SEARCH · PubMed Health

Results for “Predatory Behavior”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources

PubMed2002

Potential for the use of elicitors of plant resistance in arthropod management programs.

Plants protect themselves from arthropod herbivores both directly, by expressing biochemical and morphological traits that interfere with herbivore development or behavior, and indirectly, by facilitating the action of natural enemies of herbivores. These direct and indirect resistance mechanisms are not always expressed at maximal levels by plants, but rather can be induced to higher levels by a variety of stimuli, most notably prior herbivory. The recent discovery of chemical elicitors of induced responses has led to interest in manipulating the inducible responses of plants for crop protection. Applications of elicitors of induced responses made at appropriate times during the growing season of a crop have the potential of activating both direct and indirect mechanisms of plant resistance and thereby simultaneously augmenting host-plant resistance and biological control. This strategy may serve as an important component of a multifaceted, ecologically-based pest management program and is unlikely to precipitate the rapid evolution of countermeasures by target pests. However, this strategy will not be appropriate in all crops or against all arthropod pests. The conditions under which the use of an elicitor is likely to be successful are discussed, and examples of the successful use of elicitors are reviewed.

Agriculture↗

PubMed1998

Head-related transfer functions of the barn owl: measurement and neural responses.

Sounds arriving at the eardrum are filtered by the external ear and associated structures in a frequency and direction specific manner. When convolved with the appropriate filters and presented to human listeners through headphones, broadband noises can be precisely localized to the corresponding position outside of the head (reviewed in Blauert, 1997). Such a 'virtual auditory space' can be a potentially powerful tool for neurophysiological and behavioral work in other species as well. We are developing a virtual auditory space for the barn owl, Tyto alba, a highly successful auditory predator that has become a well-established model for hearing research. We recorded catalogues of head-related transfer functions (HRTFs) from the frontal hemisphere of 12 barn owls and compared virtual and free sound fields acoustically and by their evoked neuronal responses. The inner ca. 1 cm of the ear canal was found to contribute little to the directionality of the HRTFs. HRTFs were recorded by inserting probetube microphones to within about 1 or 2 mm of the eardrum. We recorded HRTFs at frequencies between 2 and 11 kHz, which includes the frequencies most useful to the owl for sound localization (3-9 kHz; Konishi, 1973). Spectra of virtual sounds were within +/- 1 dB of amplitude and +/- 10 degrees of phase of the spectra of free field sounds measured near to the eardrum. The spatial pattern of responses obtained from neurons in the inferior colliculus were almost indistinguishable in response to virtual and to free field stimulation.

Acoustic Stimulation↗

PubMed2006

The impact of exploiting grazers (Scaridae) on the dynamics of Caribbean coral reefs.

Coral reefs provide a number of ecosystem services including coastal defense from storms, the generation of building materials, and fisheries. It is increasingly clear that the management of reef resources requires an ecosystem approach in which extractive activities are weighed against the needs of the ecosystem and its functions rather than solely those of the fishery. Here, I use a spatially explicit simulation model of a Caribbean coral reef to examine the ecosystem requirements for grazing which is primarily conducted by parrotfishes (Scaridae). The model allows the impact of fishing grazers to be assessed in the wider context of other ecosystem processes including coral-algal competition, hurricanes, and mass extinction of the herbivorous urchin Diadema antillarum. Using a new analytical model of scarid grazing, it is estimated that parrotfishes can only maintain between 10% and 30% of a structurally complex forereef in a grazed state. Predictions from this grazing model were then incorporated into a broader simulation model of the ecosystem. Simulations predict that scarid grazing is unable to maintain high levels of coral cover (> or = 30%) when severe hurricanes occur on a decadal basis, such as occurs in parts of the northern Caribbean. However, reefs can withstand such intense disturbance when grazing is undertaken by both scarids and the urchin Diadema. Scarid grazing is predicted to allow recovery from hurricanes when their incidence falls to 20 years or less (e.g., most of Central and South America). Sensitivity analyses revealed that scarid grazing had the most acute impact on model behavior, and depletion led to the emergence of a stable, algal-dominated community state. Under conditions of heavy grazer depletion, coral cover was predicted to decline rapidly from an initial level of 30% to less than 1% within 40 years, even when hurricane frequency was low at 60 years. Depleted grazers caused a population bottleneck in juvenile corals in which algal overgrowth caused elevated levels of postsettlement mortality and resulted in a bimodal distribution of coral sizes. Several new hypotheses were generated including a region-wide change in the spatial heterogeneity of coral reefs following extinction of Diadema. The management of parrotfishes on Caribbean reefs is usually approached implicitly through no-take marine reserves. The model predicts that depletion of grazers in nonreserve areas can severely limit coral accretion. Other studies have shown that low coral accretion can reduce the structural complexity and therefore quality of the reef habitat for many organisms. A speculative yet rational inference from the model is that failure to manage scarid populations outside reserves will have a profoundly negative impact on the functioning of the reserve system and status of non-reserve reefs.

