Australia’s native biota has evolved in the absence of large ungulates such as those found on other continents (Mulvaney and Kamminga 1999; Janis 2008). Over the past two centuries, however, large ungulate grazers and browsers have been introduced into Australia with varying degrees of success (Ridpath 1991 and references therein). Those introduced into the tropical monsoon region of northern Australia encountered year-round high day and night temperatures, strong annual cycles of high humidity and aridity, annual season rainfall resulting in annual cycles of vegetation growth and senescence, extreme variability in the start and length of the wet and dry seasons, and low-quality vegetation on very infertile tropical soils. The introductions of ungulates into these environments have provided unique opportunities for research into the dynamic relationships between feral mammals and new environments, as well as an opportunity to explore various hypotheses about invasion ecology.

The Asian water buffalo (Bovidae: Bubalus bubalis Lydekker) (or, simply, buffalo) is the most successful of seven introductions of domesticated ungulate grazers that subsequently became feral in the tropical monsoonal region in the north-central region of the continent (Ridpath 1991). From no more than 100 domesticated buffalo released into the wild in the mid-1800s, buffalo numbers grew to ~400 000 in less than 150 years, occupying an area ~224 000 km2 across the major river systems of the north colloquially referred to as the ‘Top End’ of Australia (Ridpath 1991; Skeat et al. 1996; Petty et al. 2007; Figure 21.1).