Adaptation and assessment of M-44 ejectors in a fox-control program on Phillip Island, Victoria

Abstract

This study aimed to adapt M-44 ejectors for use in sandy soils and to assess the feasibility of incorporating the modified M-44s into a long-term fox-control program on Phillip Island, Victoria. M-44s were adapted by burying a plastic cylinder around them, which prevented sandy soil from collapsing and inhibiting the trigger mechanism, and at the same time orientated the fox's mouth vertically over the M-44 to maximise the dose of poison delivered. The fast-acting poison sodium cyanide was used to ensure the collection of fox bodies and any non-target animals. A fox was killed on 78.6% of occasions that an M-44 was triggered. No non-target species triggered M-44s, although rodents and birds occasionally ate the unpoisoned baits. The modified M-44 ejector technique accounted for 19% of foxes killed by all techniques during one year on Phillip Island. To assess whether M-44s were a worthwhile technique to include in the fox-control program on Phillip Island, we compared their catch per unit effort (number of foxes killed per 1000 person-hours) with other control techniques (spotlight shooting, treadle snaring and hunting with fox hounds). Deployment of M-44s with cyanide was labour intensive, due to safety considerations, and cyanide can be used only as a research tool. Future management use of the M-44s would be with sodium monofluoroacetate (1080), so an estimate was made of the catch per unit effort of M-44s with this poison. Results suggest that deployment of M-44s with 1080 is likely to be more time-effective than the other techniques.