Stranded dolphins can tell researchers a lot about the health of dolphin populations and potential dangers to human health. But figuring out how many wash ashore is difficult because scientists rely heavily on the public to report sightings. To better understand how and where ordinary citizens are most likely to report the beached mammals, researchers in a recent study used an unusual tactic: dolphin decoys.

To make the fake dolphins, the researchers worked with the University of South Alabama’s Department of Theater and Dance in the U.S. Each of the 12 decoys was made with environmentally friendly material filled with sand so they would stay put in the four different locations where researchers placed them: popular and unpopular beaches and marshes of Dauphin Island in Alabama. The decoys remained there for a week each during peak tourist times and in the offseason. Researchers affixed a tag to each dolphin with a phone number asking passersby to report their find and leave the decoy in place. Trained observers also looked for the decoys and used drones to search for them from above.

Not surprisingly, the public reported 2.5 times more dolphins during high tourist season as compared to the offseason. Trained observers found more decoys than the public, but the public did find two decoys that observers missed. Drones were slightly more successful than both.

Since using the dolphin decoys, researchers now know how to better allocate resources to find real stranded dolphins. In the high season on popular beaches, leave it to the public, Jennifer Bloodgood, a wildlife veterinarian and biologist at Cornell University who is the recent study corresponding author, told Mongabay. But for more remote beaches and hard-to-get-to marshes, trained observers and drones are the way to go.

In the last decade, citizens have reported 127 stranded dolphins on Dauphin Island. Since the public found 58% of the decoy dolphins in the study, the researchers extrapolated there were likely 219 dolphin strandings during that period.

Understanding how many dolphins died and their causes of death can help inform our understanding of potential risks to human health, Bloodgood said.

Many dolphins die from infectious diseases. In some cases, the infectious agent can affect people too; in others, considered zoonotic diseases, the agent can transfer from an animal to a person, according to Bloodgood.

For instance, a pathogen shed by feral hogs can harm both dolphins and people. Bloodgood said that after a heavy rain, hog feces carrying the pathogen can run off into the ocean, making it unsafe for both dolphins and people. So if researchers suddenly find more dead dolphins with the pathogen washing ashore, they’ll know the water is potentially dangerous for people as well.

“Better understanding why they die can teach us more about what’s going on in the environment as a whole and how that could affect us,” Bloodgood said.

Banner image courtesy of Ponti et al. (2024).