A relatively new concern of the current California Condor Recovery Program relates to organochlorine pesticide contamination in marine mammals along the west coast of North America. DDT is the best known of these contaminants, although DDE, a breakdown metabolite, is as toxic and far more persistent in the environment. Studies of condor eggshells prior to the widespread use of DDT in the 1940s, found that shells averaged 33% thicker than those during DDT use.
Although DDT has been banned in the United States since 1972, it bioaccumulates (gets more and more concentrated as it moves up the food chain) and binds to fats. These properties allow it to persist in blubber of long-lived marine mammals. Research has shown that historic populations of condors from more northern parts of the range, Monterey Bay and northward, had high portions of their diet comprised of marine resources, likely including marine mammals.
Recently, condors released in Big Sur by the Ventana Wildlife Society have begun feeding often on seals, sea lions, and whales. Recent evidence of eggshell thinning and high concentrations of DDE in reintroduced condors in Big Sur that feed regularly on pinnipeds have renewed concerns over the potential negative effects this could have on the reintroduced birds ability to breed. Such effects could slow overall progress toward achieving the many goals outlined for California condor recovery. For this reason, examination of organochlorine contamination in marine mammals is considered a major priority by condor biologists.
Currently, a data gap exists regarding the examination of organochlorines in marine mammals along the northern California coast. Filling in this information gap is critical to understanding the current level and geographic extent of this threat to potential reintroduced condor populations.
The Yurok Tribe's Wildlife Program biologists plan to collect blubber from dead marine mammals washed up on beaches between Fort Bragg and the Oregon border to test it for organochlorine contaminant levels. Surveys will be done for these mammals with the help of the U.S. Coast Guard, Group Air Station Humboldt Bay. The Air Station has agreed to donate flight time from standard patrols to assist with locating carcasses for sampling. Other groups including: Redwood National and State Parks, Mad River Biologists, Arcata Fish and Wildlife Office, and researchers from Humboldt State University are also helping on this project through information on marine mammal carcass locations, help with collecting samples, and with storage of tissues. This project is ongoing and will likely take until at least the spring of 2011 to complete.