Diet, Keystone Resources and Altitudinal Movement of Dwarf Cassowaries in Relation to Fruiting Phenology in a Papua New Guinean Rainforest

Abstract

I recorded plant community phenology for three years, classified each fruiting species according to pattern (continually, annually, biennially or one-year fruiting) and documented what cassowaries consumed versus this fruit availability through dung analyses. Dwarf cassowaries are 25 kg ratites whose diet consists of over 91% fruit year-round. Although the study site had aseasonal rainfall, it experienced an annual fruit lean season. During peak fruit periods cassowaries preferred predictable, synchronously fruiting annual and biennial species over continually fruiting species. However, during the lean season they had to rely on continually fruiting species, as they were almost the only fruits available over a 3–4 month period each year at the site. Cassowary diet is much more diverse than that of other specialized frugivores, perhaps because they are non-volant and can consume large quantities of fruit without the ballast limitations experienced by volant frugivores. Fruit availability and cassowary signs at three different altitudes over a 5-month period suggested that some individuals move altitudinally to follow fruit availability. I suggest that these are the females and that males remain to incubate eggs (the lean season is also the incubation season) and live mostly off their fat reserves.