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California sea lion Thunder
Press Release

30 Percent of Patients in 2023 Experienced Some Form of Human or Dog Disturbance

April 24, 2024
  • Behavior

Behavior change needed: 30 percent of marine mammal patients rescued by The Marine Mammal Center in 2023 experienced some form of human or dog disturbance

The Center reports that year over year data highlights these interactions are both a tourist and a local issue according to beach survey data conducted by experts.

The Marine Mammal Center, the world’s largest marine mammal hospital, reports that internal data gathered the last two years on the impact of human-wildlife interaction highlights a complex and concerning threat for marine mammals along 600 miles of California coast and inland areas.  

The Center’s Electronic Animal Record System team reports that wildlife disturbance by people and dogs was a contributing or direct factor in more than 200 cases of marine mammals being rescued and admitted to the Center’s Sausalito hospital in 2023. This accounts for 30 percent of all patients admitted last year, up from 26 percent in 2022.  

Of the 200 plus cases of disturbance last year, people getting too close was the most common form of behavioral disturbance the Center’s experts documented and increased from 2022. This type of behavior, which involves crowding around an animal and not giving it appropriate space, can lead to increased stress levels, separate moms from their pups, and disrupt rescue operations -- hindering the Center’s goal to give these sick and/or injured marine mammals a second chance at life. 

The Center is utilizing a multi-pronged approach this year, including continued work with behavior change experts, to address the issue of human-wildlife interaction. These initial efforts have identified factors behind specific beachgoer behavior, and are part of a wider plan to engage with tourists and small businesses in key interaction hot spot areas with information about how to safely share our shores and local waterways with marine wildlife.  

“Marine mammal disturbance along our vast 600-mile California response range is both a tourist and a local issue that we’re dedicating more resources toward to help find solutions,” says Adam Ratner, Director of Conservation Engagement at The Marine Mammal Center. 

Our research shows that the vast majority of people on the beaches want to help these animals, but they don’t know how to best help. Our work is focused on trying to help empower them to take the right actions to protect marine mammals.

Two core groups were identified by behavior change experts, utilizing both in-person beach and online surveys. The first archetype, “the wildlife protector,” mostly represents a local individual trying to help because of their passion for wildlife, but can unfortunately take actions that result in more harm for the animal. The other identified archetype, “the experience seeker,” largely represents a tourist seeking out an experience with marine life and is heavily influenced by what they see on social media.

California sea lion Thunder at the pool's edge
Thunder, a juvenile male California sea lion, was rescued in San Francisco after reports that people were trying to feed him and off-leash dogs were nearby. / Photo by Bill Hunnewell © The Marine Mammal Center
California sea lion Slacker rests on the pool ledge
Slacker, a juvenile male California sea lion, was rescued in Pacifica after the animal was reportedly surrounded by people taking photos. / Photo by Bill Hunnewell © The Marine Mammal Center
northern elephant seal pup Mustard
Mustard, a female northern elephant seal pup, was rescued in Watsonville after being harassed by a beachgoer who was petting and sitting next to the animal. / Photo by Bill Hunnewell © The Marine Mammal Center
northern elephant seal pup Muniz
Muniz, a northern elephant seal pup, was rescued in Jenner after being surrounded by a large group of beachgoers. / Photo by Bill Hunnewell © The Marine Mammal Center

In the San Francisco Bay Area specifically, interactions with sick, older California sea lions last fall stood out in large part due to an outbreak of leptospirosis, a bacterial infection that can cause kidney failure and death in sea lions. These behaviors can increase stress to an already sick animal and potentially increase the risk for disease transmission between people and animals. 

Thunder, a juvenile male California sea lion, rescued on July 16, 2023, at Ocean Beach in San Francisco, is a standout case that highlights the impact of disturbance. A member of the public reported to the Center’s hotline that people were trying to feed the sea lion and off-leash dogs were also nearby. Trained volunteer responders who arrived on scene found the sea lion in poor body condition and immediately initiated a safe rescue. 

Thunder was treated for leptospirosis, malnutrition, and other ailments. The sea lion was successfully released back to the wild in Point Reyes National Seashore on September 20, 2023. 

Similar to 2022, last year’s data also reveals that these incidents were just as prevalent in the summer and fall as they were during the Center’s busy spring pupping season.  

You Can Help

As the world’s largest marine mammal hospital, The Marine Mammal Center would like to remind the public that they play an important role in the conservation of marine mammals by keeping these safe wildlife viewing tips in mind:

Keep Your Distance

Give marine mammals space to rest by enjoying them from a safe distance of at least 150 feet both on local beaches and in the water, and keeping dogs on a leash.

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Call the Experts

If you see a marine mammal in distress, do not intervene. Instead, call The Marine Mammal Center’s hotline at 415-289-SEAL (7325). Our experts will monitor the animal and, if necessary, send trained responders to rescue it safely.

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Use Your Zoom

It’s OK to take photos and admire the animals, but if an animal reacts to your presence, then you’re too close. No SEAL-FIES please!

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2023 Disturbance Breakdown by County (all species)

San Luis Obispo – 27 cases (13% of all cases)
Monterey – 63 cases (31% of all cases)
Santa Cruz – 51 cases (25% of all cases)
San Mateo – 21 cases (10% of all cases)
Marin – 14 cases (7% of all cases)
San Francisco – 9 cases (4% of all cases)
Sonoma – 12 cases (6% of all cases)
Mendocino – 5 cases (2% of all cases)
Solano – 0 cases (0% of all cases)
Alameda – 1 case (>1% of all cases)

Data collected from The Marine Mammal Center’s Electronic Animal Records System.

For more information or to set up an interview on this topic, please contact us at


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