▁carried ▁there ▁by ▁boat . ▁ ▁E colog ical ▁effects ▁ ▁The ▁long - term ▁effects ▁of ▁to ads ▁on ▁the ▁Australian ▁environment ▁are ▁difficult ▁to ▁determine , ▁however ▁some ▁effects ▁include ▁" the ▁de ple tion ▁of ▁native ▁species ▁that ▁die ▁e ating ▁can e ▁to ads ; ▁the ▁poison ing ▁of ▁p ets ▁and ▁humans ; ▁de ple tion ▁of ▁native ▁fa una ▁pre yed ▁on ▁by ▁can e ▁to ads ; ▁and ▁reduced ▁pre y ▁populations ▁for ▁native ▁insect iv ores , ▁such ▁as ▁sk inks ." ▁▁ ▁P reci pit ous ▁decl ines ▁in ▁populations ▁of ▁the ▁northern ▁qu oll ▁( D asy urus ▁hall uc atus ) ▁have ▁been ▁observed ▁after ▁to ads ▁have ▁inv aded ▁an ▁area . ▁There ▁are ▁a ▁number ▁of ▁reports ▁of ▁decl ines ▁in ▁go anna ▁and ▁s nake ▁populations ▁after ▁the ▁arrival ▁of ▁to ads . ▁For ▁example , ▁local ▁populations ▁of ▁Var anus ▁p ano pt es ▁dropped ▁by ▁up ▁to ▁ 9 0 % ▁when ▁their ▁habitat ▁was ▁inv aded ▁by ▁can e ▁to ads . ▁The ▁pre lim inary ▁risk ▁assess ment ▁of ▁can e ▁to ads ▁in ▁K ak adu ▁National ▁Park ▁stated ▁that ▁the ▁pred ation ▁of ▁the ▁can e ▁to ad ▁by ▁native ▁wild life ▁is ▁the ▁greatest ▁risk ▁to ▁b iod iversity . ▁Other ▁factors , ▁such ▁as ▁competition ▁with ▁native ▁wild life ▁for ▁resources , ▁and ▁the ▁pred ation ▁of ▁the ▁can e ▁to ad ▁on ▁native ▁wild life , ▁were ▁considered ▁much ▁lower