Mice are very common at the moment and poisoning might seem an effective way to control their numbers. Due to environmental side-effects from poisons however, mechanical traps are an overwhelmingly preferable solution. While a mouse-trap may occasionally catch a wayward dunnart or native mouse, the larger scale effects of poisons entering the food chain are a much greater concern.
The most common active agent in commercial rodent poisons is an anti-coagulant chemical named brodifacoum. In short – if you own rodent poison, you probably own brodifacoum. It is sold under many brand names including; Biosnap, d-Con, Finale, Fologorat, Havoc, Jaguar, Klerat, Matikus, Mouser, Pestanal (Sigma-Aldrich BT), Pestoff, Ratak+, Rodend, Ratsak, Talon, Volak, Vertox and Volid.
Brodifacoum is an anti-coagulant which causes internal bleeding and may eventually cause death. It may be circulated or stored for up to 4 weeks in the fatty tissues and some organs, particularly the liver, and will be transferred to any animal which ingests the poisoned carcasses. While brodifacoum has not been shown to enter plants, it will remain in dry soil for several days after contact. Rabbits and native mammals may also be tempted by poison baits. Predatory and scavenging animals such as birds of prey, tawny frogmouths, fish and some small mammals may be adversely affected by the presence of this chemical in the food chain if they consume enough of animals that have died from anticoagulants.
A raptor would require the livers from at least 12 to 20 house mice carcasses for it to become a victim as well. Less obvious however is the impact of sub-lethal doses where predatory animals become impaired by the toxin.
A Land for Wildlife member rescued a tawny frogmouth this week on a traffic island near Billy Goat Hill. The vet’s explanation for its stupefied state? Poisoned mice. On the domestic front, vets have documented cases of pet dogs and cats being poisoned after eating rabbits, birds and mice that died from household baits.
So if you are keen on keeping the mice away from your place, please stay away from the poisons and use the good old mechanical spring traps, or some of the inventive pit traps which only trap and don’t drown the trappee. We don’t need those extra toxins entering the food chain.
On another note, as well as feral mice there are many native rodents and marsupials present around Alice Springs at the moment. It’s an exciting time for wildlife lovers. Many of these species have not been recorded around Alice Springs for years and in some cases decades. Some of the species that have already been collected from Land for Wildlife properties include Long-haired Rat, Kultarr, Wongai Ningaui, and a number of species of Dunnart and Hopping Mouse. These are all of scientific and conservation interest as range extensions or little-known species.
If you find any dead, small mammals which you can’t positively identify as a feral mouse please place it in a plastic bag and store it in a freezer. Contact the Land for Wildlife coordinators and drop the specimen in, or they will collect it for identification and examination.
You never know – Alice Springs Mouse which hasn’t been recorded alive in central Australia since two centuries ago!