Postconflict (PC) behaviors, including reconciliation and consolation, have been observed in many primate and several nonprimate species. Using the PC-matched control (MC) method, PC behavior was examined in two groups (n=13) of captive western lowland gorillas, a species for which no conflict resolution data have been published. Analyses of 223 conflicts showed significantly more affiliation between former opponents after a conflict when compared to control periods, indicating reconciliation. Results also showed significantly more affiliation between the victim and a third-party after a conflict, indicating consolation. Both solicited and unsolicited consolation were observed. The majority of the affiliative interactions observed for both reconciliation and consolation were social proximity, which suggests that unlike most nonhuman primates, proximity, rather than physical contact, may be the main mechanism for resolving conflicts in western lowland gorillas. PC behavior was not uniform throughout the groups, but rather varied according to dyad type.

It has been suggested that providing multiple computers with automatic reward dispensers as enrichment to captive orangutans (Pongo spp) (as opposed to a single computer, with a care-staff person delivering reinforcers) might help improve behavioural outcomes. The purpose of the current study was to test this hypothesis by providing two computers with automatic reward dispensers to eight orangutans housed in four male-female pairs at Zoo Atlanta, USA. Subjects were observed for ten days during each of three phases: a baseline phase (during which, no computer was provided); immediately followed by Phase 1 (during which, one computer system was provided to each pair of subjects); immediately followed by Phase 2 (during which, two computer systems were provided to each pair). Data were collected in 1-h sessions using instantaneous scan sampling. There was no habituation to the computer system, nor were there any significant increases in aggression, rough scratching, and abnormal behaviours in either computer phase, which indicates that computer-joystick systems are effective as enrichment for captive orangutans. However, a high level of interest in the computer was shown by only a few individuals, which highlights a need to take into consideration individual differences when providing computerised enrichment to captive non-human primates. It would also be advisable to provide other forms of enrichment to increase activity levels for individuals which are not interested in interacting with a computer, as well as to help increase the diversity of behaviours being stimulated by the enrichment.

We examined object permanence in black-and-white-ruffed lemurs (Varecia variegata) at Zoo Atlanta. A series of visible and invisible displacement tasks with suitable controls were presented to five adult subjects. Subjects performed significantly above chance on all regular tasks, except for the double invisible displacements. Subjects failed visible and invisible controls. Failure on the control trials did not appear to be because subjects used the "last box touched" strategy (subjects did not choose the last box touched significantly more than expected by chance). However, a substantial percentage of choices was made to the last box touched by the experimenter. There was no significant difference between this percentage, and the percentage of choices made to the baited box (on both visible and invisible controls), which indicates that subjects were drawn to both boxes which the experimenter visited/touched, and thus failed the controls. Based on the results from the present study, we believe that there is no evidence that black-and-white ruffed lemurs understand visible and invisible tasks in the traditional object permanence battery.

The nonadjacent double invisible displacement task has been used to test for the ability of different species to mentally represent the unperceived trajectory of an object. The task typically requires three occluders/boxes in a linear array and involves hiding an object in one of two nonadjacent boxes visited in succession. Previous research indicates that 19-, 26-, and 30-month-old children and various nonhuman species cannot solve these displacements. It has been hypothesized that this is because individuals are unable to inhibit searching in the unbaited center box that was never visited by the experimenter. It has been suggested that presenting the task in a large-scale locomotor space might allow individuals to overcome this inhibition problem. In the present study, we tested orangutans on adjacent and nonadjacent double invisible displacements with the traditional setup (experiment 1) and in locomotor space with boxes placed 1.22 m apart (experiment 2). In both experiments, subjects were able to solve adjacent, but not nonadjacent, trials. The failure on nonadjacent trials appeared to be because of an inability to inhibit sequential search on the second choice as well as because of a large number of first-choice errors (directly choosing an incorrect box). The current results support previous findings that orangutans exhibit some constraints when representing the invisible trajectory of objects.