Drones shooting vaccine-covered candy bombs are innovative attempt to save ferrets

Randy Machett, a U.S. Fish and Wildlife (FWS) biologist, describes it as a “glorified gum ball machine.” It’s actually a drone with a special purpose – shooting vaccine-laced M&M candy bombs at prairie dogs in an attempt to protect them, and the black-footed ferrets that eat them, from sylvatic plague.

The vaccine drop, which will be targeting prairie dogs, will be taking place at the UL Bend National Wildlife Refuge located in north-eastern Montana. The refuge has been an important site in the recovery of the ferrets since 1994. The black-footed ferret is one of the most endangered mammals found in North America.

The sylvatic plague is a flea-borne disease that entered America in the 1800s through rats coming in on ships landing in California. It is carried by fleas on prairie dogs, and the black-footed ferrets are totally dependent upon those rodents for their food and shelter. The ferrets eat the prairie dogs and take over their burrows, which means the demise of prairie dogs would be disastrous for the species.

It is difficult to vaccinate individual ferrets against the disease, and it is also virtually impossible to protect prairie dogs over a wide area. Machett says FWS has tried dropping the vaccine while walking around, but the territory to be covered is just too large. Spraying burrows with insecticides to kill the fleas is also very labor-intensive, and is also not a long-term solution.

The vaccine-candy-bomb plan would drop a large quantity of vaccine uniformly over a large area. The tiny bombs are M&M candies smeared with vaccine-laden peanut butter that lab tests show is irresistible to prairie dogs. A dye is added to the mix that colors animals’ whiskers once they eat it, so scientists can see that they have gotten the treatment.

A drone carries the device that dispenses the vaccine. The device uses GPS to reliably drop vaccines at 30-foot intervals. It can also fire the candies to the left and right, enabling it to drop three vaccines at once. The device was created from a modified fish-bait machine.

Machett says that that machine “is the fastest, cheapest way to distribute the vaccine.” FWS hope that the oral vaccine can be used to mitigate plague sites of tens of thousands of acres every year.

The U.S. population of black-footed ferrets has been reduced to only 300 animals found in isolated sites across the U.S. In 1981 they were thought to be extinct except for a few animals brought into captivity for breeding. The current population came from a mere seven ferrets that were selectively bred.

Prairie-dogs, though considered a pest by many, are known as a “keystone” species. They are important to a range of animals including coyotes, eagles and owls.

Photo credit: J. Michael Lockhart / USFWS