Animals↗

PubMed2001

Brief exposure to female odors "emboldens" male mice by reducing predator-induced behavioral and hormonal responses.

In rodents, where chemical signals play a particularly important role in determining intersexual interactions, various studies have shown that male behavior and physiology is sensitive to female odor cues. Here we examined the effects of brief (1 min) and more prolonged (60 min) preexposure to the odors of a novel estrous female on the behavioral and hormonal responses of sexually experienced and inexperienced male mice, Mus musculus, to subsequent predator (cat and weasel) odor exposure and potential predator risk. Brief, but not prolonged, preexposure to the odors of an estrous female decreased the aversion and avoidance responses of male mice to cat odor in a Y-maze preference test, with the extent of responses being affected by a males prior sexual experience. Similarly, brief, but not prolonged, preexposure to female odors markedly attenuated the analgesic responses elicited in male mice by weasel odor. Brief exposure to a novel estrous female by itself had no significant immediate effects on either corticosterone or testosterone levels in the males. However, brief, but not prolonged, preexposure to the odors of an estrous female attenuated the marked increase in corticosterone and decrease in testosterone that were induced in males by exposure to weasel odor. The decreases in aversive responses to, and effects of, predator odor exposure that are induced by brief exposure to a novel estrous female may reflect a greater risk taking and boldness in males that could directly facilitate access to an immediately, and possibly transiently, available novel sexually receptive female.

Animals↗

PubMed2003

Venom variation and chemoreception of the viperid Agkistrodon contortrix: evidence for adaptation?

Previous studies of chemoreceptive behavior in vipers suggest that snakes focus on the scent of envenomated tissue to track their prey following envenomation. Other studies have indicated a correlation between qualitative differences in venom biochemistry and geographic variation in diet. The North American copperhead (Agkistrodon contortrix) varies geographically in diet and venom biochemistry; snakes were collected from three populations (Kansas, Texas, and Louisiana) that are known to have different prey preferences. Behavioral experiments were conducted to assess whether copperheads preferred envenomated prey more than nonenvenomated prey, as do other species of vipers studied thus far. Additional experiments tested the ability of copperheads to distinguish between envenomated prey from different geographic populations, and between geographic populations of copperheads and two other species of viper. Results indicated that copperheads prefer envenomated prey to nonenvenomated prey. In envenomated-prey discrimination experiments, copperheads distinguished between envenomated prey from different geographic populations, and some snakes distinguished envenomated prey of A. contortrix from those of A. piscivorns and Sistrurus catenatus. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to study the variation of venom biochemistry in this species and two other taxa (A. piscivorus and S. catenatus), and confirmed intraspecific and interspecific variation of venom proteins. Relative potency of the venom from different populations as indicated by time to immobilization experiments was in the order: Louisiana > Texas > Kansas. The relative potency of the venom from each population matched the order of preference in the chemoreception experiments. These results suggest that chemoreception is sensitive to subtle differences in venom biochemistry and may reflect adaptation to improve efficiency of finding envenomated prey.

