Human-Caused Bat Mortality Studied

The study's authors concluded infectious diseases are not the main worry, and that bats globally could benefit from policy, education, and conservation actions targeting human-caused mortality.

A new study by authors from the U.S. Geological Survey, New Zealand's Massey University, Montana State University, and the University of Glasgow examines the causes of bat deaths worldwide. Reports of bat deaths worldwide from human causes largely unique to the 21st century are markedly rising, according to their USGS-led analysis published in Mammal Review. This is a concern because bats play vital roles in most ecosystems; they are important pollinators and seed dispersers in tropical regions and the main predators of night flying insects in most parts of the world. They save farmers billions of dollars per year by providing natural pest control.

Along with USGS colleagues, David Hayman of Massey University; Raina Plowright of Montana State University; and Daniel Streicker of the University of Glasgow reviewed the scientific literature from 1790 to 2015 searching for annual mortality events involving more than 10 bats, then divided multiple mortality events into both natural and human-involved categories. They found and categorized 1,180 mortality events from all over the world in all.

Collisions with wind turbines and the white-nose syndrome disease in North America are the leading reported causes of mass death in bats in this century, and they surpass all prior known causes of bat mortality, whether natural or attributed to humans. "Many of the 1,300 species of bats on Earth are already considered threatened or declining. Bats require high survival to ensure stable or growing populations," said Tom O'Shea, a USGS emeritus research scientist and the study's lead author. "The new trends in reported human-related mortality may not be sustainable."

They recommend policy, education, and conservation actions targeting human-caused mortality. "Determining the most important causes of bat mortality is a first step toward trying to reduce our impact on their populations," said Hayman, a senior lecturer at Massey University.

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