sufficient to elicit feeding behavior. The results support the conclusion that paddlefish use their passive electrosensory system for planktivorous feeding.

Animals↗

PubMed1984

Effects of search cost on foraging and feeding: a three-component chain analysis.

An experiment determined whether pigeons minimize number of key pecks per food delivery and maintain their baseline intake of food while key pecking on a three-component chain schedule. Pigeons at either 80% or 100% body weight obtained all their food during baseline and contingency sessions. During baseline sessions, pecks on the left and center keys had no consequences; each peck on the right key activated the feeder. During contingency sessions, pigeons key pecked on a three-component chain schedule simulating components of a foraging chain. In the search component either 3, 9 or 15 key pecks (varied parametrically across blocks of sessions) on the left key produced a stimulus on the middle key, indicating an encounter with either the low-cost prey (3 key pecks) or an equally probable high-cost prey (21 key pecks). In the procurement component the pigeon pecked either: (a) the left key once, thus returning to the search component, or (b) the middle key either 3 or 21 times, which activated the right response key. In the handling component one peck on the right key operated the feeder. The pigeons always procured the low-cost prey and minimized the number of key pecks per hopper by procuring the high-cost prey when the search-cost ratio was high (15 key pecks) but not when it was low (3 key pecks). All pigeons maintained their baselines of eating during contingency sessions by key pecking more frequently and eating more efficiently. The 80% body-weight birds produced higher overall rates of key pecking and eating. These results have implications for ecological theories of optimal foraging and for psychological theories of learned performance.

Animals↗

PubMed1975

Ethological studies in the ant Tetramorium caespitum Mayr. II. Interspecific relationships.

The structure of relationships between the neighboring species of ants is characterized by great variability. What happens when particular individuals meet - depends upon considerable differences between individual behaviors of ants and a number of variable factors determining the actual emotional state of the workers. From these factors, it is the general structure of forces between the nests that changes slowest, and may be responsible for reaching temporary stabilization of the interspecific relationships. Invariable hierarchical structure between the species occurs very rarely: when there is an enormous supremacy of one of the species.

Animals↗

PubMed1979

The effect of luminance upon the distribution and behavior of the Eleotrid fish Gobiomorus dormitor, and its prey.

Gobiomorus dormitor success in capturing prey, cichlids, poeciliids and atherinids, is correlated with low luminance. Both prey and predator populations inhabiting rocky areas in Lake Jiloa, Nicaragua shift to deeper water during the dry season when luminance is greater. Predator and prey populations are also deeper over bright sandy areas than over rocks. Predators, during the middle of the day, attack prey significantly less in water above 3 m than in water between 3-12 m, but there is a significant increase in the number of attacks occurring above 3 m at twilight. The predator becomes more active, and the prey disappear into holes at twilight. These data suggest that conclusions concerning the importance of light in structuring the community and behavior of marine fishes can be generalized to tropical freshwater systems.

Animals↗

PubMedDate not supplied

[The neuronal correlates of the serotonin-dependent behavior of the pteropod mollusk Clione limacina].

Predatory behaviour of the carnivorous marine pteropod mollusk Clione limacina is normally induced by contact with prey. In the absence of prey, a similar behaviour can be induced by injection of serotonin (5-HT) or its precursor, L-5-hydroxytroptophan (5-HTP). It consists of non-stop fast swimming, rapid extrusions of cephaloconi and other components of the actual prey capturing. Neuronal correlates of this phenomenon were investigated using histofluorescence and intracellular recordings. Prior to treatment with 5-HTP only green fluorescence of catecholamines has been revealed. In the CNS and periphery of 5-HTP-injected hunting animals yellow fluorescence of 5-HT is present as well. In isolated pedal ganglia 5-HTP induces characteristic changes in the activity of the swim generator neurones. An initial intermittent fictitious swimming of these neurones has been changed to sustained swimming of a higher frequency and enhanced spiking per cycle. Changes in activity of 5-HT-producing pedal neurones are also described.

5-Hydroxytryptophan↗

PubMedDate not supplied

Neurotransmitters regulating feline aggressive behavior.

