Bats and babies: The chilling connection between a bat epidemic and infant mortality

Often viewed as vampiric blood suckers and rabies vectors, bats have a notoriously negative reputation invoking fear and disgust. Yet, people’s preconceived notions exclude the importance of these flying mammals. Bats are essential to the environment, the economy, and human well–being by controlling insect populations, pollinating plants, and dispersing seeds. A new study published in Science highlights how tight this human–bat linkage is, uncovering an alarming connection between declining bat populations and increased infant mortality rates. 

Since 2006, a devastating disease called white-nose syndrome (WNS) has killed millions of bats throughout North America. The disease derives its name from the white fungus, Pseudogymnoascus destructans, that grows on the skin of hibernating bats’ noses, ears, and wings. Thriving in cold, humid environments characteristic of caves and mines inhabited by bats, P. destructans spreads pervasively through bat colonies. The fungi’s extensive skin tissue damage disturbs hibernation, causing bats to deplete their energy stores essential for surviving the winter. Affected bats also struggle to regulate their body temperature, breathe normally, and maintain proper electrolyte balances. These physiological changes lead to starvation, dehydration, and death. Since its initial discovery in a New York cave, the fungus has spread rapidly to 40 U.S. states and eight Canadian provinces, decimating bat populations and resulting in local extinctions with an average mortality rate of 73%.

In counties where bats experienced disastrous declines due to WNS, infant mortality rates increased by 8%. This rise equates to a startling 1,334 infant deaths between 2006 and 2017. Underlying this connection is the role of bats in insect population control. Bats can consume their full body weight in insects each night, maintaining essential limits on insect numbers. To compensate for the decline of bats and the subsequent surge in insects, farmers increased their insecticide use by 31%. Pesticide use is linked to a variety of negative human health outcomes, including birth defects. Thus, the study suggests evidence of a causal relationship connecting WNS–induced bat loss and increased insecticide use, ultimately resulting in higher infant mortalities.

“In counties where bats experienced disastrous declines due to WNS, infant mortality rates increased by 8%. This rise equates to a startling 1,334 infant deaths between 2006 and 2017.”

Bat loss from agricultural systems has dramatic economic consequences as well. In pest control alone, bats offer estimated annual savings ranging from $3.7 billion to $53 billion. However, these estimates do not incorporate the value of bats in crop pollination nor the health and environmental costs of increased pesticide use. Therefore, bats’ full monetary benefits far exceed this range. 

The link between bats and human well–being exemplifies a larger issue occurring across the planet: loss of ecosystem services. Ecosystem services constitute the plethora of benefits humans derive from environmental processes, including food and other resources, air and water purification, soil formation, and nonmaterial benefits such as recreation and spirituality. Yet, 60% of these services are declining due to climate change, habitat degradation, biodiversity loss, and overexploitation of natural resources. By the year 2100, an estimated 9% of ecosystem services will be lost, a distressing reduction that jeopardizes the health of all Earth’s inhabitants. 

The human–bat relationship is among the multitude of inextricable connections between humanity and nature. Healthy, functioning ecosystems ensure the well–being of the human populations that rely on them. As public perception and policy continue to regard humans as distinct from and superior to nature, degradation of the environment and human health will follow. Conversely, a sustainable future is within reach through enhancing collective understanding, consideration, and management of social–ecological systems.