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Effects of methylmercury and spatial complexity on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus).

Abstract：

:Methylmercury is a globally distributed neurotoxin, endocrine disruptor, and teratogen, the effects of which on wildlife at environmentally relevant levels are largely unknown. In birds, foraging efficiency and learning may be sensitive endpoints for sublethal methylmercury toxicity, and these endpoints also may be biologically relevant at the population level. In the present study, groups of wild-caught, prefledgling white ibises (Eudocimus albus) were raised in a free-flight, open-air aviary on diets that approximated the measured range of methylmercury exposure in the Everglades ecosystem (0, 0.05, 0.1, and 0.3 mg/kg/d). The effect of methylmercury exposure on group foraging efficiency was examined by allowing birds to forage on 200 fathead minnows (Pimephales promelas) in artificial ponds for 15 min by straining the arenas' contents through a seine net and counting all remaining prey. Additionally, we varied the difficulty of foraging by these tactile feeding birds by adding multiple levels of structural complexity (e.g., increased vegetation and prey refugia) to the pond. Structural complexity affected both foraging efficiency and the rate of increase in efficiency over time (improvement). Methylmercury exposure affected foraging efficiency (p = 0.03). It did not affect foraging improvement in the face of increasingly challenging environments, however, and the dose-response relationship was nonlinear (e.g., the control and high-exposure groups were the least efficient foragers). Evidence for an effect of methylmercury on foraging efficiency therefore was inconclusive because of unpredicted results and no interaction with time or habitat complexity. These data suggest a nonlinear dose-response relationship at low levels of methylmercury exposure; future research is needed to verify this hypothesis. This appears to be the first experimental demonstration of the effects of habitat complexity on foraging efficiency in long-legged wading birds.

journal_name

Environ Toxicol Chem

journal_title

Environmental toxicology and chemistry

authors

Adams EM,Frederick PC

doi

10.1897/07-466

subject

Has Abstract

pub_date

2008-08-01 00:00:00

pages

1708-12

issue

eissn

0730-7268

issn

1552-8618

pii

07-466

journal_volume

pub_type

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Effects of methylmercury and spatial complexity on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus).