Abstract: Relatively little is known about the relationship between social behavior and specific cognitive abilities of the chicken. It is uncertain whether dominant birds have a cognitive advantage over subordinate birds that might facilitate their superior position in the social hierarchy. Likewise, it is unknown whether subordinate birds compete successfully with higher ranking birds because their cognitive capacities compensate for physical deficits. In this study, the relationship between the chicken's position in the dominance hierarchy and its performance on a cognitive task was explored. Ten pairs of New Hampshire domestic roosters (Gallus gallus) were observed to determine dominance or subordinance within dyads. All birds were then trained and tested on a visual discrimination learning task. Discriminative stimuli were orange and green plastic discs. Correct stimuli (orange or green) were randomly assigned to birds. Placement of the discs (left or right of center) was also randomly assigned and counterbalanced to avoid a side bias. Birds were rewarded with food for pecking at the correct disc. Criterion for task completion was 80% correct responses on three consecutive test sessions or 86% correct on two consecutive sessions. All subjects met the test criterion. The number of trials to criterion was compared between dominant and subordinate birds using a paired t-test. No difference was found in performance between dominant and subordinate birds (p > 0.05) suggesting that in chickens, ability to learn a novel visual discrimination task is not well correlated with rank. Additional studies, particularly using different learning paradigms, are needed to confirm these results.

Abstract: Many animals appear to monitor changes in other individuals' dominance ranks and social relationships and to track changes in them. However, it is not known whether they also track changes in very transient relationships. Rapid recognition of a temporary separation between a dominant male and a sexually receptive female, for example, should be adaptive in species where subordinate males use opportunistic strategies to achieve mating success. Dominant male baboons (Papio hamadryas ursinus) form sexual consortships with oestrous females that are characterized by mate guarding and close proximity. To assess whether subordinate males track temporary changes in the status of other males' consortships, we conducted playback experiments using a two-speaker paradigm. In the test condition, subjects heard the consort male's grunts played from one speaker and his consort female's copulation call played from a speaker approximately 40 m away. This sequence suggested that the male and female had temporarily separated and that the female was mating with another male. In a control trial, subjects heard another dominant male's grunts played from one speaker and the female's copulation call played from the other. In a second control trial, conducted within 24 h after the consortship had ended, subjects again heard the consort male's grunt and the female's copulation call played from separate speakers. As predicted, subjects responded strongly only in the test condition. Eavesdropping upon the temporal and spatial juxtaposition of other individuals' vocalizations may be one strategy by which male baboons achieve sneaky matings.

Abstract: To test whether mineral recommendations for horses are likely to guarantee adequate mineral provision for black rhinoceroses (Diceros bicornis), we investigated the apparent absorption (aA) of macro- and microminerals in eight black rhinoceroses from three zoological institutions in a total of 32 feeding trials with total faecal collection, with additional data from three unpublished studies (18 feeding trials). Feeds and faeces were analysed for Ca, P, Mg, Na, K, Fe, Mn, Cu, Zn and Co. The resulting aA coefficients, and the linear relationships of apparently absorbable dietary mineral content to total dietary mineral content [per 100 g dry matter (DM)], were compared with data for domestic horses. Rhinoceroses had significantly higher aA coefficients for Ca and Mg (because of a higher calculated 'true' absorption), and lower ones for Na and K (because of calculated higher endogenous faecal losses). High absorption efficiency for divalent cations is hypothesized to be an adaptation to a natural diet of particularly high Ca:P ratio (approximately 14:1); an effective removal of Ca from the ingesta guarantees sufficient P availability at the fermentation site in the hindgut. Higher faecal losses of Na and K are hypothesized to be linked to a higher faecal bulk per DM intake in black rhinoceroses as compared with horses because of a generally lower digestive efficiency. There were no relevant differences in the absorption patterns of microminerals. In particular, there were no discernable differences in Fe absorption within the rhinoceroses for diets with and without tannin supplementation. Several of the zoo diets assessed in this study were deficient in Cu, Mn or Zn, and most contained excessive levels of Fe when compared with horse requirements. The findings of this study indicate that differences in mineral absorption between occur even between species of similar digestive anatomy; that in particular, Ca absorption might vary between hindgut fermenters with Ca:P ratio in their natural diet; that Na might be a particularly limiting factor in the ecology of free-ranging rhinoceroses; that moderate doses of tannins do not seem to markedly influence mineral absorption; and that diets for captive animals should contain adequate, but not excessive mineral levels.

Abstract: The effects of the size of the environment on animals' spatial reorientation was investigated. Domestic chicks were trained to find food in a corner of either a small or a large rectangular enclosure. A distinctive panel was located at each of the four corners of the enclosures. After removal of the panels, chicks tested in the small enclosure showed better retention of geometrical information than chicks tested in the large enclosure. In contrast, after changing the enclosure from a rectangular-shaped to a square-shaped one, chicks tested in the large enclosure showed better retention of landmark (panels) information than chicks tested in the small enclosure. No differences in the encoding of the overall arrangement of landmarks were apparent when chicks were tested for generalisation in an enclosure differing from that of training in size together with a transformation (affine transformation) that altered the geometric relations between the target and the shape of the environment. These findings suggest that primacy of geometric or landmark information in reorientation tasks depends on the size of the experimental space, likely reflecting a preferential use of the most reliable source of information available during visual exploration of the environment.