Light Pollution Impacts Reproductive Behavior of Lemurs

It turns out that light pollution may be having more of an effect on the environment than expected. Scientists have found that excess lighting can override the natural reproductive cycle of lemurs, making them sexually active out of season.

"The natural light/dark cycle allows living organisms to time a variety of behavioral and physiological rhythms, including migration, accumulation of reserves, dormancy and reproduction," said Thomas Le Tallec, one of the researchers, in a news release "We postulate that chronic exposure to light pollution could impact the human reproductive function as well. Night work and artificial light are associated with menstrual irregularities, decreased fertility, spontaneous abortions and pre-term births. However, this is only a hypothesis and rigorous studies are needed."

In this case, researchers examined mouse lemurs, which are highly sensitive to day length. In winter, male lemurs are sexually inactive and the testes are not visible. In the summer, when it's lighter, the males become more sexually active with fully functioning gonads.

In order to better examine how light affects these primates, the researchers placed sexually inactive male lemurs inside special climate chambers, where the level of light was controlled by fluorescent lamps. In the control group, the level of light at night was set to only equal that of the full moon. In the other group, the lemurs were exposed to yellow LED lights to mimic streetlights.

So what did they find? It turns out that after only two weeks, the light-pollution group had considerably larger testes and higher levels of testosterone.

The findings reveal that light can greatly impact reproductive behavior. This, in turn, can influence entire ecosystems. This, in turn, shows that policies to mitigate light pollution in environmentally sensitive areas may be an important part of conservation practices.

"By reducing air pollution we can reduce the scattering of light in the atmosphere and thus reduce light pollution," said Le Tallec.