Synthetic gentle at evening discovered to trigger in depth deaths and disrupt copy in desert rodents

(A) Housing construction in daylight and at night. Eight pens arranged side by side in a row were built to house spiny mice in near-natural conditions. Hollow cement blocks were used as shelters for both species. From right to left: pens in daylight, pens at night with blue, yellow and white light. Control cabinets remained dark. (B) Illuminance of the light treatment and (C) spectral distribution. Credit: Scientific Reports (2022). DOI: 10.1038/s41598-022-19805-1

A major study at Tel Aviv University’s School of Zoology tested the effects of sustained, low-intensity light pollution on two species of desert rodents: the diurnal golden spiny mouse and the nocturnal common spiny mouse.

The results were extremely disturbing: on two separate occasions, entire colonies exposed to ALAN (Artificial Light At Night) died within days, and reproduction also decreased significantly compared to control groups. “Our results clearly show for the first time that light pollution can be extremely harmful to these species, and suggest that they could be harmful to ecosystems, biodiversity and even human health,” the researchers say.

The study was conducted by Prof. Noga Kronfeld-Schor, Senior Scientist at the Israel Ministry of Environmental Protection, and Ph.D. Student Hagar Vardi-Naim, both from the Zoological Faculty of the TAU and the Steinhardt Natural History Museum. The paper was published in Scientific Reports.

Prof. Kronfeld-Schor explains: “We have been studying these closely related rodent species for years. They both live in the rocky deserts of Israel: the golden spiny mouse (Acomys russatus) is diurnal, the common spiny mouse (A. cahirinus) is diurnal and nocturnal. The two species share the same natural habitat but use it at different times to avoid competition. By comparing closely related species with different activity times, we gain new insights into the biological clock and its importance for animal and human health.”

Hagar Vardi-Naim says: “In most species studied to date, including humans, the biological clock is synchronized by light. This mechanism evolved over millions of years in response to the daily and annual cycles of sunlight – day and night and their varying lengths corresponding to the changing seasons. Different species evolved activity patterns that correspond to these changes in light intensity and day length, and evolved anatomical, physiological, and behavioral adaptations appropriate for diurnal or nocturnal activity and seasonality.”

“However, over the past several decades, people have changed the rules by inventing and making extensive use of artificial light, which creates light pollution. According to the latest studies, about 80% of the world population is exposed to ALAN, and the area is affected by light Pollution is growing at 2-6% annually. In a small and crowded state like Israel, very few places are free from light pollution. In our study, have we are closely monitoring the long-term effects of ALAN on individuals and populations under near-natural conditions. “

In the study, the researchers placed 96 spiny mice of both species, equal numbers of males and females, in eight spacious outdoor enclosures in the TAU Zoological Research Garden. The enclosures simulated living conditions in the wild: all animals were exposed to natural environmental conditions, including natural light-dark cycles, ambient temperatures, humidity and precipitation.

Each enclosure contained shelters, nesting materials, and access to adequate amounts of food. The experimental pens were exposed to ALAN at low intensity (similar to a street light in urban areas) with different wavelengths (colors) for 10 months: two pens were treated with cool white light, two with warm white (yellowish) light and two with blue light, while two pens were treated at night remained dark and served as controls.

All animals were tagged to allow close monitoring of behavioral changes and physical condition. The experiment was conducted twice in two consecutive years.

Prof. Kronfeld-Schor says: “The average lifespan of spiny mice is 4-5 years and our initial plan was to monitor the effects of ALAN on the same colonies and measure the impact on reproductive performance, welfare and longevity. But the dramatic results thwarted our plans: In two independent events in two different enclosures exposed to white light, all animals died within a few days.”

“We had seen no preliminary signs, and autopsies at TAU ​​School of Medicine and the Kimron Veterinary Institute in Beit Dagan revealed no abnormal findings in the dead spiny mice, and no protection against an unidentified pathogen. No abnormal mortality was recorded in any of the other enclosures, and as far as we are aware, no similar event has ever been documented by researchers.”

Other results also suggested that exposure to ALAN disrupted reproductive success in spiny mice. Hagar Vardi-Naim says: “In the wild, both species of spiny mice breed primarily in the summer, when temperatures are high and the newborn pups are most likely to survive. However, artificial light seemed to confuse the animals. The common spiny mice began breeding year-round but produced a lower number of pups per year.”

“Winter-born pups are not expected to survive in the wild, which would further reduce the reproductive success of the species in the wild. but the number of young was reduced by half compared to the control group, which continued to thrive and reproduce normally. These results are consistent with the fact that in seasonal long day breeders, the cue for reproduction is day length.”

Additional testing revealed that exposure to ALAN caused physiological and hormonal changes — most notably in levels of cortisol, a key stress hormone involved in the regulation and operation of many physiological pathways, including regulation of the immune system. Laboratory tests showed that exposure to blue light increased cortisol levels in golden spines, while white light lowered cortisol levels in winter golden spines.

Prof. Kronfeld Schor says: “Our results show that light pollution, especially cold white and blue light, increases mortality and disrupts reproduction, and thus can affect the fitness and survival of species in the wild. This adverse effect can have far-reaching consequences. consequences of the current widespread incidence of light pollution.”

“Our unambiguous results are an important step in understanding the impact of light pollution on biodiversity and will help us to promote science-based policies, particularly with regard to the use of artificial light in both built and open spaces. In future studies, we plan to investigate what caused the numerous deaths in the pens exposed to ALAN, with a focus on the effect of light pollution on the immune system.

More information:
Hagar Vardi-Naim et al., Fitness consequences of chronic exposure to different wavelengths of light pollution in nocturnal and diurnal rodents, Scientific Reports (2022). DOI: 10.1038/s41598-022-19805-1

Provided by Tel-Aviv University

Citation: Artificial light at night found to cause extensive deaths and reproductive failure in desert rodents (2023 January 10) retrieved January 10, 2023 from https://phys.org/news/2023-01- artificial-night-extensive-deaths-disrupt.html

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