Why did four whales wash up in San Francisco Bay in a week and a half?

The juvenile minke whale had been spotted swimming around San Francisco Bay for nearly a week by the time she beached herself off the coast of Emeryville April Scientists had thought she seemed healthy but after an examination they determined she was acting abnormally and had to be euthanized due to illness It was the fourth whale death in the San Francisco Bay in a week and a half The other three were gray whales the first of which a -foot-long female washed up at Black Sands Beach in the Marin Headlands March Its cause of death remains unknown RELATED Surfers chased out of water by sea lion the latest in a string of aggressive behavior at California beaches On April a deceased adult male gray whale was exposed floating east of Angel Island its cause of death is also not known according to the Marine Mammal Center Then a subadult male gray whale washed ashore at Fort Point Rock Beach near the Golden Gate Bridge in San Francisco April and scientists determined that it likely died due to a vessel strike according to the mammal center Taken together the deaths have raised the specter of past unique mortality events that caused whales to die in higher-than-normal numbers This is distinctive mentioned Kathi George director of Cetacean Conservation Biology at the Marine Mammal Center in Sausalito It takes me back to several years ago when we did have a large number of strandings happen at the same time Related Articles Whalefest Monterey stars a whale skeleton abalone races on April - Juvenile minke whale that was beached off Emeryville euthanized Bob the Minke Whale uncovered dead after week in California harbor Commercial Dungeness crab season closing in Monterey Bay Researchers investigate death of gray whale identified on Bay Area beach While the unusually high number of whales beaching in such a short span is abnormal the number of whales who have died around the bay for the year has remained in line with typical levels scientists say This is the normal time of year when gray whales are doing their northward migration from Mexico up to Alaska so it s not uncommon for us to have gray whales in and around San Francisco Bay in April and May each year stated Moe Flannery who leads the marine mammal necropsy gang at the California Academy of Sciences Although they seem high because they re concentrated into a short period of time the numbers of dead and stranded are not any different than the contemporary previous years Whales can die for a number of reasons from diseases to malnutrition to vessel strikes George commented It s coincidental that everything happened in a week and a half but there are a lot of whales out there right now and chosen of their physical condition that they re in when they arrive in the bay may make them more susceptible to human impacts if they re not as healthy she reported Scientists began observing whales entering the San Francisco Bay around as they completed their annual migration between Mexico and the sub-Arctic George revealed The whales do not feed while they are in their breeding grounds in Mexico and expend a lot of capacity mating nursing babies and giving birth before facing a long journey back north to their feeding grounds she added Because of this resource expenditure scientists have seen the gray whales attempt to feed in new locations including San Francisco Bay George stated Their increased appearance in the bay could also potentially be explained as whales seeking a place to rest before continuing the migration or a reaction to circumstances change warming ocean temperatures and prey availability The Marine Mammal Center has tracked at least individual whales swimming in the bay this year and sightings of gray whales have been broadcasted almost every day since mid-March George mentioned The majority of the whale sightings have been informed east of Angel Island commented Giancarlo Rulli the associate director of constituents relations for the Marine Mammal Center Between and gray whales were dying in much higher numbers due to an rare mortality event which was declared by the National Oceanic and Atmospheric Administration Fisheries Gray whales lost more than of their population in four years Rulli announced During this time there were gray whale strandings in the United States according to NOAA These whales basically left the Arctic with a half tank Rulli disclosed The food sources that they were normally accustomed to eating that were highly nutritious for this massive -to- mile journey had moved farther away due to circumstances change and as a upshot these whales were left to forage on food matter that was much less nutritious Between January and April which was the first year of the remarkable mortality event dead gray whales washed up on California s coast Flannery mentioned Seven have so far this year George noted that whether the current deaths could be the start of an atypical mortality event is still under discussion and review adding that the content collected from these strandings will help scientists understand the bigger picture of what s happening We re not there yet she commented adding that scientists have to look at their migratory range holistically Whales will continue to appear in the bay through mid-May as they continue their migration north George commented Flannery added that anyone using the water necessities to be more aware of the animals that are sharing that habitat