Gray whales are increasingly entering San Francisco Bay outside their traditional migration routes, but nearly one in five do not survive, often due to ship strikes. Researchers documented 114 individual whales from 2018 to 2025 and linked many deaths to vessel traffic and malnutrition amid climate-driven food shortages. The findings highlight urgent needs for protective measures in the busy waterway.
Gray whales, which normally migrate between Arctic feeding grounds and Baja California lagoons, have begun foraging in San Francisco Bay since 2018. This detour coincides with climate change disrupting their Arctic food supply, leading to a population drop of more than half since 2016 and fewer calf sightings, according to the National Oceanic and Atmospheric Administration. In 2025 alone, 36 whales entered the bay, sometimes in groups exceeding 10 individuals. Researchers cataloged 114 unique whales using public photos and surveys from 2018 to 2025, identifying them by skin markings. Only four returned in multiple years, suggesting the bay serves as a desperate stop for thin, hungry animals. Of 70 gray whales found dead in the region between 2018 and 2025, 30 showed vessel strike injuries, and many others bore signs of starvation. Scientists matched 21 of 45 identifiable strandings to their catalog, finding at least 18% of documented bay visitors died locally, with over 40% of trauma deaths from ships. > Gray whales have a low profile to the water when they surface, and this makes them difficult to see in conditions like fog which are common to San Francisco Bay, explained Josephine Slaathaug of Sonoma State University, lead author of the study published in Frontiers in Marine Science. > At least 18% of the individuals identified in San Francisco Bay later died in the area, said co-author Bekah Lane of the Center for Coastal Studies. The researchers call for vessel speed limits, route adjustments, and better monitoring to curb strikes, the bay's biggest threat.