In South Texas, government agents patrol a barrier line that snakes some 500 miles along the course of the Rio Grande. Their mission: to protect their country from would-be invaders. But these aren’t the U.S. Border Patrol—they’re employees of the U.S. Department of Agriculture. And their purpose is to keep out the ticks that carry cattle fever, a deadly bovine disease endemic to Mexico.
The USDA’s “tick riders,” as they are called, are tasked with keeping infected cattle from straying deeper into Texas, where the deadly fever poses a serious threat to the beef industry. Whenever they find a stray or infected cow, they track it down and dip it in pesticide to kill the ticks and prevent them from spreading. Yet despite their best efforts, the tick riders’ challenge has recently increased, as more and more of the hardy ticks find their way across the border.
A large part of the problem is that cattle fever ticks also have another host: Nilgai antelope, a species native to India that was imported to North America in the 1930s as an exotic target for game hunters. These antelope, like the ticks themselves, and the pathogen they carry, are considered an invasive species. They are cursed not only for their role as a disease vector, but because they eat native plants and compete with cattle for food.
That’s why, unlike native white-tailed deer—which also host ticks—they are subject to an unrestricted hunting season, and the U.S. Fish and Wildlife Service sponsors regular Nilgai hunts in protected areas.
The differences in how authorities treat domesticated cattle, native deer and wild, imported antelope illustrate a stark divide in ecology. For decades, both scientists and laypeople have referred to organisms like the Nilgai as “alien,” “exotic” and “invasive.” But as long as ecologists have warned about the danger of invasive species, others have asked whether this kind of language—which carries connotations of war and xenophobia—could cloud the science and make rational discussion more difficult. Click on the following sentence to access the full story.
In an era of renewed focus on borders, it’s hard to ignore the similarities between how we talk about non-native animals—hyper-fertile “foreigners” colonizing “native” ecosystems—and the words some use to discuss human immigration. And as international relations have become more heated, so too has the debate among researchers over the pointed rhetoric we use to talk about animals, plants and micro-organisms that hail from elsewhere.