The experiments described in this review reveal that the expression and modulation of aggressive responses in the cat are organized by two distinct sets of pathways. One set of pathways is associated with the elicitation of a specific form of attack behavior. It includes the medial hypothalamus and its projections to the PAG for the expression of defensive rage behavior and the lateral hypothalamus and its descending projections for the expression of predatory attack behavior. The primary focus of the present review is upon the analysis of defensive rage behavior. It was demonstrated that the pathway from the medial hypothalamus to the PAG, which appears to be essential for elicitation of defensive rage, is powerfully excitatory and utilizes excitatory amino acids that act upon NMDA receptors within the PAG. The other pathways examined in this review arise from different nuclei of the amygdala and are modulatory in nature. Here, two facilitatory systems have been identified. The first involves a projection system from the basal complex of amygdala that projects directly to the PAG. Its excitatory effects are manifest through excitatory amino acids that act upon NMDA receptors within the PAG. The second facilitatory pathway arises from the medial nucleus of the amygdala. However, its projection system is directed to the medial hypothalamus rather than the PAG. Its neurotransmitter appears to be substance P that acts upon NK1 receptors within the medial hypothalamus (see Figure 10). It has yet to be determined whether substance P acts upon any of the other neurokinin receptor subtypes. It should also be pointed out that the substance P pathway from the medial amygdala to the medial hypothalamus functions to suppress predatory attack behavior elicited from the lateral hypothalamus. In this network, it is likely that the modulatory effects of the medial amygdala require the presence of a second, inhibitory pathway from the medial hypothalamus that innervates the lateral hypothalamus. At the present time, the neurochemical nature of this second pathway remains unknown, although it is suggested that such neurons may be GABAergic. One major inhibitory pathway was also identified. It arises principally from the central nucleus of the amygdala and projects to the PAG. Its powerful suppressive effects upon PAG elicited defensive rage behavior are mediated through opioid peptides that act upon mu receptors within the PAG. While the present series of studies have begun to define the structural and functional nature of the neural systems that regulate aggressive behavior, our understanding of the overall mechanisms regulating different forms of aggressive behavior remains incomplete.(ABSTRACT TRUNCATED AT 400 WORDS)

Aggression↗

PubMed1993

Evidence that substance P is utilized in medial amygdaloid facilitation of defensive rage behavior in the cat.

The present study was designed to test the hypothesis that a major excitatory mechanism for the expression of feline defensive rage behavior involves the medial nucleus of the amygdala which utilizes substance P as a neurotransmitter in a direct output pathway that supplies the medial hypothalamus. In phase I of the experiment, stimulating electrodes were implanted into the medial amygdala and cannula electrodes were implanted into the medial and lateral hypothalamus from which defensive rage and predatory attack behavior could be elicited by electrical stimulation, respectively. Response latencies for defensive rage were significantly lowered after dual stimulation of the medial amygdala and medial hypothalamus relative to single stimulation of the medial hypothalamus alone. In phase II, dose- and time-dependent decreases in medial amygdaloid-induced facilitation of defensive rage were observed after the i.p. administration of the NK1 antagonist, CP-96,345 (0.05, 2 and 4 mg/kg). In phase III of the study, the effects of microinjections of CP-96,345 placed directly into defensive rage sites within the medial hypothalamus (0.05, 0.5 and 2.5 nmol) upon medial amygdaloid modulation of this response were assessed. Again, intracerebral administration of this antagonist blocked the facilitatory effects of medial amygdaloid-induced facilitation of defensive rage in a manner parallel to that observed with peripheral administration of the NK1 antagonist. The results suggest that the medial amygdala facilitates defensive rage by acting through a substance P mechanism at the level of the medial hypothalamus. Other experiments revealed that peripheral administration of the NK1 antagonist: (1) had little upon the latency or threshold for elicitation of defensive rage, suggesting that the medial amygdaloid-substance P facilitatory mechanism acts in a phasic rather than tonic manner; and (2) also blocks the suppressive effects of medial amygdaloid stimulation upon predatory attack behavior elicited from the lateral hypothalamus. The latter finding suggest that similar neurochemical mechanisms regulate medial amygdaloid modulation of both forms of hypothalamically elicited aggression. The final aspect of this study utilized the combination of retrograde-tracing of amygdaloid neurons into the medial hypothalamus after microinjections of Fluoro-Gold into defensive rage sites, and the immunocytochemical analysis of substance P neurons within the amygdala. The data indicated that large numbers of retrogradely and immunocytochemically positive labeled cells were identified in the medial nucleus, including many that were double-labeled.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗

PubMed1993

Genetic analysis of different kinds of aggressive behavior.

