Fruit choice by the dwarf cassowary, Casuarius bennetti, over a three year period in Papua New Guinea

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)



First Committee Member

Theodore H. Fleming - Committee Chair


I recorded plant phenology, cassowary diet, and fruit characteristics from May 1990 through May 1993 at the Crater Mountain Biological Research Station in Papua New Guinea to determine which plant traits were most important to cassowary fruit choice. Rainfall was aseasonal, but there was an annual fruit lean season from December through March and supra-annual masting in multiple families in even numbered years. Continuously fruiting species were almost all that was available during the lean seasons. Cassowary diet was over 90% fruit year-round. Cassowaries have a more diverse diet than other specialized frugivores, probably because they are non-volant and so do not need to avoid excess weight. Cassowaries obtain required nutrients by the shear quantity of fruit they consume. Fruit size and seed size were strongly correlated. Arillate fruits were higher in lipid and protein content than other fruits, but drupes (preferred by cassowaries) also tended to have high protein concentrations. Fruit color was not important for cassowary fruit choice. Large crop size was preferred when all available species were compared, but was not a significant preference when considering only plant species consumed by cassowaries. This was because many shrub species (continuous low-level fruiting patterns and small crop size) were not found in the cassowary diet. Although thousands of fruits were available on these species, cassowaries did not consume them, suggesting that cassowaries forage at known fruit sources and do not search for fruits in route or randomly. Reliable species (those with annually synchronous fruiting) were highly preferred over continually (asynchronous) fruiting species. These seasonally fruiting species also tended to have higher protein content and larger crops than continuously fruiting species. Cassowaries preferred drupes whose large seeds pass quickly through the gut; drupes also tended to be higher in protein than other fruit types. Cassowaries are obligate frugivores that eat fruits of a wide variety of taxa, but do not consume all available fruits randomly. These birds avoid small unpredictable species and prefer large, predictable, nutritious species.


Biology, Botany; Biology, Ecology; Biology, Zoology

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