SANTA CRUZ -- Scientists at UC Santa Cruz have stumbled upon a surprising discovery: coyotes, familiar denizens of field and hill, seem to be developing a taste for seafood, including elephant seal carcasses.

Preliminary data from UCSC biologist Paul Koch's research team suggest that ancient coyotes that roamed the Central Coast long ago rarely got their food from the sea. A graduate student in Koch's lab, Rachel Reid, investigated the diets of those animals and modern-day coyotes by comparing fossil bones and recent excrement samples from several sites in Santa Cruz and Monterey counties.

Despite evidence of elephant seals at Elkhorn Slough in Moss Landing 2,000 years ago, the fossil remains suggest coyotes hardly ever snacked on young seals or even fish, according to Reid, who recently presented the data at the Society for Vertebrate Paleontology meeting in Los Angeles.

"We're just getting a hint of how coyotes behaved in the past," said Koch, dean of the Physical and Biological Sciences Department at UCSC.

The ecological changes that would result from coyotes eating a lot more seafood aren't yet clear. But land animals that eat marine life often forge connections between land and sea, Koch said, so the nutrients they bring ashore could eventually mean bigger bands of coyotes on the Central Coast.


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Bones and feces have little in common, but chemical signatures in both offer clues to an animal's diet. Reid compared the two by testing the ratios of two elements common to all life -- carbon and nitrogen. One specific form, or isotope, of nitrogen is particularly rich in marine life. Animals -- including humans -- that eat a lot of seafood incorporate more of this type in their cells. Likewise, carbon isotopes are found in different proportions in land and sea life.

Comparing samples

Simply by comparing the amounts of carbon and nitrogen isotopes in a sample, researchers can tell whether an animal skipped the fish course. Five of 17 excrement samples had carbon and nitrogen proportions consistent with a marine diet, but only two ancient bone samples out of 15 had any such traces.

"We've only looked at a few places and are going to be studying coyotes in the fossil record at several other places," Koch said.

Coyotes have never been fussy eaters -- one reason their populations have been expanding across the country. The omnivores have been known to devour pets, small mammals, snakes -- and even rubbish. Since marine mammal carcasses and dead fish have been washing ashore for eons, it isn't clear why ancient coyotes might have stayed away from them.

"We don't know for sure why coyotes behaved that way, but one possibility is grizzly bears," Reid said. Hunters or fishermen living along the coast, she added, may have been another reason.

Grizzlies in other parts of the world relish salmon and seafood. But their appetite for livestock caused them to be hunted to extinction. Although the grizzly is the Golden State's official state animal and adorns the state flag, the last California grizzly was killed in Tulare County in 1922. So now, the theory goes, coyotes may be taking advantage of the coast while it is clear.

"Potentially, just having marine foods available could increase the number of coyotes in the area," said Seth Newsome, an animal ecologist at the University of New Mexico.

Alaskan wolves

Newsome pointed to a study of coastal Alaskan wolves that revealed a similar pattern. The wolves had been blamed for a decline in the populations of caribou and moose populations -- their traditional prey. But scientists who studied the wolves' diets were surprised to find that they were also eating salmon and marine animal carcasses.

The seafood allowed the wolves to thrive even as the number of caribou and moose declined. In a similar way, the addition of seafood to the coyote diet may help them thrive in the Monterey Bay region.

"It is one potential way that this change could impact other parts of the ecosystem, even inland," Newsome said.

There's no official count yet to show that coastal coyote numbers have increased. But biologists at Año Nuevo State Reserve, where a large colony of elephant seals assembles each winter, say the new research doesn't surprise them.

"Any given day, if you walk the beach at low tide, you will find coyote tracks on the beach," said Patricia Morris, a UCSC research biologist who has worked at Año Nuevo for nearly three decades. "I don't census coyote populations or anything like that. But I think I see their tracks more frequently than I used to in the past."