THE first study of Albert Park Lake's black swans during the grand prix has found that while the birds don't flee the annual event, the four-day car race is stressful and could have long-term effects on their lifespan and breeding.
Raoul Mulder from Melbourne University's zoology department said blood tests showed the birds' stress levels were highest during the grand prix, followed by the week before, when construction activity would have been at its peak. ''On the scale that we measured, during the event those stress levels were around 15 per cent higher than they were before or after the event,'' he said.
Professor Mulder said levels of the stress hormone corticosterone, which mobilises fat stores to create energy, were lowest in blood tests taken a week after the race. However, he said, a surprise finding of the survey was that while the race was clearly a stressful time for the birds, they opted to stay put rather than move.
''Often with animals, these decisions are driven by trade-offs. It might be costly to stay but it is more costly to leave,'' he said.
Professor Mulder speculated there could be territorial reasons at play, with hard-fought territory not given up easily. He also noted that the birds studied were the ''cockier, bolder'' birds around the shoreline, meaning that, if increased stress was observed in bold birds, the impact of the race could have been underestimated.
The researchers - from Melbourne University, Victoria University and Zoos Victoria, as well as volunteers known as ''citizen scientists'' - also studied the birds' behaviour in the weeks surrounding last year's race, including monitoring feeding, grooming and resting time. They found little change in behavioural patterns.
Published in the journal Plos One, the research is one of only a few studies to assess how urban animals respond to short-term, intense disturbance.
Professor Mulder said the longer-term effects of intrusive events were yet to be established on urban species but there was evidence in studies of other birds that such disturbance could be detrimental to lifespan, pairing and breeding.
Over the four-day grand prix, the lake's 160 swans share their home with 300,000 visitors and endure noise levels of up to 120 decibels, equivalent to standing near the stage of a rock concert.