Severe Weather Takes Heavy Toll in Texas

By Merlin Tuttle
3/2/21

Given overall warming trends, we weren’t surprised to see some 70 to 80° F days in January and February of 2021. But that hardly tells the full story!

Beginning on February 10th, historically low temperatures were recorded across Texas. For eight consecutive days (February 10–18), the temperature hovered between 37° and 9° F with six inches of snow on the ground in Austin, Texas. The first reasonable feeding opportunity for bats likely didn’t occur before the 21st.

The last similar event occurred 32 years ago in 1989. In a 9-day period (December 16–24) the daily temperature ranged from 51 to 4° F but remained below freezing for only two days versus seven in 2021. Fewer people were concerned in those days, but at least hundreds of killed bats were reported.

Brazilian free-tailed bats about to emerge from their day roost in a bridge crevice in Austin, Texas.

The recent event, Winter Storm Uri, created a disaster for overwintering Brazilian free-tailed bats (Tadarida brasiliensis). Encouraged by warming trends, more and more bats have remained in their summer roosts year-round instead of migrating south for winter. In recent years, hundreds of thousands have overwintered in bridge crevices of Central Texas, especially in the Austin area. Additionally, over the last four decades, an estimated 1,000 more annually have remained in Bracken Cave.

Unlike many other temperate-zone bats, Austin’s free-tails are not true hibernators. They do store fat in the fall and can survive for more than six weeks without feeding when roosting at 41° F. In Central Texas, they emerge and successfully feed when evening temperatures are 50° F or above, and in traditional winters they seldom would need to wait more than 10 days between feedings.

To survive for eight days with average temperatures well below freezing would be an extreme challenge. Bats have the largest surface area per volume of any warm-blooded animal, and active free-tails maintain body temperatures of roughly 102° F. Following the recent weather crisis, just warming up to go hunting was undoubtedly prohibitive for many, and it’s difficult to imagine that the insects the bats depend on for food would have been immediately abundant. Even though daytime temperatures averaged 78° F over four consecutive days beginning on February 21st.

Many concerned Austinites wondered why accumulations of dead and dying bats steadily grew through at least the 25th, despite the return to warm weather. The answer is two-fold. Many bats likely were still alive but too weakened to go hunting. Some of those may take a week or more to die. Also, those that literally froze to death could take weeks to fall from their roosting crevices. Tendons in their toes are designed to automatically lock the bats’ claws firmly to the roosting crevice until consciously released. Thus, a bat may hang in place long after its death

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Bat Flash! Premature Speculation Revives Scary Headlines

8/13/2020

By Merlin Tuttle

A study published July 28th in Nature Microbiology titled, “Evolutionary origins of the SARS-CoV-2 lineage responsible for the COVID-19 pandemic,” implies a direct bat origin at a time when analyses remain woefully incomplete. Nevertheless, news media continue to sensationalize inconclusive speculation in a manner that needlessly demonizes bats and circumvents the scientific process:

BBC NEWS“COVID-19: Infectious coronaviruses circulating in bats for decades”

Popular Science—“The virus that causes COVID-19 has been silently brewing in bats for decades”

The Philadelphia Inquirer—“The next coronavirus may already be circulating in bats, study suggests”

Live Science—”Ancestors of coronavirus have been hiding out in bats for decades, ready to infect humans.”

Millions of tourists have safely observed bats close up in Austin, Texas without harm. Bat-watchers add millions of dollars to Austin's economy each summer.

None of these articles mentions either the exceptional value of bats or how rare it is to contract any disease from a bat. Readers need rational advice, not more cause for panic!

Failure to find an intermediate ancestor for SARS-CoV-2 is not a basis for concluding that bat-to-human transmission has occurred. There is a massive under-sampling of other species. It is even possible that the virus now causing COVID-19 evolved its deadly characteristics after arrival in humans. Much more sampling of possible hosts will be required before we can conclude where it came from.

The implied contention that bats are uniquely dangerous hosts of deadly coronaviruses is premature and inconsistent with current evidence. There is evidence of a horseshoe bat role in the early evolution of a SARS-like coronavirus. Nevertheless, Wenzel agrees, “common knowledge regarding SARS viruses is apparently not well supported.” There is a critical need to survey coronaviruses, far beyond bats. Finding the true source of COVID-19 transmission to humans is key to future prevention.

No patient zero has been found, leaving the route of transmission to humans a mystery. It is time to halt media headlines that misrepresent facts, risking the survival of already threatened bats, and diminishing confidence in science.

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