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PubMed2000

[Impact of starvation on predation by male adult Chrysopa septempunctata].

The predation on Schizaphis graminum by male adult Chrysopa septempunctatata at various levels of starvation was examined in this paper. Th results showed that the functional reactive types of predator were not altered by its starvation duration, and the amount(Na) of catched S. graminum by C. septempunctata within 24 hrs varied with duration time(t), which could be expressed by the model: Na = 100/(1 + e-0.3088 - 0.0996t). The relationship between predation rate(v) and time(x) could be described as v = 6.7117 x-0.7928. The male adult predators preferred feeding on the young preys.

Animals↗
PubMedDate not supplied

[Extra-oral digestion and the problem of parasitism in Parasitengona mites (Acariformes)].

An analysis of the extra-oral digestion in Parasitengona being a highly specialized group of Acariform mites is carried out from the viewpoint of functional morphology and ecology. The significance of the extra-oral digestion in the life strategy of these mites and their larval parasitism is also evaluated. The morphological pre-adaptations of this mode of feeding as well as its probable evolutionary consequences are demonstrated by an example of trombiculid mites (Trombiculidae). It is shown, in particular, that parasitism in general may be considered as a particular life scenario implying that the feeding preferences of the organism are evolutionary formed in a close association with other organisms, which provide a parasite with a feeding substrate mainly already prepared for utilization. Based on this assumption, all Parasitengona, including both larval and post-larval instars, irrespectively of the size of their potential victim, preferably should not be considered as parasites, but as micro-predators.

Adaptation, Physiological↗
PubMed2005

Perspective: the evolution of warning coloration is not paradoxical.

Animals that are brightly colored have intrigued scientists since the time of Darwin, because it seems surprising that prey should have evolved to be clearly visible to predators. Often this self-advertisement is explained by the prey being unprofitable in some way, with the conspicuous warning coloration helping to protect the prey because it signals to potential predators that the prey is unprofitable. However, such signals only work in this way once predators have learned to associate the conspicuous color with the unprofitability of the prey. The evolution of warning coloration is still widely considered to be a paradox, because it has traditionally been assumed that the very first brightly colored individuals would be at an immediate selective disadvantage because of their greater conspicuousness to predators that are naive to the meaning of the signal. As a result, it has been difficult to understand how a novel conspicuous color morph could ever avoid extinction for long enough for predators to become educated about the signal. Thus, the traditional view that the evolution of warning coloration is difficult to explain rests entirely on assumptions about the foraging behavior of predators. However, we review recent evidence from a range of studies of predator foraging decisions, which refute these established assumptions. These studies show that: (1) Many predators are so conservative in their food preferences that even very conspicuous novel prey morphs are not necessarily at a selective disadvantage. (2) The survival and spread of novel color morphs can be simulated in field and aviary experiments using real predators (birds) foraging on successive generations of artificial prey populations. This work demonstrates that the foraging preferences of predators can regularly (though not always) result in the increase to fixation of a novel morph appearing in a population of familiar-colored prey. Such fixation events occur even if both novel and familiar prey are fully palatable and despite the novel food being much more conspicuous than the familiar prey. These studies therefore provide strong empirical evidence that conspicuous coloration can evolve readily, and repeatedly, as a result of the conservative foraging decisions of predators.

Adaptation, Physiological↗
PubMed1997

The effect of body size on prey choice by Rivulus luelingi Seegers 1984 (Aplocheiloidei: Rivulidae).

The effect of body size of Rivulus luelingi (10-15, 20-25, 30-35, 40-45, 46-50 mm length classes) on predation of three size class combinations of Culex sp larvae (small-medium, small-large, medium-large) was studied in the laboratory by means of analyses of preference, specific overlap, and actual number of prey eaten. The smallest experimental R. luelingi size class (10-15 mm) was gape limited. Experimental diets were affected by prey choice and morphological constraint. Preference for the smaller prey, in each prey type combination, was negatively correlated with predator body size, and the converse was true for the larger prey. Preference for any prey size depended on the available prey distribution. There was a correlation between the number of each prey size eaten and predator size in each prey size combination, except for the small prey in the small-medium combination. Specific overlap analysis revealed asymmetries in diet overlap. Feeding success increased non-linearly with R. luelingi body length for two prey size distributions; longer individuals had a disproportionally high feeding success. Preference analysis was more accurate than either specific overlap or actual number of prey eaten. The three kinds of analysis resulted in blocks of contiguous size classes with similar resource utilization, which were considered to have a high chance of interacting competitively.

