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PubMed2006

[Control effect of natural enemies on Plutella xylostella under ecological restoration condition].

A field study on the life table of diamondback moth (DBM) Plutella xylostella showed that the population increase index of DBM in chemical control plot was 52.52, while that of four continuous generations of DBM in ecological restoration plot was 16. 9, 7.16, 3.71 and 4.02, respectively, indicating that the control effect of natural enemies on target pest was greatly improved. The main factor affecting the first and forth generations of DBM was the parasitism of Cotesia plutella, while those affecting the second and third generations of DBM were the predator of the 4'h instar larva and the parasitism of Trichogramma, with the corresponding exclusive index of population control (EIPC) being 1.39, 1.54, 1.56 and 1.74, respectively. There was an obvious time lag effect of natural enemies on their target pest, and thus, to protect and multiply the population of natural enemies in the field should be the key point of fully exerting the potential of natural enemies in their pest control.

Animals↗
PubMed1987

A descriptive study of dairy goat predation in Louisiana.

Questionnaires concerning herd size, housing and management, and previous instances of predation were mailed to 124 goat owners in Louisiana. Postcards were mailed over a period of one year on a monthly basis, to the 84 individuals who responded to this questionnaire. Owners were asked to indicate whether they had seen predators on their property and whether any goats were injured or killed by the predators. Upon receipt of any postcard with a "yes" answer to either of these questions, a telephone interview was conducted to determine the exact circumstances of predator experience. The interview format included time, physical circumstances, and detailed questions about the actions of the predator and the goats. In 85% of the cases, the predators sighted were reported as dogs, and most of these were thought to be pets, rather than wild. Instances of attacks occurred most frequently during periods of reduced light. No clear seasonal pattern of attacks emerged. Four management factors were associated with a reduction in number of attacks; penning the goats at night, use of a night light, proximity of the herd to an occupied residence, and presence of a dog.

Animal Husbandry↗
PubMed2003

The effects of early experience on subsequent feeding responses in the Tegu, Tupinambis teguixin (Squamata : Teiidae).

The purpose of this study was to assess the effects of early feeding experiences on subsequent responses to prey in the tegu, Tupinambis teguixin. Five-day old lizards were exposed to the odors of various prey and control substances on cotton-tipped applicators with the tongue-flick attack score (TFAS) chosen as the dependent variable. Each lizard was exposed to four stimuli: two controls (deionised water and cologne), and extracts from a mouse Mus musculus, and a lizard Ameiva ameiva, in a repeated measures, randomized block design, receiving one stimulus training session / day over a 40-day period. Tongue-flicks directed toward the applicator were counted over a 1 min period as well as the amount of time that elapsed from the first tongue flick to any bite that may have occurred. Live neonatal mice (but not A. ameiva), offered on a weekly basis, were used as a food source for tegus over a 10-month period. After 10 months, tegus were exposed to applicators containing control odors as well as those containing extracts from mice and lizards (A. ameiva). Mouse extracts elicited significantly higher TFAS as compared to those elicited by A. ameiva or control odors, suggesting that prey odors encountered in the environment shortly after hatching can influence prey preferences by these lizards later in life. These results also indicate that tegu lizards can learn to use specific odor cues associated with naturally occurring prey as releasers for subsequent hunting behaviors.

Age Factors↗
PubMed1994

Small cardioactive peptide B increases the responsiveness of the neural system underlying prey capture reactions in the pteropod mollusc, Clione limacina.

Effects of small cardioactive peptide B (SCPB) on cerebral neurons which underlie prey capture in the carnivorous pteropod mollusc, Clione limacina, were investigated. SCPB in concentrations of 10 microM and higher produced direct activation of cerebral ganglion neurons underlying extrusion of buccal cones used in prey capture. SCPB in lower concentrations, between 1 and 5 microM, did not have a noticeable effect on the membrane potentials of these neurons; however, it significantly increased their responsiveness to sensory inputs from the tactile stimulation of the head, and their ability to generate afterdischarge activity. SCPB immunoreactivity was observed in cell bodies in buccal, cerebral, pedal, and intestinal ganglia, as well as in the anterior esophagus and in buccal cones where fibers stained intensely. These electrophysiological and immunohistochemical data suggest that SCPB may have a physiological role in feeding arousal in Clione.

Action Potentials↗
PubMed2000

Optimal intraguild foraging and population stability.

This article explores effects of adaptive intraguild predation on species coexistence and community structure in three species' food webs. Two Lotka-Volterra models that assume a trade-off between competition and predation strength are considered in detail. The first model does not explicitly model resource dynamics and is considered with both nonadaptive and adaptive intraguild predation; in the latter case predators choose their diet in order to maximize their instantaneous population growth rate. The second model includes resource population dynamics. Effects of adaptive intraguild predation on the community structure along a gradient in environment productivity are analyzed and compared with some experimental results of protist food webs. Conditions under which intraguild predation is adaptive are discussed for both models. It is proved that if intraguild predators are perfect optimizers then intraguild predation should decrease with increasing environmental productivity and adaptive intraguild predation is a stabilizing factor provided environmental productivity is high enough.

Adaptation, Biological↗
PubMed1985

Permanent coexistence in general models of three interacting species.

