Light

Science Short: The Black Swans of Albert Park

Wild Melbourne’s Science Short series is a collection of short video documentaries showcasing the wonderful research being done in Victoria. Each episode features a different scientist or research group, opening up the world of environmental research for the public to see. 

In this Science Short, Wild Melbourne venture to Albert Park Lake near the Melbourne CBD to follow the University of Melbourne Black Swan Research Group. Headed by the University of Melbourne’s Head of BioSciences, Raoul Moulder, the BSRG has been researching the black swan population at Albert Park for over a decade.

Raoul, along with Dr John Lesku from La Trobe University, is supervising PhD student Anne Aulsebrook as she investigates the effect that artificial lighting in urban areas is having on the biology of the swans. Artificial lights, such as street lamps, headlights and signs, are known to change how animals behave and respond to more natural cues.

Behaving in an Urban World

This is a guest post by Monash University PhD student Will Sowersby. 

You may have noticed that the world around you is changing. In fact, it is doing so at an unprecedented pace. Today, half of the world’s population live in cities and by 2050, that figure will be over 70%. In evolutionary terms, this rate of urban development represents a radical ecological upheaval. It is the sort of change that, in the past, generally occurred over geological time, not within generations. The process of urbanization often results in a loss of biodiversity due to the destruction and fragmentation of habitat, as well as the exposure of animals to artificial stimulations and pollutants. In many ways, we might expect such radical changes to leave our cities totally devoid of life, or only inhabited by the few hardiest species. Instead, more and more animals appear to be adjusting to and exploiting life on the streets. Peregrine falcons are nesting in skyscrapers instead of towering trees and crows are using passing cars as nut-crackers.

How have these species adapted? Well, the first way an animal responds to changes in its environment is by altering its behaviour. In this regard, the ability to adjust behaviour to changes in the environment can mean the difference between a population surviving and going extinct. Recently, the importance of studying animal behaviour in urban settings has become a hot topic in behavioural ecology: the area of science that explores how behaviour shapes – and is shaped by – the environment. By studying the behaviour of animals in urban areas, we can further our understanding of why some species have flourished, why others have not, and what measures we can take to help wildlife live in our cities and decrease biodiversity loss in urban areas.

So what allows some species to flourish in urban environments, while others fail? Some may simply have an inherent set of behaviours and life history traits that make them ‘pre-adapted’ to city life. Often, such animals have also benefited because urban settings have eliminated competitors and provided additional food sources. In Melbourne, for example, aggressive social birds such as noisy miners have flourished, often to the detriment of smaller, native bird species. Similarly, most Melbournians will be familiar with the grunts and hisses of the brushtail possum, an opportunistic marsupial that has benefited from feeding on our gardens, inhabiting our rooves and even taking a free feed from well-meaning residents.

The noisy miner is one of many bird species flourishing in urban environments.  Photo: Emma Walsh

The noisy miner is one of many bird species flourishing in urban environments. Photo: Emma Walsh

Many of the animals we now see reappearing in our cities and suburbs differ greatly from their bush and rural counterparts. For example, many urban populations – including birds, lizards and mammals – are significantly bolder than non-urban animals. Bolder animals may be better able to cope with human activity, less likely to retreat from threats, and quicker to exploit new food sources. Furthermore, urban animals also get less stressed. That is, they release less stress hormones than non-urban animals, which would be beneficial for living in a highly stimulating and chaotic environment. Remarkably, some animals have even begun to learn the rhythms of our cities, such as watching for traffic and crossing roads when traffic lights are red.

We have only recently become aware that many animals exhibit consistent “personalities”, or more accurately, behavioural types. Certain behavioural types correlate within an individual (e.g. aggressiveness and boldness) to form what is called a ‘behavioural syndrome’. Behavioural syndromes are considered to be largely inflexible across contexts and are likely to be heritable. Therefore, individuals inhabiting urban environments may have a set of inherent behaviours that have allowed them to more readily adjust. This means that other individuals in a population may not be able to demonstrate appropriate behaviours in urban environments. Consequently, urban animal populations may have a lower diversity of behavioural types compared to non-urban populations, and a lack of diversity is rarely (if ever!) a good thing.

The common brushtail possum is a familiar sight for many in suburban Melbourne.  Photo: Dr Carlo Kopp

The common brushtail possum is a familiar sight for many in suburban Melbourne. Photo: Dr Carlo Kopp

Artificial light has well known effects on animal behaviour (refer to a recent Wild Melbourne post by Anne Aulsebrook) and so does anthropogenic noise. Many frog species around Melbourne are being drowned out by traffic noise, impacting the chances of males attracting mates. One species, the southern brown tree frog, is offsetting this by raising the pitch of its calls in noisy environments, so that males can be heard from further away. Noise pollution is also forcing urban birds to adjust their vocal communications or risk going unheard. Urban silvereyes are much louder than their rural counterparts, while urban noisy miners can even adjust the volume of their calls depending on whether they are near busy or quiet roads. 

Chemical pollutants that are getting into the environment are also having a dramatic effect on the behaviour of wildlife. For example, hormones used in agriculture in Australia, which leach into our waterways, can alter the mating behaviour and morphology of freshwater fish. Furthermore, chemicals used in the human female contraceptive pill are the likely cause of feminization in fish, which has a significant impact on their ability to breed.

