The Rainforest Gardener
Cassowaries require a high diversity of fruiting trees to provide a year-round supply of fleshy fruits. Cassowaries prefer fallen fruit and are sometimes referred to as frugivores (fruit-eaters), but they are actually omnivores and will also eat small vertebrates (such as snails and frogs, small birds and eggs), invertebrates, fungi, carrion and plants. After cyclones, when fruit is scarce, these may become an important part of their diet.
Cassowaries (like many other birds) are known to eat soil, particularly when food is scarce, probably to supplement the low mineral content of fruits. They’ve also been observed foraging in mangroves, and it is thought that females may hunt for crabs to increase their calcium intake before breeding.
Cassowaries have been recorded as eating over 238 species of plants, and they play an important role in maintaining the diversity of rainforest trees. Cassowaries are one of only a few species that can disperse large rainforest fruits and are the only long distance dispersal agent for large seeded fruits.
Cassowaries swallow fruit whole, digesting the pulp, and passing the seeds unharmed in large piles of dung, distributing them over large areas throughout the rainforest.
A ready-made fertiliser, the dung helps many kinds of seed to grow. Other animals sometimes feed on the seeds in cassowary droppings, helping to distribute them further.
The cassowary’s gentle digestive system, and short intestines, may also help to protect them from absorbing a harmful level of toxins from some of the fruits they eat.
The cassowary is considered a keystone species because of its critical role in maintaining the ecological balance of the rainforest. Protecting cassowary habitat and food plants benefits many other rainforest plants and animals.
Without cassowaries, some species of rainforest plants would have no means of distribution. If cassowaries were to disappear from an area, some of these species may eventually become locally extinct, threatening other species that depend on them and changing the forest dynamic.