Monopolization and cooperation: number of locations affects cooperation and partner preference in long-tailed macaques

Cooperation in animals is often measured in a group setting using the loose string-pulling paradigm to reveal the effects of dominance and social bonds on participation and cooperation. Yet typically only one highly monopolizable cooperation location is provided, contrasting with less monopolizable settings where food can be obtained at multiple locations. We addressed the effect of monopolization on cooperation, partner preference and communication by providing captive, group-living long-tailed macaques, Macaca fascicularis , with one, three or five cooperation locations in a group setting. Although the level of cooperation increased only slightly with more locations, the subjects’ participation changed drastically. With only one cooperation location, two adolescent males formed the primary cooperating dyad. With three or five locations, cooperation became more evenly distributed and the adolescent male dyad cooperated more with other individuals. Communication related to cooperation was not observed and the macaques did not seem to understand the need for a partner, although cooperation improved over time. Our study indicates that tasks with one location may reflect cooperation only in a highly monopolizable setting and may lead to specific partner preferences that would not arise in less monopolizable settings. This raises the question of whether performance in other cognitive tests that require the participation of more than one subject in a group setting could also be affected by the number of test locations.