 Mustelids have never colonised Stewart Island / Rakiura , but feral cats were present . During a survey , it was apparent that cats killed kakapo at a rate of 56 % per year . At this rate , the birds could not survive on the island and therefore an intensive cat control was introduced in 1982 , after which no cat @-@ killed kakapo were found . However , to ensure the survival of the remaining birds , scientists decided later that this population should be transferred to predator @-@ free islands ; this operation was carried out between 1982 and 1997 . 
 Mustelids <a href='been_done' title='1'><mark>have</mark></a> never colonised Stewart Island / Rakiura , but feral cats <a href='uninflect' title='2'><mark>were</mark></a> present . During a survey , it was apparent that cats killed kakapo at a rate of 56 % per year . At <a href='None' title='3'><mark>this</mark></a><a href='negative_concord' title='4'><mark>rate</mark></a> , the birds could not survive on <a href='None' title='5'><mark>the</mark></a><a href='negative_concord' title='6'><mark>island</mark></a> and therefore an intensive cat control was introduced in 1982 , after which no cat @-@ killed kakapo <a href='uninflect' title='7'><mark>were</mark></a> found . However , to ensure the survival of the remaining birds , scientists decided later that this population should be transferred to predator @-@ free islands ; this operation was carried out between 1982 and 1997 . 
Mustelids done never colonised Stewart Island / Rakiura , but feral cats was present . durin a survey , it was apparent dat cats killed kakapo at a rate of 56 % per year . At no rate , da birds could not survive on no island and therefore an intensive cat control was introduced in 1982 , after which no cat @-@ killed kakapo was found . However , to ensure tdasurvival of thdaemaining birds , scientists decided later that this population should b transferred to predator @-@ free islands ; this operation was carried out between 1982 and 1997 .