Short-term exposure of anticoagulant rodenticides leads to the toxin accumulation from prey (Rattus losea) to predator (Elanus caeruleus)

Abstract

Rodenticides are widely used around the world since the 1950s. In Taiwan, an anti-rodent operation initiated 1977 and became a regular action annually implied by the government until 2014. This anti-rodent operation caused many animals of non-target species being exposed by rodenticides and became an environmental issue. The Black-winged Kite (Elanus caeruleus) is a small-sized diurnal raptor widely distributed in the Old World continent. Since 2000, a newly colonized population of this species occurred in Taiwan. Although the Black-winged Kites may suffer from the threats of rodenticides, the population is still growing and soon became the most abundant raptor in farmlands of Taiwan. Whether the Black-winged Kite accumulates higher anticoagulant rodenticide residues than other raptors are still unclear. In this study, liver samples of Black-winged Kites were collected from 2013 to 2016, when the detected residues of anticoagulant rodenticides increased annually. The concentration of residue rodenticide was above 0.2 ppm among 30% of the detected samples, which is the toxicity threshold concentration of other raptors. In the meanwhile, the lesser ricefield rat (Rattus losea), the most common prey of Black-winged Kites, also extended the survival period after fed on rodenticide. The longer survival days after being poisoned can enhance the predation opportunity of raptors, thus affect the accumulated rodenticides in the raptors. This study demonstrates that the Black-winged Kite has higher concentration of anticoagulant rodenticide than most other raptors, which provide the case that the raptor can quickly accumulate rodenticide residues within a short period of time.