The cassowaries are large, flightless ratite birds that are found in the rainforests of Papa New Guinea, Australia, and some of the surrounding islands (Sanft 1975). Weighing up to 85 kg, these birds are second in size only to the ostrich. Native peoples hunted the cassowaries and valued them as livestock; it was reported that a Papuan could trade a cassowary for a wife or eight pigs. Cassowaries have a horn-like helmet on their heads (known as a casque), that protects their heads as they run through dense forests with an outstretched neck (Sanft 1975). There are three species in the family casuariidae, this paper will focus on the large-casqued Australian Cassowary (also known as the Southern Cassowary).
Southern Cassowaries are primarily frugivores, with a diet consisting of a variety of different species of fallen fruits, but including some invertebrates and small vertebrates (Moore 2007). Cassowaries minimally process fruit seeds, as they lack gizzard stones, so the seeds are voided fully intact (Moore 2007). The Southern Cassowary plays an important role in seed dispersion, research has found the seeds of hundreds of plant species in droppings, with a disproportionately high level of large seeds (Bradford et al. 2008).
Cassowaries perform an important seed dispersal function, as no other species disperses large seeds over distances greater than 2 km (Bradford et al. 2008). In other rainforests, there are several species that fill this important role, so in Australia the Southern Cassowary is recognized as a keystone species (Moore 2007).
Male cassowaries incubate clutches of 2-5 eggs and care for the newly hatched young, a function of female birds in most species (Moore 2007). Males and females are both polyamorous, often breeding with multiple members of the opposite gender in one breeding season. The breeding season of the Southern Cassowary is flexible, as the rainforest is frequently suitable for raising young, but peak breeding occurs from June to November. Cassowaries do not breed every year; a majority of male cassowaries breed once every three years (Moore 2007).
Along with ostriches, Southern Cassowaries are the only birds in the world that have physically attacked and killed humans (Kofron 1999). Seventy-five percent of cassowaries that attacked humans had been previously fed by humans, and 73% of the attacks were in an attempt to solicit food. Thus feeding cassowaries causes them to become more aggressive, altering their normal behavior (1999). The feeding of cassowaries, like bear populations in North American, may cause them to be drawn to human developed areas, putting them into dangerous situations not occurring in their natural habitats (i.e. traffic accidents). This danger must be mitigated, as the Southern Cassowary is endangered in Australia (Kofron 1999).
In Australia, there are several likely causes of the endangerment of the Southern Cassowary, including habitat loss, predation by humans and dogs, car accidents, and nest predation by pigs (Crome and Moore 1990). A majority of the most suitable land for the cassowaries has already been cleared or developed, and at the time of this study there was additional tourism development planned in areas with high cassowary density. Wild pigs destroy Southern Cassowary nests, feed on their eggs, and compete for fruit with the birds. Crome and Moore urge the conservation of the cassowary, not just for the sake of the species, but for maintaining rainforest dynamics through the bird’s seed dispersal (1990).
Southern Cassowaries are unique birds that play a critical role in dispersing the seeds of rainforest foliage. Although they can be dangerous to humans, this is aberrant behavior caused by human interference. The conservation of the Southern Cassowary is an important undertaking that requires further research, public education, and habitat restoration.
