Some Effects of DDE and PCB on Mallards and Their Eggs

Abstract

In 1971, 4 groups of mallards (Anas platyrhynchos), each consisting of 4 drakes and 10 hens equally divided into 2 replicates per group, were fed untreated feed or feed containing 40 ppm p,p'DDE, 40 ppm PCB, or 40 ppm DDE + 40 ppm PCB. The feeding period began a month before egg laying, which started in February and continued through June. All eggs were collected daily, and mean shell thickness indices were alike in the control and PCB groups. They were reduced by 17 percent in the DDE group and 19 percent in the DDE + PCB group. The contents of 12 eggs randomly selected from the DDE group contained 373 ppm DDE lipid-basis, and 13 eggs from the DDE + PCB group contained mean residues of 344 ppm DDE + 364 ppm PCB. Egg production was similar in all groups for about the first seven weeks, then it dropped markedly in the DDE + PCB group. Part, but not all, of this group's lower production of intact eggs was due to egg eating. This behavior accounted for 18 of 282 eggs observed lost in the DDE + PCB group, 6 of 394 eggs in the PCB group, and none in the control and DDE groups. Although there was no significant change in shell-thinning or DDE residues when PCB was added to the diet, the reduction in the number of intact eggs produced by the DDE + PCB group suggests that the two compounds may nevertheless interact to influence reproductive success. J. WILDL. MANAGE. 39(3):508-513 Pesticide-induced eggshell thinning has been reported for a number of birds (Anderson and Hickey 1972, Cooke 1973). This generally has been attributed to p,p'-DDE ( 1,1-dichloro-2,2-bis [p-chlorophenyl] ethylene), a metabolite of p,p'-DDT (1,1, 1-trichloro-2,2-bis [p-chlorophenyl]ethane). However, it has not been established satisfactorily whether other environmental pollutants interact with DDE to enhance eggshell thinning, or to create additional problems. Anderson and Hickey (1972) stressed the potential complications of mixtures of pollutants in nature. One group of chemicals logically suspected to interact with DDE is the polychlorinated biphenyl (PCB) complex. PCBs, together with DDE, are among the most commonly reported environmental pollutants (Risebrough et al. 1968, Peakall and Lincer 1970, Dustman et al. 1971). Laboratory studies with combinations of these two compounds in gallinaceous birds have demonstrated simple additive effects in direct toxicity (Heath et al. 1972, Kreitzer and Spann 1973). PCB alone has not induced significant eggshell thinning in experimental studies involving at least five species of birds (Peakall and Peakall 1973). The experiment described here was undertaken (1) to determine if a PCB would enhance DDE-induced eggshell thinning in mallards, and (2) to explore the possibility of other effects on reproduction by exposure to a combination of DDE and PCB. This research was supported by the Denver Wildlife Research Center of the U.S. Fish and Wildlife Service and National Science Foundation Grant GB-11649 to the Institute of Marine Resources, University of California, Berkeley. We thank A. H. Jones, C. P. Breidenstein, and M. Friend for critical advice. Additional assistance was provided by I. T. Anderson, L. R. DeWeese, M. Evett, M. A. Haegele, D. B. Knapp, M. A. MacDonald, C. J. Nasman, and R. E. White. 508 J. Wildl. Manage. 39(3):1975 This content downloaded from 157.55.39.183 on Thu, 26 May 2016 04:54:11 UTC All use subject to http://about.jstor.org/terms DDE AND PCB EFFECTS ON MALLARDS * Risebrough and Anderson 509