Israeli scientists: gentle air pollution kills rodents

Animals around the world are now living at night under skies suffering from light pollution caused by overuse of artificial lights, TPS reported. Nighttime lighting in urban areas obscures the stars that migratory birds rely on for navigation. This lures animals into dangerous places and disrupts their sleeping patterns. But new Israeli research shows that this phenomenon actually kills animals.

The study from Tel Aviv University’s Faculty of Zoology examined the effects of sustained, low-intensity light pollution on two species of desert rodents — the golden spiny mouse, which is active during the day and sleeps at night, and the nocturnal common spiny mouse, which sleeps during the day.

“The average lifespan of spiny mice is 4-5 years and our initial plan was to observe the effects of artificial light on their colonies at night and measure the impact on their reproduction, welfare and lifespan. But the dramatic results thwarted our plans. Noga Kronfeld-Shor, Chief Scientific Advisor to the Israel Ministry of Environmental Protection.

“In two separate cases, in two different enclosures, all animals exposed to white light died within a few days. We hadn’t noticed any preliminary signs, but the autopsies at Tel Aviv University Faculty of Medicine and Kimron Veterinary Institute in Beit Dagan showed no abnormalities on the spiny mouse carcasses,” explained Prof. Kronfeld-Kurz.

“We hypothesize that nocturnal exposure to artificial light weakened the animals’ immune responses, rendering them defenseless against an unidentified pathogen. Such an unusually high mortality rate has not been recorded in any of the other enclosures, and to our knowledge no similar event has been documented by researchers,” she said.

The results were recently published in the London edition of Scientific Reports.

“In most species studied to date, including humans, the biological clock is synchronized by light. This mechanism evolved over millions of years as a result of the diurnal and annual cycles of sunlight – day and night and their differing durations corresponding to the changing of the seasons,” explains Hagar Vardi-Naim, a doctoral student at Tel Aviv University and one of the study leaders.

“Different species have evolved activity patterns that correspond to these changes in light intensity and day length, and have evolved anatomical, physiological, and behavioral adaptations appropriate for diurnal or nocturnal activities and seasonality. However, in recent decades, humans have changed the rules with the invention and widespread use of artificial light, leading to light pollution,” she adds.

From a total of 96 specimens, an equal number of male and female spiny mice were housed in eight outdoor enclosures. The enclosures stimulated natural living conditions: all animals were exposed to natural environmental conditions, including the natural light/dark cycle, ambient temperature, humidity and precipitation. Each enclosure contained shelters and access to sufficient food.

For 10 months, the experimental pens were exposed to low-intensity artificial light at night, similar to that from streetlights in urban areas. Some of the rodents were exposed to cool white light, others to warmer yellow-white light, others to blue light, and the rest were left in the dark as a control group. The animals were observed for changes in behavior and physical condition.

The experiment was repeated the following year.

The researchers found that light pollution also affected the rodents’ ability to reproduce.

“In the wild, both species of spiny mice breed primarily in the summer, when temperatures are high and the newborns have the best chance of survival. However, artificial light seems to confuse the animals,” says Vardi-Naim.

“Common spiny mice began to breed year-round but gave birth to a smaller number of young per year. The prediction is that winter-born young would not survive in the wild, further reducing the reproductive success of this species,” she explained.

Vardi-Naim added that reproduction was affected differently in golden spiny mice. “Colonies exposed to artificial light at night continued to reproduce throughout the summer, but the number of young was halved compared to the control group, which developed and reproduced normally.”

Vardi-Naim noted that, according to recent studies, around 80 percent of the world’s population is exposed to artificial light at night, and the area affected by light pollution is increasing by 2 to 6 percent annually. “In a small and overpopulated country like Israel, very few places remain untouched by light pollution,” concluded Vardi-Naim.

Illustrative photo from Alexa’s photos: https://www.pexels.com/photo/brown-and-white-mice-2280794/