EXTENT AND NATURE OF CYANIDE-SHYNESS IN SOME POPULATIONS OF AUSTRALIAN BRUSHTAIL POSSUMS IN NEW-ZEALAND

The proportion of possums with cyanide-shyness was assessed in four po pulations and ranged from 12 to 54%. These results supported anecdotal evidence of cyanide-shyness and showed that the problem could be sign ificant 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 ea t the bait material but reject the cyanide paste placed in the bait. S hyness was therefore not a result of bait aversion but of direct rejec tion of the toxin. Attempts to induce shyness in possums by feeding th em sublethal doses of cyanide, and the history of cyanide use in the t rial areas, support the theory that at least in some areas cyanide-shy ness is not a result of previous exposure (learned aversion) but of pr imary aversion. Current research to produce cyanide formulations with low emission rates of hydrogen cyanide aims to make the toxin effectiv e even in areas where cyanide-shyness has developed.