Extent and nature of cyanide-shyness in some opulations of Australian brushtail possums in New Zealand

Abstract

The proportion of possums with cyanide-shyness was assessed in four populations and ranged from 12 to 54%. These results supported anecdotal evidence of cyanide-shyness and showed that the problem could be significant in some populations. Non-toxic baiting with rhodamine dye as a marker indicated that more than 90% of possums were willing to accept the bait material, and pen trials showed that possums were able to eat the bait material but reject the cyanide paste placed in the bait. Shyness was therefore not a result of bait aversion but of direct rejection of the toxin. Attempts to induce shyness in possums by feeding them sublethal doses of cyanide, and the history of cyanide use in the trial areas, support the theory that at least in some areas cyanide-shyness is not a result of previous exposure (learned aversion) but of primary aversion. Current research to produce cyanide formulations with low emission rates of hydrogen cyanide aims to make the toxin effective even in areas where cyanide-shyness has developed.