Skyrail Nature Diary
Cassowary Plum
August 2008
A favourite food of Tropical North Queensland’s iconic flightless bird, the Southern Cassowary (Casuarius casuarius), is the aptly named Cassowary Plum (Cerbera floribunda).
The Cassowary Plum fruits are a good match for the Southern Cassowary, in that they are big, bright and colourful. The fruit is large and egg-shaped, with a smooth, bright blue coloured skin.
Interestingly, the Cassowary Plum fruits contain a sap which is poisonous to humans and to most animals. However, the Southern Cassowary is able to eat the toxic fruit, due to the unique nature of its digestive system. The Cassowary has a short and fast digestive system, which passes most fruits relatively undigested.
Also, the stomach of the Cassowary is filled with a rare combination of digestive enzymes, which render it immune to the Cassowary Plum’s toxic alkaloids.
The Cassowary Plum and the Southern Cassowary have a mutually beneficial relationship. While the Cassowary Plum provides an important food source for the Cassowary, the Cassowary, in turn, assists with the spread and germination of the tree.
The Cassowary is the only bird large enough to eat the Cassowary Plum fruits intact. It swallows the large fruits whole and passes them, mostly undigested, through its stomach, which is said to gently massage the outer layer of the fruits, helping them to germinate. In fact, Cassowary Plum fruits are more likely to germinate once they have been passed through the stomach of a Cassowary!
The Cassowary Plum tree is related to the exotic Frangipani (Plumeria alba) and can grow to around 30 metres in height. When it reaches approximately three years in age, the tree will begin to produce fragrant white flowers with distinctive red centres. The flowers are followed by the large, blue fruits.
Another animal that manages to eat the poisonous Cassowary Plum fruit is the White-tailed Rat (Uromys caudimaculatus). The White-tailed Rat tears the toxic flesh off the fruit, before feeding on the seed kernels inside.
Selected pictures courtesy of Wet Tropics Management Authority
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