USGS and NASA Collaborate to Develop New High-Tech Flipper Tag to Study Social Networks of Sea Otters

Scientists from the USGS Western Ecological Research Center and U.S. Fish and Wildlife Service search for southern sea otters along the California coast. (Public domain.)

In the Future of Wildlife Tracking, Sea Otters Have Their Own Social Network

Whereas we might carry cell phones or tablets, each sea otter has a small, solar-powered tag clipped carefully to one of its flippers. When the sea otters gather to nap at the ocean’s surface, their tags boot up, and check in with one another. Who else did the sea otter interact with today, where, and when?

For Joseph Tomoleoni of the U.S. Geological Survey and Zachary Randell of Oregon State University, this future would refine our understanding of sea otters’ community structure, movements, distributions, survival rates, and even disease transmission among individuals. Currently, USGS biologists like Tomoleoni and Brian Hatfield use radio transmitters, binoculars, and high-powered spotting scopes to track sea otters from shore. For hours at a time, they painstakingly record the otters’ location and behaviors off the California coast.

Yet, this lengthy, labor-intensive process happens only when the weather cooperates; if a storm rolls through, or if conditions along the coast are otherwise unfavorable, the scientists can’t collect their data. Because Tomoleoni, Randell, and Hatfield can only survey sea otters from the beach during daylight hours with reasonable weather, they get a part rather than the whole picture of sea otter ecology.

To increase the ease and capacity for gathering large amounts of information from sea otters and other wildlife, USGS scientists have teamed up with the National Aeronautics and Space Administration (NASA) to design two new types of wildlife-tracking tag. The first is a lightweight, solar-powered GPS unit that could eventually open avenues for researchers to study the movements and behaviors of animals as small as a songbird. The second is a peer-to-peer network tag which could pave the way for scientists to study wildlife “social networks.”

It Takes Engineers and Biologists 

GPS tags are the go-to device for biologists studying wildlife and their habitat. The tags’ strength resides in their ability to accurately calculate an animal’s location using transmissions received either by satellites or by the same cellular networks that people use.

However, most of the energy needed to power the device and transmit data is stored in a small battery. Although larger batteries supply more energy and allow devices to collect data for longer durations, they are also more weight for the animal to carry.

“We want the new tags to apply to a broad range of species, from polar bears to songbirds,” says Susan De La Cruz, a wildlife biologist and USGS-lead on the project.

To accomplish this, De La Cruz and colleagues at USGS teamed with NASA engineers Chad Frost and Dayne Kemp to design a GPS device that wouldn’t sacrifice accuracy, sophistication, and lifespan for size and weight. Within a year, the team had a working prototype: a solar-powered GPS unit that could be produced for a quarter of the price of current models and weighed only about a third that of a house key.

USGS and NASA collaborated to develop a prototype, miniaturized GPS tag to support wildlife biologists in their research. The new tag weighs about a third that of a house key. (Public domain.)

USGS wildlife biologist and team member Michael Casazza plans to use this prototype to study the movements and habitat use of waterfowl within California’s Central Valley. His research will help landowners, duck clubs, and non-profit conservation groups manage the Central Valley’s wetland habitats for millions of waterfowl migrating through the Pacific Flyway each year.

Peeking into the “Social Networks” of Wildlife

Today, the USGS-NASA team is attempting to integrate the new solar-powered GPS unit with a peer-to-peer network tag. Traditional GPS tags store data on the location of a single animal. Adding the peer-to-peer network capacity would allow each tag to share its data when tagged animals come within range of one another. By tracking the rates at which the tags gather data, scientists can learn about connectivity within and among species, their distributions across their range, and other complex questions.

The prototype tag also wouldn’t need to use precious energy to transfer large amounts of information to a satellite. Instead, it could communicate at low-power with base stations, or with bigger, more powerful tags capable of both storing greater amounts of data and transmitting these data farther via satellite or cellular network from the back of a larger animal.

