The cypress trees of the Louisiana wetlands are threatened by the exploding population of nutria, a type of South American rodent introduced into the area in the 1930s in hopes of starting a nutria fur industry. Unfortunately, no one wanted the fur, and now the rodents number in the millions. A park ranger has suggested introducing the South American jaguar, the nutria's natural predator, into the Louisiana wetlands as a way to control the nutria population. Which of the following, if true, casts the most doubt on the ranger's plan to introduce jaguars as an effective way to control the nutria population?