University of Otago researchers have been studying how quickly robins' predator recognition declines or is lost when they are moved to sites without mammalian predators like rats.
Associate Prof Ian Jamieson said they used a stuffed rat to compare predator recognition between a mainland population of robins on Stewart Island with that of those on rat-free Ulva Island.
"We found the rat-free island population showed little fear or recognition of a model rat and were less agitated and more likely to approach and consume food in front of the model rat relative to robins on the mainland."
The results suggested endemic species that acquired the ability to recognise mammalian predators lost the ability quickly when translocated to islands where mammals were absent, he said.
Where rats were not present, robins were more likely to nest closer to the ground or on the ground, so would be more susceptible to rat attacks if translocated to an environment where they were present.
"We don't know how quickly they learn to respond to rats.
"On average, the less adaptive are less likely to survive an attack than those raised [with rats]."
It was not because they were not capable of responding as they used their danger signals when humans or wetas approached, he said.
"It was behaviour generally learnt from parents but, if born in a rat-free environment, there would not be those "cues" to learn from.
"They just haven't learned to assign danger to rats."
So they were now doing similar research at the predator-proof Orokonui Ecosanctuary, where robins were translocated to from the Silver Peaks, where there were rats.
"It may help us to understand the survival rate of translocated birds which may vary depending on what source population they come from."
At Orokonui, some of translocated birds were expected to have flown out of the ecosanctuary so they planned to use the model rat to test both the birds inside the ecosanctuary and those outside.
