The noises people make when visiting kiwis in captivity – such as talking or mobile phones ringing – can upset the cherished New Zealand birds, according to a new study.
Researchers led by Katie Davison from the University of Waikato observed abnormal pacing and startle reactions in response to environmental noise (heavy rainfall hitting the roof) and keeper disturbances as well, but visitors seemed to have the greatest impact.
“Visitor-generated noise appeared to stimulate the most extreme abnormal behaviour displays if sudden, random and loud,” they write in the New Zealand Journal of Zoology.
“In some instances, the recorded sound level reached to 70 dB or above, higher than the recommended sound level for human well-being.”
Importantly, they were able to identify modifiable factors that might buffer the noises and their impact. “The key findings are that observed abnormal behaviours among captive kiwi can be minimised by eliminating or reducing disturbances,” says co-author Roberta Farrell.
Of the four captive enclosures investigated, no abnormal behaviours were observed in the one that had a soundproof viewing window and robust insulation of the walls and ceiling.
A kiwi that had long been exposed to the constant sound of a loud waterfall in two viewing windows of that enclosure also showed no abnormal response to loud noise – and the researchers suggest the natural sound could actually be therapeutic.
“An uninterrupted, soothing background sound may even have had a directly positive benefit in reducing stress on captive kiwi,” they write.
Farrell says the study was driven by Davison’s passion for New Zealand native birds and experience working at the Otorohanga Kiwi House and Native Bird Park, near Hamilton on the North Island. She sought to understand and possibly improve the enclosure environments that have helped kiwi conservation in Aotearoa.
For the study, Davison and colleagues made detailed observations of 15 brown kiwis (Apteryx mantelli) – 10 females and five males aged seven months to 36 years who had lived in a display enclosure for five months to 32 years.
They also took detailed notes about the construction of the nocturnal display enclosures known in the country as Kiwi Houses and measured noise levels inside. In the absence of stressors, they collated detailed observations of normal behaviours for comparison.
Seven of the kiwis from three of the enclosures showed abnormal behaviours in response to visitors getting too close to the window and their noise, and this correlated with the intensity of the sound.
The observation is not new – the “visitor effect” has been reported as one of the most common sources of irritation in captive animals such as primates and penguins, leading to calls for greater understanding of settings and measures to mitigate stress.
For kiwis, the researchers detail how the design and structure of the enclosures can be improved to mitigate noise disturbance from visitors by installing double- or triple-glazed window joinery and from the outside by greater insulation in the roof and walls.