We address the question of the long term coexistence of three interacting species whose dynamics are governed by the ordinary differential equations xi = xifi(i = 1,2,3). In order for any theory in this area to be useful in practice, it must utilize as little information as possible concerning the forms of the fi, in view of the great difficulty of determining these experimentally. Here we obtain, under rather general conditions on the equations, a criterion for judging whether the species will coexist in a biologically realistic manner. This criterion depends only on the behaviour near the one or two species equilibria of the two dimensional subsystems, the behaviour there being relatively easy to examine experimentally. We show that with the exception of one class of cases, which is a generalization of a classical example of May and Leonard [21], invasibility at each such equilibrium suitably interpreted is both necessary and sufficient for a strong form of coexistence to hold. In the exceptional case, a single additional condition at the equilibria is enough to ensure coexistence.

Animals↗
PubMed1982

Response characteristics and stratification of tectal neurons in the toad Bufo bufo (L.).

In the optic tectum of Bufo bufo the activity of single neurons was recorded during the presentation of moving visual stimuli. The location of the recorded cells was marked iontophoretically by means of alcian blue dye. A total of 132 cells were studied, most of which showed clear differences within their responses to a square and to rectangles oriented either horizontally or vertically. The cells were found primarily within the tectum layers 8 and 6. The majority of them preferred the square to the horizontal bar, and this stimulus to the vertical one. Another group responded best to the horizontal rectangle. Relatively few cells were found in which the vertical stimulus was preferred to the horizontal one. A considerable number of tectal cells showed a change of stimulus preference if the stimulus velocity was changed. No clear correlation between response types and anatomical distribution within the tectum layers could be found.

Animals↗
PubMed1987

Effect of chlorpheniramine on muricide induced by thiamine deficiency: pharmacokinetic and behavioral studies.

Chlorpheniramine (5-10 mg/kg) showed a dose-dependent suppressive effect on muricide induced by thiamine deficiency at 1 hr after oral administration. The ED50 value for muricidal suppression was about 7.1 mg/kg (95% confidence limits, 5.4-9.3 mg/kg). The maximum effect of muricidal suppression lasted for 1-2 hr after oral dosage (10 mg/kg). Chlorpheniramine was detectable at 10 min in the blood and brain of thiamine deficient killer-rats by using a high-performance liquid chromatographic method. Maximum brain and blood levels of chlorpheniramine appeared at 45 and 60 min, respectively. In terms of regional distribution, the highest levels were measured in the limbic system, especially in the hippocampus. Although neither blood nor brain levels of chlorpheniramine reflect its pharmacological activity, it can easily enter the brain and suppress muricide more potently than imipramine.

Aggression↗
PubMed2000

Antipredatory behavior as an index of heavy-metal pollution? A test using snails and caddisflies.

The loss of behaviors that organisms use to avoid predation may serve as a sensitive indicator of pollution. We tested the hypothesis that a correlation exists in the field between heavy metal levels and antipredator behaviors. We examined the antipredator behavior of aquatic caddisfly larvae and snails at sites in the Coeur d'Alene basin of Northern Idaho which varied in their levels of heavy metals. We tested the antipredator response of Physella columbiana snails at 10 polluted lakes downstream from the Bunker Hill Environmental Protection Agency (EPA) Superfund cleanup site. We then compared their behavior to snails at 14 reference lakes. We placed the snails in a plastic testing apparatus, exposed them to an extract of crushed snail, and then monitored their movements to a normally preferred shaded area. We also tested the behavior of caddisfly larvae from 36 sites from a total of 6 streams/rivers adjacent to the Superfund site. Sites were located upstream and downstream of abandoned mines. We located active larvae of four genera, simulated predation by grasping the animals between thumb and forefinger (the larvae respond to being grasped by withdrawing into their case), lifted them from the water for 3 s, and then placed them in an adjacent, slower section of the stream. We then recorded how long it took each larvae to partially emerge from its case and attempt to move away. Unlike reference site snails, snails from heavy metal-polluted environments failed to exhibit antipredator behaviors in response to crushed conspecifics. These results are consistent with previous laboratory studies. We found no effect of heavy metals on the antipredatory behavior of caddisfly larvae.

Animals↗
PubMed2006

On the barn owl's visual pre-attack behavior: I. Structure of head movements and motion patterns.

Barn owls exhibit a rich repertoire of head movements before taking off for prey capture. These movements occur mainly at light levels that allow for the visual detection of prey. To investigate these movements and their functional relevance, we filmed the pre-attack behavior of barn owls. Off-line image analysis enabled reconstruction of all six degrees of freedom of head movements. Three categories of head movements were observed: fixations, head translations and head rotations. The observed rotations contained a translational component. Head rotations did not follow Listing's law, but could be well described by a second-order surface, which indicated that they are in close agreement with Donder's law. Head translations did not contain any significant rotational components. Translations were further segmented into straight-line and curved paths. Translations along an axis perpendicular to the line of sight were similar to peering movements observed in other animals. We suggest that these basic motion elements (fixations, head rotations, translations along a straight line, and translation along a curved trajectory) may be combined to form longer and more complex behavior. We speculate that these head movements mainly underlie estimation of distance during prey capture.

Animals↗