Key Points:
- Urban sea lions utilize the extensive haul-out opportunities provided by buoys, floating docks, and other urban infrastructure.
- Dense aggregations of sea lions in many coastal cities suggest they may be synanthropic, yet more research is needed to characterize the patterns and drivers of sea lion populations in urban areas.
Strange encounters with urban sea lions are a familiar tale that regularly make local news headlines in many coastal cities. For instance, in San Diego, an eight-month old sea lion pup recently took up residence in an ocean-front restaurant and was quite obviously grumpy (pictured) when it came time for her deportation by a marine mammal rescue team (link). In the same area, another sea lion pup allegedly climbed 145 steps from the beach below to hang out in a gift shop and only left after being bribed with salmon (link). In yet another episode, a paddle boarder captured this video as a young sea lion who climbed aboard, bummed a ride, and perhaps overstayed her welcome:
Sea lions are smart and versatile. Though they fit many of the characteristics of synanthropes, and are clearly a common inhabitant of many coastal cities, particularly on the West Coast of North America, their population dynamics with respect to urbanization have yet to be thoroughly studied.
It’s possible sea lions capitalize on urban environments in a manner similar to terrestrial mesopredators (mid-sized consumers) like raccoons and coyotes, that are dietary generalists and behaviorally flexible. However, raccoons and coyotes particularly benefit from the cornucopia of food resources in terrestrial urban environments that’s provided by human trash and/or small domesticated pets. There’s no evidence thus far that urbanization enhances food resources for marine mesopredators. Alternatively, urban sea lion populations may benefit from fewer predators in urban areas – as raccoons and coyotes do – yet this has not been well studied. While some smaller sharks are known to inhabit urban estuaries, urbanization is thought to have negative impacts on many marine predators (link). Yet, it remains unclear whether urban-related patterns in apex consumers are strong enough to drive synanthropy among mesopredators like sea lions.
What is evident is that sea lions utilize the extensive haul-out opportunities provided by urban infrastructure. Sea lions are a common fixture on buoys and floating docks in many cities, often causing quite a headache for port authorities. For instance, in the late 1980s, sea lions took over a major dock at a popular tourist destination in San Francisco en masse and have maintained their territorial claim to the site ever since, effectively barring entry to humans and eliminating the dock as usable infrastructure for the port (though it came with other tourist benefits: link). Some cities attempt to prevent such take-overs by requiring sea lion deterrents at public harbors and waterfronts (link).