Various kinds of aggressive behavior such as spontaneous intermale aggression, predatory aggression (locust-killing behavior), and irritable (shock-induced) aggression were investigated in inbred strains of mice. Genotype was shown to affect significantly the phenotypic variety of these kinds of aggression. There were, however, no interstrain correlations either between intermale aggression and predatory behavior or between intensity of intermale, shock-induced aggression and locust-killing behavior. Moreover, the intermale aggression level (percentage of fighting mice in each strain) did not correlate with the intensity of fighting. It has been shown by Mendelian analysis on C57BL/6J and BALB/c strains that these indices of intermale aggression are under different genetic control. The selection of Norway rats over 20 generations for reduced fear-induced aggressiveness toward man resulted in a decrease in irritable aggression and loss of an aggressive response to man. No changes in intermale and predatory aggression, however, were found. Hence, different kinds of aggressive behavior--intermale, predatory, and fear-induced aggression--seem to be controlled by different genetic mechanisms.

Aggression↗

PubMed2000

Neuroplasticity in specific limbic system circuits may mediate specific kindling induced changes in animal affect-implications for understanding anxiety associated with epilepsy.

In two complementary experiments, we studied the effects of low frequency stimulation (LFS) of the amygdala on behavioral effects of kindling in rats and cats. These studies tested the hypothesis that kindling induced long term potentiation (KLTP) in amygdala circuits underlies interictal behavioral change. Since LFS can depotentiate LTP, it was predicted that LFS should both depotentiate KLTP and reverse behavioral effects of kindling. In cats, the effects of LFS on KLTP of amygdala efferents was studied, and related to behavioral effects. Partial ventral hippocampal kindling in cats and right amygdala kindling in rodents lastingly increased defensive response to rats in cats, and anxiety-like behavior (ALB) in the elevated plus-maze in rats. In addition, partial kindling reduced predatory attack behavior in cats independent of its effects on defensive response. Partial kindling also induced KLTP of amygdala efferent transmission to ventromedial hypothalamus (VMH) and periaqueductal gray (PAG) in left and right hemispheres. Depotentiation of amygdala efferent KLTP by bilateral amygdala LFS selectively reduced KLTP in right amygdala efferents. At the same time, defensive behavior, but not attack behavior, was returned to levels seen prior to partial kindling. Defensiveness returned to post kindling levels between 44 and 76days after LFS. At the same time, LTP was restored in the right Amygdalo-PAG pathway only. These findings suggest that lasting change in affect produced by kindling depends on LTP of right amygdala efferent transmission to PAG, replicating studies of the effects of FG-7142 on brain and behavior in the cat. The findings suggest further that the spectrum of behavioral changes produced by partial kindling are dependent on changes in a variety of neural circuits, and that amygdala efferent transmission changes are responsible for changes in defensive behavior, but not attack behavior. Effects of LFS were not due to damage, as thresholds to evoke amygdala efferent response were unchanged. Other data suggest KLTP and depotentiation in right Amygdalo-PAG may reflect changes in glutamate receptor density/synapse number. Kindling effects on rat ALB persisted for at least 1month. Bilateral but not unilateral amygdala LFS reversed the effects of kindling on risk assessment in the plus maze for at least 3weeks. Bilateral LFS also reversed the effects of kindling on open arm exploration, but effects were shorter lived, appearing at 1day but not 3weeks after kindling and LFS. These findings are consistent with other studies which suggest that amygdala neuroplasticity in separable amygdala circuits mediates lasting changes in open arm avoidance and risk assessment. Taken together, the findings of both studies support the hypothesis that a form of LTP of specific amygdala circuits underlies lasting changes in affect produced by limbic kindling. Clinical implications of these findings are discussed.

