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.