Abstract: The Alex Studies: Cognitive and Communicative Abilities of Grey
Parrots. By I. M. PEPPERBERG. Cambridge, Massachusetts:
Harvard University Press (1999).

Abstract: Assessing the animal welfare state is a challenge given the subjective individual cognitive and emotional processing involved. Electroencephalography (EEG) spectrum analysis has proved an ecologically valid recording situation to assess the link between brain processes and affective or cognitive states in humans: a higher slow wave/fast wave ratio has been associated with a positive internal state. In particular, a high production of theta power (3-8 Hz) has been related to positive emotions. On the other hand, it has been hypothesized that a left hemisphere (LH) dominance may be associated with a better welfare state. Here, we test the hypothesis that individual differences in the resting-state quantitative EEG power spectrum of adult horses (N = 18) and its lateralization pattern may reflect individual subjective perception of their conditions of life and welfare state. The results show clear individual differences in the proportions of the different waves and their inter-hemispheric distribution. Three different EEG power spectrum profiles were highlighted, from a bilateral predominance of theta waves in horses in a more positive welfare state to a bilateral predominance of beta waves in horses with clear expressions of compromised welfare. Interestingly, particular correlations were found between wave power activity and welfare parameters. We found a negative correlation between the number of stereotypic behaviours per hour and the median proportion of theta waves in the left hemisphere. and between the overall state (total chronic stress score) of welfare and gamma production in the right hemisphere (RH). These findings go along the hypothesis of a particular involvement of the left hemisphere for positive processing and of the right hemisphere for negative processing. However, the pattern of laterality did not appear as the most important feature here as both extreme clusters in terms of welfare showed bilateral predominance of one wave type. It is possible that hemispheric specialization makes more sense during acute emotion-inducing conditions rather than in this resting-state context (i.e. in absence of any high emotion-inducing stimulation), although the opposition gamma versus theta waves between both hemispheres in the horses with an intermediate welfare state is noticeable and intriguing. It seems that bilateral but also LH theta activity is a promising neurophysiological marker of good welfare in horses, while a bilateral or RH high production of gamma waves should alert about potential welfare alterations. Quantitative resting-state EEG power spectrum appears as a highly promising tool for exploring the brain processes involved in the subjective perception of chronic welfare, as a useful complementary tool for welfare assessment.

Abstract: The Minnesota Zoological Garden established a bachelor (i.e. all-male) group of 8 Przewalski horses (Equus przewalskii) in 1984. Possible methods for mixing males emerged through preliminary introductions and review of the relevant literature. These included: (1) grouping colts (<=3 years old) after removing them from their natal bands; (2) introducing adult stallions to colts in spacious, controlled environments to reduce the risk of combat-related injury or death associated with largely unpredictable adult temperament; (3) introducing more than 1 animal at a time to established groups. Based on the frequency and orientation of agonistic interactions observed among the bachelors, a linear dominance hierarchy was discerned among the 4 adult stallions; all 4 colts were determined to be of equally low or seemingly non-ranking status. Social rank among the adults was most influenced by individual temperament, and contention for rank was limited almost exclusively to the 3 lower-ranking stallions; the alpha male participated in 73% of all agonistic interactions observed, but was identified as the recipient in less than 3% of these interactions. Intra-band associations were detected in the bachelor group. The most prevalent of these was among the 4 colts, found together in over 70% of the observations. Other affinities commonly observed were between the colts (as a sub-group) and different stallions. The dominant stallion, the colts' most frequent companion, actively discouraged the 3 lower-ranking stallions from associating with the colts. Further, the colts were subjected to significantly fewer agonistic behaviors than the non-alpha stallions (per colt=1.05+/-0.24 h-1; per non-alpha stallion=2.01+/-0.04 h-1). These findings support the hypothesis developed by other workers for ungulates that young bachelors are sheltered from aggression by association with an alpha male. With one exception, adult associations were rarely noted. Although combat-related injuries (superficial wounds and temporary lameness) were common among the bachelors, few required medical attention. No permanent disabilities or deaths have occurred since the group's inception. The existence of social organization and intra-band associations in the bachelor group support the suggestion that such groups were once a natural part of this species' social milieu. Bachelor groups are therefore recommended as an ethologically sound, space- and cost-effective means of managing “surplus” (i.e. non-harem) male Przewalski horses.

Abstract: Most birds rely on imprinting and experience with conspecifics to learn species-specific recognition cues. Australian brush-turkeys (Alectura lathami) do not imprint and form no bonds with parents. They hatch asynchronously, disperse widely and meet juvenile conspecifics at an unpredictable age. Nevertheless, in captivity, hatchlings respond to other chicks. A recent study, which involved the use of robotic models, found that chicks prefer to approach robots that emit specific visual cues. Here, we evaluated their response to acoustic cues, which usually play an important role in avian social cognition. However, in simultaneous choice tests, neither 2-day-old nor 9-day-old chicks preferred the choice arm with playback of either chick or adult conspecific calls over the arm containing a silent loudspeaker. Chicks of both age classes, however, scanned their surroundings more during chick playback, and the response was thus consistent in younger and older chicks. We also presented the chicks with robotic models, either with or without playback of chick calls. They did not approach the calling robot more than they did the silent robot, indicating that the combination of visual and acoustic cues does not evoke a stronger response. These results will allow further comparison with species that face similar cognitive demands in the wild, such as brood parasites. Such a comparative approach, which is the focus of cognitive ecology, will enable us to further analyse the evolution and adaptive value of species recognition abilities.

Abstract: There is no information on whether the daily foraging movements of fish shoals are the result of chance, the collective will of all shoalmates, or the leadership of a few individuals. This study tested the latter possibility. Shoals of 12 golden shiners, Notemigonus crysoleucas, were trained to expect food around midday in one of the brightly lit corners of their tank. They displayed daily food-anticipatory activity by leaving the shady area of their tank and spending more and more time in the food corner up to the normal time of feeding. Past this normal time they remained in the shade, even on test days when no food was delivered. Most of these experienced individuals were then replaced by naïve ones. The resulting ratio of experienced:naïve fish could be 5:7, 3:9 or 1:11. On their own, naïve individuals would normally spend the whole day in the shade, but in all tests the experienced individual(s) were able to entrain these more numerous naïve fish out of the shade and into the brightly lit food corner at the right time of day. Entrainment was stronger in the 5:7 than in the 1:11 experiment. The test shoals never split up and were always led by the same fish, presumably the experienced individuals. These results indicate that in a strongly gregarious species, such as the golden shiner, a minority of informed individuals can lead a shoal to food, either through social facilitation of foraging movements or by eliciting following behaviour.