With the Monterey Bay in the background, President Clinton (2nd L) is joined by Vice President Al Gore (2nd R), Stanford University student Nancy Eufemia (R) and University of California at Santa Barbara student Raphael Sagarin during a tour to see the tidal pools at the Hopkins Marine Research Center June 12. (© Reuters )

Raphael D. Sagarin, a marine ecologist who pioneered new ways of thinking about protecting national security through the lens of the environment and animal behavior, died May 28 after being hit by a pickup truck near Tucson. He was 43.

Dr. Sagarin was bicycling on a two-lane highway when he was hit by a truck driven by a man who police say was inebriated. Gary L. Colvin was arrested and charged with manslaughter, according to Arizona Department of Public Safety spokesman Quentin Mehr.

At his death, Dr. Sagarin was an associate research scientist at the University of Arizona. He had won broad acclaim in academic and policy circles for his innovative approach to protecting national security as well as key habitats.

His 2012 book, “Learning From the Octopus: How Secrets From Nature Can Help Us Fight Terrorist Attacks, Natural Disasters, and Disease,” suggested policymakers could learn critical defense techniques by studying how animals have evolved over time to counter threats they face in the wild.

Dr. Sagarin, known as Rafe, explained in a 2012 interview with National Public Radio that he started thinking about the need for security experts to adapt while working as a science adviser to then-Rep. Hilda L. Solis (D-Calif.) in the aftermath of the Sept. 11, 2001, terrorist attacks.

As U.S. Vice President Al Gore (R) and Stanford University student Nancy Eufemia look on, University of California at Santa Barbara student Raphael Sagarin (L) talks to President Bill Clinton during a tour of tidal pools at the Hopkins Marine Research Center in Monterey Bay June 12. (© Larry Downing / Reuters/Reuters)

“I’d watch these other Capitol Hill staffers, and I noticed that they’d just put their hand over the keys in their pockets so they didn’t have to waste 30 seconds putting it on the conveyer belt though the security screening — and that didn’t set off the alarm when they did that,” he said. “It just made me think, adaptable organisms are going to figure out a way to get around this.”

He argued that decentralized decision-making — in the same way millions of cells in an octopus’s arm can transform its color based on environmental changes, without a signal from the animal’s brain — would serve the military better than a centralized, top-down command system.

The Defense Department eventually hired Dr. Sagarin as a consultant, although he initially faced skepticism among academics and military officials.

The science director at Stanford University’s Center for Ocean ­Solutions, Larry Crowder, who first collaborated with Dr. Sagarin when they were both faculty members at Duke University, remembered sitting on a grant-making panel when the ecologist first proposed bringing together experts from wildly different fields to address homeland threats.

“I thought, ‘This is ridiculous. What do evolutionary ecologists have to tell national security experts?’ ” Crowder said. “The conclusion people came to was, maybe we are doing government wrong. Rafe consistently came up with really novel ideas that were counter to the narrative that was out there, that were on the edge. And he turned out to be right.”

Raphael David Sagarin was born on June 20, 1971, in New Haven, Conn. His family spent summers on Cape Cod, an experience that fostered a connection to the ocean he pursued for his entire professional career.

He received a bachelor’s degree in science in earth systems biology from Stanford in 1994 and a doctorate in ecology, evolution and marine biology from the University of California at Santa Barbara in 2001. He was the author of three books as well as roughly four dozen scholarly articles and book chapters.

On New Year’s Eve in 1999, he married Rebecca Masten Crocker. Survivors include his wife and two daughters, Ella and Rosa, all of Tucson; his parents, Mary and ­Jacob Daniel Sagarin of Guilford, Conn.; and two brothers.

During the course of his ­research at Stanford’s Hopkins Marine Station, in Pacific Grove, Calif., Dr. Sagarin and three colleagues compared the abundance of the shore species off the Hopkins rocks in the early 1990s to those in the same area marked by a researcher in the early 1930s. Their findings, published in the journal Science, provided some of the first evidence that southern species were moving north because of ocean warming.

Dr. Sagarin also guided then-President Bill Clinton and Vice President Al Gore along the Monterey Bay’s intertidal pool in June 1998, the day Clinton announced a 10-year extension of an oil drilling ban off U.S. coasts.

“He was equally comfortable out in Baja California, wading in a tidal pool, as he was in Washington, D.C., with his suit and tie on,” Crowder said.

Most recently, Dr. Sagarin was working to create a functioning model of the Gulf of California within the experimental station Biosphere 2, near Oracle, Ariz.

In Washington, colleagues recalled, Dr. Sagarin pushed for a more comprehensive approach to ocean management and stronger federal protections for the sea while serving as the associate director of Duke’s Nicholas Institute for Environmental Policy Solutions between 2006 and 2009. He then joined the University of Arizona.

Dr. Sagarin had a whimsical side. He was a founding member of the Beaver Queen Pageant, a festival in Durham, N.C., that was started as a way to protect beavers from a proposed construction project and now raises money for the Ellerbe Creek watershed. Audience members pay judges a “bribe” in support of their favorite beaver-oufitted contestant. In 2008, he served as one of the contest’s ­judges under the alias Nacho Rafa.

Nicole St. Clair Knobloch, who worked with Sagarin at the Nicholas Institute, recalled the two of them stopping off at the Museum of Natural History ice rink in 2007 on the way to a Capitol Hill strategy session. “I will never forget seeing Rafe skating around with his overcoat on, skates under his trousers, smiling and contented, before our meeting,” she wrote in an e-mail. “I always laughed with him, more than with hardly anyone else.”

CORRECTION: An earlier version of this story incorrectly reported the location of Stanford’s Hopkins Marine Station as “near Santa Barbara.” It is in Pacific Grove, Calif., near Monterey.