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--Petroleum fouling has many deleterious consequences for marine vertebrates, ranging from increased energy expenditure to the death of the organism. We measured circulating levels of reproductive and adrenocortical hormones in Magellanic Penguins (Spheniscus magellanicus) that were partially covered with petroleum following a marine oil spill off the Patagonian coast, and in a non-oiled control group. Levels of luteinizing hormone, androgens and estradiol, but not progesterone, were lower in oiled penguins than non-oiled control birds. Corticosterone was higher in oiled than control females, but did not differ and was basal in males. Few of the pairs with an oiled partner later established nests with eggs. Even low levels of oil fouling in Magellanic Penguins appear sufficient to interfere with reproduction. Oiled penguins that were held captive for washing had elevated levels of corticosterone, and appeared to be stressed both by captivity and by the washing process. Received 19 November 1993, accepted 27 May 1994. ENCOUNTERS WITH FLOATING PETROLEUM are harmful to marine birds and mammals in several ways. Direct physical effects include: (1) loss of thermal insulation (Erasmus et al. 1981, Bourne 1985) causing drastic increases in overall energy expenditure (Lambert et al. 1982, Culik et al. 1991); (2) loss of ability to float or fly (and thus ability to forage; Trivelpiece et al. 1984) resulting in increased energetic costs of locomotion (Culik et al. 1991); and (3) death from exposure. Penguins, because they live at the water surface, are particularly at risk of oil fouling (Culik et al. 1991, Gandini et al. 1994). Petroleum ingested by the animal during attempts to clean itself can cause numerous physiological problems, including gastrointestinal lesions, renal and hepatic pathologies, hemolytic anemia, and increases in parasites (Fry and Lowenstine 1985, Fry and Addiego 1987, Gandini et al. 1994). In addition, suppression of the endocrine system by ingested petroleum has been experimentally demonstrated, including decreases in pituitary hormones (Harvey et al. 1982, Cavanaugh et al. 1983), gonadal steroids (Cavanaugh and Holmes 1982, Harvey et al. 1982), and adrenocortical steroids (Gorsline and 3 Present address: Department of Biology, Pomona College, 609 N. College Ave., Claremont, California 91711, USA. Holmes 1982, Gorsline 1982). Experimentally induced ingestion of petroleum also has been shown to reduce reproductive success in some breeding seabirds in the wild (Trivelpiece et al. 1984, Fry et al. 1986). Both physical and physiological effects can occur at low levels of oil fouling (Fry et al. 1986, Culik et al. 1991). There have been no previous studies of the hormonal effects of oil fouling in accidentally oiled breeding birds at low levels of body coverage. We demonstrate suppression of luteinizing hormone and sex steroid hormones, and elevation of corticosterone in lightly oiled Magellanic Penguins (Spheniscus magellanicus) at the beginning of the breeding season following an accidental crude-oil spill.

Hormonal and Reproductive Effects of Low Levels of Petroleum Fouling in Magellanic Penguins (Spheniscus magellanicus)