The effect of two glyphosate formulations on a small, diurnal lizard (Oligosoma polychroma)
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Formulations of glyphosate-based herbicides continue to dominate the global herbicide market, while there continue to be concerns regarding the impact of this herbicide on non-target organisms. Research also indicates that the additives within certain glyphosate formulations, such as surfactants, are actually more toxic than the glyphosate active ingredient alone. Concerns arise in particular when glyphosate formulations are proposed for vegetation control in areas inhabited by rare or threatened species. Although the effect of glyphosate on birds and mammals is well studied, reptiles remain neglected in ecotoxicological studies. We investigated whether dermal exposure to two different commercial glyphosate formulations affected performance measures in the New Zealand common skink (Oligosoma polychroma). Fifty-eight skinks were each placed in a box of straw to simulate field conditions and sprayed once with Agpro Glyphosate 360, Yates Roundup Weedkiller (both at the label-specified concentrations of 144 mg glyphosate per 1 L water), or water (control). Agpro Glyphosate 360 contained ethoxylated tallow amine at a concentration of <200 g/L, while the surfactant within Yates Roundup Weedkiller was unknown. Following treatment skinks were kept in captivity and sampled for selected temperature and mass over a four-week period. Neither glyphosate formulation had a significant impact on mass. However, skinks treated with Yates Roundup Weedkiller selected significantly higher temperatures across 3 weeks following exposure. This heat-seeking behaviour could be a fever response to increase metabolism and thereby counteract physiological stress.
KeywordsRoundup Skink Selected temperature Herbicide Surfactant Performance measures
We are grateful to Lynn Adams and the New Zealand Lizard Technical Advisory Group for advice on the logistics of this project. We also appreciate the assistance of Helen Day, Jacqui McIntosh, Dave McIntosh, Shanna Rose and Katrina Keogh with skink husbandry and capture. Clayson Howell and Trevor James provided technical advice on New Zealand herbicide formulations. This manuscript was improved by the input of Anna Carter, Lindsay Anderson, Scott Weir and five anonymous reviewers. This research was supported by Ngati Toa with permission from DOC (permit 35981-FAU) and the VUW Animal Ethics Committee (permit #2012R33). A VUW Graduate Scholarship financially supported Joanna Carpenter.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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