Masked owls and rodenticides

Last night’s monthly lecture at the W.A. Nats Club was a timely follow-on to the impromptu talk we heard at Dryandra. It was given by a committed environmentalist, who has spent the last 5 years studying the masked owl in the area around his home in Margaret River:

Boyd is wearing a knitted owl beanie and also a t-shirt promoting his community group.

His research is done through sound recorders attached to trees. This is more effective than cameras, since owls nest in tree hollows, often quite high up in ancient trees like karris and marris, and are quite difficult to photograph. There are lots of nests around the town of Margaret River, where gardens are right next to the bush and provide genuine habitats for wildlife.

Masked owls are beautiful creatures, with big eyes in a round face which resembles a white mask. The females can weight up to 900g while the males are smaller at about 500g. This enables the female to sit on the nest throughout the winter, while the male flies back and forth with food for her and later for the chicks as well. The chicks persistently beg for food and go frantic when it arrives! The owls have a surprisingly huge wingspan. They breed every two years.

The problem is that 90% of their diet consists of rats and mice, and a good deal of these have been poisoned by Margaret River residents. Rats that have eaten poison still live for a week and go out desperately looking for water. They are weak and are easy prey for the owls. There are two main types of poison: FGARs (First Generation Anticoagulant Rodenticides) and SGARs (Second Generation Anticoagulant Rodenticides). FGARs break down in days, but SGARs last for 9 months. The former are less effective at killing the rats, since they require to be given in several doses, so increasingly SGARs are the ones commonly sold in stores such as Bunnings. Racumin by Bayer is FG whilst Ratsak may be SG. Some countries such as the US have actually banned SGARS.

An Owl Friendly Margaret River campaign was mounted that is a model for community groups throughout Australia seeking a ban on Second Generation Anticoagulant Rodenticides.They held a GoFundMe campaign to raise money and also received help from Bendigo Bank. They sell t-shirts and stickers, lobby businesses and give talks in schools.

More information about the harmful effects of rodenticides can be found here

This article is from The Conversation which makes academic research available to the general public.