Agkistrodon↗

PubMed2006

Wind generated by an attacking bat: anemometric measurements and detection by the praying mantis cercal system.

The wind-sensitive cercal system, well-known for mediating terrestrial escape responses, may also mediate insect aerial bat-avoidance responses triggered by wind generated by the approaching bat. One crucial question is whether enough time exists between detection and capture for the insect to perform a successful evasive maneuver. A previous study estimated this time to be 16 ms, based on cockroach behavioral latencies and a prediction for the detection time derived from a simulated predator moving toward a simulated prey. However, the detection time may be underestimated since both the simulated predator and prey lacked certain characteristics present in the natural situation. In the present study, actual detection times are measured by recording from wind-sensitive interneurons of a tethered praying mantis that serves as the target for a flying, attacking bat. Furthermore, using hot-wire anemometry, we describe and quantify the wind generated by an attacking bat. Anemometer measurements revealed that the velocity of the bat-generated wind consistently peaks early with a high acceleration component (an important parameter for triggering wind-mediated terrestrial responses). The physiological recordings determined that the mantis cercal system detected an approaching bat 74 ms before contact, which would provide the insect with 36 ms to perform a maneuver before capture. This should be sufficient time for the mantis to respond. Although it probably would not have time for a full response that completely evades the bat, even a partial response might alter the mantid's trajectory enough to cause the bat to mishandle the insect, allowing it to escape.

Air Movements↗

PubMed2005

Putting prey back together again: integrating predator-induced behavior, morphology, and life history.

The last decade has seen an explosion in the number of studies exploring predator-induced plasticity. Recently, there has been a call for more comprehensive approaches that can identify functional relationships between traits, constraints on phenotypic responses, and the cost and benefits of alternative phenotypes. In this study, we exposed Helisoma trivolvis, a freshwater snail, to a factorial combination of three resource levels and five predator environments (no predator, one or two water bugs, and one or two crayfish) and examined ten traits including behavior, morphology, and life history. Each predator induced a unique suite of behavioral and morphological responses. Snails increased near-surface habitat use with crayfish but not with water bugs. Further, crayfish induced narrow and high shells whereas water bugs induced wide shells and wide apertures. In terms of life history, both predators induced delayed reproduction and greater mass at reproduction. However, crayfish induced a greater delay in reproduction that resulted in reduced fecundity whereas water bugs did not induce differences in fecundity. Resource levels impacted the morphology of H. trivolvis; snails reared with greater resource levels produced higher shells, narrower shells, and wider apertures. Resource levels also impacted snail life history; lower resources caused longer times to reproduction and reduced fecundity. Based on an analysis of phenotypic correlations, the morphological responses to each predator most likely represent phenotypic trade-offs. Snails could either produce invasion-resistant shells for defense against water bugs or crush-resistant shells for defense against crayfish, but not both. Our use of a comprehensive approach to examine the responses of H. trivolvis has provided important information regarding the complexity of phenotypic responses to different environments, the patterns of phenotypic integration across environments, and the potential costs and benefits associated with plastic traits.

Analysis of Variance↗

PubMed2004

Is prey predation risk influenced more by increasing predator density or predator species richness in stream enclosures?

The direct lethal impacts and the indirect effects predators have on prey characteristics, such as behavior, have fitness consequences for the prey. Whether the level of predation risk that prey face in the presence of multiple predator species can be predicted from a null model that sums the risk from each predator species in isolation is unclear. In field enclosures, we tested whether the predation risk experienced by Stenonema mayfly larvae from a dragonfly larva ( Boyeria vinosa) and a hellgrammite ( Corydalus cornutus) together matched the predictions of the multiplicative risk model. We then compared whether any deviations from the model's predictions were larger in the presence of two predator species than in the presence of an equivalent density of individuals from either predator species alone, to determine if unique effects arise for the prey in the presence of multiple predator species. We also determined if prey moved preferentially into predator-free refuge spaces or decreased their movement in the presence of predators. Stenonema's risk of predation was reduced compared to the model's prediction, but no unique multiple predator species effects were present because this risk reduction was comparable in magnitude to the level exhibited in the presence of each predator species alone. The prey did not move into predator-free refuge spaces in the presence of predators in the field enclosures. Thus, these predators appear to interfere interspecifically and intraspecifically, which may facilitate the coexistence of the predators and the prey.

