Feral pigs are well established in the lowland tropical forests of northeastern Queensland, Australia. Circumstantial evidence, e.g. the presence of a Melanesian tick, an exotic nematode and a dominant coat colour other than black, indicates that they do not originate from escaped domestic animals as feral pigs throughout other parts of Australia. It is likely that the ancestral population was established from animals originating from islands to the north and northwest of Australia, i.e. pigs domesticated from naturally occurring wild pigs in Indonesia and southeastern Asia. Pigs in lowland rainforests show relatively stable populations with a high reproductive potential in age classes 4–7. Seasonally there are negative interactions between residents and pigs. Pigs not only damage gardens and fruit orchards due to their rooting, they are also important vectors of zoonoses. Feral pigs are carriers of 11 Leptospirosis serovars, some of which are important zoonoses, e.g. L. australia, L. hardjo and L. zanoni. They also have a high burden of parasites. Lice Hematopinus suis and thorny headed worm Macracanthorhynchus hirudinaceous have been more frequently found in females than in males, whereas males seem to be more susceptible to ticks Ambylomma cyprium cyprium. The infection with lungworms Metastrongylus sp. is higher in younger pigs than older ones indicating that lungworms represent a major mortality factor of young pigs. In contrast, kidney worm Stephanurus dentatus and thorny headed worm is present at all ages. Leptospirosis, lung worm and kidneyworm are known causes of infertility and/or mortality in pigs and can be assumed to contribute to the lower than expected population density in this environment.