Abstract: In mammals, olfactory cues are extensively used in many aspects of maternal care to ensure the coordination of mother-infant interactions and consequently the normal development of the offspring. Outside the period of parturition and lactation, when the young are not a behavioral priority, olfactory cues play an inhibitory role on maternal responsiveness since in most mammalian species studied so far, nonpregnant females find the odor of young aversive. On the contrary at the time of parturition, a shift in the hedonic value of infantile odors occurs so that the young now become a very potent stimulus and this sensorial processing constitutes an important part of the maternal motivational system. Moreover, infants' odors provide a basis for individual recognition by their mothers and some species (ungulates) have developed highly specialized mechanisms for processing of the infant signals. Perception of the smell of the young also regulates various aspects of maternal behavior. Dodecyl propionate, a compound released by of pup's preputial glands, has been shown to influence anogenital licking behavior, a fundamental pattern of maternal behavior in rodents. While there is no functional specificity of either the main or the accessory olfactory systems in the development of maternal behavior amongst species, it appears that only the main olfactory system is implicated when individual odor discrimination of the young is required. Neural structures, such as the main olfactory bulb, undergo profound changes when exposed to offspring odors at parturition. These changes in synaptic circuitry contribute both to maternal responsiveness to these odors, to their memorization, and to effects of long-term maternal experience.

Abstract: A study was conducted to determine the relationship between discrimination reversal learning and performance tasks in horses. Ten yearling and seven 2-year-old mares and geldings of Arabian (n = 4), Quarter Horse (n = 9), and Thoroughbred (n = 4) breeding were given a two-choice discrimination task in which either a black or a white bucket contained a food reward for ten trials per day during 19 test days. The spatial position of the buckets was varied on a random schedule. The rewarded bucket color was reversed each time a subject met criterion of eight correct choices per day for 2 consecutive days. Discrimination reversal testing was followed by 6 days of performance tasks: three crossing a wooden bridge and three jumping an obstacle to reach food and conspecifics, within a maximum allotted time of 15 min day-1. Total reversals attained by the horses were low (x = 1.5 +/- 0.9). All subjects did attain at least one reversal, and six had two or more reversals. No differences (P > .05) were detected between ages or sexes, nor among breeds in discrimination reversal learning or performance test measurements. However, there was a trend towards a breed difference (P <= 0.09) in the mean number of correct responses to the first reversal criterion. Correlations between reversal learning results and performance task results were extremely low, indicating that the discrimination reversal learning test was not useful for predicting success at these performance tasks. Results from the two performance tasks also showed little correlation (r = 0.04, P < 0.91), indicating that horses might not use the same approach when solving the problem of crossing these two obstacles. The overall poor performance of the horses on the discrimination reversal task suggests horses may have difficulty reversing previously learned tasks.

Abstract: Seven experiments were conducted on four miniature pigs to determine: (1) whether the pigs can discriminate between people wearing the same coloured clothing; (2) what cues they rely on if they could discriminate. For 2 weeks before the experiments began, the pigs were conditioned in a Y-maze to receive raisins from the rewarder wearing dark blue coveralls. They were then given the opportunity to choose the rewarder or non-rewarder in these experiments. Each session consisted of 20 trials. Successful discrimination was that the pig chose the rewarder at least 15 times in 20 trials (P<0.05: by χ2-test). In Experiment 1, both rewarder and non-rewarder wore dark blue coveralls. By 20 sessions, all pigs successfully identified the rewarder. In Experiment 2: (1) both wore coveralls of the same new colours or (2) one of them wore coveralls of new colours. They significantly preferred the rewarder even though the rewarder and/or non-rewarder wore coveralls of new colours. In Experiment 3, both wore dark blue coveralls but olfactory cues were obscured and auditory cues were not given. The pigs were able to identify the rewarder successfully irrespective of changing auditory and olfactory cues. In Experiment 4, both wore dark blue coveralls but covered part of their face and body in different ways. The correct response rate decreased when a part of the face and the whole body of the rewarder and non-rewarder were covered. In Experiment 5, both wore dark blue coveralls and changed their apparent body size by shifting sitting position. The correct response rate increased as the difference in body size between the experimenters increased. In Experiment 6, the distance between the experimenters and the pig was increased by 30 cm increments. The correct response rate of each pig decreased as the experimenters receded from the pig, but performance varied among the pigs. In Experiment 7, the light intensity of the experimental room was reduced from 550 to 80 lx and then to 20 lx. The correct response rate of each pig decreased with the reduction in light intensity, but all the pigs discriminated the rewarder from the non-rewarder significantly even at 20 lx. In conclusion, the pigs were able to discriminate between people wearing coveralls of the same colour after sufficient reinforcement. These results indicate that pigs are capable of using visual cues to discriminate between people.

Abstract: Many mammalian species are highly social, creating intra-group competition for such things as food and mates. Recent research with nonhuman primates indicates that in competitive situations individuals know what other individuals can and cannot see, and they use this knowledge to their advantage in various ways. In the current study, we extended these findings to a non-primate species, the domestic goat, using the conspecific competition paradigm developed by Hare et al. (2000). Like chimpanzees and some other nonhuman primates, goats live in fission-fusion societies, form coalitions and alliances, and are known to reconcile after fights. In the current study, a dominant and a subordinate individual competed for food, but in some cases the subordinate could see things that the dominant could not. In the condition where dominants could only see one piece of food but subordinates could see both, subordinates' preferences depended on whether they received aggression from the dominant animal during the experiment. Subjects who received aggression preferred the hidden over the visible piece of food, whereas subjects who never received aggression significantly preferred the visible piece. By using this strategy, goats who had not received aggression got significantly more food than the other goats. Such complex social interactions may be supported by cognitive mechanisms similar to those of chimpanzees. We discuss these results in the context of current issues in mammalian cognition and socio-ecology.

Abstract: Individual recognition is an essential component of interactions in many social systems, but insects are often thought incapable of the sophistication necessary to recognize individuals. If this were true, it would impose limits on the societies that insects could form. For example, queens and workers of the paper wasp Polistes fuscatus form a linear dominance hierarchy that determines how food, work and reproduction are divided within the colony. Such a stable hierarchy would be facilitated if individuals of different ranks have some degree of recognition. P. fuscatus wasps have, to our knowledge, previously undocumented variability in their yellow facial and abdominal markings that are intriguing candidates for signals of individual identity. Here, I describe these highly variable markings and experimentally test whether P. fuscatus queens and workers use these markings to identify individual nest-mates visually. I demonstrate that individuals whose yellow markings are experimentally altered with paint receive more aggression than control wasps who are painted in a way that does not alter their markings. Further, aggression declines towards wasps with experimentally altered markings as these novel markings become familiar to their nestmates. This evidence for individual recognition in P. fuscatus indicates that interactions between insects may be even more complex than previously anticipated.
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