Swarms of tiny, bloodthirsty vampire bats are spreading their wings further northward toward the US-Mexican border. Scientists led by a team at V
Swarms of tiny, bloodthirsty vampire bats are spreading their wings further northward toward the US-Mexican border.
Colonies of the two-inch-long creatures have long plagued cattle ranches south of the border, parasitically extracting blood from livestock.
The bats cost Mexican ranchers over $46.7 million per year due to the deaths of rabies-infected animals, according to a 2020 report by the United States Department of Agriculture (USDA).
Researchers believe warming temperatures make 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 to US soil between five and 20 years in the future.’ The bats could cost lives as rabies-infected specimens climb up the North American continent, spreading the fatal disease
Above, in red (left), estimated vampire bat distributions from 1901 to 2019, with the deeper reds showing the highest likelihood, based on the researchers’ confidence in their data and models. In blue (right), an ‘uncertainty map’ revealing potential areas of vampire bat expansion
Past reports by the USDA estimate that the entry of vampire bats into south Texas could drain between $7 to $9 million out of the local livestock industry in terms of rabies deaths alone.
But the bats could also cost lives as rabies-infected specimens climb up the continent, spreading the fatal disease.
‘It’s a difficult situation that we’d like to address as soon as possible, so vigilance is crucial,’ a spokesperson for the Texas Farm Bureau, Gary Joiner, told Wired.
‘This bat species causes a lot of concern in agriculture due to its ability to transmit diseases, injure livestock, and cause infections,’ Joiner said.
‘Rabies is the most obvious issue because of livestock welfare and potential to infect humans.’
While human deaths from rabies are currently rare in the United States, killing only one to three people a year according to the US Centers for Disease Control and Prevention (CDC), those deaths are increasingly caused by infected bats.
Although vampire bats rarely bite people, the creatures will strike when threatened, and their expanding habitat means more chances of hostile interactions.
According to Luis Escobar, an assistant professor of wildlife conservation at Virginia Tech who has tracked the bats’ advancement northward, efforts to vaccinate the bats themselves from rabies could backfire.
‘Rabies can reduce populations of bats from 10 to 80 percent,’ Escobar said. ‘Imagine if we had too many vampire bats because we didn’t have this virus.’
Vampire bats cost Mexican ranchers over $46.7 million per year due to the deaths of rabies-infected animals, according to a 2020 report by the United States Department of Agriculture (USDA). Past USDA reports estimate the bats could cost another $7 to $9 million in South Texas
Some wildlife managers have experimented with a rabies vaccine gel that wild-caught bats then distribute themselves back at their roosts, where the social species groom one another.
But Escobar worries that the technique risks exploding vampire bat populations.
‘We don’t know what the ecological effects of disrupting the circulation of this virus in bats are going to be,’ he said.
Instead, researchers, as well as USDA representatives, suggest ranchers might want to 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 vampire bats prey on.
‘Landowners will want to consider whether or not to vaccinate their animals,’ said Mike Bodenchuk, director of the USDA’s Wildlife Services division in Texas, while trying to tamp down exaggerated fears.
‘They’re not going to come across the border by the millions,’ he noted. ‘It’s going to be a slow trickle for a while.’
This vampire bat species, Desmodus rotundus, tends to thrive in hot and humid regions where temperatures don’t fall below 50 degrees Fahrenheit.
Late last month, Escobar at Virginia Tech and a team of international conservation scientists published the results of their examination of 120 years of climate records, seasonal vampire bat captures, and other data, like 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 significantly shifted its distribution northward,’ as they wrote in the journal Ecography, ‘a natural invasion into northern Mexico at an average rate of 9.76 km per year [6.06 miles per year].’
Escobar and his coauthors added that their large database analysis matches prior work that used DNA evidence to chart the bat migrations.
‘Genetic assessments have demonstrated that D. rotundus from Mexico is expanding its range northward rapidly,’ they noted. ‘[but] disagreements between previous modeling efforts have shown that further study is still warranted.’