The Surprising Way Marine Mammals Are Poisoning California Condors
More than 40 years after being banned, DDT has reared its ugly head again.
Somewhere along the beautiful coast of Big Sur,a California Condorsinks its beak into the decaying flesh of a dead sea lion. It’s a gruesome sight, but it's not unusual—even 10,000years agocondors were feastingon the carcasses of washed-up marine mammals. The difference between thenand nowis that today'sdeceased pinnipedscome chock-full of harmful toxins, the rotting legacy of decades of poor environmental regulations in the United States.
It's theorized thatbeached mammals mighthave actually kept condors from going extinct at the end of the Pleistocene, whenthey were steadilydeprived of thecorpses of prehistoric land animals such asmammoths, sabercats, and giant sloths. But new research published last month in suggests that those marine scraps couldnow be putting the endangered vultures at greater riskby exposing them to an old,familiar foe for conservationists: DDT.
Because sea lionsare at the top of the marine foodchain, they’re often tainted with toxins that are found in fish, cephalopods, and other aquatic prey. Among those contaminants is the pesticideDDT, which wasdumped in large quantitiesoff of the Los Angelescoast between the 1940s and the 1970s. Scientists think thatall California sea lions may be vectors of the poison, given that they swim these waters as they head to theChannel Islands each year to breed.
To see if condors were ingesting DDT and other contaminants associated with marine mammals (like fire retardants), UC San Diego ecologist Carolyn M. Kurle and her team analyzed and compared the blood collected from coastal and inland condors during routine health work-ups. They also checked the blubber of deadpinnipeds and whalesin Monterey County, California.
As expected, the coastal birds posted significantly higher levels of contaminants than the inland individuals. Anotherrevealed that the coastal condors are laying eggs with thinner shells than their inland counterparts, causing them to be20 to 40 percent less successfulreproducing.
This development isjust anothersetback in the efforts to restorethelarge, charismatic bird's populations.In 1987, there were only22 California Condors leftalive in the world. But by the mid-1990s, scientists were releasing their captive-reared descendants back into the wild. Today there are more than 400 of the birds in captivity and the wild. The species’ range now extends throughout California, as well as Arizona, Utah, and Baja California, Mexico.
Despite this success,there are still many roadblocks to the condor’s comeback—the main one beinglead-based ammunition, which the birds consume while scavenging on bullet-ridden carcasses. Lead wreaks havoc on the vultures'digestive system, causing the animal toto death. In the past, condors living near Big Sur were thought to be at lower risk of lead poisoning because they have the advantage of being able to feed on marine mammals. Indeed,published earlier this year confirmed that individuals foundon the coast tend tolive longerthan those that stick to inland habitats.
While lead ammunition can at leastbeeliminated from the ecosystem (California, for example, is ), there's not much to be done about the pollutants that persist in the waters long after they've been restricted.Kurle hopes that this research will underscore the long-term consequences of harmfulpesticidesby exposing theireffect on a beloved and imperiled species. "These things have been banned since the 1970s, but they're still wreaking havoc environmentally,” she says. “What are we doing now that we're going to be paying for inthe next 50 years?"