Swarms of tiny, bloodthirsty vampire bats are spreading their wings further north toward the U.S.-Mexico border.
Scientists led by a team at Virginia Tech said they expect an “invasion of vampire bats on U.S. soil in five to 20 years,” with sightings now occurring just 30 miles outside Texas.
Colonies of the five-centimeter-long creatures have long plagued cattle ranches south of the border, drawing blood from the livestock as a parasite.
According to a 2020 report from the United States Department of Agriculture (USDA), the bats cost Mexican ranchers over $46.7 million per year due to the deaths of rabies-infected animals.
Researchers believe rising temperatures are making North America more hospitable to the bloodthirsty creatures.
Scientists led by a team at Virginia Tech now say they expect an “invasion of vampire bats on U.S. soil” in five to 20 years. The bats could cost lives as rabies-infected specimens climb the North American continent and spread the deadly disease
Above, in red (left), the estimated distribution of vampire bats from 1901 to 2019, with the deeper shades of red having the highest probability based on researchers’ confidence in their data and models. In blue (right) an “uncertainty map” showing potential areas of vampire bat spread
Previous USDA reports estimate that the invasion of vampire bats into South Texas could take between $7 million and $9 million off the local livestock industry due to rabies deaths alone.
But the bats could also cost lives as rabies-infected specimens climb the continent and spread the deadly disease.
“It is a difficult situation that we want to address as quickly as possible, so vigilance is critical,” a Texas Farm Bureau spokesman, Gary Joiner, told Wired.
“This species of bat is a major concern in agriculture because it can transmit disease, harm livestock and cause infections,” Joiner said.
“Rabies is the most obvious concern due to animal welfare and the potential to infect humans.”
Although rabies deaths are currently rare in the United States, with only one to three people dying per year, according to the U.S. Centers for Disease Control and Prevention (CDC), these deaths are increasingly caused by infected bats.
Although vampire bats rarely bite humans, the creatures strike when threatened, and their expanding habitat increases the likelihood of hostile interactions.
Efforts to vaccinate the bats themselves against rabies could backfire, according to Luis Escobar, an assistant professor of wildlife conservation at Virginia Tech who has tracked the bats’ northward advance.
“Rabies can reduce bat populations by 10 to 80 percent,” Escobar said. “Imagine if we had too many vampire bats because we didn’t have this virus.”
According to a 2020 report from the United States Department of Agriculture (USDA), vampire bats cost Mexican ranchers over $46.7 million per year due to the deaths of rabies-infected animals. Previous USDA reports estimate the bats could cost an additional $7 million to $9 million in South Texas
Some wildlife managers have experimented with a rabies vaccine gel that wild-caught bats then distribute in their roosts, where the social species groom one another.
But Escobar fears the technique could lead to an explosion in vampire bat populations.
“We don’t know what the ecological impact of disrupting the circulation of this virus in bats will be,” he said.
Instead, researchers and USDA officials suggest that ranchers should follow the lead of their Mexican and Colombian counterparts and vaccinate their livestock and pets.
And local governments may want to vaccinate wild animals that prey on vampire bats.
“Landowners are going to want to think about whether or not to vaccinate their animals,” said Mike Bodenchuk, director of the USDA’s Texas Division of Wildlife Services, trying to quell overblown fears.
“They won’t come across the border a million times,” he noted. “It’s going to be a slow trickle for a while.”
This species of vampire bat, Desmodus rotundus, tends to thrive in hot and humid regions where temperatures do not fall below 50 degrees Fahrenheit.
Late last month, Virginia Tech’s Escobar and a team of international conservation scientists released the results of their examination of 120 years of climate records, seasonal vampire bat captures and other data, such as cattle rabies deaths, logged by the Regional Information System for the Epidemiological Surveillance of Rabies .
The researchers found that “the bat’s geographic range has shifted its distribution significantly northward,” as they wrote in the journal Ecography, “a natural invasion of northern Mexico at an average rate of 6.1 miles (9.76 km) per year.” [6.06 miles per year].’
Escobar and his co-authors added that their extensive database analysis is consistent with previous work that used DNA evidence to record bat migrations.
“Genetic studies have shown that D. rotundus from Mexico is rapidly expanding its range northward,” they noted. ‘[but] Disagreements between previous modeling efforts have shown that further research is still needed.