A new study examines the impacts of invasive feral pigs, a favorite prey of vampire bats, on ecosystems in rural Brazil.
The distribution of feral pigs — which are also known as wild boars, or “javali” in Portuguese, and are actually the same species as the domestic pig (Sus scrofa) — has increased five-fold since they were first recorded in Brazil in 2007.
A group of Brazilian researchers found that not only might populations of vampire bats (Desmodus rotundus) explode as a result of this invasion of feral pigs, but associated threats, such as the spread of infectious diseases, could increase as well. The results of their study were published in the journal Frontiers in Ecology and the Environment earlier this month.
The wild boar is becoming a dominant mammal in Brazil’s Atlantic forest and could potentially invade the Amazon region, as well, according to Felipe Pedrosa, an ecologist from São Paulo State University in Brazil who studies the impacts of feral pigs on biodiversity and co-authored the study.
The natural range of Sus scrofa is mostly in Europe and Asia, but the species, which is considered one of the worst invasive species in the world, has been introduced in Australia, South America, and the USA. As wild boars invade new territory, damage to crops such as maize, sugarcane, and soybeans as well as predation of native birds and mammals usually increases as well. The study notes that this trend has been shown in all ecosystems invaded by wild boars, from Australia to Hawaii and Texas.
But the researchers discovered the potential for an unprecedented effect that could occur in Brazil. As their numbers increase, feral pigs provide an ever-increasing blood supply to vampire bats, increasing the bat’s population in turn. Vampire bats are a threat to livestock and humans alike throughout the tropical Americas due to their role as a “reservoir” of several infectious diseases, including rabies, the researchers say.
Incidence of rabies among vampire bats is about three for every two hundred individuals, or 1.4 percent of vampire bat populations. Because the species is relatively rare in the wild, and cattle and dog vaccination programs are practiced intensively in Brazil, the chances of humans contracting rabies are relatively low — but the researchers say their observations have led them to believe there is a significant chance of an increase in human rabies cases nonetheless, in addition to increased transmission of disease to other wildlife.