Animals↗

PubMed2006

Prey risk allocation in a grazing ecosystem.

Understanding the behaviorally mediated indirect effects of predators in ecosystems requires knowledge of predator-prey behavioral interactions. In predator-ungulate-plant systems, empirical research quantifying how predators affect ungulate group sizes and distribution, in the context of other influential variables, is particularly needed. The risk allocation hypothesis proposes that prey behavioral responses to predation risk depend on background frequencies of exposure to risk, and it can be used to make predictions about predator-ungulate-plant interactions. We determined non-predation variables that affect elk (Cervus elaphus) group sizes and distribution on a winter range in the Greater Yellowstone Ecosystem (GYE) using logistic and log-linear regression on surveys of 513 1-km2 areas conducted over two years. Employing model selection techniques, we evaluated risk allocation and other a priori hypotheses of elk group size and distributional responses to wolf (Canis lupus) predation risk while accounting for influential non-wolf-predation variables. We found little evidence that wolves affect elk group sizes, which were strongly influenced by habitat type and hunting by humans. Following predictions from the risk allocation hypothesis, wolves likely created a more dynamic elk distribution in areas that they frequently hunted, as elk tended to move following wolf encounters in those areas. This response should dilute elk foraging pressure on plant communities in areas where they are frequently hunted by wolves. We predict that this should decrease the spatial heterogeneity of elk impacts on grasslands in areas that wolves frequently hunt. We also predict that this should decrease browsing pressure on heavily browsed woody plant stands in certain areas, which is supported by recent research in the GYE.

Animals↗

PubMed2003

Rheotaxis and prey detection in uniform currents by Lake Michigan mottled sculpin (Cottus bairdi).

Lake Michigan mottled sculpin, Cottus bairdi, exhibit a lateral-line mediated, unconditioned orienting response, which is part of the overall prey capture behavior of this species and can be triggered in visually deprived animals by both live (e.g. Daphnia magna) and artificial (e.g. chemically inert vibrating sphere) prey. However, the extent to which background water motions (e.g. currents) might mask the detection of biologically significant stimuli like these is almost entirely unknown, despite the fundamental nature and importance of this question. To examine this question, the orienting response of mottled sculpin was used to measure threshold sensitivity to a nearby artificial prey (a 50 Hz vibrating sphere) as a function of background noise level (unidirectional currents of different flow velocities). Because many fish show unconditioned rheotaxis to uniform currents, we also measured the fish's angular heading relative to the oncoming flow in the absence of the signal. Frequency distributions of fish headings revealed positive rheotaxis to flows as low as 4 cm s(-1) and an increasing degree of alignment with the oncoming flow as a function of increasing flow velocity. Sculpin positioned in the upstream direction were able to detect relatively weak signals (estimated to be approx. 0.001-0.0001 peak-peak cm s(-1) at the location of the fish) in the presence of strong background flows (2-8 cm s(-1)), and signal levels at threshold increased by less than twofold for a fourfold increase in flow velocity. These results are consistent with the idea that lateral line canals behave as high-pass filters to effectively reject low frequency noises such as those caused by slow d.c. currents.

Animals↗

PubMed2002

Contact with maternal parent and siblings affects hunting behavior, learning, and central nervous system development in spiderlings of Hogna carolinensis (Araeneae: Lycosidae).

