Tel Aviv University Study Finds 100% Mortality in Two Desert Rodent Species Exposed to Constant Nighttime LED Lighting

All wild rodents exposed to artificial light at night died during a Tel Aviv University experiment that measured immune-system performance under conditions simulating street lighting. The study, titled “Artificial light at night disrupts immune rhythms in wild rodents under semi-natural conditions,” was published in the journal Environmental Pollution on May 9, 2026.

35-fold increase in mortality risk compared with a control group kept under natural light-dark cycles that included the sun, moon and stars.

Researchers captured golden spiny mice (Acomys russatus) and common spiny mice (Acomys dimidiatus) from the Judean Desert and placed them in outdoor enclosures at TAU’s Zoological Garden, also known as the I. Meier Segals Garden for Zoological Research.

Half the enclosures were illuminated at night with white LED lights at intensities that replicate standard street lighting; the remainder experienced only natural conditions.

Doctoral student Hagar Vardi-Naim, who carried out the study, said large parts of every mammal’s body are regulated by an internal biological clock with a 24-hour rhythm based on the natural light-dark cycle. She stated that exposure to light pollution completely muddled the rhythms of lymphocyte levels and immune response.

The team measured the percentage of lymphocytes in the mice’s blood at several points in the 24-hour cycle.

M. Animals exposed to an antigen during those rest hours produced far more antibodies than those challenged during active hours.

“Exposure to light pollution, however, completely muddled these rhythms. Instead of a daily cycle of peaks and lows in the level of lymphocytes and immune response, we observed a complete flattening of the daily patterns." — Hagar Vardi-Naim ALAN exposure caused complete flattening of those daily patterns. Pathology exams showed that the immune systems of the exposed mice had stopped working to protect the body. Prof. Noga Kronfeld-Schor, who supervised the work with Prof. Yariv Wine, said all mice exposed to ALAN died during the study. Kronfeld-Schor, rector of TAU’s School for Environment and Sustainability and a former chairman of the zoology department, stated that illumination that is not moonlight weakens the immune system. The researchers concluded that ALAN should be regarded as an environmental health risk with broad implications for wildlife, human health and the ecosystem. Just last month, researchers at Ben-Gurion University of the Negev headed by Yael Lehnardt published a study on the impact of noise on animals, especially birds. The Jerusalem Biblical Zoo consulted TAU researchers on protecting animals from light pollution caused by neighborhood expansion in Givat Masua. Attempts were made to reduce nighttime lighting at the Western Wall, but authorities opposed the changes for security reasons or public preference. Light pollution is present even at Mitzpe Ramon in the Negev, a recognized stargazing and astro-tourism destination. Israel has not passed any legislation on limits for artificial light at night. The study received positive reactions from colleagues in the US and Europe. The spiny mice used in the experiment share the same geographical habitat in the Israeli desert but differ in activity times. Golden spiny mice are active by day while common spiny mice are nocturnal. The enclosures were designed to simulate a natural environment as closely as possible. Vardi-Naim noted that the findings, while obtained from rodents, have implications for all living creatures, including humans. She emphasized that studies show animals with weakened immune systems can transmit diseases to humans and that the human immune system may respond similarly.”