Growling grass frogs are one species that may be suffering due to traffic noise.  Photo: Peter Robertson

Growling grass frogs are one species that may be suffering due to traffic noise. Photo: Peter Robertson

How can we use our knowledge of animal behaviour to minimise the impacts of urbanisation and to encourage animals to return to our urban spaces? We should firstly feel encouraged by the fact that we can coexist with wildlife. By offering native animals a wide choice of native vegetation and large, undeveloped areas in our cities, we can increase both the diversity of species and the diversity of individuals within species in our urban spaces. By knowing how and when animals move through the landscape, we can create safer passageways for them. Already, road-crossing structures are allowing some of Victoria’s rare arboreal marsupials to safely cross highways, while crossing structures are helping red crabs on Christmas Island to make their annual migration. Elsewhere, cities are turning the lights off in large buildings at night, so that migratory birds are not distracted as they fly past. We could do the same here in Melbourne (at key times during the year), along with implementing stricter pollution controls (particularly in sewage and wastewater treatment plants), lowering noise pollution, decreasing vegetation clearance, not feeding wild animals and keeping cats inside (particularly at night). Ultimately, a city shared with wildlife is not only healthier for us, but also far more interesting. By beginning to understand the creatures around us, we can make sure our cities are not only home for us, but for them too.

Banner photo courtesy of Anne Aulsebrook.

The Dark Side of Bright Light

  

This is a guest post by Melbourne University PhD student Anne Aulsebrook.

If you take a walk around Melbourne at night, you don’t need a torch. Our streets are brightly lit with streetlights, headlights, advertisements, security lights and floodlit buildings. From the air, Melbourne is a spectacular labyrinth of white and gold. But while light at night has benefits, it can cause harm to wildlife – and to us.

The transformation of night

For billions of years, light has been a reliable signal of time. Sunlight indicates time of day, prompting the dawn singing of songbirds. Day length indicates time of year, triggering seasonal behaviours in birds, mammals and insects. These natural light cycles are possibly the most predictable environmental cues alongside which life has evolved.

Artificial light has completely transformed the night environment. It even lights up our skies. Today, more than 60% of Australians live under skies that are perpetually brighter than a full moon. In evolutionary terms, artificial light is an extremely recent, rapidly growing phenomena. Take, for example, sports matches after dark. Night-time sports matches became possible less than 140 years ago and Melbourne’s first floodlit footy match was only 80 years ago. Today, sporting venues around Melbourne are floodlit every night, adding to the already brightly lit night skies. 

  

Sports venues around Melbourne are brightly lit every night - sometimes even when they are empty. Photo: Anne Aulsebrook

Sports venues around Melbourne are brightly lit every night - sometimes even when they are empty. Photo: Anne Aulsebrook

Impacts on wildlife

This kind of artificial light has noticeable effects on animal behaviour. Birds in brightly lit urban areas begin singing up to 1.5 hours before sunrise, whilst some species’ perception of day length is affected, causing urban animals to breed earlier in the year. Some bats avoid light at night, which limits when and where they can forage. Other species might be attracted to light, such as the “overabundant” seagulls at the MCG.

Blackbirds begin their seasonal reproductive development almost a month earlier, when exposed to light at night. Photo: Tom Aulsebrook.

Blackbirds begin their seasonal reproductive development almost a month earlier, when exposed to light at night. Photo: Tom Aulsebrook.

The impacts of light go deeper than behaviour, too. Light has physiological effects, mainly through its effect on melatonin. Melatonin is an ancient hormone, found in all organisms, from bacteria to humans. Light suppresses melatonin production, so that the levels of this hormone are high at night and low during the day. In birds and mammals, this daily pattern in melatonin regulates other day-night (or circadian) rhythms, such as sleep.

Recent research indicates that even dim light at night, such as light in an urban environment or from an e-Reader, can suppress melatonin production. This has huge implications for both humans and wildlife. Besides affecting circadian rhythms, melatonin also has effects on the immune system, seasonal reproductive function, and ageing. There is even evidence to suggest that low melatonin levels increase the risk of breast cancer.

Light at night is not just a problem for major cities, either. Brighter nights are being experienced across Victoria and even in developing countries. Worldwide, night sky brightness increases by an average of six percent every year. For ecologists, astronomers, health practitioners and many others, this is a growing cause for concern.

Many buildings, such as those at Flinders Street and Federation Square, are floodlit at night for aesthetic reasons. Photo: Anne Aulsebrook

Many buildings, such as those at Flinders Street and Federation Square, are floodlit at night for aesthetic reasons. Photo: Anne Aulsebrook

So what can we do?

We can start by questioning the way we use light.

Firstly, we can ask if it is necessary. Light is not always serving the purpose that we think it is. For example, a recent report in Britain found no effect of street lighting on crime or traffic collisions.

Secondly, we can ask whether the lighting is efficient. Often, we are lighting up more than what is required, such as nearby parks, backyards or the sky.

Thirdly, we can ask if light is too bright. Our vision is often better than we give it credit for and bright lights can even make it harder to see due to glare.

Finally, we can consider the spectra of lighting. Light in the blue part of the spectrum has the greatest effect on melatonin production. It can also be particularly attractive to mosquitoes and moths. Consequently, in some situations light bulbs that emit less blue light might be best.

By using artificial light more efficiently and considerately, we can minimise the impact on Victorian wildlife, as well as ourselves. We might even get a better view of the night sky, adding to the allure of our already beautiful city and state. 

The cover photo was taken by Anne Aulsebrook.