The purpose of this study was to determine the effects of early experience (rearing conditions) on the central nervous system (CNS) and behavior of spiderlings of Hogna carolinensis (Lycosidae). We were interested in whether or not spiderlings that were allowed to remain in contact with their maternal parent and siblings (enriched condition, EC) would exhibit differences in CNS development or subsequent behavior when compared with those reared in isolation (improverished condition, IC). Spiderlings emerged from their egg sacs and climbed onto the dorsal surface of their mother's abdomen where they remained until their yolk supply was depleted (5 days). They dispersed on day 6 after emergence. We compared the ability of 16-day-old EC and IC spiderlings to capture prey in a linear runway and to learn a complex maze (spatial learning). We also compared certain aspects of CNS development (brain weight, total number of brain cells, volume of central body and protocerebral neuropil) in EC and IC spiderlings. Results indicated that EC subjects are more efficient at capturing moving prey (crickets) and exhibited improved performance (significantly fewer blind alley errors) in the maze. The volume of the protocerebral neuropil in 6-day-old EC animals increased 30% over a 5-day period after emergence as compared to IC animals of the same age. The volume of the central body of EC animals increased 34.8% over the same time period. On day 6 after emergence, the weight of the protocerebrum was significantly greater in EC versus IC subjects. There were no significant effects of rearing condition (EC vs IC) or age (1- and 6-day-old spiderlings) on the total number of nerve cells in the protocerebrum, suggesting that the difference in protocerebral weight was due primarily to differences in supporting glial tissues and neuropil matrix. In conclusion, the data suggest that early contact with the maternal parent and siblings is of vital importance to CNS development in lycosid spiderlings and can influence the capacity for spatial learning as well as the ability to capture prey.

Animals↗

PubMed1997

Harvesting in discrete-time predator-prey systems.

Fisheries for assemblages of interacting species with seasonal recruitment occur throughout temperate and boreal regions of the world ocean. Such systems are conveniently modeled within a difference-equation framework. Here, we examine the dynamic behavior of discrete-time models for an exploited predator-prey system. We contrast the dynamic properties of an aggregate production model and an age-structured model in which recruitment and mortality are explicitly considered. The joint effects of harvesting and interspecific interactions on the stability of the system are defined and contrasted with results for single species systems. We demonstrate that harvesting is a potentially stabilizing factor in the production model and in an age-structured model in which juveniles are harvested and that the relative magnitude of the interaction between predator and prey strongly affects the exploitation levels at which stabilization occurs. In contrast, harvesting is potentially destabilizing (i.e., results in complex dynamics) in an age-structured model with harvesting of adults only; again, the magnitude of the interaction determines the stability boundaries, with stronger interactions leading to a broader range of stable parameter space. In both the aggregate production model and the age-structured model with harvesting of juvenile predator and prey, exploitation effectively reduces the intrinsic rate of increase of the populations; for prey, this effect is amplified by high predation mortality rates. Sustainable levels of exploitation for both predators and prey are lower for the case where juveniles are harvested. Predators and resource harvesters can be viewed as competitors for the prey, and sustainable harvest levels are directly affected by the magnitude of predation mortality. These considerations expand the scope of issues to be resolved in fishery management to include factors such as trade-offs between mean yield and the potential for intrinsic variability and the role of predator-prey interactions in shaping the dynamics of exploited systems.

Age Factors↗

PubMed2000

Light-limitation on predator-prey interactions: consequences for metabolism and locomotion of deep-sea cephalopods.

