How researchers can maximize biological insights using animal-tracking devices

Biologgers allow us to see with unprecedented precision how animals move and behave in the wild. But that's only part of the picture, according to a UC Santa Cruz ecologist renowned for using biologging data to tell the deeper story about the lives of marine mammals in a changing world.

In a new opinion piece published on October 30 in Trends in Ecology and Evolution, researchers present a framework intended to underscore the value of biologging data for testing important questions about the natural world. They urge that now is the time to build upon "discovery-based science," where observations are presented as research findings—by framing data collection, analysis, and interpretation around specific questions posed by scientific theories.

"We emphasize the power and promise of theory-driven research," said study lead author Roxanne Beltran, assistant professor of ecology and evolutionary biology. "For example, if we hypothesize that animals take more risks when they're more hungry, can we use biologging tools to test and refine this theory by measuring both hunger and risk-taking in wildlife?"

In other words, instead of doing research that concludes with describing the data, researchers can now begin with a general idea of how the natural world works, and then use biologgers attached to animals to strategically test whether that idea is supported by data.

How biologgers can help generalize insights 

In their review, the team demonstrates how biologgers can be a powerful tool for testing hypotheses and refining theories via case studies of elephant seals, whooping cranes, and mule deer. These case studies demonstrate that observations made from biologgers can lead to insights that inform hypotheses and refine ecological theories. Using ecological theory to link the physiology, sociality, and demography of an animal with its environmental context allows for a better understanding of these systems, the piece states.

For example, depth-measuring biologgers attached to northern elephant seals revealed that, at certain points, the animals stopped swimming and started passively drifting. This previous research led to the hypothesis that seals might drift because they are asleep, and that this might be due to differences in physiology.

With biologgers, researchers were able to confirm that seals with superior body condition (more body fat) skipped foraging at night to sleep in the safety of darkness. In contrast, seals with inferior body condition (less body fat) foraged at night, when it was more efficient, but then risked sleeping during the day when risk of predation from sharks and killer whales was higher. This led to support of state-dependent risk-taking theory, backed by biologging data, that wild animals are more likely to take risks when they are in poorer body condition.

“We've used these case studies as examples of the many exciting opportunities for new insights across finer temporal scales and broader spatial scales than ever before,” Beltran said. “We hope that our framework makes others feel excited and motivated by how much potential we have to apply these biologging tools and generate ecological insights in the next couple of decades.”

More inclusivity in ecology research

In addition to her marine ecology research, Beltran has strongly advocated for diversity, equity, and inclusion in STEM through the development of actionable field guides on anti-racism, community building, and inclusive research experiences. In this new piece, she calls for open access to biologger data so scientists without the resources to acquire expensive technology can still contribute to the field.

Eighteen of the article's authors are early-career researchers, including graduate students, postdocs, and research technicians like Conner Hale, who contributed by conceptualizing the case studies into a graphic for the paper. She started in Beltran's lab as an undergraduate field assistant three years ago and now works with Beltran full time.

“I was involved from the ground up in creating Figure 2. Working on it allowed me to improve my science communication skills, gain experience in simplifying text into an image, and collaborate with my team, which are skills that will benefit me as I continue to pursue a career in research,” said Hale (Carson, ‘22, marine biology). “I'm currently doing the kind of research that I hope to pursue in grad school, and getting this experience now is setting me up for success.”

Beltran said collaborating with colleagues locally and internationally was crucial for showing the scientific community how biologgers can be used to produce more holistic research in the years ahead. “I knew that I could lead a much more powerful paper if I brought together a large group of young researchers who had unique but complementary visions for the future of the field,” she explained.  

The future of biologging

One exciting next step identified by the researchers is to expand the scale of inquiry. For instance, researchers could leverage theories about species interactions to motivate the simultaneous tagging of predators and prey in the same ecosystem. Mathematical models could then be used to create simulations of populations, communities, and ecosystems under climate change scenarios that would ultimately inform evidence-based conservation solutions.

“When disciplines are new, they necessarily begin with discovery of patterns,” Beltran said. “We believe that transitioning toward process-based insights will allow biologging science to continue having an enormous impact on our understanding of the natural world.”

Other co-authors of the paper from UC Santa Cruz include A. Marm Kilpatrick, Arina Favilla, Allison Payne, Danial Palance, Daphne Shen, Dan Costa, Natalie Storm, and Patrick Robinson. The team also included contributors from the University of Idaho, University of Washington, University of Wyoming, UC Davis, UC San Diego, Stanford University, Monterey Bay Aquarium Research Institute, National Institute of Polar Research in Japan, and University of Southampton in the UK.

The paper, “Maximizing biological insights from instruments attached to animals,” was funded by a Packard Fellowship in Science and Engineering, a Beckman Young Investigator award, an Office of Naval Research Young Investigator award, and a generous private donation through the Elysea Fund.