Oviposition site selection: pesticide avoidance by gray treefrogs

Area of Science:

• Environmental Toxicology
• Amphibian Ecology
• Ecotoxicology

Background:

• Glyphosate herbicides impact non-target organisms, yet their effect on amphibian oviposition site selection is unknown.
• Previous research shows pesticide and predator cues increase tadpole mortality.
• Amphibian breeding site selection is crucial for offspring survival.

Purpose of the Study:

• To investigate if adult gray treefrogs avoid oviposition sites containing glyphosate (Roundup).
• To determine if avoidance behavior is amplified by the presence of predatory cues.
• To assess the impact of herbicide concentration on amphibian reproductive decisions.

Main Methods:

• An outdoor experiment utilized artificial ponds with four treatments: predatory fish cue, Roundup (2.4 mg glyphosate acid equivalent/L), combined cue and Roundup, and a control.
• Oviposition site choice was assessed by quantifying the number of gray treefrog egg masses laid in each treatment.
• The study focused on behavioral responses of adult amphibians to environmental contaminants.

Main Results:

• Gray treefrogs significantly avoided oviposition in pools treated with Roundup and/or predatory fish cues.
• The majority of eggs were laid in control pools, indicating a preference for uncontaminated sites.
• Avoidance behavior was observed even when herbicide was present alone.

Conclusions:

• Adult gray treefrogs demonstrate avoidance of glyphosate-contaminated oviposition sites, potentially protecting offspring from lethal herbicide exposure.
• This study provides the first evidence that environmentally relevant concentrations of herbicides can alter amphibian oviposition site selection.
• Further research is critical to determine the ecological relevance of these findings given field concentration variability.