The fallacy of assuming death by predation.
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Animal Population Groups↗
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Results for “Predatory Behavior”
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Prey-size selection by Triops longicaudatus (Notostraca: Triopsidae) feeding on immature stages of Culex quinquefasciatus.
The tadpole shrimp, Triops longicaudatus, was found to be a size-dependent predator of Culex quinquefasciatus larvae in the laboratory. However, changes in tadpole shrimp size were accompanied by changes in prey-size preference: larger-sized predators consumed an increasing proportion of larger prey items. Very large tadpole shrimp may be nonselective predators of this mosquito species. Quantified behavioral observations indicated that while second instar mosquito larvae were encountered significantly less frequently than were fourth instar larvae or pupae, they were captured at significantly greater rates and with shorter handling times. It is hypothesized that prey vulnerability has an important influence on tadpole shrimp prey size "preferences."
Animals↗
[Odonata as bio-regulators of mosquito larval phases].
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Animals↗
On the structural adaptations of the bill, skull-elements, tongue, and hyoid of some Indian insect-eating birds.
The study of the functional morphology of the feeding apparatus of some Indian insect-eating birds reveals suitable adaptational changes in the structure of their bill, skull-elements, tongue, and byoid in different degrees, depending on the nature of their partial adaptation to secondary food-habits. The hooked tip of the upper beak in Muscicapa and Dicrurus, sharp tomial edges of both the beaks in Turdoides and the long, gradually curved bill in Merops are some of the suitable adaptations of the bill for food-getting. The dimensional variations of the skull and its kinetic elements may be correlated not only with the food-habits of birds studied, but also with the patterns of jaw and tongue muscles possessed by them. A comparatively greater width of the cranium and height of the lower jaw in Turdoides and Dicrurus provide wider areas for the origins and insertions of the adductor muscles. The skull in all the birds studied is pro-kinetic. The kinesis of the upper jaw, however, depends on several factors of which the angles of placement of the quadrate-pterygoid-palatine components, the nature of the naso-frontal hinge and the resultant "torques" produced by differential forces of muscles are very significant. The upper jaw kinesis is best developed in Merops and Orthotomus. The variations in the structure of the tongue and hyoid may also be correlated with various movements of the tongue in both primary and secondary food-adaptations.
Animals↗
Fish predation as a factor in the distribution of Lake Malawi gastropods.
Gastropod densities in Lake Malawi, Africa drop dramatically below 4.5 m water depth. Weed beds disappear and the number of molluscivorous cichlids increases below this depth. When molluscivores were excluded from open sand habitat by cages, due to migration and reduced predation, the density of snails increased by 40-60% within a week. Alternatively, when adult Cyrtocara placodon were placed into the cages, snail density equaled the controls. The molluscivores disproportionately consumed snails of the genus Bulinus relative to those of the more heavily armoured genus, Melanoides. Cichlid molluscivores are hypothesized to be responsible for preventing the thin shelled bilharzia vector snail, Bulinus globosus, from successfully invading the open shore areas of Lake Malawi. Lake Malawi may be relatively free of this human disease because of snail predation by cichlids.
Africa, Southern↗
Estimation of mosquito predation by the water bug Diplonychus indicus Venkatesan & Rao.
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Animals↗
[Interaction of different forms of aggressive behavior in the rat].
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Aggression↗
[Chemical danger signal in the "predator-prey" system in fishes].
Studies have been made on peculiarities of defensive reaction in Phoxinus phoxinus to external metabolites produced by the pike Esox lucius and excreted into the basin. It was shown that the skin and mucose of the pike contain low molecular weight substances (m. w. about 1300) which being introduced into the basin serve as a chemical signal of danger to Phoxinus phoxinus.
Animal Communication↗
[The hypothalamic mechanisms of the regulation of neocortical activity in representative predators (cats)].
On complex behavioural model (preference reaction), studies have been made of the effect of stimulation of two different hypothalamic nuclei, i.e. ventromedial and mammillary ones, on the conditioned reflex activity in cats. It was shown that stimulation of the ventromedial nucleus (in contrast to that of the mammillary one) exerts more complex differentiated effect on the higher nervous activity. Similar effect may be induced by subcutaneous administration of beta-endorphin. The data obtained are discussed in relation to the development of two different mechanisms of hypothalamic influence on neocortical activity.
Acoustic Stimulation↗
Hunting behavior of wild chimpanzees in the Taï National Park.
Hunting is often considered one of the major behaviors that shaped early hominids' evolution, along with the shift toward a drier and more open habitat. We suggest that a precise comparison of the hunting behavior of a species closely related to man might help us understand which aspects of hunting could be affected by environmental conditions. The hunting behavior of wild chimpanzees is discussed, and new observations on a population living in the tropical rain forest of the Taï National Park, Ivory Coast, are presented. Some of the forest chimpanzees' hunting performances are similar to those of savanna-woodlands populations; others are different. Forest chimpanzees have a more specialized prey image, intentionally search for more adult prey, and hunt in larger groups and with a more elaborate cooperative level than savanna-woodlands chimpanzees. In addition, forest chimpanzees tend to share meat more actively and more frequently. These findings are related to some theories on aspects of hunting behavior in early hominids and discussed in order to understand some factors influencing the hunting behavior of wild chimpanzees. Finally, the hunting behavior of primates is compared with that of social carnivores.
Animals↗
Developmental changes in responsivity to threat are stimulus-specific in rats.
