On Galápagos beaches, human presence conclusively affects sea lions

Penn researchers, in conjunction with Galapagueño high school students, found that on more crowded beaches, the endangered animals are less aggressive to people.

Person standing outside on a rocky beach holding a clipboard and wearing a t-shirt that reads "Penn." Three sea lions lay on the beach at the front of the photo.
Twice a week between June and December of 2017 and 2018, local Galapagueño students observed sea lion behavior at four local beaches. The community scientists assessed how frequently the animals growled, barked, and moved toward the observer, as well as conducted an overall census of the animals. (Pre-pandemic image: Courtesy Michael Weisberg)

On beaches across the Galápagos, sea lions share space with people. But until recently, it wasn’t clear how that cohabitation influenced the endangered animals. 

“In Puerto Baquerizo Moreno, the sea lions live on the edge of the town at the waterfront,” says Michael Weisberg, a University of Pennsylvania researcher who has worked on the islands since 2017. “The town’s population was increasing—it’s getting close to 10,000 people—and before COVID-19 tourism was, too.”  

There had also been sea lion–human clashes, like a fireworks display that sent the frightened animals fleeing the beach for the water. Weisberg and colleagues, including locals like Ernesto Vaca, hoped to employ a scientific approach to understanding the situation. So, they enlisted Justin Walsh and Karen Kovaka, at the time Penn Ph.D. students, to help create a research project. The aim was to increase knowledge about sea lion behavior and engage local high school students and Penn undergraduates. 

After 21 months of data collection and analysis of three types of sea lion behavior, the research team substantiated what it had suspected: Humans conclusively affect the sea lions. 

On more crowded beaches, the animals respond less aggressively to people, likely because they’ve either acclimated to a human presence or because those with low tolerance for people avoid such disturbed sites. Beyond that, the researchers discovered that as animal group size increases, the sea lions become more aggressive toward each other but less aggressive toward humans. The researchers published their findings in the journal Wildlife Biology.

“We confirmed that the increasing population of Galápagos can change the behavior of animals, and that’s something to be taken very seriously. Developing the beaches there further will really have an impact, and this is something the community has discovered for itself through its engagement with this project,” Weisberg says. “This worked well for us, in part, because it’s an issue this community cares about. It’s something salient to their day-to-day life.” 

The protocol

As sea lion populations have decreased, from around 40,000 individuals in the late 1970s to about 16,000 in 2001—a level from which it hasn’t moved since—the issue has become more urgent, says Walsh, now a postdoctoral researcher in the lab of Yun Ding in Penn’s Department of Biology.

“We really wanted to understand the effect of human disturbance on sea lions,” he says. “My role was trying to design a project that was rigorous enough that we could actually try to learn something about the sea lion population but also manageable enough that a group of high school students could handle it and we could manage this from afar.” 

The back of a person holding a clipboard with many numbers written down. Sea lions dot the beach ahead.
The community scientists were international baccalaureate students at the UAE-San Cristóbal School who participated in Project LAVA, an initiative co-led by Weisberg in his role as co-director of the Galápagos Education and Research Alliance. They received training both in the classroom and in the field. (Pre-pandemic image: Courtesy of Michael Weisberg)

The community scientists were international baccalaureate students at the UAE-San Cristóbal School who participated in Project LAVA, an initiative co-led by Weisberg in his role as co-director of the Galápagos Education and Research Alliance (GERA). After receiving training, both in the classroom and the field, students went out twice a week between June and December of 2017 and 2018. 

On four beaches—Playa Mann, Playa de Oro, Playa Zona Naval, and Playa de los Marinos—selected for their varying degrees of human disturbance and their proximity to the school, the students first conducted what’s called an approach assay. “Essentially, this works by walking toward a wild animal and recording how it responds,” Walsh says. “We thought this could be a good way to understand how sea lions were reacting across the different beaches.” 

Students started six meters (about 20 feet) away from each animal and walked forward, getting as close as two meters (about 6.5 feet). After each encounter, they scored the animal’s response on a zero-to-five scale, with zero meaning the sea lion’s eyes were closed and the animal didn’t react and five meaning the animal growled, barked, and moved toward the observer. “We considered fours and fives to be especially aggressive reactions,” Walsh says.  

“Student safety was the most important factor, more important than getting data,” he adds. “The sea lions aren’t particularly dangerous, but there is the occasional bite. We made sure the students knew it was OK if they couldn’t get the data they were after sometimes. We stressed the fact that science is messy; it’s challenging, and it’s not going to be perfect.” 

After the approach assay, the community scientists conducted an overall census of the animals, including age, sex, and group size for their assigned sea lions. Their final task each session entailed 15 minutes of pure observation, recording any time an animal in their group called, growled, barked, or challenged another animal. 

The human impact

On Playa Mann, the beach the researchers found most affected by people, the animals reacted the least. “Maybe sea lions with a high tolerance for humans tend to go to that beach, and those with a low tolerance don’t,” Walsh says. “What we think is more likely is that they’re becoming acclimated to humans. You see this in other species in California, for example.”  

It’s unclear how much such adaptation matters. “There’s evidence across the animal kingdom that acclimation to humans can be a good thing,” he says. “Animals learn that, for the most part, humans aren’t a threat. This results in decreased stress and, in general, animals doing better. But it could also be problematic, particularly given the headaches the sea lions can cause for the local population.” 

The researchers also discovered that the larger the group size of animals, the more aggressive they were toward each other and the less they paid attention to the people around. Walsh says there’s no indication of a link between these behaviors and human disturbance, however. 

Although some of GERA’s projects were able to continue remotely during the pandemic, this one took a hiatus, according to Weisberg. He and Deena Weisberg, GERA’s other co-director and an assistant professor at Villanova University, plan to pick it back up once it’s safe do to so, with a new cohort of Galapagueño community scientists. “These high school students, they know more about these sea lions than anyone else in the world,” Weisberg says. “Participating really engages them very deeply in the process of conservation.” 

Funding for the research came from the University of Pennsylvania’s School of Arts & Sciences and Office of the Vice Provost for Global Initiatives, as well as the National Science Foundation (Grant STS-1947096). 

Michael Weisberg is professor and chair of the Philosophy Department in the School of Arts & Sciences at the University of Pennsylvania. He has co-directed the Galápagos Education and Research Alliance since 2017.

Justin Walsh is a postdoctoral researcher in the lab of Yun Ding in the Department of Biology in the School of Arts & Sciences at the University of Pennsylvania.

Other contributors to the work included Karen Kovaka, an assistant professor at Virginia Polytechnic Institute and State University, Deena Weisberg, an assistant professor at Villanova, and Ernesto Vaca of the San Cristóbal Association of Naturalist Guides.