Research into the effects of pesticides on amphibians has been conducted at Trent University in Peterborough, Ontario since 1989. Short-term exposures have been used to assess the sensitivity to pesticides of native amphibians such as wood frogs (Rana sylvatica), bullfrogs (R. catesbeiana), green frogs (R. clamitans), leopard frogs (R. pipiens), American toads (Bufo americanus) and spotted salamanders (Ambystoma maculatum). Low concentrations of pesticides were used in order to mimic concentrations that might occur in water following typical field applications. The low concentrations employed often cause only sublethal effects such as paralysis and an inability to move away from a gentle prod (used to test escape and predator avoidance behaviour). Pesticides that have been studied include the insecticides permethrin, fenvalerate, fenitrothion, tebufenozide and endosulfan and the herbicides triclopyr, glyphosate, hexazinone, triallate, trifluralin and bromoxynil.

In one study, for instance, we exposed neural stage embryos and newly hatched tadpoles of green frogs to low levels of the herbicide glyphosate. Following 96 hours of exposure to the herbicide, surviving animals were moved to fresh water. Nominal glyphosate concentrations of 1.2 to 4.0 ppm initially caused tadpoles paralysis from which they eventually recovered. During the first 24 hours of exposure to 8.0 ppm, all tadpoles either died or were completely paralyzed. Furthermore, almost all of the survivors from the first 24 hours of exposure died before the completion of the 96-hour exposure period. Follow-up tests indicated that much of the toxicity could be attributed to the surfactant used in the Round-Up formulation of glysophate

Bruce Pauli, Environment Canada, Canadian Wildlife Service, National Wildlife
Research Centre, Hull, Quebec, K1A 0H3
(819) 953-2634 phone
(819) 953-6612 fax

Dr. M Berrill, Biology Department, Trent University, Peterborough Ontario, K9J7B8
(705) 748-1455 phone
(705) 748-1205 fax