The majority of the 22 primate species known to eat fungi spend less than 5% of their feeding time doing so. The Goeldi's monkey (Callimico goeldii), a small South American primate, devotes up to 63% of its feeding time to the consumption of Auricularia auricula, A. mesenterica, Ascopolyporus polyporoides and A. polychrous. This may be as much as 6.1kg/animal/year of fresh weight of fungus consumed by an animal weighing half a kilogram; in comparison, the average person in the U.S.A. consumes 1.9 kg/person/year of fresh weight of mushrooms. The nutritional benefits of mycophagy appear to be relatively few, but need to be investigated further. Mycophagy by Goeldi's monkeys may be a strategy for reducing feeding competition during the dry season and likely affects the monkeys' home range size and distribution pattern.

This review summarizes information on the behavioural ecology of mixed-species troops (interspecific associations) formed by different species of callitrichines, small New World monkeys, in western and central Amazonia. The formation of mixed-species troops is an integral part of the biology of several species of this subfamily. Niche separation between associated species is obtained through vertical segregation which results in differences in the prey spectrum. The degree of niche separation is a predictor for the stability of mixed-species troops. Individuals may benefit from the formation of mixed-species troops through increased safety from predators, increased foraging efficiency, and/or increased resource defence. Costs of mixed-species troop formation are probably very low and mainly relate to patterns of interspecific behavioural interactions. We point to gaps in our knowledge and suggest pathways for future research into mixed-species troops.