Danilo Mainardi

Karyotype and intermale aggression in wild house mice: Ecology and speciation

Social aggression shown by male mice from two races from upper Valtellina in Italy with 2n=24 and 26 chromosomes, respectively, was contrasted in dyadic encounters. In encounters with mice of the same karyotype 2n=26 were uniformly more aggressive than their 2n=24 counterparts. When resident mice from both these races were tested against intruders of the other karyotype, 2n=26 mice again were more likely to prove aggressive and to eventually dominate their partners even when they were the intruder. Perhaps those behavioral differences account for the apparent replacing of the 2n=24 chromosome race by the 2n=26 variety in geographical areas where they overlap.

Escape-reaction of captive young red-legged partridges (Alectoris rufa) reared with or without visual contact with man

Abstract It was noted that adult birds of Alectoris rufa , hatched and reared in captivity, cannot survive in nature after their release for restocking for hunting. An attempt was made to ascertain what effect various kinds of visual experiences with man during the first 2 months of life might have on the escape-response of young individuals. It was observed that absence of visual contact with man during the 48 h after hatching causes fear of human beings in those individuals when 2 months old. Conversely, subjects which were in visual contact with man during the 48 h after hatching did not show this tendency to escape in front of him. The possible links between this finding and the phenomenon of imprinting, together with the need for new rearing techniques, are discussed.

PARENTAL AGGRESSION DISPLAYED BY FEMALE MICE IN RELATION TO THE SEX, REPRODUCTIVE STATUS AND INFANTICIDAL POTENTIAL OF CONSPECIFIC INTRUDERS

SUMMARY The parental aggression of female mice (Mus domesticus Rutty) towards strange conspecifics known to vary in their tendency to commit infanticide was examined. Twenty-four hours after stud males removal, resident lactating females (with pups aged 3–5 days) were confronted with the following types of intruders: the reintroduced stud, i.e. the father of the pups, a strange father, sexually naive and recently sexually experienced (24 hr prior testing) males, virgin females. Parental attack was mainly elicited by sexually naive and recently sexually experienced males which were also most likely to kill and cannibalize pups. The stud males did not show infanticide and were never attacked. Remarkably, strange fathers were rarely attacked by lactating females and they rarely killed unrelated pups. The data seem to support the view that lactating female mice might be capable of assessing the infanticidal potential of conspecific intruders and of adopting the most appropriate behavioural strategy. Although ...

The predatory behaviour of captive wild kestrel, Falco tinnunculus L.

Abstract The predatory behaviour of captive wild kestrels was investiga ted to ascertain whether prolonged captivity, with no predation opportunities, could affect prey capture. Thirty kestrels were ob served. After a 48‐hour fast they were offered a live laboratory mouse. The behaviour before and after prey appearance, and la tency to predation were recorded. There was no difference in cap ture efficiency correlated with kestrel age, but adults performed preening significantly more often than young birds. Moreover, a clear inverse correlation was found between the latency of preening and of predation. Therefore, prolonged captivity associated with inactivity does not seem to exert a negative influence on predation in this species.

On the role of the demonstrator for the solution of a problem in the house mouse

The present experiment was designed in order to look into the effects which exposure either to a demonstrator performing the task or to the task in itself had on young mouses skill in solving a problem. Three experimental groups were organized. In the first group the pups spent 7 days with a demonstrator solving the problem; in the second one they spent the same amount of time with an adult unable to solve the problem. In the third group each pup spent 7 days with only the task at its disposal. At the end of this period all pups were tested to assess the degree of skillfulness reached during the training. Results showed that the animals with the demonstrator were the better performers in solving the problem.

Further analysis of a case of social learning in the house mouse (Mus domesticus)

Groups of experimentally naive Swiss mice, 20 days old, were exposed to a varying quality of socially transmitted information needed to solve a food-finding problem. The problem consisted of opening a rotating door of an apparatus. Mice that lived with a demonstrator opening the apparatus and mice that lived with an adult manipulating but not opening the apparatus were the most efficient animals in solving the problem. In addition other groups of mice had different non-social experiences with the problem. The data indicate that these animals did not improve their ability in performing the task compared with control animals. In essence the present results suggest that mice were capable of learning aspects of the opening techinque by social learning rather than by trial and error.

Influence of social status on paternal behaviour in mice

Abstract House mice (Mus musculus domesticus) in triads of one female and two males showed differences in parental behaviour and the influence of male social status. Every test consisted in putting a strange test-pup into the cage of the triad. Many parental activities and particularly retrieving were recorded. The results demonstrated the social dominance of the female on the males, while, the males maintained their hierarchy status, whether the female was present or not. The “killer” dominant male was less interested in parental care than the “normal” dominant male. The origin of such behaviour in relation to the possible social situation of the “killer” male in a natural environment is discussed.

Thyroid hormone pattern and aggressiveness in mice blood sampled immediately after fighting

Abstract Endocrine changes may modulate isolationinduced aggressiveness in Mus musculus. Significant differences in the blood levels of T4, T3 and rT3 in males classified as dominant, submissive and reared in isolation have previously been obtained. Isolated mice appear homologous to socially dominant animals as far as aggressiveness is concerned. The endocrinological results support this hypothesis. In that experiment dominant and submissive males, after an open fight, lived together 4 days in a stable hierarchy of two, and were then sacrificed. To find out if levels of peripheral thyroid hormones in dominant and submissive males differ before fighting or depend on living together in a restricted environment of one dominant and one submissive male, the animals in the present experiment were immediately sacrificed after fighting. The results are different from the previous ones, demonstrating that the differences in endocrine functions previously observed are present only when the social hierarchy is stable.

Risposte differenziali del piccione viaggiatore e normale alla sollecitazione rotatoria

Summary The : variations in the electric activity of the cerebellum during and after rotation of the animals have been recorded in domestic and homing pigeons, as well as stationary and migratory turtle doves. Various types of electrodes were used: 1) external, 2) inserted into the sides of the vermen, 3) bifilar microelectrodes and 4) concentrical electrodes laid on the vermen. Electrical recordings were effected simultaneously with those of the tangential and centripetal acceleration forces determined by the rotation. In all cases a rimareable increase in the amplitude of the cerebellar potential during the action of tangential and centripetal acceleration was noted. A higly characteristic reaction in the form of rhylmical prolonged « after discharges » was found to be present whit homing pigeons and migratory turtle doves, while it was absent in domestic pigeons and stationary doves.

Food aversion learning in mice (Mus domesticus): different salience of rice and oats

Abstract The present experiments were carried out to test the hypothesis that mice are able to form an aversion to foods that are a natural part of their diet: rice and oats. Both in Experiment 1 and 2, subjects were exposed to rice or oats and then intraperitoneally injected with LiCl in two different doses (0.16 or 0.24 M). Animals of independent groups were tested to verify the effects of the treatment at three different times after the injection (2 h, 24 h, or 6 days). Subjects of Experiment 1 were fed with commercial diet from weaning till the beginning of the experiment, whereas subjects of Experiment 2 were bred from weaning with a special purified diet to avoid any taste like those of rice and oats. The results of the two experiments showed that mice were able to form aversion to rice when injected both with 0.16 and with 0.24 M LiCl, and that the effect of treatment remained unchanged till six days after the injection. On the contrary, mice showed aversion to oats only when tested 24 h or six day...