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Results for “Appetitive Behavior”

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At least 1,243 records · Page 69Linked to original sources
PubMed1982

A predator prey model with age structure.

A general predator-prey model is considered in which the predator population is assumed to have an age structure which significantly affects it fecundity. The model equations are derived from the general McKendrick equations for age structured populations. The existence, stability and de-stabilization of equilibria are studied as they depend on the prey's natural carrying capacity and the maturation period m of the predator. The main result of the paper is that for a broad class of maturation functions positive equilibria are either unstable for small m or are destabilized as m decreases to zero. This is in contrast to the usual rule of thumb that increasing (not decreasing) delays in growth rate responses cause instabilities.

Aging↗
PubMed1987

Prey localization by surface wave ray-tracing: fish track bugs like oceanographers track storms.

Surface-feeding fish accurately determine direction and distance to the center of a concentric wave stimulus, even if only a single, short lasting wave train is presented. It has been suggested that one cue used by these fish to localize the wave center is the distance dependent frequency modulation of the initial part of a wave stimulus. Here we show how the distance information contained in the fractional frequency change of a capillary wave group can be decoded. We suggest that wave source localization in surface-feeding fish in part is based on a principal similar to that used by oceanographers to track storms by the frequency change of forerunners of swell.

Animals↗
PubMed1983

The physical dimensions and biological meaning of the coefficients in the Volterra competition equations and their consequences for the possibility of coexistence.

Exact definitions in physical and biological terms of the coefficients in Volterra's (1926, 1931) original competition equations are indispensable for the understanding of the system. In agreement with Volterra's own, but not quite sufficient specifications, it is tried in this paper to give more precise definitions of the parameters used by Volterra. This leads to some consequences; i.a. that there does not exist a "principle of competitive exclusion". In order to allow for competitive exclusion - or for stabilization - the Volterra equations need additional biophysical specifications and mathematical modifications. Some such modifications are proposed, for instance for aggressive interference as a function of population numbers.

Animals↗
PubMed1983

Square-root models for the Volterra equations and the explicit solution of these models.

Volterra's (1926) equations for competition and predator-prey interactions are modified by introduction of root terms. A critical comparison with the original equations shows that the dynamic properties of the systems remain essentially alike, while the modification allows for explicit solution of the differential equations. Detailed solutions and numerical examples are given.

Animals↗
PubMed1996

Behavioural evidence that d-fenfluramine-induced anorexia in the rat is not mediated by the 5-HT1A receptor subtype.

These studies investigated the involvement of the 5-HT1A receptor in mediating d-fenfluramine-induced anorexia in the rat. Non-deprived, d-fenfluramine-treated (3.0 mg/kg) rats consumed a reduced amount of a palatable wet mash and showed a temporal advance in the behavioural sequence consistent with satiety. Thus, rats treated with d-fenfluramine ceased feeding and began resting before corresponding controls. Pretreatment with the selective 5-HT1A receptor antagonist WAY-100,635 (1.0 mg/kg) had no effect on either the reduced mash consumption or behavioural satiety sequence of d-fenfluramine-treated animals at a dose which was found to attenuate the anorexia induced by the 5-HT1A receptor agonist 8-OH-DPAT (0.5 mg/kg). Pretreatment with the non-selective 5-HT antagonist metergoline (1.0 mg/kg) attenuated the d-fenfluramine-induced reduction of mash consumption and the advanced offset of feeding. Metergoline pretreatment had no effect on the advanced onset of resting observed in d-fenfluramine-treated animals. These data suggest that d-fenfluramine reduces food intake, perhaps by enhancing satiety, via a mechanism which does not involve the 5-HT1A receptor subtype. The implications of these results to the utility of the behavioural satiety sequence as a measure of postprandial satiety are discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

The appetence behaviour of two South African paralysis-inducing ixodid ticks.

The appetence responses of the ixodid ticks Ixodes rubicundus and Rhipicephalus punctatus to various stimuli were quantified under laboratory conditions. A greater percentage of I. rubicundus generally responded to the different stimuli at lower than at higher temperatures while the converse was usually true for R. punctatus. Radiation heat and shadowing evoked a response in the greatest percentage of I. rubicundus, whereas CO2 and host odour were responsible for a similar reaction in R. punctatus. A single perturbation of the substrate caused more than 50% of I. rubicundus to respond while constant perturbation resulted in a progressive decrease in the proportion of ticks reacting. Significantly more R. punctatus than I. rubicundus were attracted to a CO2 trap and the R. punctatus were also attracted to the trap over a greater distance. Significantly more older than younger ticks of both species responded to the various stimuli.

Animals↗