The final prototype of the USGS-NASA flipper tags. USGS scientists will first use the flipper tags on sea otters to learn more about their lives along the coast.(Credit: Chad Frost, NASA. (Public domain.)

In time, De La Cruz plans to use the new tags to understand interactions amongmultiple species of migratory and wintering birds that use recovering tidalmarshes and managed waterbird habitat in California’s San Francisco Bay. Her results are helping the U.S. Fish and Wildlife Service and other agencies manage migratory bird populations that rely on coastal estuaries such as San Francisco Bay for food and shelter as they migrate along the Pacific Flyway.

Biologists like Tomoleoni, Randell, and Hatfield provide resource agencies like the U.S. Fish and Wildlife Service (FWS) with scientific information that helps inform conservation and management of wildlife populations and their habitats. Following years of population declines, FWS listed the southern sea otter as “threatened” under the Endangered Species Act in 1977. With the peer-to-peer network tag, USGS biologists can establish a more detailed understanding of how and how often sea otters interact. Such information can help the FWS and other partners predict how threats like white shark attacks might affect their numbers. Their findings will aid the FWS with ongoing efforts to increase sea otter populations, and restore their unique presence within ecosystems where they once thrived.

The Future of Wildlife Tracking Tags

Another ambitious, collaborative project co-led by USGS wildlife biologist Josh Adams aims to combine the peer-to-peer network tag with biosensors. Adams and colleagues plan to use the peer-to-peer network tag to reveal how seabirds like the albatross use their sense of smell to hunt.

Adams is collaborating with a separate team of NASA engineers and researchers at the University of California, Davis to develop small, carbon nanotube sensors that can detect dimethyl sulfide (DMS), a chemical compound produced when microscopic animals crush and consume the cells of equally tiny plants at the ocean’s surface.

“Dimethyl sulfide is one of the compounds that give the ocean its unique smell. Oftentimes we’ll remark while working at sea, that the ocean smells different, alive, and that smell indicates ocean productivity,” says Adams.

Adams, who has tracked thousands of seabirds at sea, hypothesizes that seabirds will change their flight behavior in response to differing concentrations of dimethyl sulfide. Areas with high concentrations of DMS likely have a healthy food web, including minuscule plants and animals that transfer the energy of the sun through the marine food chain to larger predators like fish, seabirds and marine mammals. Together, the DMS sensor and peer-to-peer network tag will allow Adams and his colleagues to better understand how the ocean environment influences seabird navigation, movement, and foraging. A strong link between DMS and seabird behavior could aid in the identification and conservation of key seabird habitats and assist with marine spatial planning for offshore renewable energy.

In the future, De La Cruz hopes to combine the new GPS tag technology developed with NASA with another USGS-NASA product: a tiny, 3-D printed battery developed in collaboration with Eben Paxton of the USGS Pacific Island Ecosystems Research Center. This technology would allow engineers to create their own battery design and produce their own device, rather than relying on preexisting parts. Perhaps someday, researchers will generate batteries so compact that they could fit on an insect. Results from this battery project bring De La Cruz’s goal to decrease the size of GPS tags closer to reality.

With the new, miniature tags and networking technology, biologists and ecologists throughout the world can conduct more reliable research studies on wildlife in diverse ecosystems. From inland marshes to the open waters of the ocean, scientists will be able to learn more about the earth’s unique environment — with some help from the wildlife.

This project is headed by NASA and the USGS Western Ecological Research Center, and funded by the USGS Innovation Center. Other partners include the Monterey Bay Aquarium, California Department of Fish and Wildlife, Sea Mammal Research Unit, Oregon State University, the University of California, Santa Cruz, and the University of California, Davis.

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About is dedicated to raising awareness about California's threatened sea otters and the role research plays in the species recovery and conservation. It's a collaboration of the Monterey Bay Aquarium, U.C. Santa Cruz, U.C. Davis, U.S. Geological Survey, U.S. Fish & Wildlife Service, California Department of Fish and Wildlife, among others. is also home of the world's first HD live stream of southern sea otters in the wild.