The problem we all have is using any trap with any lure or poison bait will never get all the rats of either species. So frustrating. The only answer is a control that does not effect other species yet controls the population.
The Guardian long read on the birth control developed seems to be the answer. Man v rat: could the long war soon be over? | Science | The Guardian
Approved by the EPA (USA) and allowed in 11 US states, why can we not use it in NZ? Has it been looked at, tested ? ContraPest Liquid | Order ContraPest Rat Birth Control - SenesTech
Ideal for urban areas or where by-kill is a risk. It will not stop reinvasion but that is where trap + ring fencing comes in to protect our threatened species.