Methylmercury: Reproductive and Behavioral Effects on Three Generations of Mallard Ducks

Three generations of mallard ducks (Ana~ platyrh!lncllo.s! "-'ere fed either a control diet or a diet containing 0.5 ppm mercury in the form of methylmercury. The !~vel$ of men.-ury in adult tissues and eggs remained about the same over 3 generations. The methylmercury di~ had no effect on adult weights or weight changes during the reproductive season. Females fed a diet containin~ 0.5 ppm mercury laid a greater percentage of their eggs outside their nestboxes than did controls, and also laid fewer eggs and produced fewer ducklings. Methylmercury in .the diet appeared to result in a small amount of ~ggshell thinning. Ducklings from parents fed methylmercury were less responsive th;m controls to tape-recorde<i mat~mal calls, but were hyper-responsive to a fri~htenin£ stimulus in avoidance tests ; there were no significant differences in locomotor activity in an open-field test. The purpose of this paper is to describe reproductive and behavioral effects of methylmercury on 3 generations of mallard ducks. Findings for the 1st and 2nd generations were reported earlier (Heinz 1974, 1975, 1976b, 1976c, Heinz and Locke 1976). Here, I have combined the data for all 3 generations to determine changes from generation to generation and overall effects that might not have been statistically significant in the analysis of single generations . To my kno"\o·ledge, there have been no reported multiple generation studies on the effects of mercury or any other environmental pollutant on waterfowL Such studies have been reported for Japanese quail (Cotur-nix coturni:r japonica) (Carnio and McQueen 1973), ring-necked pheasants (Phasianus colchicus ) {Dahlgren and Linder 1974), and ring doves (Streptopelia risoria ) (Peakall et aL 1972). I thank the following people for their help in the study: C. S. Cruger, R B. Frederick, D. C. Gray, R. G. Heath, P. A. Heinz. G. Hensler, and N. C. ~filler. J. B. Eld~r provided the !v1orsodren U$ed in chis study and others. 394 J. WILDL MANAGE. 4.3(2):394-401