Marisa Mainardi

Kinship and familiarity as factors affecting social transfer of food preferences in adult Mongolian gerbils (Meriones unguiculatus).

Experiments were carried out with Mongolian gerbils (Meriones unguiculatus) to assess whether a socially mediated acquisition of diet selection exists in this species. Results showed that a gerbil was influenced in its diet choices by information extracted during a brief period of interaction with a familiar conspecific that had recently eaten a novel food. Data revealed that the acquisition of a food preference from a conspecific depends on the existence of a social bond between the interacting gerbils. Either genetic relatedness (being brother or sister raised in different litters) or familiarity (being bred in the same litter or being member of a reproductive pair) is necessary for the transfer of information. Unfamiliar and unrelated observer gerbils did not selectively choose their demonstrators food.

The effect of demonstrator age and number on duration of socially-induced food preferences in house mouse (Mus domesticus)

Present research was undertaken to investigate whether the transfer of food preference from a demonstrator mouse to an observer can be influenced by their relative age. In experiment 1 an adult female mouse, the observer, was allowed to interact with a recently-fed demonstrator which was a pup of her litter or an adult female mouse. The observer was then tested to assess whether it acquired a preference for the demonstrators diet. The results showed that a pup demonstrators influence on an adults food preference is shorter-lasting than an adult demonstrators influence. Experiment 2 was aimed to investigate whether many demonstrators have an additive effect in influencing their observers choice. The results indicated that multiple pup demonstrations do not increase longevity of food preferences induced by pup demonstrators. Moreover, the longevity of an adult observers preference for its demonstrators food is reduced by the exposure to multiple adult demonstrators. Results are discussed in terms of demonstrators reliability and of social constraints that could affect social transfer of food information in the house mouse.

The inhibitory effects of fluprazine on parental aggression in female mice are dependent upon intruder sex

Lactating resident mice respond differently to male and female intruder conspecifics, showing defensive attack towards the former and offensive attack towards the latter. The effects of fluprazine (1-5 mg/kg) on this differential response pattern have been assessed. Although fluprazine increased the latencies of attack on male intruders, a very much more potent inhibitory effect was observed on attacks directed towards female intruders. Fluprazine also modestly reduced social investigation of female intruders and increased nest-oriented behaviour irrespective of the intruders sex. As the pattern of attack on intruders, exploration, fear responses and maintenance behaviour all remained largely intact under drug treatment, it seems unlikely that the drugs inhibitory action on attack involves fear potentiation and/or olfactory impairment. It is suggested that the greater sensitivity of offensive attack to the inhibitory actions of fluprazine may reflect the relative degree of threat to resident parental investment posed by male and female conspecific intruders.

Familiarity and relatedness: Effects on social learning about foods by Norway rats and Mongolian gerbils

In recent experiments in which the social influences on feeding in Mongolian gerbils were investigated, observer gerbils acquired food preferences from conspecific demonstrators only if the demonstrators and observers were either related or familiar. Even then, the effects of demonstrator gerbils on observers’ food choices lasted less than 24 h. In similar experiments with Norway rats, the familiarity/relatedness of demonstrators and observers had little effect on social learning, and the demonstrators’ influence on observers’ food choices lasted many days. We examined the causes of these differences and found that, after observer gerbils interacted with either unfamiliar or familiar conspecific demonstrators that had been fed using procedures typically used to feed demonstrator rats, they showed long-lasting social learning about foods, whereas observer rats interacting with conspecific demonstrators that had been fed as demonstrator gerbils normally are fed showed effects of familiarity/relatedness to demonstrators on their social learning about foods. Procedural differences, rather than species differences, seem to be responsible for reported inconsistencies in social learning about foods by rats and gerbils.

Preputial glands, dominance and aggressiveness, in mice

Abstract The preputial glands are androgen-dependent and apparently used in pheromonal signalling in rats and mice. With light and electron microscopy (LM and EM) these glands from socially dominant and socially subordinated members of pairs of male laboratory ‘TO’ strain mice were compared with those from individually-housed counterparts. The glands of both dominant and individually housed animals were well-developed and actively secreting having acini at different stages of maturation with numerous normal cytoplasmic organelles and healthy oval-shaped nuclei. The glands from subordinated animals were less developed, had fewer, smaller lipid droplets and fewer cellular organelles; the nuclei were shrunken and lobulated; and the cells often contained autophagic vacuoles, which are also found in castrated mice. The data suggest that the reduced gonadal function typical of subordinated mice compared with the other two categories exprcsses itself in preputial structure and function. The aggressiveness induce...

Comparing different forms of male and female aggression in wild and laboratory mice : An ethopharmacological study

The purpose of this study was to compare the effects of 2 mg/kg fluprazine (a serotonergic psychoactive drug with antiaggressive properties) on intrasexual attack, infanticide, and predation (on an insect larva) in males and females of wild and Swiss mice. The results showed that, in both stocks of mice, fluprazine significantly inhibited intrasexual and infanticidal attack in both sexes, but predatory attack was not altered by the drug treatment. Motivational and neural substrates underlying intrasexual attack and infanticide appear, thus, to be related to each other, and similarly modulated in both males and females. Conversely, predatory attack seems to be under a different neurohumoral control. The similar regulation of proximal mechanisms of aggressive behavior observed in wild and Swiss mice suggests a common neurobiology of aggression. For this reason, the outbred laboratory Swiss mice appear to be a reliable model for studies on causal and functional mechanisms of aggression.

Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.

Involvement of various senses in responses to individual housing in laboratory albino mice: 1. The olfactory sense

Abstract ‘Isolation’ of male mice is much used to induce aggressiveness but, as practised in most laboratories, does not preclude communication between neighbouring conspecifics. This study examines the influence of olfaction on individual housing-induced social conflict between male laboratory mice. Attempts were made both to eliminate and to intensify the exposure to presumably socially meaningful odours. First, the effects of acute and chronic anosmia induced by application of four per cent zinc sulphate solution to the nostrils were determined in mice from a range of ages and social experiences. Secondly, the influences on the subsequent aggressiveness of the individually-housed male mice were estimated after introducing into their cages odoriferous bedding from groups of male and of female conspecifics. Both acute and chronic anosmia depressed the attacks directed towards ‘standard opponents’; indeed the chronic treatment virtually abolished this behaviour. Adding odoriferous bedding from the cages o...

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.

Effects of ambient temperature on nest construction in four species of laboratory rodents

Abstract This study concerns the effects of three different ambient temperatures (10, 15 and 20–22°C) on the nest‐building activities of non‐reproductive female laboratory house mice; rats; Mongolian gerbils and golden hamsters. Nest‐building behaviour was assessed in terms of the quantity of shredded paper utilized and the type of construction (plate, bowl or covered) on a daily basis over 14 consecutive days. Mice and rats used more material and tended to build more complex nests at lower ambient temperatures. Female gerbils used more nesting material at the highest temperature and least at 15°C. However, female gerbils built the most elaborate structures at the lowest temperature. The use of more material at 20–22°C was not reflected in a better nest. Female hamsters used considerably more material at the two lower temperatures, and at the lowest temperature built nests that were superior in quality to those generated by controls (20–22°C). Measurement with a digital probe confirmed that temperatures w...