Effects of brodifacoum and diphacinone exposure on four species of reptiles: tissue residue levels and survivorship

Abstract

BACKGROUND Anticoagulant rodenticides are used worldwide to control pest rodent species. However, the risks posed to non‐target reptiles have not been well characterized. In this study, 46 giant ameivas (Ameiva ameiva), 39 boa constrictors (Boa constrictor), 33 wood turtles (Rhinoclemmys pulcherrima), and 47 green iguanas (Iguana iguana) were orally dosed with one of two levels of either diphacinone or brodifacoum anticoagulant in propylene glycol solutions. Dosages were derived using daily food intake (DFI) equations, converting DFI to an equivalent anticoagulant bait amount and gavaging the solution volume needed to deliver the quantity of anticoagulant in that amount of bait. Animals were dosed on days 0 and 7 and monitored for a further 7 days for signs of anticoagulant intoxication and differences in behaviors and postures. At necropsy on day 14, animals were examined for thoracic and abdominal bleeding, and both tissue and organ samples were taken for histology. Liver and whole‐body anticoagulant residues were assessed. RESULTS No turtles or boas died due to anticoagulant exposure. However, anticoagulant intoxication was suspected in one iguana dosed with brodifacoum. A few treated ameivas died but exhibited no hemorrhaging. Liver residue levels were higher than whole‐body remainder residue levels for all species. Unlike the other species, turtles had higher diphacinone residue levels than brodifacoum. CONCLUSION Turtles and boas exhibited a relative insensitivity to diphacinone and brodifacoum, while the lizards appeared to be somewhat more sensitive to these compounds. This study provides data for future assessments of the risks to these species associated with anticoagulant use. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

Postmortem findings of secondary brodifacoum poisoning in a kestrel (Falco tinnunculus)

“…Anticoagulant rodenticides (ARs) are widely used for vertebrate pest control. They interfere with blood clotting by inhibiting the enzyme vitamin K epoxide reductase, leading to severe internal haemorrhage in mammals, birds and fishes, whereas reptiles seem to be more resistant 12 . On necropsy, signs of acute AR toxicosis in raptors are haemorrhages either externally or in a variety of bodily sites, including meninges, thymus, renal tissue, coelomic cavity, liver, pericardial sac, gastrointestinal tract, nasal cavity, joints and muscles 11 .…”

Snake scales record environmental metal(loid) contamination

“…Long-lived taxa such as turtles and crocodilians are particularly suitable bioindicators due to their longevity and affiliation with water (Buah-Kwofie et al 2018;Rowe 2008;Slimani et al 2018); however, the use of high trophic tier snakes is becoming increasingly common (Haskins et al 2019;Hopkins et al 2004;Lettoof et al 2020b;Liu et al 2019;Schwabenlander et al 2019). Reptiles respond to contaminant exposure differently to other taxa such as birds and mammals in several ways: they can ingest and accumulate high concentrations of contaminants that would be fatal to other taxa (Hopkins et al 2005;Weir et al 2015); they are generally more resistant to the toxicological effects of contaminants (Chin et al 2013;Finger et al 2016;Mauldin et al 2019); and their slower energy expenditure results in longer contaminant depuration times (Linder et al 2010;Rueda et al 2016).…”