distance group calling. Their function is to ensure adequate spacing between the home ranges of different family groups. These vocalisations are known as duets, and generally involve the male and female. If a neighbouring group is within earshot of these calls they will respond with their own duetting. The white-eared titi is arboreal, spending most of its time in the lower strata of the forest. It may enter the main canopy when travelling longer distances and may also cross small areas of open ground, though the latter is rare. During normal movement through its environment it is quadrupedal and mostly walks, clambers and leaps, but it can also bound and climb. It leaps small distances, no more than a few body lengths, between trees where vegetation is not thick enough to support its primary forms of locomotion. When travelling on the ground it is said to use a "bounding movement" whereby it leaps more than off the ground. The titi monkey prefers branches which are less than in diameter and its tail never touches the support it is on. Ecology There is relatively little known about the ecology of the white-eared titi or even titi monkeys in general, and few studies have focused on the white-eared titi. It is diurnal, commencing activity around sunrise and continuing until sunset. Food availability may influence activity times; if there is an abundance of food in the warmer months when plants are fruiting titi monkeys may start earlier, or if there is a lack of food, titi monkeys may remain at the feeding tree into the evening. The titi monkey usually rests during the middle of the day and has two main feeding periods, in the morning and in the afternoon. It has an increased period of feeding towards the end of the day. In total, the titi monkey is active for an average of 11.5 hours, 2.7 hours of which is spent feeding. Titi monkeys sleep on branches at least above the ground. In the same manner as resting during the day, titi monkeys huddle together and twine tails to sleep. Though there is little published research on the diet of the white-eared titi, titi monkeys in general are omnivores that eat fruit, leaves, insects, and seeds. They mostly eat leaves, especially protein-rich young leaves and leaf buds, so a significant period of the day is spent resting to digest the cellulose. They