A study by Tel Aviv University and the Open University found that artificial lighting at night throws crickets out of sync with the day and night cycles, disrupts cricket chirping and movement, and may harm the reproductive ability of wild populations.
A joint study by Tel Aviv University and the Open University confirms a previous study that examined the effects of light pollution on nocturnal animals, conducted under laboratory conditions, and determines that artificial lighting also disrupts the cricket cycle in nature. However, the new study slightly qualifies the findings and states that in nature the damage is to a lesser extent compared to laboratory conditions.
And there was darkness, and there was light.
The nocturnal cricket is the male's call to the females to come and mate with him. Therefore, the researchers explain, disrupting its normal course could harm reproduction and even put the crickets at increased risk of predation, which threatens the survival of the population. The current study is a continuation of a preliminary study conducted three years ago, which found that exposure to light pollution under laboratory conditions severely disrupts the cricket's chirping times, to the point of extreme conditions known as 'free running', when each individual chirps whenever "it feels like it," according to its own internal rhythm, and not necessarily at night. Now, in the new study, the researchers sought to examine the effect of lighting on crickets outside the laboratory, at the Tel Aviv University Zoological Garden, under conditions as close to nature as possible.
The study was led by Prof. Amir Ily and Dr. Keren Levy. from the School of Zoology in the George S. Wise Faculty of Life Sciences, and Prof. Anat Barnea from the Department of Natural Sciences at the Open University. Also participating in the study were Yoav Wigerzin from Prof. Ily's lab, and Stan Moeref from Prof. Barnea's lab. The article was published in the journal Science of the Total Environment.
"The distinction between day and night, between light and darkness, is one of the foundations of life on Earth. But humans, who are diurnal animals, disrupt the natural order through artificial lighting at night. This lighting often negatively affects animals in the environment, disrupting natural behaviors that have developed over millions of years of evolution," explains Dr. Levy.
"We asked ourselves whether it was possible that the laboratory conditions themselves caused confusion among the crickets. Perhaps in nature the cricket chirps when it hears the "choir" of its friends, but in the laboratory it was isolated and did not hear them? Perhaps in nature it distinguishes between day and night through temperature changes, while in the laboratory a uniform temperature prevailed 24 hours a day? We hypothesized that in natural conditions the crickets benefit from some compensation that does not exist in laboratory conditions, something in the environment that helps them distinguish between day and night despite the artificial lighting. To test this, we set up a semi-field experiment, that is, in conditions as close as possible to natural conditions," explains Prof. Ily.
Less but still annoying
For the study, the researchers hung 6 vivariums (aquarium-like containers intended for terrestrial animals) throughout the Tel Aviv University Zoological Garden, containing soil, food, a shaded area, and a temperature gauge. The vivariums were closed with a metal mesh on top and were permeable to light and air, so that the temperature and lighting inside were natural. At any given time, a single male cricket was in each vivarium, whose behavior was recorded for two weeks, after which it was replaced by another. In total, the experiment was carried out over two years, during the months of April to November, that is, during the spring, summer, and fall seasons, and about 120 crickets participated in it.
The study findings revealed that even in nature, the effect of light pollution is extremely significant: the higher the lighting intensity, the greater the disruption in the crickets' sense of time. However, the disruption was less extreme compared to laboratory conditions. For example, in an experiment conducted in the laboratory, 80% of the crickets lost synchronization with the times of day and night even under relatively weak lighting. In contrast, in nature, the loss of synchronization in 80% of the crickets was observed only under much stronger lighting.
"This is a significant finding, indicating that there are factors in nature that moderate and balance the effect of light pollution, at least at low light intensities. A specific test revealed that temperature has no effect, but we still do not know what the balancing factor is," says Dr. Levy.
"In our study, we showed that artificial lighting at night disrupts the behavior of crickets and causes them to chirp during the day, not only in the laboratory, but also under natural conditions. The findings raise a variety of questions, such as: What happens to crickets that chirp during the day? Are they more vulnerable to predators without the protection of darkness? And how do females respond to a male that chirps during the day? Do they respond to his courtship call? These and other questions, which are material for further research, suggest that disrupting chirp times as a result of artificial lighting may harm the reproduction and survival of the cricket population," says Prof. Ily, concluding, "It is also known from many studies that light pollution also harms a wide range of insects and other animals. Therefore, we are appealing to the public to turn off lights at night where they are not needed - in the garden or on the balcony, at home, at work and on the street. Only in this way can we protect the animals that live around us and need the hours of darkness."
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