Effects of DDE and PCB (Aroclor 1260) on experimentally poisoned female little brown bats (Myotis Lucifugus): Lethal brain concentrations

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Abstract
Adult female little brown bats (M. lucifugus) were collected in a church attic in North East, Cecil County, Maryland [USA]. Mealworms (Tenebrio molitor) containing organochlorine pollutants were fed to the bats as follows: 5 bats were dosed at 480 ppm DDE, 12 at 150 ppm DDE, 5 at 1000 ppm polychlorinated biphenyl (PCB; Aroclor 1260) and 12 at 15 ppm PCB. Bats (7) were fed untreated mealworms. The objective was to elevate brain levels of DDE and PCB to lethality and measure these concentrations. During 40 days of dosage, 1 DDE-dosed bat and 2 PCB-dosed bats died after exhibiting prolonged tremoring that characterized organochlorine poisoning. After dosage, surviving bats were starved to elevate brain levels of toxicants and 3 additional DDE-dosed bats tremored before dying. Mean brain concentration of DDE diagnostic of death was estimated as 603 ppm (range, 540-670 ppm). This mean was 16-18% higher than means for Mexican free-tailed bats (Tadarida brasiliensis) and common grackles (Quiscalus quiscula) and may indicate less sensitivity. Lethal brain concentrations of Aroclor 1260 were 1300 and 1500 ppm. Values were higher than values (Aroclor 1254) for brown-headed cowbirds (Molothrus ater). During starvation, DDE-dosed bats lost weight .apprx. 24% faster than controls. If smaller amounts of stored DDE caused increased metabolic rates of nonfeeding bats, as during hibernation or migration, the result could be premature energy depletion and increased mortality.