During early ontogeny, stimuli that pose a threat to an animal change. Unrelated adult male rats may kill young rats, but infanticide ends around weaning. Predation, on the other hand, may increase during early ontogeny when rats begin to extend their activity range. We investigated the developmental course of two defensive responses, immobility and analgesia, in young rats exposed to an adult male rat or to predator cues. Preweaning 14-day-old rats became immobile and analgesic when exposed to the male and showed immobility but not analgesia when exposed to cat odor. On Day 26, around weaning, the presence of the male rat no longer induced immobility and analgesia whereas cat odor produced higher levels of immobility and analgesia compared to control and male-exposed animals. This developmental change in responsivity may reflect the differences in the risk of being harmed by a male or a cat during different periods of ontogeny.
Animals↗
Functional morphology of prey capture in the sturgeon, Scaphirhynchus albus.
Acipenseriformes (sturgeon and paddlefish) are basal actinopterygians with a highly derived cranial morphology that is characterized by an anatomical independence of the jaws from the neurocranium. We examined the morphological and kinematic basis of prey capture in the Acipenseriform fish Scaphirhynchus albus, the pallid sturgeon. Feeding pallid sturgeon were filmed in lateral and ventral views and movement of cranial elements was measured from video sequences. Sturgeon feed by creating an anterior to posterior wave of cranial expansion resulting in prey movement through the mouth. The kinematics of S. albus resemble those of other aquatic vertebrates: maximum hyoid depression follows maximum gape by an average of 15 ms and maximum opercular abduction follows maximum hyoid depression by an average of 57 ms. Neurocranial rotation was not a part of prey capture kinematics in S. albus, but was observed in another sturgeon species, Acipenser medirostris. Acipenseriformes have a novel jaw protrusion mechanism, which converts rostral rotation of the hyomandibula into ventral protrusion of the jaw joint. The relationship between jaw protrusion and jaw opening in sturgeon typically resembles that of elasmobranchs, with peak upper jaw protrusion occurring after peak gape.
Animals↗
Stabilizing dispersal delays in predator-prey metapopulation models.
Time delays produced by dispersal are shown to stabilize Lotka-Volterra predator-prey models. The models are formulated as integrodifferential equations that describe local predator-prey dynamics and either intrapatch or interpatch dispersal. Dispersing individuals may (or may not) differ in the duration of their trips; these differences are captured via a distributed delay in the models. Our results include those of previous studies as special cases and show that the stabilizing effect continues to operate when the dispersal process is modeled more realistically.
Animals↗
Population-level consequences of antipredator behavior: a metaphysiological model based on the functional ecology of the leaf-eared mouse.
We present a predator-prey metaphysiological model, based on the available behavioral and physiological information of the sigmodontine rodent Phyllotis darwini. The model is focused on the population-level consequences of the antipredator behavior, performed by the rodent population, which is assumed to be an inducible response of predation avoidance. The decrease in vulnerability is explicitly considered to have two associated costs: a decreasing foraging success and an increasing metabolic loss. The model analysis was carried out on a reduced form of the system by means of numerical and analytical tools. We evaluated the stability properties of equilibrium points in the phase plane, and carried out bifurcation analyses of rodent equilibrium density under varying conditions of three relevant parameters. The bifurcation parameters chosen represent predator avoidance effectiveness (A), foraging cost of antipredator behavior (C(1)'), and activity-metabolism cost (C(4)'). Our analysis suggests that the trade-offs involved in antipredator behavior plays a fundamental role in the stability properties of the system. Under conditions of high foraging cost, stability decreases as antipredator effectiveness increases. Under the complementary scenario (not considering the highest foraging costs), the equilibria are either stable when both costs are low, or unstable when both costs are higher, independent of antipredator effectiveness. No evidence of stabilizing effects of antipredator behavior was found.
Animals↗
The value of fat reserves and the tradeoff between starvation and predation.
It is shown that in a range of models, the probability that a forager dies from starvation is, to a good approximation, an exponential function of energy reserves. Using a time and energy budget for a 19g passerine, we explore the consequences, in terms of starvation and predation, of various levels of energy reserves. It is shown that there exists an optimal level L* of reserves at which total mortality (starvation plus predation) is minimized. L* increases when the environment deteriorates as a result of a decrease in either temperature or mean gross gain or an increase in the mean search time. The effect of combined deteriorations is greater than the sum of their individual effects. At L*, the probability of predation is much higher than the probability of starvation. A simple analytic model suggests that this result will be fairly general, but also indicates conditions under which the result might not hold.
Adipose Tissue↗
Delays in recruitment at different trophic levels: effects on stability.
Predator prey models in which there is a delay in recruitment in both species and only adults interact are formulated and studied. Stability results show that the length of delays in recruitment in the prey are more critical than the length of recruitment delays in the predator. Thus the destabilizing effect of recruitment delays may be less important in higher trophic levels than some single species models indicate. Variance in the recruitment delay is shown to be an important stabilizing influence.
Age Factors↗
Top predator persistence in differential equation models of food chains: the effects of omnivory and external forcing of lower trophic levels.
Persistence criteria are given for the highest trophic level predator in ordinary differential equation models of food chains exhibiting arbitrary omnivory and external supplementation of food source or an intermediate predator. The results are expressed in terms of inequalities involving the bounds on the intrinsic growth and interaction rates. Whether omnivory or external forcing enhances persistence is discussed, particularly for the examples of three-, four-, and five-link Lotka-Volterra food chains.
Animals↗
A mathematical model with young predation.
We generalize the model of [21] in which the author considered a predator-prey system with predators eating only the young ones (or eggs) of the prey species. The prime assumption of the present paper is that the birth rate (per unit individual per unit time) of predators depends not only on the current prey egg-level but also on all previous prey egg-levels. It is seen that under this assumption an otherwise stable system may be stable as well as unstable leading to the conclusion that young predation with time delay is less stable than without it. Finally for the model of [21] we prove a result which shows that large predation rates help in the co-existence of both predator and prey species.
Aging↗