Bats are disappearing in large numbers after losing their way due to imidacloprid, and their droppings contain excessive pesticides and heavy metals

The common pesticide imidacloprid not only makes bees disappear, according to a team led by Wu Chung-hsin, a professor in the Department of Life Science at National Taiwan Normal University and an authority on bat research in the country, the rapid disappearance of bats in recent years is also inextricably linked to imidacloprid.

Over the past 4 to 5 years, the team collected bat droppings from all over Taiwan and found large amounts of pesticide and heavy metal residues, so they launched an investigation. Because bats rely on echolocation to catch insects for a living, the study found that when bats eat insects contaminated with imidacloprid or the heavy metal manganese, it damages the central nervous system and the echolocation system in their brains, causing them to lose their way. Bats can then no longer fly normally in the air, and may even lose the ability to catch insects and die. The results of this study were published last year in the international academic journal Neuroreport.

(Above) Light trails recorded as a normal bat flies in a classroom

The insecticide imidacloprid also causes bats to lose their way and lose their hearing

Among the findings, when the research team tested bat droppings in central and southern Taiwan, they found that imidacloprid residues were generally 6.5 to 9 ppb. Dr. Lin Ching-lung of Wu Chung-hsin's team in the Department of Life Science at National Taiwan Normal University said that for many years international research has found that imidacloprid harms the nervous system of bees, and on closer investigation it was found that what imidacloprid damages is a neurotransmitter in the bee brain called "acetylcholine", but this type of neurotransmitter is not only found in bees; bats actually have it too.

Dr. Lin Ching-lung explained that when bats eat insects contaminated with the pesticide imidacloprid and it accumulates to a certain amount, the "hippocampus" and "entorhinal cortex" in the brain that help with positioning and navigation are damaged. These two types of nerve cells cause bats to lose their navigation system and memory-learning functions, which in turn causes bats to lose their way. In addition, they found that excessive intake of the heavy metal manganese also causes bats to lose their way.

In addition to analyzing bat droppings collected in the wild, Wu Chung-hsin's team also actually used Taiwanese leaf-nosed bats in ultrasound spectrogram and flight-trajectory experiments and found that in Taiwanese leaf-nosed bats that ate high doses of the heavy metal manganese or imidacloprid, the neurons in the brain used to control hearing and vocalization became inflamed and produced cell apoptosis reactions, causing the bats' ultrasound spectrograms to become incomplete and their originally regular flight paths to become very chaotic.

The twitching of the bat in the video below is an acute poisoning phenomenon caused after ingesting insects with a high dose of imidacloprid.

Expert: imidacloprid should be avoided as much as possible; Bureau of Animal and Plant Health Inspection and Quarantine: there is no need for excessive worry

Wu Chung-hsin said that in the past the academic world always thought that imidacloprid only harmed the nerve cells of insects and would not affect mammals, but through research over these years it has been found that the nervous systems of mammals are also affected. Although there may be many kinds of environmental factors that cause bats to lose their way, imidacloprid is indeed one of them, so in the use of pesticides, if it can be avoided it should be avoided as much as possible.

Internationally, there is already consensus that neonicotinoid pesticides such as imidacloprid cause phenomena such as bees losing their way worldwide. 4 years ago the European Union took the lead in imposing restricted-use bans on pesticides such as imidacloprid, and last year the U.S. Environmental Protection Agency began prohibiting the use of such pesticides during crop flowering periods and bee pollination periods, and launched a preliminary risk assessment of neonicotinoid pesticides.

In addition, bat droppings can be used to make the traditional Chinese medicine yemingsha (bat feces). With heavy metals and pesticide residues at such levels, are there safety concerns? In response, the Department of Chinese Medicine said that at present there is no maximum residue limit for imidacloprid specifically established for the traditional Chinese medicine yemingsha. The allowable limits for pesticide residues in traditional Chinese medicine have been under review for the past one to two years. At present there are very few pesticide items with regulations, only chlorine-containing pesticides such as DDT and DEHP. For the pesticide residue regulations of other traditional Chinese medicine materials, a draft will be proposed this year.

Feng Hai-tung, deputy director-general of the Bureau of Animal and Plant Health Inspection and Quarantine, said that the dose of imidacloprid fed in Professor Wu's team's laboratory was too high and would simply not occur in the environment, because under normal conditions the insects would have been poisoned to death long ago; and as for the portion collected from bat droppings, the general residue level was about 6.5 to 9 ppb, which is even lower than our country's allowable limit for imidacloprid in vegetables (0.1 to 3.5 ppm) (1 ppm is 1000 ppb), so there is no need for excessive worry about this.