How artificial light effects mammals

Light pollution is significantly affecting the breeding patterns of native Australian mammals, new La Trobe University research has found.

Light pollution in urban fringe areas is significantly affecting the breeding patterns of native Australian mammals, new La Trobe University research has found. 

The groundbreaking research has revealed artificial night lighting has delayed the breeding season of Tammar Wallabies, which could severely reduce populations in years to come.  

Researcher Kylie Robert, who is a senior lecturer in La Trobe's Department of Ecology, Environment and Evolution, said the findings could be applied to many species of nocturnal mammals.  

"Light pollution is growing at a faster rate than any other human made disturbance and it's having an increasing impact on wildlife," Dr Robert said. 

"Wildlife in urban areas and urban fringes are the most at risk. Studies have been conducted on birds before but to our knowledge, no study has ever examined the impacts of light pollution on the reproductive timing of wild mammals." 

Mammals such as the wallaby are heavily dependent on light levels as seasonal indicators. Their breeding season is timed especially so offspring are born when food and water are in abundance for nursing mothers.  

However, artificial night lighting affects the melatonin levels in mammals, which is their internal signal of when to reproduce.

More alarmingly, there is an increasing growth rate in the use of energy efficient LED lighting. Despite the energy-efficient benefits of LED's there is growing concern for their impacts on wildlife as they emit wavelengths in the blue spectra that further impact melatonin.

The delayed breeding season will see young born when there are reduced food sources, which would force malnourished mothers to abandon their offspring.  

Dr Robert and her team coincidentally discovered the impacts while working on another project on Garden Island, WA. The island is home to a large Naval base, which is heavily lit during the night with artificial lighting.

The team observed that the wallabies living near the naval base entered their breeding season later than those wallabies living in natural bush land, free from artificial light. 

"These results are very exciting because it means we can start mitigating the cause of the problem," Dr Robert said.

"We are currently working on developing wildlife friendly lighting which removes the blue wavelength light spectra in LED globes."  

The article will be published in the Royal Society journal, Proceedings of the Royal Society B, on Wednesday 30 September.

Image: Michelle McFarlane

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