It may be strange to think of tadpoles as having personality, but like all animals, every wood frog behaves slightly differently—even as a larva. Scientists believe that these variations might turn some animals into “superspreaders” that change how diseases spread through a population. To put this theory to the test, scientists assigned 160 wood frog larvae (Lithobates sylvaticus) boldness rankings, based on their foraging and movement patterns and how quickly they moved toward new food. They then infected select individuals with ranavirus—a deadly virus that has been implicated in the global amphibian decline. Since the water filter in each tank contained an ultraviolet light that killed any free-floating virus, disease could only be transmitted directly from one larva to another. The researchers found that bolder larvae—those who moved faster toward food sources and spent less time swimming alone in the water—caused more infections than their passive peers, they report online today in Biology Letters. Bolder animals were also more likely to pick up an infection, which the scientists suggest could be due to their increased interactions with infected peers. Another possibility—one that the team is examining now—is whether bolder behavior results in immunological trade-offs. Identifying superspreaders may be crucial for preventing disease outbreaks, not just in amphibians, but in humans and other animals as well.
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