By Tim Stephens, UC Santa Cruz
As young elephant seals grow up, males and females diverge dramatically in their size, diets, migration patterns, and even how likely they are to survive. A new research project led by Roxanne Beltran, assistant professor of ecology and evolutionary biology at UC Santa Cruz, is investigating how the increasing size differences in developing elephant seals relate to differences in their behavior and in the perils they face at sea.
“We know little about how elephant seals and other wild animals die—whether they get eaten by predators or aren’t able to find enough food—and the consequences are huge for understanding the patterns we see in nature,” Beltran said.
Her new project is funded by a four-year, $1.2 million grant from the National Science Foundation (NSF). This spring, Beltran’s team outfitted 32 juvenile elephant seals with a newly developed “biologger,” a sophisticated tracking device that records each seal’s diving behavior, migration route, and feeding success and transmits the data back to the researchers via satellite. Even if a seal dies during its months-long foraging migration, Beltran and her colleagues will have detailed information about its life at sea.
Co-principal investigator Daniel Costa, professor of ecology and evolutionary biology and director of UCSC’s Institute of Marine Sciences, and other UCSC researchers have been studying the elephant seals at the NRS’s Año Nuevo Island Reserve for decades, using increasingly sophisticated tagging technology to track their migrations and study their behavior at sea. Tags that transmit data via satellites are not new, but older ones were limited in the amount of data they could transmit. While scientists could track migration routes in real time, they couldn’t get detailed data on feeding behavior until they recovered the tags after the seals returned to the beach at Año Nuevo.
The tags are also expensive, so they have been used mostly to track adult seals, which return to Año Nuevo with greater reliability than juveniles.
“Historically, young seals have been underrepresented in tracking studies,” Beltran said. “Juveniles tend to have high mortality rates, and juvenile males are the worst if you want to get your instruments and data back. But these new tags make it worthwhile to tag juvenile males so we can find out why they have higher mortality rates than females.”
While female elephant seals travel great distances in the open ocean during their foraging migrations, males tend to forage along the coasts where prey is more concentrated, but where there is also more danger from sharks and killer whales. Scientists think the males may pursue a riskier foraging strategy because of the advantages of growing big fast—large size is a critical factor in the fierce competition between males for access to females during the breeding season.
Beltran’s study will provide some hard data for evaluating this hypothesis. “Our entire field has a sampling bias, because we usually only get information from the animals that survive,” Beltran said. “By studying the animals that don’t make it, we hope to get a better idea of what’s happening out in the ocean.”
Beltran’s team is also launching an interactive animal tracking website for students and the public, and they will be visiting K-12 classrooms to engage students throughout the Monterey Bay region. In addition to Beltran, the outreach team is led by three other members of her research team, graduate students Salma Abdel-Raheem, Dan Palance, and Allison Payne.
“This is a great opportunity for students in the local area to be exposed to this exciting elephant seal science and to the scientists who work with these amazing animals,” Beltran said. “We can visit up to 32 classrooms this fall, and each classroom will be able to follow an individual seal that we’ve tagged.”
The NSF research funding does not cover these outreach efforts, however, so Beltran is looking for donors to sponsor the classroom visits. Donations will cover travel expenses for the outreach team and classroom materials. More information is available on the team’s crowdfunding page.
Interested teachers can apply for a classroom visit using an online form.
“The more donations we get, the more students we can reach,” Beltran said. “With small contributions from enough donors, we hope to inspire around 1,000 students each year.”
Año Nuevo Island Reserve is one of the 41 reserves in the UC Natural Reserve System. Featuring examples of California’s major ecosystems, reserves are managed for research, university-level teaching, and education.