The present study attempts to correlate the metabolism and locomotory behavior of 25 species of midwater Cephalopoda from California and Hawaii with the maximal activities of key metabolic enzymes in various locomotory muscle tissues. Citrate synthase (CS) and octopine dehydrogenase (ODH) activities were used as indicators of aerobic and anaerobic metabolic potential respectively. CS activity in mantle muscle is highly correlated with whole-animal rates of oxygen consumption, whereas ODH activity in mantle muscle is significantly correlated with a species' ability to buffer the acidic end-products of anaerobic metabolism. Both CS and ODH activities in mantle muscle declined strongly with a species' habitat depth. For example, CS and ODH activities ranged respectively from 0.04 units g(-1) and 0.03 units g(-1) in the deep-living squid Joubiniteuthis portieri, to 8.13 units g(-1) and 420 units g(-1) in the epipelagic squid Sthenoteuthis oualaniensis. The relationships between enzymatic activities and depth are consistent with similar patterns observed for whole-animal oxygen consumption. This pattern is believed to result from a relaxation, among deep-living species, in the need for strong locomotory abilities for visual predator/prey interactions; the relaxation is due to light-limitation in the deep sea. Intraspecific scaling patterns for ODH activities may, for species that migrate ontogenetically to great depths, reflect the counteracting effects of body size and light on predator-prey detection distances. When scaled allometrically, enzymatic activities for the giant squid, Architeuthis sp., suggest a fairly active aerobic metabolism but little burst swimming capacity. Interspecific differences in the relative distributions of enzymatic activities in fin, mantle, and arm tissue suggest an increased reliance on fin and arm muscle for locomotion among deep-living species. We suggest that, where high-speed locomotion is not required, more efficient means of locomotion, such as fin swimming or medusoid arm propulsion, are more prevalent.

Amino Acid Oxidoreductases↗

PubMed1998

Kinematics of aquatic and terrestrial prey capture in Terrapene carolina, with implications for the evolution of feeding in cryptodire turtles.

Studies of aquatic prey capture in vertebrates have demonstrated remarkable convergence in kinematics between diverse vertebrate taxa. When feeding in water, most vertebrates employ large-amplitude hyoid depression to expand the oral cavity and suck in water along with the prey. In contrast, vertebrates feeding on land exhibit little or no hyoid depression. In this study we compared the kinematics of terrestrial and aquatic prey capture within one species of turtle, Terrapene carolina, in order to determine whether an individual species can modulate the magnitude of hyoid depression between air and water. High-speed video (250 frames per second) showed that hyoid depression was over three times greater in aquatic than in terrestrial feedings, indicating that T. carolina is able to modulate hyoid depression magnitude depending on the medium in which feeding occurs. In addition, we observed medium-dependent modulation of hyoid depression in another turtle, Heosemys grandis, and large-amplitude hyoid depression during aquatic feeding in Kinosternon leucostomum, Platysternon megacephalum, and juvenile Chelydra serpentina. In all of these turtles, hyoid depression produced oral cavity expansion during aquatic feeding, but the earthworm prey were never sucked toward the predators. Prey were captured by neck extension (ram feeding), and we conclude that the function of hyoid depression during aquatic feeding in cryptodire turtles is to prevent the forward motion of the predator from pushing the prey away (compensatory suction). Aquatic feeding is probably the primitive condition for all extant turtles, and thus terrestrial feeding in T. carolina and other turtles is a secondarily derived characteristic. We conclude from this historical pattern that it is not appropriate to use extant turtles in attempts to reconstruct the terrestrial feeding mechanisms of primitive amniotes.

Animals↗

PubMed2000

Effects of prey type on motor pattern variance in tetraodontiform fishes.

It is unclear whether the high variance of electromyographic parameters measured in feeding teleost fishes reflects functionally significant motor variation that is under control of the fish, or functionally insignificant variation characteristic of EMG data. We addressed this issue by examining the effect of three prey, differing in physical characteristics, on the feeding motor pattern in three fishes of the Order Tetraodontiformes: the filefish, Monacanthus hispidus; the triggerfish, Balistes capriscus; and the puffer, Sphoeroides nephelus. EMG recordings were made from subdivisions of the mouth closing adductor mandibulae muscle and the mouth opening levator operculi muscle in four fish from each species feeding on live fiddler crabs, live shrimp, and pieces of cut squid mantle. Analysis of variance was used to test for effects of prey type on the standard deviation of muscle burst duration, burst onset time, and average burst amplitude in the adductor muscles. The filefish exhibited a doubling of standard deviation of burst duration in all muscles when feeding on fiddler crabs; triggerfish showed increased standard deviations in onset times and duration of two muscles when feeding on squid mantle; and the puffer showed no effects of prey on motor variability. The observation that prey type can elicit more than a doubling in the standard deviation of some EMG traits indicates that a large portion of the within-prey type variance is under direct control of the individual fish, suggesting an even greater level of fine motor control in teleost feeding mechanisms than previously recognized.