Animals↗
PubMed1991

Scopolamine-induced alterations in predatory behaviour pattern in cats.

Predatory behaviour in its full pattern (i.e., following the mouse, killing it and consuming the carcass) was tested in semi-natural conditions in cats. Consumption of minced horse meat was tested as well. Centrally acting scopolamine hydrobromide injected i.p. did not suppress predatory motivation, since following the prey and killing it were preserved. The executory phase of predation (i.e., the killing grip) was severely disturbed and the consumption of the mouse as well as meat was totally inhibited. Peripherally acting scopolamine methylnitrate administered into another group of cats under the same conditions generally did not affect predatory pattern, though meat and mouse consumption was disturbed to some extent. It is concluded that central muscarinic involvement in predatory behaviour in cats is limited to sensorimotor control of jaw movements.

Animals↗
PubMed2001

Behavioral and neurochemical changes following predatory stress in mice.

This article had several objectives. First it aimed at investigating the anxiogenic-like behaviors elicited by unavoidable cat exposure and/or cat odor across nine strains of mice (BALB/c, C57BL/6, C3H, CBA, DBA/2, NMRI, NZB, SJL, Swiss) in a modified version of the free-exploration test. The second objective was to investigate possible neurochemical changes following cat exposure in Swiss mice by measuring the turnover of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) in several brain regions known to be involved in the modulation of emotional processes (hippocampus, hypothalamus and striatum). Finally, the third objective was to examine the effects of anxiolytic drug treatments on the anxiogenic responses elicited by a cat odor (i.e. a feces) in Swiss mice previously exposed to a cat using the free-exploration test. Results from the strain comparison showed that mice could be divided into three distinct groups: two non-reactive strains (NZB and SJL) which were relatively insensitive to predatory exposure and/or odor; five intermediate-reactive strains (Swiss, NMRI, CBA, C3H and BALB/c) which displayed clear anxiogenic-like responses only when exposed to both cat and, subsequently, to feces; and two high reactive strains (C57BL/6 and DBA/2) which showed anxiogenic-like reactions following cat exposure, regardless of the stimulus (clay or feces) present in the free-exploration cage. Neurochemical data revealed that, while brain levels of NA, DA, 5-HT in cat exposed Swiss mice were not significantly different from those of control animals, turnover rates of these monoamines were increased in the hippocampus (NA and 5-HT), hypothalamus and striatum (DA) after cat exposure. Results from pharmacological experiments indicated that repeated administration of the 5-HT reuptake inhibitor fluoxetine (5-20 mg/kg, twice a day, for 5 days) completely abolished avoidance of the cat feces in Swiss mice previously exposed to the predator. Neither acute nor repeated administration of the classical anxiolytic diazepam was able to reduce avoidance behavior of the anxiogenic stimulus in the free-exploration test. Taken together, these findings indicate that the exposure of mice to unavoidable predatory stimuli is associated with behavioral and neurochemical changes consistent with increased anxiety.

Animals↗
PubMed2006

Animal behavior: who will croak next?

A recent study with the predatory bat Trachops cirrhosus has shown the importance for this species of social learning about novel prey using auditory, rather than visual or olfactory, cues.

Animals↗
PubMed2005

Pilot study of the relationship between drug misuse and violence among drug addicts in Greater Accra, Ghana: the south of Saharan Africa case.

The purpose of this study is to explore the relationships between drug use/misuse and the prevalence of violence in sub-Saharan Africa. This study was undertaken as a pilot study to provide direction for a large-scale, systematic, countrywide or regional analysis. Hypotheses tested include the following: 1) drug use/misuse is related to violent behavior; 2) drug use/misuse is related to predatory violent behavior; and 3) drug use/misuse increases the likelihood that those addicted to drugs will commit violent acts. In order to test these hypotheses, two data sets were used to increase the robustness of the study. The first data set was collected during the summer of 1996, and was based on a self-reported survey of 117 subjects (17 women and 100 men), from different neighborhoods in Greater Accra and from different ethnic groups, mean age of 32, most were unemployed. The second data set was collected during the summer of 1997, based on a self-reported survey of 216 (45 women and 171 men) subjects from different neighborhoods in Greater Accra, from different ethnic groups, mean age of 31, most of whom were also unemployed. All hypotheses were confirmed by analysis of the data collected. This suggests that an expanded, countrywide study using the same procedures and instrumentation would provide a meaningful foundation for sound decisions by governmental officials and policy-makers in dealing with drug use and violence in Ghana. Further, the approach could serve as a model for other countries addressing similar problems.

