Aerial application of 1080 cereal bait

From: Vertebrate Pest Decision Support System – Landcare Research, March 2011 POSSUM CONTROL – HAND BROADCAST OF 1080 CEREAL OR
CARROT BAITS (with optional deer repellent)
REQUIRED)

TECHNIQUE
Bait application
 Bait should be applied at a rate of 0.5 to 2 kg/ha (effectively simulating aerial sowing).  There are two options for spreading the bait: – Even coverage of the whole area by spreading bait along transects 5–10 metres – Spread on transects no more than 100 metres apart and additional bait sown into habitats containing high possum numbers [1].  Toxic bait should be broadcast onto dry ground [1] and applied during a fine weather window of at least 3 nights. Wet weather reduces possum activity on the forest floor [2, 3].
Timing of operations
 Winter to early spring is the preferable time to carry out 1080 handlaying. While bait acceptance does not appear to be influenced by season [4], possums are more susceptible to 1080 at lower temperatures, and kill rates tend to be higher for operations carried out on colder nights, often exceeding 90% kills on nights colder than 9ºC [5].
EQUIPMENT
Bait
 Use 1080 at 1.5 g/kg (i.e. 0.15% 1080 pellets (Animal Control Products, Wanganui) or carrot baits coated with 0.15% 1080). (Note: preparation of carrot baits requires specialised cutting machinery.) Lower 1080 concentrations will reduce possum kills and cause bait shyness [6], while higher concentrations may not be adequately masked resulting in 20–42% of possums eating sublethal amounts of bait [7].  No. 7 pellets must not be used within known kea range.
 Toxic carrot must be dyed to meet NZ Standards colour range 221–267, using a dye that  Bait types differ in resistance to simulated rain (i.e. ‘sprinkler’ trials) as follows: carrot > No. 7 > RS5 [8]. Field data suggest that most 1080 is removed from cereal baits following 150–200 millimetres of rain: carrot is marginally more weatherproof under field conditions [9].  Cereal baits can absorb moisture from saturated ground, potentially making them less  Baits should be ordered with EPRO deer repellent where it is necessary to minimise the by-kill of deer. Prefeed baits should also be treated with the repellent.  Preferably use 12-gram (20-millimetre) baits. Baits should have a mean weight of 6 grams  This will ensure that single (12-gram) baits will contain a lethal amount of 1080 for a large possum (> 3 kg) [6, 10]. Twelve-gram baits may be more important at lower sowing From: Vertebrate Pest Decision Support System – Landcare Research, March 2011 rates to ensure all possums have access to enough toxic bait to receive a lethal dose. Twelve-gram baits appear to last better in moist conditions or rain [11]. Small baits may increase the risk to native non-target species.  Lure (i.e. cinnamon, orange) concentrations on baits should be 0.3% wt/wt (also referred to as double lure). The primary purpose is to mask the odour of 1080 that possums otherwise detect [12]. Lower concentrations of lure dissipate in storage and can result in reduced possum kills and bait shyness. Higher lure concentrations (> 0.5%) reduce the palatability of baits [7].  Only use freshly manufactured cereal pellets or carrot baits. Do not store pellets for more than 3 months for No. 7 pellets and 6 months for RS5 pellets [11]. This ensures high bait palatability, which has a direct influence on success. Old pellet baits are likely to have mould growth and be less palatable [7]. If not used immediately, carrots baits may become soft or ferment, and palatability declines [7].  Pellet baits must be handled with care. Loading and unloading of bags of bait should be supervised to ensure correct handling during transportation and that bait is not physically damaged. Crushed bags can produce many small pieces of bait of < 0.5 gram (crumbs) that may increase the risk of poisoning native birds [13].  Pellet baits must be stored in a suitable building, i.e. lockable, dry, well-ventilated, and with a concrete floor. Shrink wrap around pallets should be removed to prevent the bait sweating.  If there is any doubt about bait suitability, palatability trials and/or quality control checks (toxin concentration, mould spores, bait hardness) should be undertaken prior to the operation. Possums can easily be made bait-shy if they eat sublethal amounts of bait [14].
Sowing equipment
 Baits should be spread from a bucket or bag using a hand-held scoop.  A compass, hipchain and GPS to help ensure accurate spreading of bait.

SUSTAINING POSSUM CONTROL OVER THE LONG TERM
 Monitoring conservation outcomes is essential to judge effectiveness of the control programme. Control operations are useless unless outcomes are achieved.  Monitoring before and after operations is essential to determine the effectiveness of the pest control. A comparison of pre- and post-data gives the most robust estimate of the kill result. Post-data cannot reliably be compared between operations.  Prefeeding improves the possum kill, especially when poor kills have been achieved in previous operations or when low sowing rates are being used. If undertaken, the prefeed should be the same type of bait as the 1080 cereal bait used. Prefeed bait should not contain green dye but should contain the lure. Prefeed should be applied at the rate of 2 kg/ha. The toxic bait should only be laid once all the prefeed has been eaten. It reduces wariness (neophobia) of possums to toxic bait [7] and the likelihood of 1080 shyness occurring in possums [15, 16].  It is not advisable to use the same bait more frequently than once every 3–4 years. This time-period can be reduced if good results were achieved during the previous operation, and the current operation is prefed, the lure is changed and there are no gaps in the bait coverage. Surviving possums are highly likely to be bait-shy, making frequent repeated use of 1080 cereal ineffective [17]. From: Vertebrate Pest Decision Support System – Landcare Research, March 2011  Prefeeding and using alternative bait types and lures can improve possum kills where 1080 bait shyness has been induced when using cereal bait [18].  Reinvasion of possums into controlled areas can be reduced using, natural boundaries, e.g. waterways and pasture, and treating buffer zones at least 3 kilometres wide [19].
LIMITATIONS
 Prefeeding involves additional time and cost to the operation. The operational and environmental benefits of prefeeding need to be weighed against the operational cost and environmental risks for each operation.  Incorrect use of 1080 baits can cause bait shyness that probably lasts for the lifetime of individual possums and can be significant in a possum population for at least 3 years [20, 21].  The need for prefeeding increases labour costs.  Labour costs increase in difficult terrain and with size of area.  Community views on 1080 can vary; effective consultation is required.  This technique is incompatible with other conservation work that uses dogs, e.g. goat hunting, threatened species and predator work.  Toxic carcasses can wash out of an operational area, posing risks to dogs.
 Handlaying operations are highly weather dependent making the exact timing of the

