Background levels of DDT and its metabolites (ZDDT) were extremely low or not detected in five species of forest-dwelling bats in northeastern Oregon, i.e., areas not sprayed with DDT in 1974. Other organochlorine pesticides were rarely found and no polychlotinated biphenyls (PCBs) were detected at any time during the study. Four of five species of bats showed significant changes in Z:DDT residues in, their carcasses following the single DDT spray application. Myotis californicus and M. volans showed the highest postspray carcass residues, 6.90 and 6.21 ppm (wet weight). respectively. Lasionycteris noctivagans and Eptesicus fuscus also showed an increase; however, M. evotis exhibited no significant postspray change. By 1977 (3 years postspray), residues declined and only M. californicus and M. volans contained levels that were significantly above those in the nonspray (control) area. We are uncertain if the elevated residue levels resulting from the DDTspray project adversely affected any of the bats. An attempt to relate bat catcass ZDDT residues to food habits, through analysis of stomach contents, yielded no clear relationships.
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Organochlorine residues in bats after a forest spraying with DDT