Toxicity of a glufosinate- and several glyphosate-based herbicides to juvenile amphibians from the Southern High Plains, USA

Pesticide toxicity is often proposed as a contributing factor to the world-wide decline of amphibian populations. We assessed acute toxicity (48 h) of a glufosinate-based herbicide (Ignite^® 280 SL) and several glyphosate-based herbicide formulations (Roundup WeatherMAX^®, Roundup Weed and Grass Killer Super Concentrate^®, Roundup Weed and Grass Killer Ready-To-Use Plus^®) on two species of amphibians housed on soil or moist paper towels. Survival of juvenile Great Plains toads (Bufo cognatus) and New Mexico spadefoots (Spea multiplicata) was reduced by exposure to Roundup Weed and Grass Killer Ready-To-Use Plus^® on both substrates. Great Plains toad survival was also reduced by exposure to Roundup Weed and Grass Killer Super Concentrate^® on paper towels. New Mexico spadefoot and Great Plains toad survival was not affected by exposure to the two agricultural herbicides (Roundup WeatherMAX^® and Ignite^® 280 SL) on either substrate, suggesting that these herbicides likely do not pose an immediate risk to these species under field conditions.