Bottlenose Dolphins Migrate to Bay Area for First Time as Water Temperatures Rise in North, Central California

As water temperatures rise in northern and central California, bottlenose dolphins migrate to the Bay Area, as confirmed by scientists for the first time.

After spending their entire lives in Southern California and Baja, Mexico, bottlenose dolphins have made the Bay Area their permanent home.

At all different times of the year, they have explored the boundaries of San Francisco Bay, joined surfers in catching waves at Ocean Beach, and been spotted by hikers with their gray-mottled backs at Stinson and Montara Beach.

Adapting to Water Temperature Rise

The animals' intelligence may be assisting them in modifying their behavior to climate change. They are a part of a population known as California coastal bottlenose dolphins. A new study has for the first time documented their decades-long migration north, which started when water temperatures in Central and Northern California increased. They might end up being a success story in the midst of global warming due to their capacity for adaptation and the discovery of new habitats.

David Weller, the director of the Southwest Fisheries Science Center marine mammal and turtle division, which is part of the National Oceanic and Atmospheric Administration, said that Bottlenose dolphins are a prime illustration of a few species that are likely to be more successful than other species when it comes to adaptation and the capacity to endure in the changing environment.

He explains that if sea ice disappears, for example, polar bears and walruses are in serious trouble. In contrast, bottlenose dolphins can successfully adapt to, invade, and use habitats that they have not previously had.

Weller is a co-author of the study published recently in the Aquatic Mammals Journal.

Weller adds that although there are some fossil records of bottlenose dolphins in San Francisco Bay, they have probably been absent from the area for hundreds of years.

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Ernestina the Bottlenose Dolphin

Similar to how whales can be located by distinctive markings on their tails, dolphins can be recognized in photographs by distinctive patterns of notches seen on their dorsal fins.

The majority of the dolphins in the study are still roving, regularly moving between the Bay Area, San Diego, Monterey Bay, and Ensenada in the hunt for food. Based on photographic evidence, some dolphins appear to be Bay Area regulars.

In 2017, a pair that had also been spotted in San Diego broke the world distance record held by a bottlenose shark that had circled Italy by swimming more than 1,500 miles to Puget Sound.

Bill Keener, the lead author of the study, said that the time it takes them to swim from Montara Beach, where he was using binoculars to try and spot dolphins in the surf in November, to Half Moon Bay, is only a couple of hours. Two days prior, a group that included Ernestina the dolphin had been spotted there. The dolphins are constantly traveling up and down the coast.

Keener, a Marine Mammal Center cetacean field researcher in Sausalito, later learned that a few weeks later, the distinctive notch pattern on Ernestina, a female dolphin sighted in the Bay Area for 15 years, allowed for her identification. Ernestina had most likely spent time on the Mendocino Coast.

Dolphin Notches

As opposed to a distinct offshore dolphin population of the same species, coastal bottlenose dolphins have a limited habitat range of about 500 to 1,000 yards from the shore, according to Keener.

Over time, they develop their notches as a result of aggressive play and sex with one another which causes tears in the delicate skin on their dorsal fins.

According to Sonar, North of Santa Barbara had not previously been reported as a range of coastal bottlenose dolphins. During the 1983 El Nio, which brought warm water to Monterey Bay and a group of daring dolphins along with it. In the Bay Area, sightings were few until around 2006. During this time, a group of dolphins was flagged up swimming past San Francisco's Ocean Beach, according to the San Francisco Chronicle. At the same time, one was spotted for the first time on the San Mateo coast.