Effect of cortical and hippocampal lesions on hoarding behavior in the albino rat.
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Young and aged mice of the A/J and C57BL/6J inbred strains were given a series of behavioral tests which measured activity of various kinds, emotionally, operant learning, sensory discrimination, and alcohol preference. In general, compared with young mice, aged mice were less active, similar in emotionally, learned the operant discrimination as well, but extinguished more slowly, had poorer discrimination for sweet and bitter taste stimuli, and preferred alcohol to a lesser degree. Strain differences were obtained for most of these tests, and age-strain interactions occurred frequently indicating that behavioral changes occur at different rates for groups which differ in genetic constitution.
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The effects of ambient temperature and of sex on nest-building behavior were studied in a laboratory colony of gray short-tailed opossums, small, Brazilian marsupials. At 24 degrees C, both males and females used more nesting material and built larger nests of better quality than at 27 degrees C. Although both males and females built nests using the mouth, forelegs, hindlegs and tail, females built nests more reliably at the higher temperature and used more nesting material than males at both temperatures. These findings are discussed with respect to the thermoregulatory and reproductive characteristics of marsupials.
Host bird species of the Eurasian Cuckoo, Cuculus canorus, often display egg-discrimination behaviour but chick-rejection behaviour has never been reported. In this paper, we analyse a host-cuckoo association in which both population dynamics and evolutionary dynamics are explored in a discrete-time model. We introduce four host types, each with their own defence behaviour, displaying either egg or chick rejection, neither or both, We also introduce fitness functions for each of these host types. Although we can characterize the long term behaviour in many cases by a simple heuristic argument which is in accordance with common views in ecology, there are a number of other phenomena that are not explained within this framework: we describe stable oscillatory behaviour and coexistence of two defensive host types. We analyse the scenarios in which chick rejection may establish itself and give a first explanation as to why this defence trait has never been recorded in nature. We find that chick rejectors generally are at an intrinsic disadvantage with respect to a host type that rejects eggs. Hosts benefit more from rejecting cuckoo eggs than cuckoo chicks, and our model suggests that this is chiefly responsible for the absence of chick rejection. Moreover, even though it seems that chick rejection must be useful as an extra defence, it is shown that hosts with both defence strategies are less likely to establish themselves in competition with egg-rejectors than hosts which reject chicks only. These results provide insight in the extent to which adaptations may be perfected by natural selection.
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There are approximately 75 species of American opossums (didelphids). Systematic behavioral research has been reported for only a small number of species, namely, Monodelphis domestica and Didelphis virginiana. Observational studies and field reports on several other didelphid species have also been published. The current review covers behavioral studies on didelphids including research on territoriality, reproductive behaviors, parturition, maternal behaviors, nest-building, vocalizations, scent-marking, circadian rhythms, swimming, locomotion, discrimination learning, maze learning, operant learning, problem box learning, exploration, death-feigning, predatory behavior, and prey manipulation. Didelphid behavior is compared in several contexts with eutherian mammals. Other than death-feigning, which has only been reported for one or two didelphid species, the behaviors observed in didelphids are qualitatively similar to those of eutherian mammals. Nevertheless, differences can be seen in prey manipulation and spatial maze behavior. Social interactions appear to be sparser in opossums than in most eutherian mammals. However, the scarcity of systematic research on didelphid behavior still prevents firm conclusions regarding these ancient and interesting mammals. Futher research on didelphids is warranted, particularly since they provide a natural comparison group for small generalist eutherians.
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The evolution of parasite resistance has often been assumed to be governed by antagonistic selection pressures. Defense against pathogens, by mounting an immune response, confers evident benefits but may also incur costs, so that the optimal level of defense is expected to depend on the balance between benefits and costs. Although the benefits of immune surveillance are well known, estimates of costs are still equivocal. Here we studied the behavioral and physiological modifications associated with exposure to a nonreplicating antigen (lipopolysaccharide [LPS] of Escherichia coli) in a passerine species, the house sparrow (Passer domesticus). We further investigated whether the behavioral and physiological changes provoked by LPS induced measurable repercussions on life-history traits, such as the breeding effort and reproductive success. Finally, we tested whether the trade-off between immune activation and breeding effort was modulated by the workload required to feed the brood. Exposure to LPS reduced activity and increased body mass loss of captive individuals; similarly, LPS injection induced a dramatic drop in feeding rate and reproductive success of breeding females. However, this reduction depended on brood size, suggesting that the strength of the trade-off between immune activation and reproduction was affected by the workload required to feed the brood. Overall, this study stresses the magnitude of costs associated with mounting immune responses and the ecological and evolutionary consequences for natural populations.
The neural substrate subserving magnetic orientation is largely unknown in vertebrates and unstudied in mammals. We combined a behavioral test for magnetic compass orientation in mole rats and immunocytochemical visualization of the transcription factor c-Fos as a marker of neuronal activity. We found that the superior colliculus of the Zambian mole rat (Cryptomys anselli) contains neurons that are responsive to magnetic stimuli. These neurons are directionally selective and organized within a discrete sublayer. Our results constitute evidence for the involvement of a specific mammalian brain structure in magnetoreception.
Injected progesterone induces incubation behavior much faster, and in a higher percentage of cases, in doves with previous breeding experience thanin those without such experience. The nature of the animal's previous experience is thus one of the variables influencing behavioral responses to exogenous hormones.
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