Harmful algae bloom suspected of killing 11 burros at Death Valley National Park

Death Valley National Park rangers are warning the public about an algae bloom that could harm more animals as well as humans visiting the park.

Rangers state 11 burros died near Owls Hole Spring and while the cause of death is under investigation, they believe the animals died due to the bloom.

Water in Owls Hole Spring "should be considered unsafe for humans or pets to drink or touch" and that people and pets should not go near any of the burro carcasses.

Rangers said only dead burros have been found but other animals were likely affected.

"I hate to see any animal suffer," said Superintendent Mike Reynolds. "The National Park Service is working to remove feral burros from Death Valley, for their own safety and to reduce impacts to native wildlife."

The park has removed 43 burros in recent years and the Peaceful Valley Donkey Rescue has captured 256 burros from the park since 2018. The park has funding to resume roundups in fiscal year 2026.

Why is the water dangerous?

Algae and cyanobacteria occur naturally in the water and are more likely to grow into a harmful algae bloom when water is slow-moving, warm, and contains high levels of nitrogen and phosphorous, which can come from things like fertilizer or sewage, according to the Centers for Disease Control.

All three of those conditions existed at Owls Hole Springs. The water is stagnant, the burros defecated in the water, and the park experienced its hottest summer on record this year.

From June to August, the average daily temperature at Death Valley National park was 104.5 degrees Fahrenheit, which passes the previous record which was set in 2021 and 2018.

July was the park's hottest month event with nine consecutive days above 125 degrees Fahrenheit.