The exposure and toxicity of pesticides to amphibians

Amphibians and pesticides
al. (1994) estimated that soil ingestion rate in box turtles and Eastern painted turtles were 4.5% and
5.9% of the diet respectively.
2.2.5. Avoidance
Six studies were found that addressed avoidance and pesticides in amphibians. Three of these (Pauli et
al. 1999, Wojtaszek et al 2004, 2005) referred to effects of exposure of tadpoles to pesticide
formulations on the ‘avoidance reaction’ to a negative stimulus (prodding) rather than avoidance of
pesticide contaminated habitats. The remaining three addressed avoidance of contaminated
environments under laboratory conditions.
Gertzog et al (2011) determined the avoidance response of adult eastern red-backed salamanders
(Plethodon cinereus) to a filter paper substrate contaminated with one of three formulations at 1%,
10% or 100% of the normal application rate. The tested formulations were Spectracide Brush Killer
(9.74% 2,4-D + 4.78%Dichlorprop-p + 1.65% Dicamba + surfactant), Bayer Advanced Brushkiller
Plus (8.8% Triclopyr + surfactant) and Roundup Weed and Grass Killer Concentrate Plus
(18%Glyphosate isopropylamine salt + 0.73% Diquat dibromide + POEA). Salamanders avoided all
formulations applied at full rate and Bayer Advanced Bruskiller and Roundup at 10% of the
application rate. No formulation was avoided at 1% of the application rate.
Takahashi (2007) investigated the effects of contamination of potential oviposition sites with the
formulation Roundup Weed and Grass Killer (18% Glyphosate isopropylamine salt + Diquat
dibromide + 0.73% POEA) on the behaviour of the gray treefrog complex (Hyla versicolor and Hyla
chrysoscelis). Frogs were found to avoid water treated at 2.4mg a.e./L when selection oviposition sites
although it is unlikely that such a concentration would be encountered frequently.
Mendez et al (2009) exposed adult American toads (Bufo americanus) to soil contaminated with
technical atrazine (99.2%) at field relevant concentrations (based on measured residues). These
represented concentrations immediately after application and the lower levels found 50 days later. The
toads did not show any avoidance of the treated soil.
Other studies have been made of the avoidance of nitrate fertilisers by amphibians. Egea-Serrano et al
(2008) tested the avoidance of ammonium chloride, isolated or combined with sodium nitrite and
sodium nitrate, in aquatic habitat by Pelophylax perezi froglets. Nitrogen contaminated treatments
were not avoided although significant inter-individual variation in avoidance was observed.
Gaglione et al, (2011) tested the avoidance of urea contaminated substrates by red-backed salamanders
(Plethodon cinereus). They found avoidance on both filter paper and soil substrates for this species
although the response was often not clear until 60 to 120 minutes of exposure.
Marco et al, (2001) investigated the avoidance of urea contaminated paper towel substrate by three
forest dwelling species (Plethodon vehiculum, Rhyacotriton variegatus, and Taricha granulosa). In
this study all three species demonstrated avoidance of substrate treated with urea at a rate of 225 kg
N/ha. In a similar study of the response of Triturus boscai to an ammonium nitrate contaminated filter
paper substrate (Ortiz-Santaliestra et al. 2005) found a concentration related avoidance response.
However, while Hatch et al (2001) found that newly metamorphosed western toads (Bufo boreas) and
cascades frogs (Rana cascadae) avoided paper towels contaminated with urea fertiliser, they did not
avoid potentially lethal concentrations when applied to soil substrates. Juvenile long-toed salamanders
(Ambystoma macrodactylum) also failed to avoid urea contaminated soil.
These results indicate that while amphibians can avoid some pesticide or fertiliser applications under
certain conditions, the response seems to be mixed depending on the species, substrate and toxicant. It
Supporting publications 2012:EN-343 38
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