A 18-foot orca that had suffered a head wound was found dead on a beach in the Point Reyes National Seashore last week, a National Park Service spokesman said.
The male orca, a juvenile or young adult, washed ashore Thursday or Friday on a beach adjacent to McClures Beach, NPS spokesman John Dell'Osso said.
The Marine Mammal Center in the Marin Headlands and the California Academy of Sciences in San Francisco were informed of the incident, he said.
Academy spokeswoman Stephanie Stone said some blood clots found in the orca's head suggest that blunt force trauma caused its death.
"It's unlikely this trauma was caused by a collision with a boat, since orcas are so fast and could easily out-maneuver a boat. It's possible that the trauma was caused by an interaction with another orca," Stone said.
The California Academy of Sciences is working to collect scientific samples for additional research, Stone said.