Abstract: This study investigates the ability of horses to recall a feeding event in a two-point choice apparatus. Twelve horses were individually tested whereby they were maintained immobile in a test arena and visually and aurally experienced the delivery of food into one of two feed goals. The horses were then released to make their choice in two experimental contexts: immediate release after experiencing the delivery of food, and release 10 s after food delivery. Each horse performed 40 immediate-release (IR) trials, followed by forty 10-s release trials over a 3-day period. In addition, the same horses were tested 3 months later in the spring with the same number and sequence of trials. Results were analysed by log-linear analysis of frequencies. Results showed that while horses were able to achieve the correct feed goal choice in the immediate-release trials, they were unsuccessful with the 10-s release trials. This suggests that there are limitations in recall abilities in horses, in that they may not possess a prospective type of memory. There are welfare and training implications in these findings concerning the effects of overestimating the mental abilities of horses during training and the effects of delays in reinforcements.

Abstract: Research in comparative social cognition addresses how challenges of social living have formed the cognitive structures that control behaviours involved in communication, social learning and social understanding. In contrast to the traditional psychological approach, recent investigations take both evolutionary and functional questions into account, but the main emphasis is still on the mechanisms of behaviour. Although in traditional research `comparative' meant mainly comparisons between humans and other primates, ethological influences have led to a broadening of the spectrum of species under study. In this review, we evaluated how the study of dogs broadens our understanding of comparative social cognition. In the early days of ethology, dogs enjoyed considerable interest from ethologists, but during the last 20 years, dogs have rarely been studied by ethological methods. Through a complex evolutionary process, dogs became adapted for living in human society; therefore, the human environment and social setting now represents a natural ecological niche for this species. We have evidence that dogs have been selected for adaptations to human social life, and that these adaptations have led to marked changes in their communicative, social, cooperative and attachment behaviours towards humans. Until now, the study of dogs was hindered by the view that they represent an `artificial' species, but by accepting that dogs are adapted to their niche, as are other `natural' species, comparative investigations can be put into new light.

Abstract: Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus “mark test” for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation.

Abstract: With their vertically elongated body form, giraffes generally feed above the level of other browsers within the savanna browsing guild, despite having access to foliage at lower levels. They ingest more leaf mass per bite when foraging high in the tree, perhaps because smaller, more selective browsers deplete shoots at lower levels or because trees differentially allocate resources to promote shoot growth in the upper canopy. We erected exclosures around individual Acacia nigrescens trees in the greater Kruger ecosystem, South Africa. After a complete growing season, we found no differences in leaf biomass per shoot across height zones in excluded trees but significant differences in control trees. We conclude that giraffes preferentially browse at high levels in the canopy to avoid competition with smaller browsers. Our findings are analogous with those from studies of grazing guilds and demonstrate that resource partitioning can be driven by competition when smaller foragers displace larger foragers from shared resources. This provides the first experimental support for the classic evolutionary hypothesis that vertical elongation of the giraffe body is an outcome of competition within the browsing ungulate guild.

Abstract: Breeding groups with multiple stallions occur sympatrically with single-stallion breeding groups in feral horse, Equus caballus, populations. Mutualism and reciprocal altruism between stallions have been proposed to explain the origin and functioning of multistallion bands. However, empirical support for these hypotheses is contradictory and incomplete. Furthermore, there are no explicit tests of the predictions that each hypothesis makes about stallion behaviour and social structure. We compared nine multistallion and 18 single-stallion bands in the Kaimanawa Ranges, New Zealand. Compared with agonistic behaviours, affiliative behaviours were relatively unimportant in the relationships between stallions within bands. The number of stallions in the band did not have a positive influence on mare group size, stability, home range quality or reproductive success in bands. Furthermore, there was a positive relationship between aggression ('intolerance') by the dominant towards subordinate stallions and the subordinates' effort in mare group defence ('helping') but a negative relationship between helping effort by subordinates and their proximity to, and mating with, the bands' mares. Therefore, the predictions of the mutualism and reciprocal altruism hypotheses were not supported. Indeed, for some of the predictions we found the opposite outcomes to be true. Multistallion bands had significantly poorer reproductive success, and dominant stallions were less tolerant of subordinates that helped most and reduced their access to mares. Nevertheless, in all other respects Kaimanawa stallions in multistallion bands behaved like those described elsewhere. Thus, we reject cooperative hypotheses for multimale breeding groups in horses and discuss the mate parasitism and consort hypotheses as better alternatives. Copyright 2000 The Association for the Study of Animal Behaviour.