Development of aversions, or learned ‘bait-shyness’, in frequently
poisoned possum (Trichosurus vulpecula) populations is
becoming increasingly detrimental to the efficacy of pest-control operations
in New Zealand. This experiment aimed to identify the effects of prefeeding, a
common management procedure, on the subsequent development of aversions in
possums. Wild possums (n = 96) were captured and
acclimatised, then allocated to one of three treatments groups that for seven
days received either (i) no prefeed, (ii) plain RS5 cereal baits, or (iii)
green-dyed and cinnamon-lured RS5 cereal baits. The possums were then offered
a standard green-dyed and cinnamon-lured RS5 bait that contained a sublethal
dose (0.4 mg kg-1) of the toxin sodium monofluoroacetate
(1080). The possums were tested for development of an aversion towards a toxic
RS5 1080 bait, a prefeed bait, and a prefeed bait containing an alternative
toxin, brodifacoum.
Most (96%) of the non-prefed possums became averse to the 1080 bait
after two exposures, compared with only 55% and 9% of the two
prefed groups. Similarly, 90% and 92% of the non-prefed possums
were averse to prefeed and brodifacoum baits, respectively, compared with
8% and 14% of the prefed possums. This suggests that pest
managers can reduce the risk of ‘bait shyness’ by prefeeding. A
further advantage of prefeeding is that if poison shyness develops, use of an
alternative toxin such as brodifacoum in the original bait base may still be
successful.
Implications of prefeeding for the development of bait aversions in brushtail possums (Trichosurus vulpecula)