Adult↗
PubMed1980

[Maternal behaviour and mother-young relationships in spiders].

Most species of spiders leave their egg-sacs in a sheltered place. However, some of them look after or carry their egg-sacs until the spiderlings hatch. Others extend their maternal behaviour to feeding their young by regurgitation or by the distribution of prey. The adaptative aspect of this maternal behaviour is shown by a reduced rate of reproduction in the species whose care of progeny is the most sophisticated. The maternal care of the egg-sac depends on the physiological state of the female, that state, in turn, being maintained by the presence of the egg-sac. The tolerance exhibited by the mother towards her offspring implies at least two mechanisms: (i) inhibition of predatory behaviour in response to the movements of an offspring at a distance, (ii) inhibition of cannibalism when in contact with an offspring. The parental relationship can be complemented by cooperation between the young that involves a tolerance mechanism probably close to that of social spiders.

Animals↗
PubMed2005

Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition.

To date, most studies of nest site selection have failed to take into account more than one source of nest loss (or have combined all sources in one analysis) when examining nest site characteristics, leaving us with an incomplete understanding of the potential trade-offs that individuals may face when selecting a nest site. Our objectives were to determine whether northern flickers (Colaptes auratus) may experience a trade-off in nest site selection in response to mammalian nest predation and nest loss to a cavity nest competitor (European starling, Sturnus vulgaris). We also document within-season temporal patterns of these two sources of nest loss with the hypothesis that flickers may also be constrained in the timing of reproduction under both predatory and competitive influence. Mammalian predators frequently depredated flicker nests that were: lower to the ground, less concealed by vegetation around the cavity entrance and at the base of the nest tree, closer to coniferous forest edges and in forest clumps with a high percentage of conifer content. Proximity to coniferous edges or coniferous trees increased the probability of nest predation, but nests near conifers were less likely to be lost to starlings. Flickers may thus face a trade-off in nest site selection with respect to safety from predators or competitors. Models suggested that peaks of nest predation and nest loss to eviction occurred at the same time, although a competing model suggested that the peak of nest loss to starlings occurred 5 days earlier than the peak of mammalian predation. Differences in peaks of mammalian predation and loss to starlings may constrain any adjustment in clutch initiation date by flickers to avoid one source of nest loss.

Animals↗
PubMed2002

Predatory response of brown tree snakes to chemical stimuli from human skin.

The brown tree snake (Boiga irregularis) is an exotic pest species on Pacific islands, most notably on Guam where it has caused considerable ecological and economic damage. On Guam, the snake commonly associates with people and can be found near or in human habitations. Bites are common, approximately 1 of 1200 emergency room visits to Guam hospitals were reported to be the result of B. irregularis bites; 80% of these victims were attacked while sleeping. Most of the attacks occurred on fingers and hands and the attacks appeared to be predatory, rather than defensive, in nature. In order to characterize the mechanism releasing this unusual behavior, we measured the predatory response of B. irregularis to chemical stimuli from humans and controls using a lab population that originated from Guam and a wild population from the species' native range in Queensland, Australia. To quantify behavior we measured the proportion of snakes displaying predatory behavior to each of the stimuli, the latency to attack, and the number of tongue-flicks displayed. We quantified predatory behavior using the tongue-flick attack score for repeated measures [TFAS(R)], a common method for quantifying predatory behavior in squamate reptiles. Captive brown tree snakes responded to human skin stimuli with feeding behavior, including predatory attacks, at the same frequency as they did to prey stimuli derived from mice, while never responding to controls with such behavior. Captive snakes also responded to human skin stimuli and prey stimuli with significantly higher TFAS(R) scores than to controls, although there were no differences between the human and mouse stimuli. Wild-caught animals in Australia also responded with predatory attacks to human skin stimuli, while not showing predatory behavior to a blank control and with higher TFAS(R) scores to human skin stimuli than to the control. As B. irregularis is a generalized predator that relies heavily on chemical signals to recognize prey, we hypothesize that the snakes recognize compounds on human skin that may be shared with other prey.

Animals↗