POPULATION-DYNAMICS OF FERAL PIGS (SUS SCROFA) IN A TROPICAL RIVERINE HABITAT COMPLEX

I employed mark-recapture techniques to monitor trends in the population density of feral pigs in a tropical woodland habitat containing cereal crops, and compared density indices in this habitat with other similar habitat not containing cereal crops. Over the duration of the study there was no significant trend for increase or decrease but population density fluctuated seasonally between 2.2 and 3.5 pigs km(-2) in the woodland site containing cereal crops. A numerical response model was developed relating observed exponential rate of increase of feral pigs to antecedent rainfall. The model estimated the maximum exponential rate of increase ((r)max) of feral pigs to be 0.065+/-0.017 (s.e.) month(-1) or 0.781+/-0.21 (s.e.) year(-1). Comparison of indices of population density of feral pigs in woodland habitat with cereal crops and similar woodland habitat without cereal crops demonstrated that the presence of intensive cereal cropping increased population density of feral pigs almost four-fold. Population density in the woodland habitat without cereal crops was estimated to be 0.8 pigs km(-2). I interpret the response to rainfall and the variation in density in response to an increase in the amount of available food as evidence that feral pig populations are limited primarily by food availability.