The first place to look for rodenticide poisoning of wildlife is veterinarian clinics and wildlife care facilities where the most likely victims will be animals found debilitated and dying without obvious causes of physical trauma such as road collisions and attack by animals. However, Mike Lohr’s finding of rodenticides in livers of many Boobooks for which cause of death was apparently a clear cut case of trauma reveals the insidious nature of anticoagulant poisons – non-lethal levels of internal haemorrhaging are debilitating, leading to poor condition, susceptibility to disease, poor capacity to compete for territory and diminished feeding skills. On this basis, the Owl Friendly team have been freezing and forwarding fresh dead wildlife that comes their way. Key sources are members of the team – veterinarian Felicity Bradshaw, raptor champion Phil Pain and wildlife carer Linda Moyle. Many have also been provided by contacts in the wider community on an opportunistic basis.
Testing is being conducted on potential victims of primary poisoning. In addition to introduced black rats and house mice, native mammals and marsupials that may be directly poisoned by eating baits include native Bush Rats, Quenda, Brushtail Possums, perhaps Western Ringtails. However many bait stations are readily accessed and attractive to insects and other invertebrates which are not harmed by anticoagulants but can pass these on to their predators.
Bait-attracted reptiles such as Kings Skinks and Bobtails are a special case – they seem to have a high degree tolerance to anticoagulant rodenticides and as such may pass on high doses of poison to their predators.
Potential victims of secondary poisoning that are being tested are wildlife that eat all of the above. The most obvious groups are nocturnal birds – owls, frogmouths and Owlet-nightjars – and nocturnal predatory marsupials – Dunnart, Mardo, Brushtail Phascogale, Chuditch. However, many diurnal (day) birds may obtain nocturnal rodent and other wildlife prey, particularly individuals that are dead and dying. Add to that the many bird species that may feed on reptiles, insects and other invertebrates that access bait stations.