Observations on effects of feral pig (Sus scrofa) age and sex on diet

Abstract

Context Feral pigs (Sus scrofa) are a destructive invasive species that cause damage to ecologically sensitive areas. Management of biodiversity and of feral pigs assumes the diet of pigs of different ages and sexes are similar. Aims We aimed to investigate effects of feral pig age and sex on broad feral pig diet to identify potential at-risk native wildlife species so as to improve biodiversity and feral pig management. Methods Diet was determined by macroscopic analysis of the stomach content of 58 aerially shot feral pigs of mixed ages and sexes. The study occurred in the Macquarie Marshes, New South Wales, a Ramsar wetland of international significance. Results Feral pigs were largely herbivorous, with vegetable matter being found in all stomachs and contributing to a majority of the food material that was present in each stomach, by volume. Adult feral pigs had significantly more grasses and crop material in their stomachs than juveniles, while juveniles had significantly more forbs in their stomachs than adult feral pigs. Vertebrate prey items included frogs, lizard and snake, but no threatened wildlife species. Conclusions Juvenile and adult feral pigs differed in their diet, especially with regards to plant material, which has not been reported previously. There was, however, no difference in the consumption of vertebrate wildlife species between juvenile and adult, or male and female feral pigs. Slow-moving, nocturnal amphibians and reptiles were the most common vertebrate item recorded. Implications Biodiversity and feral pig management should recognise plant diet differences between demographic segments of the feral pig population. Further research is recommended to determine if diet differences also occur for threatened wildlife species, which will require more intensive nocturnal sampling.