Animals↗

PubMed1999

Exposing rats to a predator impairs spatial working memory in the radial arm water maze.

This series of studies investigated the effects of predator exposure on working memory in rats trained on the radial arm water maze (RAWM). The RAWM is a modified Morris water maze that contains four or six swim paths (arms) radiating out of an open central area, with a hidden platform located at the end of one of the arms. The hidden platform was located in the same arm on each trial within a day and was in a different arm across days. Each day rats learned the location of the hidden platform during acquisition trials, and then the rats were removed from the maze for a 30-min delay period. During the delay period, the rats were placed either in their home cage (nonstress condition) or in close proximity to a cat (stress condition). At the end of the delay period, the rats were run on a retention trial, which tested their ability to remember which arm contained the platform that day. The first experiment confirmed that the RAWM is a hippocampal-dependent task. Rats with hippocampal damage were impaired at learning the location of the hidden platform in the easiest RAWM under control (non-stress) conditions. The next three experiments showed that stress had no effect on memory in the easiest RAWM, but stress did impair memory in more difficult versions of the RAWM. These findings indicate that the capacity for stress to impair memory is influenced not only by the brain memory system involved in solving the task (hippocampal versus nonhippocampal), but also by the difficulty of the task. This work should help to resolve some of the confusion in the literature regarding the heterogeneous effects of stress on hippocampal-dependent learning and memory.

Analysis of Variance↗

PubMed1999

Verreaux's eagles (Aquila verreauxi) as potential predators of hamadryas baboons (Papio hamadryas hamadryas) in Eritrea.

In this paper we describe for the first time encounters of Verreaux's eagle (Aquila verreauxi) with hamadryas baboons (Papio hamadryas hamadryas) in the central highlands of Eritrea (15 degrees 22' N, 38 degrees 58' E, 2300 m). During 12 h of observation on 4 days, we observed four encounters of Verreaux's eagles with baboons, of which three can be classified as possible attacks. The baboons always responded with alarm calls. In three cases some immatures rushed to adult group members and clung to them, particularly to the adult male. Adult males threatened the eagle, and the whole group did not flee. The response of baboons towards smaller raptors like tawny eagles (Aquila rapax) and black kites (Milvus migrans) was very different. The adult baboons gave no alarm barks but scanned the raptors. The permanent presence of a pair of Verreaux's eagles in the home range of the baboons may represent a considerable predation pressure, at least for immature baboons.

Animals↗

PubMed1998

Reduced prefrontal and increased subcortical brain functioning assessed using positron emission tomography in predatory and affective murderers.

There appear to be no brain imaging studies investigating which brain mechanisms subserve affective, impulsive violence versus planned, predatory violence. It was hypothesized that affectively violent offenders would have lower prefrontal activity, higher subcortical activity, and reduced prefrontal/subcortical ratios relative to controls, while predatory violent offenders would show relatively normal brain functioning. Glucose metabolism was assessed using positron emission tomography in 41 comparisons, 15 predatory murderers, and nine affective murderers in left and right hemisphere prefrontal (medial and lateral) and subcortical (amygdala, midbrain, hippocampus, and thalamus) regions. Affective murderers relative to comparisons had lower left and right prefrontal functioning, higher right hemisphere subcortical functioning, and lower right hemisphere prefrontal/subcortical ratios. In contrast, predatory murderers had prefrontal functioning that was more equivalent to comparisons, while also having excessively high right subcortical activity. Results support the hypothesis that emotional, unplanned impulsive murderers are less able to regulate and control aggressive impulses generated from subcortical structures due to deficient prefrontal regulation. It is hypothesized that excessive subcortical activity predisposes to aggressive behaviour, but that while predatory murderers have sufficiently good prefrontal functioning to regulate these aggressive impulses, the affective murderers lack such prefrontal control over emotion regulation.

Affect↗