It may sound far-fetched but it happened. On a small island near Hawaii named Palmyra, there was a rat problem. Black Rats. Black rats are awful creatures that can climb trees and even the sides of houses. They are not frightened by people and they eat anything… birds, eggs, coconuts, crabs… whatever there is to eat. These rats had been on the island of Palmyra since World War II and after being made a wildlife sanctuary, the Natural Conservancy and U.S. Fish and Wildlife Service decided the rats had to go. It took effort and time but in 2011 the rats were gone. Guess what else was gone? Yep… the mosquitoes. Well, the Asian Tiger Mosquitoes that is. They are pretty awful creatures as well. They are daytime biters that carry chikungunya, Zika, dengue fever, and yellow fever. But it seems that on Palmyra their only real blood supply was the black rat. After the black rats were eradicated, the mosquitoes followed shortly thereafter.
Before we get too excited it’s important to note that there are still mosquitoes on Palmyra, just not the Asian Tiger. The Culex (night biter) is still alive and well and carrying diseases like West Nile and bird malaria and a few other things. But this strange occurrence of removing one unwanted species leading to the disappearance of another is a first. And it gives a little insight as to ways to continue to battle mosquitoes (there are 6 types that bite humans and live in the Hawaiian Islands). If a mosquito’s preferred host, in this case, the black rat, is removed than possibly the population could be limited. Efforts to remove mosquitoes from the larger islands in the past have worked short term, but they’ve always come back. It’s been 6 years on Palmyra and they have not returned. Palmyra is a small island and the black rat was the Asian Tiger’s main food source, other places might not be able to narrow a food source down to one. And yet it opens a window to new ideas and techniques for the continued fight to rid the world of mosquitoes and the diseases they carry.
Dave Macchia, Mosquito Control Enthusiast
This story, while interesting and carrying a glimmer of hope for small island countries, doesn’t sound like something possible here in the United States. But keep in mind that out of every small scientific discovery comes new information and sometimes small discoveries can lead to big discoveries.