Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury - PubMed (original) (raw)

Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury

Peter Frederick et al. Proc Biol Sci. 2011.

Abstract

Methylmercury (MeHg) is the most biologically available and toxic form of mercury, and can act as a powerful teratogen, neurotoxin and endocrine disruptor in vertebrates. However, mechanisms of endocrine impairment and net effects on demography of biota are poorly understood. Here, we report that experimental exposure of an aquatic bird over 3 years to environmentally relevant dietary MeHg concentrations (0.05-0.3 ppm wet weight) resulted in dose-related increases in male-male pairing behaviour (to 55% of males), and decreases in egg productivity (to 30%). Dosed males showed decreased rates of key courtship behaviours, and were approached less by courting females in comparison to control males. Within dosed groups, homosexual males showed a similar reduction when compared with dosed heterosexual males. We found an average 35 per cent decrease in fledgling production in high-dose birds over the study duration. These results are of interest because (i) MeHg exposure is experimentally tied to demographically important reproductive deficits, (ii) these effects were found at low, chronic exposure levels commonly experienced by wildlife, and (iii) effects on reproductive behaviour and sexual preference mediated by endocrine disruption represent a novel and probably under-reported mechanism by which contaminants may influence wild populations of birds.

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Figures

Figure 1.

Proportions of males nesting homosexually by treatment in each breeding season. Circles, control; inverted triangles, low; squares, medium; diamonds, high.

Figure 2.

Average rates of courtship behaviours per male per 40 min observation sessions; error bars show ± one standard error from the mean. (a) Average head bobbing rate in heterosexual males by dose group. Differences were significant between control and each dosed group (GLM, p ≤ 0.01). (b) Average head bobbing rate by pairing type. Rates were significantly different between pairing types (GLM, p ≤ 0.01) (c) Average pair bowing rate in heterosexual pairs by treatment group. Rates were significantly different between control and each dosed group (GLM, p < 0.001). (d) Average pair bowing rate by pairing type. Rates were significantly different between pairing types (GLM, p ≤ 0.01). (e) Average number of approaches per heterosexual male from females by treatment group. Significant differences were found between control and high dose groups (GLM, p = 0.0425). (f) Average number of approaches from females per dosed male, by pairing type. Rates were significantly different between pairing types (GLM, p = 0.001).

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Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury - PubMed (original) (raw)