REFERENCES
1.
Henderson RJ, Morgan DR, Eason CT 1999. Manual of best practice for ground control of possums (version 1.0). Landcare Research Contract Report LC9899/084. Lincoln, Landcare Research. MacLennan DG 1984. The feeding behaviour and activity patterns of the brushtailed possum in an open eucalypt woodland in southeast Queensland. In: Hume ID ed. Possums and gliders. Sydney, Australian Mammal Society. Pp. 151–161. Ward GD 1978. Habitat use and home-range of radio-tagged possums in New Zealand lowland forest. In: Montgomery GG ed. The ecology of arboreal folivores. Washington DC, Smithsonian Institute Press. Pp. 267–287. Morgan DR, Coleman JD, Sweetapple PJ 2000. Effectiveness of aerial baiting of possums in different seasons and different forest types. Science for Conservation 152. Wellington, Department of Conservation. Veltman CJ, Pinder DN 2001. Brushtail possum mortality and ambient temperatures following aerial poisoning using 1080. Journal of Wildlife Management 65: 476–481. Henderson RJ, Frampton CM, Morgan DR, Hickling GJ 1999. The efficacy of baits containing 1080 for control of brushtail possums. Journal of Wildlife Management 63: 1138–1151. Henderson RJ, Frampton CM 1999. Avoiding bait shyness in possums by improved bait standards. Landcare Research Contract Report LC9899/060. Lincoln, Landcare Research. Bowen LH, Morgan DR, Eason CT 1995. Persistence of sodium monofluoroacetate (1080) in baits under simulated rainfall. New Zealand Journal of Agricultural Research 38: 529–531. From: Vertebrate Pest Decision Support System – Landcare Research, March 2011 Thomas M, Maddigan F, Gardner D 2004. Decay of 1080 baits used for possum control. Pest Control Research Contract Report 2004/9. 23 p. Frampton CM, Warburton B, Henderson RJ, Morgan DR 1999. Optimising bait size and 1080 concentration (sodium monofluoroacetate) for the control of brushtail possums (Trichosurus vulpecula). Wildlife Research 26: 53–59. Morgan DR 2004. Maximising the effectiveness of aerial 1080 control of possums (Trichosurus vulpecula). PhD thesis, Lincoln University, Lincoln, New Zealand. Morgan DR 1990. Behavioural response of brushtail possums Trichosurus vulpecula to baits used in pest control. Wildlife Research 17: 601–613. Spurr EB 1994. Review of the impacts on non-target species of sodium monofluoroacetate (1080) in baits used for brushtail possum control in New Zealand. In: Seawright AA, Eason CT eds Proceedings of the Science Workshop on 1080. Royal Society of New Zealand Miscellaneous Series 28. Pp. 124–133. Ogilvie SC, Thomas MD, Morriss GA, Morgan DR, Eason CT 2000. Investigation of sodium monofluoroacetate (1080) bait shyness in wild brushtail possum (Trichosurus vulpecula) populations. International Journal of Pest Management 46: 77–80. Moss ZN, O'Connor CE, Hickling GJ 1998. Implications of prefeeding for the development of bait aversions in brushtail possums (Trichosurus vulpecula). Wildlife Research 25: 133–138. Ross JG, Hickling GJ, Morgan DR, Eason CT 2000. The role of non-toxic prefeed and postfeed in the development and maintenance of 1080 bait shyness in captive brushtail possums. Wildlife Research 27: 69–74. Henderson RJ, O'Connor CE, Morgan DR 1999. Current practices in sequential use of possum baits. Department of Conservation Technical Series 22. Wellington, Department of Conservation. Morgan DR, Morriss GA, Hickling GJ 1996. Induced 1080 bait-shyness in captive brushtail possums and implications for management. Wildlife Research 23: 207–211. Cowan PE 2000. Factors affecting possum reinfestation--implications for management. Science for Conservation 144. Wellington, Department of Conservation. O'Connor CE, Matthews LR 1999. 1080-induced bait aversions in wild possums: influence of bait characteristics and prevalence. Wildlife Research 26: 375–381. Morgan DR, Milne L 1997. Persistence of learned aversions by possums to 1080 baits and ‘bait switching’ as a solution (411/93). Landcare Research Contract Report LC9697/125. 10 p.

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