Aggression↗

PubMed1991

Enkephalinergic involvement in periaqueductal gray control of hypothalamically elicited predatory attack in the cat.

The effects of central infusion of naloxone into the midbrain periaqueductal gray (PAG) upon predatory attack behavior in the cat were studied in 12 cats. Initially, quiet biting attack was elicited by electrical stimulation of sites within the lateral hypothalamus using monopolar electrodes. Then cannula-electrodes were implanted into sites within the PAG from which electrical stimulation facilitated or suppressed the attack response. Following identification of modulatory sites within the PAG, naloxone (1.0 micrograms/0.5 microliter) was microinjected into those sites and the effects upon hypothalamically elicited attack were assessed. At nine of twelve sites in the PAG where suppression was obtained, administration of naloxone served to block those effects. Similarly, at six of eight facilitatory sites within the PAG, naloxone also blocked the modulatory effects of PAG stimulation. However, vehicle (isotonic saline) alone did not alter the modulatory effects of PAG stimulation. Administration of DAME (250 ng/0.3 microliter) into PAG modulatory sites in four cats, two which facilitated and two that suppressed the attack response, reversed the effects of naloxone at these sites. These results demonstrate that opioid peptides within the PAG play a complex role in the expression of predatory attack behavior in the cat.

Aggression↗

PubMed1998

Cholecystokinin B receptors in the periaqueductal gray potentiate defensive rage behavior elicited from the medial hypothalamus of the cat.

Defensive rage behavior is mediated over a descending pathway from the medial hypothalamus to the dorsolateral midbrain periaqueductal gray (PAG) where further integration of this response takes place. The present study sought to determine the roles of CCK-A and CCK-B receptor activation in the PAG in modulating defensive rage behavior. The 'hissing' component of the defensive rage response was used throughout the experiment as the measure of defensive rage behavior. The basic design of the experiment involved placement of monopolar electrodes into the medial hypothalamus from which defensive rage could be elicited and cannula electrodes into the dorsal PAG for purposes of identifying defensive rage sites in this region and for microinjections of CCK compounds into these sites at a later time. Microinjections of the selective CCK-B receptor antagonist, LY288513 (1.05, 4.2, 17.0 nmol/0.25 microliter), into the PAG suppressed the hissing response in a dose- and time-dependent manner. Microinjections of the CCK-B agonist, pentagastrin, (0.5 and 1.0 nmol/0.25 microliter) facilitated the occurrence of defensive rage behavior. Moreover, administration of LY288513 (17 nmol/0.25 microliter) 55 min prior to pentagastrin (1.0 nmol/0.25 microliter) delivery blocked the facilitatory effects of pentagastrin. Administration of the CCK-A antagonist, PD140548 (34 nmol/0.25 microliter), into the PAG failed to alter response latencies for defensive rage behavior. In contrast, microinjections of the CCK-B antagonist, LY288513 (4.2, 17.0 nmol/0.25 microliter), facilitated the occurrence of predatory attack behavior elicited from the lateral hypothalamus. This finding demonstrates the specificity of the effects of CCK-B receptor blockade upon hissing. A combination of immunocytochemical and retrograde tracing procedures using microinjections of Fluoro-Gold (8%, 6 microliters) into the PAG were employed to identify the possible loci of CCK neurons that project to the PAG. The data revealed that neurons labeled for both CCK and Fluoro-Gold were located in the dorsolateral aspect of the midbrain tegmentum, identifying this region as a source of CCK inputs to the PAG. Overall, the findings demonstrate that CCK-B receptors in the PAG potentiate defensive rage behavior and likely suppress predatory attack.

Animals↗

PubMed1985

The control exerted by the substantia nigra on the quiet biting attack elicited by hypothalamic stimulation in the cat.

The effects of substantia nigra (SN) (pars compacta) stimulation on the quiet biting attack evoked by hypothalamic activation in the cat were studied. The measure of the aggressive behavior was the latency of the biting which did not greatly change from one animal to another when hypothalamic stimulation was performed with the same parameters. Concurrent activation of the SN determined an inhibitory effect on the studied behavior in the form of an increase in the biting latency or loss of the attack pattern. The inhibitory role of the SN on predatory attack behavior is discussed.

Aggression↗