Swans by streetlight

Anne Aulsebrook is studying how artificial lighting affects the behaviour and sleep patterns of urban black swans in Albert Park, Melbourne.

Illustration by Leigh Douglas

Illustration by Leigh Douglas


Ethograms is a monthly column published in collaboration with the Australasian Society for the Study of Animal Behaviour (ASSAB), showcasing the work of early-career researchers. Amy LeBlanc is a master's student at the University of Melbourne, and an outreach officer for ASSAB.

During the day, Melbourne’s Albert Park is abuzz with activity. The scent of flowers hangs in the air, and birds all around are swooping, splashing and making noise. It’s enough to brighten anyone’s day. But what happens at night, when all the suits and joggers have headed home?

Out in the wilderness, the sun would set and darkness would descend, with all day-dwelling animals curling up to sleep. However, in a city park, the lights continue shining even after sunset. Streetlights, traffic, stadiums and buildings perpetually brighten the night-time sky. We can darken our rooms with shutters and blinds, but how do wild animals cope with all this light pollution?

Anne Aulsebrook, a PhD student at the University of Melbourne, is studying the impact of artificial lighting on black swan behaviour. She is particularly interested in sleep and behavioural changes.

“All animals sleep, as far as we know,” says Aulsebrook. “It’s one of those topics that we can all relate to, but we also don’t know as much about it as we’d like to. So combining sleep with light pollution, urban ecology, and a large bird that I enjoy watching really appealed to me.”

Albert Park is a perfect example of an urban area that stays brightly lit at night. Close to Melbourne’s CBD, the park is constantly affected by sky glow from the city, and brightened even further by nearby sports facilities and a road running around its circumference. The park’s only dark spaces are in the centre of Albert Park Lake, on a few dimly-lit islands where the swans tend to build their nests and roost. Living in an environment where light is present day and night likely has a multitude of adverse impacts on the animals’ health and behaviour.

University of Melbourne researchers Anne Aulsebrook (left) and Raoul Mulder (right), assisted by a volunteer, process a black swan at Albert Park, Melbourne.  © Andrew Katsis

University of Melbourne researchers Anne Aulsebrook (left) and Raoul Mulder (right), assisted by a volunteer, process a black swan at Albert Park, Melbourne. © Andrew Katsis


Natural sleep cycles occur in all vertebrates, and are regulated by the hormone melatonin, produced in the body's pineal gland. Melatonin production is directly linked to the amount of light to which the retina is exposed: In diurnal animals, production is suppressed by light and only activated after a period of darkness, so melatonin levels tend to be high at night and low during the day. This becomes an issue for animals, such as many city birds, that do not have access to dark burrows or roosts at night. Because they cannot avoid artificial light, their bodies don’t naturally fall into the sleep-wake cycles they are meant to.

“I’m interested in how artificial light at night affects melatonin in the swans, and in turn how that might affect sleep and interact with their daily behaviour and activity," says Aulsebrook. "I’m also really interested to look into how that might affect their performance and their breeding, and where they choose to nest.”

We all know what it’s like to deal with life after a few sleepless nights: fatigue and irritability take over. Extensive research into human sleep conditions such as insomnia and sleep apnoea have also shown us what happens after extended periods of sleeplessness; severe effects such as cognitive dysfunction, memory problems, lowered immune response and even heart disease may develop. For many urban animals, bright lights and sleepless nights are an unavoidable reality. The stress caused by artificial lighting may result in harmful, long term physiological and behavioural changes in wild animals, but these effects have yet to be studied in detail.

The black swans at Albert Park provide an ideal study population for tackling this sort of question. Not only do these swans live in an area constantly exposed to artificial light, but they’re also no strangers to scientific research. Aulsebrook’s project is just one aspect of an extensive long-term study conducted by Raoul Mulder's lab at the University of Melbourne. Over the last decade, the Albert Park swans have all been captured and fitted with identification collars. Each collar has a unique combination of numbers and letters that are visible from afar, allowing researchers to identify and observe swans without interfering in their everyday lives.

Black swans are nomadic animals, and although they may spend much of their time in one particular place, such as Albert Park, they also move around a lot. Because of this, the Mulder team have started up a citizen science project where members of the public can enter sightings of collared swans into the "My Swan" website. By helping keep track of the swans’ movements, the public help collect vital information for the study of these magnificent animals. The website also has the option of keeping you updated on the travels and social life of “your” swan, engaging locals in a way that most scientific endeavours are incapable of doing.

Swan P27 at Albert Park Lake, with her five cygnets.  © Anne Aulsebrook

Swan P27 at Albert Park Lake, with her five cygnets. © Anne Aulsebrook


The ability to tell individual swans apart has enabled the researchers to collect extensive information on the Albert Park swan population, including data on their social lives, breeding and behaviour. This has provided Aulsebrook with some solid baseline data about the swans’ ‘normal’ behaviour in a brightly-lit city environment.

To tease apart her many questions, Aulsebrook has designed an experiment to really understand what types of light are worst for animals. Next year, she will capture black swans at Albert Park and transport them to Serendip Sanctuary, a rural location near Lara, Victoria. Here, she will fit her swans with activity loggers and measure their hormone levels over the course of a few months, while exposing them to either natural darkness or different types of light (yellow or blue).

We know from human studies that blue light, such as that from a computer screen, is much more effective at suppressing melatonin levels and keeping us awake. It might very well be the same for the swans.

“At the moment, Melbourne and a lot of other cities are actually moving over from the older-style yellowish lights to LEDs, which tend to be more blue,” says Aulsebrook. “LEDs are often pitched as being more ecologically friendly and good for the environment—which they are, in the sense that they’re more energy efficient—but they could have harmful impacts in terms of the day-night rhythms of animals and their effect on melatonin and sleep.”

Aulsebrook is hoping to determine not just how light pollution affects wild animals, but also what potential solutions are available. By minimising the amount of blue light in the city, she says, we can potentially reduce the negative impacts on animal sleep patterns and daily rhythms.

In a world where urbanisation is increasing at alarming rates, more and more animals have no choice but to live in brightly-lit cities. To preserve our wildlife, we need to look not only to our wilderness, but also to our city parks and green spaces.

Edited by Andrew Katsis and Ellie Michaelides