The charismatic California sea lion (Zalophus californianus) is a marine mammal that shares many similarities with seals and walruses, all of which are considered pinnipeds, a clade that comprises thirty four unique species. More specifically, Z. californianus is in the family Otariidae, together with the fur seals and five other sea lion species that occur across the globe: the Galápagos sea lion, Australian sea lion, the South American sea lion, the Steller’s or northern sea lion, and the Hooker’s/ New Zealand sea lion. The ancestors of all these sea lion species, also the evolutionary ancestors of bears, were land mammals that around 30 million years ago evolved into the playful marine mammals we are familiar with today (Arnason et al. 2006). Unlike the “true seals,” sea lions have small, external ears, or pinna, large fore flippers that they use to swim, and the ability to rotate their hind flippers forward – an adaptation that makes them agile climbers on rocky shores. True seals on the other hand are quite helpless on land and use their rear flippers to swim. They also have an extra layer of fur that enables them to inhabit much colder waters, such as the harbors of Alaska or Maine.
Z. californianus is the only resident pinniped of the Gulf of California, commonly known as the Sea of Cortez, and is subject to special protection under Mexican law (NOM 059-ECOL-2001). As a result of extensive, past hunting for meat and pelts, the California sea lion is also listed on the IUCN Red List under the category of ‘species of least concern.’ Much of the Gulf’s population is migratory, but it is primarily males that travel long distances while adult females generally stay close to their rookeries, or breeding colonies, in order to breed and raise their pups.
The breeding season for the Gulf’s California sea lions is between May and June, months during which males show territorial behavior as they vie for control of area-based harems. Females will stay on land for several days before giving birth, and usually deliver just one pup per year. They have a twelve month reproductive cycle, and like humans, a nine month gestation period. The mother and pup stay together post-partum (after birth) for about a week before the female must return to sea to feed. These crucial feeding trips can take anywhere from 1 to 3 days, and if prey distributions change as they are currently as a result of ocean warming, the trip must be extended, and pups, absent of mother’s milk, may starve. Upon their return from feeding trips, a sea lion mother is able to recognize its young through smell and sound recognition, making the moments just after birth critical to generating a strong bond that will be vital to the offspring’s survival. During the mother’s absence, the young pups congregate in groups called kinder, in which they sleep, bark, play, and learn to walk and swim together.
For the past seven years, a group of artisanal, or small scale, fishermen from the San Jorge Bay, a region of the northern Gulf of California’s Sonoran Corridor, have been monitoring and advocating for the conservation of their local California sea lion population. Isla San Jorge, known as Bird Island to many American visitors, is a UNESCO World Heritage Site and the largest of 13 sea lion rookeries in the entire the Gulf of California. The local sea lion monitors hail from the nearby fishing community and Cooperative of Bahía San Jorge, and they aptly call themselves the Grupo Lobos, or Sea Lion Group. Members of the Grupo Lobos not only recognize the ecological, socio-economic, and cultural importance of this large breeding colony, but also the need to actively protect it from compounding threats.
These conservation actions taken on by members of the local fishing community are especially significant given that many of the region’s fisherfolk are outwardly hostile toward sea lions as a result of competition; lions often take prey-fish directly from fishermen’s nets and rip holes in the mesh to add insult to injury. We can observe similarly fraught interactions between pinnipeds and fisherfolk around the world, from San Diego to Scotland, and fisheries large and small often lead to sea lion mortality through entanglement events, collisions, and retaliation from fisherfolk.
In this local and global context, witnessing a small group of courageous and self-motivated people, young and old, from a traditional fishing community adopt stewardship as a solution inspires real ocean optimism. What is more, by uncovering key links between sea lions, ecosystem processes, and human impacts, the Sea lion Group is helping scientists and fellow fisherfolk understand the intimate workings of the northern Gulf ecosystem and how it is responding to ocean warming and other challenges such as a growing population of coastal residents. Sea lions can be considered indicator species because the state of their population can reveal broader trends in ecosystem health. Sea lions are particularly sensitive to environmental changes, and when changes in their food source occur their population is visibly affected. What is more, sea lions are one of the few species that come out of the water allowing us to count them and their offspring with relative to ease.
The organic, grassroots formation of Grupo Lobos, and the subsequent certification of its members by experts as official scientific monitors, reveals the progress that regional NGO’s, such as the Intercultural Center for the Study of Deserts and Oceans (CEDO) have made in fostering bottom-up environmental stewardship in the northern Gulf’s artisanal fishing communities. The government also plays a critical role, and Mexico’s National Commission of Natural Protected Areas (CONANP) and the Center for Research in Food and Development in Guaymas (CIAD) provide critical funding to Grupo Lobos, so that these local monitors, working in collaboration with CEDO staff, can analyze and understand data on the health, population-dynamics, and foraging (eating) habits of this critically important, top-predator of the Gulf’s rocky reefs and open ocean habitat.
As with all marine animals, there is still much to learn about California sea lions and you can support organizations like Grupo Lobos either through donations or by going on sustainable sea lion tours with certified operators. If you do go on a sea lion tour, whether it be in Puerto Peñasco or La Paz, I urge you to please follow best practices, regardless of the example set by local tour operators. These include that you:
To learn more about Grupo Lobos and the California sea lion you can visit www.cedo.org.
(This blog article was written for The Intercultural Center for the Study of Deserts and Oceans – CEDO, in Puerto Peñasco, Sonora, Mexico in 2019 by Alan Ruiz Berman with contributions from Angeles Sanchez)