The ecological implications of endozoochory in emus (Dromaius Novaehollandiae Dc) in the fire-prone heathland/woodland communities of the Northern Grampians area, Victoria

The emu (Dromaius novaehollandiae) is a large, flightless ratite bird species endemic to Australia. It is a prolific devourer of seeds and fruits, and evidence of its potential role as a seed dispersal agent is readily gained through examination of the high density of intact seeds in scats. Dispersal of seeds by the emu has never really been in question, but the implications of this dispersal, especially within fire-prone environments of southern Australia, is a topic that has yet to be explored. The notion that the emu is distributing large quantities of seeds within a fire-prone plant community is intriguing in that it incorporates both the biotic interactions associated with seed dispersal and the environmental factors associated with fire disturbance. Seed dispersal by animals is important for the long-term persistence of many species in fireprone environments. However, there is uncertainty as to what degree animals are important in determining which species emerge in the community and when (Whelan, 1986). Many fabaceous species are collected and dispersed by ant/ which seek the food reward present as an attachment (the elaiosome) on the seed (Berg, 1975; Clifford & Drake, 1981; O'Dowd & Gill, 1986). These seeds may be buried, thus avoiding direct contact with fire, but receive the heat stimulation necessary for their germination (Berg, 1981). Another dispersal strategy employed by plants is the production of fruits palatable to vertebrates. The emu disperses the relatively large fruits of many hard seeded species (e.g. Epacridaceae), stripping the fleshy coating from the fruits as they pass through the digestive tract. Passage through the gut of birds has been shown to stimulate germination of seeds in many species (Krefting & Roe, 1949; Noble, 1975b; van Balgooy, 1979), but this would not seem to make sense in a fire-prone environment where germination in most species is cued to occur in the first year following fire. Any seedling which establishes later during the inter-fire period has less time to reach reproductive maturity and produce seeds before the arrival of the next fire, and will thus contribute fewer offspring, on average, to the next generation. Digestive tract stimulation of seed germination by the emu would seem non-adaptive in a fire-prone environment. The present work seeks to resolve what role the emu does play in the dispersal and germination of plant species in such an environment