Feral pigs in north-western Australia: population recovery after 1080 baiting and further control

Abstract

The recovery rate of a population of feral pigs (Sus scrofa) in the west Kimberley in north-western Australia was determined 12 months after a 1080 (sodium fluoroacetate)-baiting program. An estimated 56 pigs were present in the 15 000-ha study area in August 2005 compared with the prebaiting levels of 250–275 pigs in 2004 (11 pigs were known to be alive on site after the 2004 baiting). This represents a population recovery of 20–23% of the 2004 prebaiting levels. Although most pigs were in good body condition, environmental conditions were quite different between the two years. In 2005, some waterholes were dry or comprised mainly muddy water with little associated shelter for feral pigs. Consequently, and in contrast to 2004, no pigs were seen, and no bait take could be attributed to feral pigs, at the four resurveyed waterholes. Most pig sightings, and activity, were close to the Fitzroy River. Fermented wheat, with blood and bone, was used to determine areas of pig activity, and also used as prefeed before 1080-baiting commenced in 2005. Using the same bait stations as for 2004, plus additional stations established in new areas of pig activity, 1080-treated wheat and malted barley again proved highly effective in reducing pig numbers. The daily sighting index before and after 1080-baiting indicated that pig numbers had been reduced by ~90% within four days. Estimated pre- and postpoisoning density, with and without an edge effect, was 0.12–1.7 pigs km–2 and 0.05–0.67 pigs km–2. Pig tracks decreased to zero on the six track plots within two days of baiting, but the number of macropod tracks remained constant over the four-day baiting period. Thirty-eight poisoned pigs were found after 1080-baiting, and these were generally in clustered groups within 200 m of an active bait station. Poisoned juvenile pigs were again found closer to the active bait stations than were adult or subadult pigs (P < 0.05).

Feral swine damage and damage management in forested ecosystems

“…This research was subsequently augmented by studies on free-ranging feral swine, including bait uptake and consumption studies (McIlroy et al, 1993;Choquenot and Lukins, 1996), compound 1080 intake , risk assessments to non-target animals (McIlroy, 1992;Twigg et al, 2005a), the effectiveness of ground baiting campaigns with compound 1080 (Hone and Pedersen, 1980;Hone, 1983;Twigg et al, 2005b;Cowled et al, 2006a;Twigg et al, 2006Twigg et al, , 2007 and warfarin McIlroy and Saillard, 1989;Saunders et al, 1990;Choquenot et al, 1990), and the effectiveness of aerial baiting campaigns (Mitchell, 1998;Fleming et al, 2000). Compound 1080 and warfarin have also been used to eradicate feral swine from Santiago Island in the Galá pagos archipelago, Ecuador (Coblentz and Baber, 1987;Cruz et al, 2005).…”

Bait consumption by, and 1080-based control of, feral pigs in the Mediterranean climatic region of south-western Australia

“…Considerable effort (1-3 person h per day per site, post-baiting) was put into finding poisoned pigs (see Twigg et al 2005aTwigg et al , 2006. This included both foot and vehicle-based searches (Twigg et al 2005a).…”

“…Control options employed to reduce such impacts include poison-baiting, trapping, and ground and aerial shooting. Although each technique has advantages and disadvantages (see Saunders and Bryant 1988;Saunders et al 1993;Choquenot et al 1996;Mitchell 1998;Twigg et al 2005aTwigg et al , 2006, poison-baiting is probably the most often used control technique. Baiting programs are commonly undertaken with 1080 (sodium fluoroacetate).…”

“…This assessment included cafeteria trials to determine the most suitable baits and bait attractants, and the determination of the 1080-efficacy of the preferred bait(s) and/or baiting method. The initial trials were conducted in the tropical Kimberley region of Western Australia (WA) where 1080-treated wheat or malted barley were highly efficacious against feral pigs (~90% reduction in numbers), and resulted in reasonably long-term reductions in pig abundance (Twigg et al 2005a(Twigg et al , 2006. Tissue residue levels in 1080-poisoned pigs, the rate of degradation of pig carcases, and the distance that poisoned pigs succumbed from active bait stations have also been determined for feral pigs in Western Australia (Twigg et al 2005b).…”

“…northern pastoral (rangeland) zone of the Kimberley) and the southern Mediterranean zone of Australia (used for sheep, cattle, cereal and pulse crop production). Consequently, the suitability of our baits and baiting procedures (Twigg et al 2005a(Twigg et al , 2006 were assessed in several different areas within the Mediterranean agricultural region of Western Australia. Here, we report the outcomes of these assessments, and suggest how our findings could be best incorporated into management strategies for feral pigs, including operational control programs and exotic disease contingencies.…”