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Abstract-Concentrations of mercury in hair, brain, and liver tissues of river otter (Lutra canadensis) from several townships in Ontario, Canada, were determined. Levels of Hg in these tissues were highly intercorrelated but differed from tissue to tissue. The highest concentration was in hair, followed by liver and brain. The high correlation between Hg in hair and brain, as well as the ease and precision of Hg determinations on hair, demonstrate that Hg in hair holds considerable promise for monitoring the Hg in otters. Within the sampled otters, Hg varied with respect to age. The Hg concentrations increased over the first two to three years of age, remained stable over the next two to three years of age, and then declined in the remaining age-groups. Mean age of otters in townships with high-Hg concentrations was about half the mean age of otters in low-Hg townships. In areas where mercury levels are high, otters may have reduced survivorship because of Hg-induced stress on their health.

Six helminths were common in lynx (Felis canadensis) throughout northern Ontario: Troglostrongylus wilsoni (Stough, 1953) Sarmiento &Stough, 1956 in the lung (54% of 127 infected), Cylicospirura felineus (Chandler, 1925) Sandground, 1932 in the stomach (91% of 360), Toxascaris leonina (von Linstow, 1902) and Toxocara cati (Schrank, 1788) in the stomach and intestine(97% and 22% of 274, respectively), and Taenia laticollis Rudolphi, 1819, and Taenia rileyi Loewen, 1929 in the intestine (94% and 47% of 275, respectively). Only Toxascaris leonina is transmitted by both lynx and canids in northern Ontario. Lynx is the only definitive host of the other common parasites. Seven helminths usually found in canids occurred infrequently in lynx: Alaria marcianae (LaRue, 1917) Walton, 1949 and immature Taenia pisiformis (Bloch, 1780) Gmelin, 1790 in 4% of those examined; and Capillaria aerophila (Creplin, 1839) Travassos, 1915, Physaloptera rara Hall &Wigdor, 1918, Ancylostoma caninum (Ercolani, 1859), Uncinaria stenocephalia (Railliet, 1884), and Taenia serialis (Gervais, 1847) Baillet, 1863 in one to three lynx each. Abundances of the common parasites varied only slightly among five forest regions, and did not differ between male and female lynx or among lynx older than kits. Cylicospirura felineus and Taenia rileyi were less abundant in kits, and Taenia laticollis and Toxocara cati tended to be more abundant in kits than in older lynx. Host condition and numbers of many of the common helminths tended to be positively correlated, but the inclusion of kits affected the result. The few helminth species established in lynx and their apparent uniform distribution in the host population may reflect the dominance of snowshoe hare in the diet.