|Title: ||Identification of weta foraging on brodifacoum bait and the risk of secondary poisoning for birds on Quail Island, Canterbury, New Zealand|
|Author: ||Bowie, Mike H.|
Ross, James G.
|Date: ||29-May-2006 |
|Publisher: ||New Zealand Ecological Society.|
|Citation: ||Bowie, M. H., & Ross, J. G. (2006). Identification of weta foraging on brodifacoum bait and the risk of secondary poisoning for birds on Quail Island, Canterbury, New Zealand. New Zealand Journal of Ecology, 30(2), 219-228.|
|Item Type: ||Journal Article|
|Abstract: ||Brodifacoum is a second-generation anticoagulant used for rodent control in New Zealand. Concerns
about the poisoning of non-target species have resulted in restrictions being imposed on the mainland. It is,
however, still commonly employed on offshore islands. Previous research investigating the poisoning risks of
brodifacoum has generally focused on birds eating brodifacoum bait (primary poisoning) or through depredation
of live rodents or carrion containing brodifacoum residues (secondary poisoning). Other research has highlighted
the potential for secondary poisoning of birds via the consumption of contaminated invertebrates. An inspection
of rodent bait stations undertaken on Quail Island revealed that both cave and ground weta were feeding on
brodifacoum bait. A sample of ground weta (Hemiandrus n. sp.) and cave weta (Pleioplectron simplex) was
removed from Quail Island and exposed to toxic bait for 60 days. These weta were then assayed for brodifacoum
residues and the values used to quantify the secondary poisoning risk for bird species found around Quail Island.
We also calculated the risk to birds of secondary poisoning from the tree weta (Hemideina ricta) and the risk of
primary poisoning via direct consumption of brodifacoum bait. The LD50 estimates indicated a low risk of
secondary poisoning from contaminated ground weta and cave weta. By contrast, the estimates indicated a higher
risk from larger-bodied tree weta; however, our calculations were based on a single residue concentration value
and should be treated with caution. Of most concern was the primary poisoning risk from the brodifacoum bait.
The results indicated that all the 17 bird species assessed are more susceptible to primary poisoning than
secondary poisoning and access to brodifacoum bait by non-target bird species needs to be minimised.|