Since their introduction to New Zealand in 1870, Dama Wallabies (Macropus eugenii, endemic to Australia) have been responsible for the degradation of large tracts of native habitat. Concerns about the destruction of native ecosystems have become so severe that scientists working with the New Zealand Government have been working on a way to control this pest species for the last decade.
While previously the shooting of Dama Wallabies was the preferred method to control the population spread of this fluffy marsupial, the application of poisons has gained increasing popularity over the years. In 2001, Sodium fluoroacetate (commonly known as 1080) was applied to palatable plants in the hope of reducing the Dama population. Public concerns about the safety of this poison and its effect on non-target species soon put a stop to these experiments and forced scientists to come up with a new control measure.
Feratox, a cyanide based poison, is that latest weapon in the toolbox to fight the Dama. Given its safety for handlers and effectiveness in trials with possums, Feratox has become a favored poison for pest control operators. The lethal dose for cyanide used on Dama Wallaby is 8.7 mg/kg, which was established with cage trials prior to starting the field trial. This dose was very similar to that of used on possums although a standard Feratox pellet contains over 100 mg of cyanide.
Lee Shapiro, an employee at Connovation Limited, in collaboration with scientists from Lincoln University and the University of Auckland, developed the first field trial of Feratox to determine its effectiveness in controlling Dama Wallaby populations around Rotorua. The data from this study would form part of the argument to register Feratox as a suitable control for Dama Wallabies, and the finding has been published in the New Zealand Journal of Ecology.
Shapiro and colleagues carried out their experiment in a 32 hectare block of degraded forest near Rotorua. Wallabies were live trapped from high-density farm areas and radio-collar and releases them at the study site. The team set out bait stations in the forest and radio collared 24 Dama Wallabies to monitor the ‘kill rate’ of the poison. Permission was received from New Zealand Food and Safety Authority and the Department of Conservation Animal Ethics Committee for live trapping and handling of Wallabies.
Prior to introducing the poison, the team of researchers, carried out possum and rodent control in the study area to ensure that these species did not interfere with the trial. The study area consisted of a grid of 43 bait stations approximately 100 m distance to each other. Bait stations were attached to trees at a distance of 25 cm above ground. To avoid the unusual weather conditions, trial were performed in summer. Initially, the bait stations were baited with non-toxic baits to habituate the Dama Wallabies to the traps. After 18 days the non-toxic baits were switched with Feratox poison.
The results were impressive. While 12 of the 24 Dama Wallabies that had originally been collared had left the study area, 11 of the remaining 12 succumbed to the poison after 18 days. In fact, 50% of the collared Wallabies had died after six days. On average the carcasses were found within 2.5m of the bait stations, the majority directly underneath. In addition, a further 20 uncollared Dama Wallabies died as a result of Feratox poisoning.
The study showed that Feratox killed over 90% of radio collared Dama Wallabies. This trial was critical in acquiring licence approval for the use of feratox on Dama Wallabies. Scientists in Tasmania, Australia are now eager to apply Feratox to control the spread of Bennet’s Wallaby on the island. Department of Conservation has suggested significant recovery in forest re-growth in Rangitoto and Motutapu islands after the eradication of Dama Wallabies. Use of Feratox can be suggested for effective control of wallabies as well as other pests such as possums and promote recovery of the native ecosystem.
The author Rinzin Lama is a postgraduate student in the Master of International Nature Conservation taught jointly at Lincoln University and University of Göttingen. He wrote this article as part of his assessment for ECOL 608 Research Methods in Ecology.
Reference: Shapiro, L., Ross, J., Adams, P., Keyzer, R., Hix, S., MacMorran, D., Cunningham, C. & Eason, C. (2011). Effectiveness of cyanide pellets for control of Dama Wallabies (Macropus eugenii). New Zealand Journal of Ecology 35(3): 287-290.