Unintentional Wildlife Poisoning and Proposals for Sustainable Management of Rodents

Abstract

In Europe, bromadiolone, an anticoagulant rodenticide authorized for plant protection, may be applied intensively in fields to control rodents. The high level of poisoning of wildlife that follows such treatments over large areas has been frequently reported. In France, bromadiolone has been used to control water voles (Arvicola terrestris) since the 1980s. Both regulation and practices of rodent control have evolved during the last 15 years to restrict the quantity of poisoned bait used by farmers. This has led to a drastic reduction of the number of cases of poisoned wildlife reported by the French surveillance network SAGIR. During the autumn and winter 2011, favorable weather conditions and high vole densities led to the staging of several hundreds of Red Kites (Milvus milvus) in the Puy-de-Dôme department (central France). At the same time, intensive treatments with bromadiolone were performed in this area. Although no misuse has been mentioned by the authorities following controls, 28 Red Kites and 16 Common Buzzards (Buteo buteo) were found dead during surveys in November and December 2011. For all these birds, poisoning by bromadiolone as the main cause of death was either confirmed or highly suspected. Other observations suggest a possible impact of bromadiolone on the breeding population of Red Kites in this area during the spring 2011. French regulation of vole control for plant protection is currently under revision, and we believe this event calls for more sustainable management of rodent outbreaks. Based on large-scale experiments undertaken in eastern France, we propose that direct control of voles at low density (with trapping or limited chemical treatments) and mechanical destruction of vole tunnels, mole control, landscape management, and predator fostering be included in future regulation because such practices could help resolve conservation and agricultural issues.

Trophic transfer of pesticides: The fine line between predator–prey regulation and pesticide–pest regulation

“…While generalists are known to have a stabilizing effect (Hanski et al, ), the benefit of specialist predators imparted to generalist predator and resulting increase in the prevalence of intraguild predation would be difficult to detect in empirical studies. Nevertheless, other generalist predators such as the endangered red kite Milvus milvus which feed on voles opportunistically, occupy areas with bromadiolone treatments and are also affected by rodenticides (Coeurdassier et al, ) and may therefore also benefit from the presence of mustelids in the ecosystem.…”

“…Voles and many small rodents are perceived as pests, but they are also keystone species, crucial to the functioning of grassland and forest ecosystems, as well as being the prey of numerous predators, including species of conservation concern (Coeurdassier et al, ; Delibes‐Mateos, Smith, Slobodchikoff, & Swenson, ). Their population cycles create pulses of resources crucial to the viability of a wide range of resident predators and the aggregation of mobile avian vole predators (Korpimaki & Norrdahl, ).…”

“…Anticoagulant rodenticides are non‐selective toxicants with deleterious effects on non‐target fauna (e.g. Coeurdassier et al, ). Despite AR being exclusively licensed for rodent control, a large number of predator species are secondarily exposed to AR (Sánchez‐Barbudo, Camarero, & Mateo, ).…”

Do bromadiolone treatments to control grassland water voles (Arvicola scherman) affect small mustelid abundance?

“…The use of bromadiolone at high WV density was forbidden during the 2000s, and an integrated pest management plan was promoted, involving the use of safer alternative methods of pest control and the limitation of chemical treatments . Thus, within a strategy of surveillance and prevention of WV damage, protocols for bromadiolone application evolved towards treatment in the low/increasing phase of the WV cycle (abundance indices between 0 and 50% of parcel occupation) and promotion of methods like trapping, mechanical destruction of vole tunnels, mole control, landscape management, and predator fostering (see http://draaf.bourgogne-franche-comte.agriculture.gouv.fr/Campagnol-terrestre-et-Campagnol (French) for more information) . Moreover, lower quantities of bromadiolone were used (7.5 kg ha −1 of authorized dry bait, compared to 20 kg ha −1 in the 1990s, being the bromadiolone concentration stable at 50 mg kg −1 during this time).…”

A negative association between bromadiolone exposure and nestling body condition in common kestrels: management implications for vole outbreaks

“…SGARs show greater acute toxicity and higher capacity to bioaccumulate than first‐generation anticoagulant rodenticides (FGARs); it has been described that the liver half‐life of SGARs can be 10 times longer than that of FGARs in nocturnal raptors (100 days and 11.7 days respectively) . These undesired effects have led to management strategies for controlling the spatiotemporal use of these rodenticides by farmers to reduce their environmental impacts . SGARs are widely used both as biocides in more urbanised areas and as pesticides in croplands, increasing the exposure to bromadiolone for non‐target species .…”