Did you know that bats provide about $1 billion worth of natural pest control in the agricultural industry in California? In fact, one colony of 150 big brown bats can eat almost 1.3 million insects per year. And one little brown bat can catch up to 1,200 mosquitoes in one hour, which can help reduce the transmission of mosquito-borne diseases like the Zika and West Nile viruses.
Bats – which are the only flying mammals – also pollinate more than 300 different species of fruit, including bananas, mangos, avocados, durian, guava and agave. Bats also pollinate many plants with flowers that open at night – evening primrose, honeysuckle and many more.
Over the years, Naomi d’Alessio has learned about these and virtually countless other facts about bats. Unfortunately, she also discovered that bat populations have been declining in California, across the U.S. and in other parts of the world due to a combination of disease, climate change, mortality from wind turbines and habitat loss (due to deforestation and urbanization).
Over half of the 150-plus species of bats in North America are currently at risk of extreme population decline over the next 15 years, according to the 2023 North American State of the Bats Report. In the U.S., half of all American bat species are in severe decline or have already been listed as “endangered,” according to Bat Conservation International (BCI). And in California, 12 of the 26 species of bats found statewide have been designated “of special concern” by the California Department of Fish and Game (CDFG) – including the Pallid bat.
“Yes, there is a decline in bats and it is happening here and elsewhere a lot,” explained Naomi. “Data in California shows that the bat populations are sparse and one of the reasons is white-nose syndrome, which is a fungus that kills the bats when they’re hibernating, and that has killed a lot of the bats that hibernate in big colonies because it spreads so easily.”
While the fungus itself is naturally occurring, people who go caving or spend time in other bat habitats play a role in spreading the deadly syndrome (known as WNS), according to Naomi.
“Humans going into caves and getting [the fungus] on the bottom of their shoes or on their clothes, and then maybe wearing that same equipment or those same boots or clothing into another cave can spread white-nose syndrome, even in places where it’s not obvious that there are bats,” she said.
“Urbanization is always a big issue as well, partly due to the loss of natural bat habitats, but also because big cities are typically very noisy places,” said Naomi.
“A bat relies a lot on its hearing, that’s why it has very big ears,” she said. “With all the noises from human activity, the Pallid bat, for instance, does not do very well in very urban environments.”