Head and body length, 18-23 cm; tail, 27-29 cm
Uknown; populations declining
Coastal secondary, lowland, evergreen and semi-deciduous forests of eastern Brazil
Uncommon senses meet common sense. Superbly sharp hearing allows Geoffroy's tufted-ear marmoset to communicate at pitches too high for the human ear to register. Smell comes into play as the dominant female secretes pheromones to prevent other females in the family group from ovulating. The little tree dweller is also big on common sense. When it sees a troop of army ants, for instance, it follows them; that way, it can make a meal of the insects and small animals that climb the trees to escape the ants. This makes a nice change from its usual diet of fruits and tree gum. But these trees are an uncertain home, threatened by relentless deforestation.