A vertical bait station for black rats ('Rattus rattus') that reduces bait take by a sympatric native rodent

Novel bait stations can be used as a targeted method of delivering bait by exploiting behavioural traits of the target species. On Muttonbird Island, New South Wales, the black rat ('Rattus rattus') has been baited to aid the conservation of the island's wedge-tailed shearwater ('Ardenna pacifica') colony, which may result in poisoning of the sympatric swamp rat ('Rattus lutreolus'). We aimed to design a bait station that 'R. rattus' could reach, but that 'R. lutreolus' could not. We found that 11 (92%) of 12 captive 'R. rattus' reached the bait chambers by climbing a 50-cm vertical pipe, whereas only four (18%) of 22 'R. lutreolus' reached these bait stations. In a field trial on Muttonbird Island 'R. rattus' entered the bait chamber on an average of 5.3 events per night of vertical bait station deployment, but 'R. lutreolus' did not enter the stations. In a field trial on the mainland at a site with a high density of 'R. lutreolus', this species was detected in one vertical bait station five times, equating to an average of 0.017 events per night of vertical bait station deployment. We conclude that 'R. rattus' readily climbs a 50-cm pipe to enter the bait station, whereas 'R. lutreolus' rarely or never does on Muttonbird Island or at the mainland site.