What Do Tree Kangaroos Eat. These species are exclusively herbivorous and they primarily feed on leaves, fresh vegetation, fruits, flowers, nuts and other plants matter. Fresh vegetation is necessary to give them extra strength while climbing; however, they have to rely on dry grasses in times of drought. Tree kangaroos diet include moss, grass, ferns, saps, bird eggs, grains, tree bark, and young birds. One of the primary sources of tree kangaroos diet is browse which is rich in fiber. They are also known to eat few tree species including alder, ficus, willow, maple, and elm. Sometimes, they also consume bamboo but these kinds of nutrients are often provided in captivity as they are not readily available in the wild. These animals eat bamboo and other foods when they are fresh.