Temporal Persistence of Bromadiolone in Decomposing Bodies of Common Kestrel (Falco tinnunculus)

Abstract

Bromadiolone is a second generation anticoagulant rodenticide (SGAR) used to control pest rodents worldwide. SGARs are frequently involved in secondary poisoning in rodent predators due to their persistence and toxicity. This study aims to evaluate the persistence of bromadiolone in liver at different stages of carcass decomposition in experimentally-dosed common kestrels (Falco tinnunculus) to understand the possibility of detecting bromadiolone in cases of wildlife poisoning and the potential risk of tertiary poisoning. Twelve individuals were divided into the bromadiolone-dose group (dosed with 55 mg/kg b.w) and the control group. Hepatic bromadiolone concentrations found in each stage of decomposition were: 3000, 2891, 4804, 4245, 8848, and 756 ng/g dry weight at 1-2 h (fresh carcass), 24 h (moderate decomposition), 72 h, 96 h (advanced decomposition), seven days (very advanced decomposition), and 15 days (initial skeletal reduction) after death, respectively. Liver bromadiolone concentrations in carcasses remained relatively stable over the first four days and raised on day 7 of decomposition under the specific conditions of this experiment, presenting a risk of causing tertiary poisoning. However, at the initial skeletal reduction stage, liver bromadiolone concentration declined, which should be considered to interpret toxicological analyses and for proper diagnosis. This experimental study provides for the first time some light to better understand the degradation of SGARs in carcasses in the wild.

Keywords: anticoagulant rodenticides; biomonitoring; bromadiolone degradation; carcass decomposition; wildlife poisoning.

Figure 1

Carcasses of common kestrel (Falco tinnunculus) in the prone position with temperature/humidity probes.

Figure 2

Water content in tissue (%) over time (decompositions days) in decaying carcasses of common kestrel (r = −0.95, p < 0.01). Numbers above circles indicate the mean water content (%) for the control and dosed individual at each time point.

Figure 3

Bromadiolone concentration in liver (ng/g, d.w.) relative to the carcass decomposition time (days) in dosed common kestrel (r = −0.20, p = 0.699, n = 6).

Figure 4

Principal component analysis (PCA) biplot of the common kestrel experiment. Vectors represent: biological variables (sex and body mass on day 0, BM₀), weather variables (i.e., internal temperature, Ti, and ambient temperature, Ta), decomposition variables (i.e., days of decomposition, DD, body mass during necropsy, BMn, liver weight, LW, and liver water content, LWC), and liver bromadiolone concentration (LB). The points represent individual birds from the bromadiolone-dose (grey) or control group (white), and D0-D15 indicates the days of decomposition.

Figure 5

Significant relationships between weather variables (ambient and internal temperatures), biological variables (sex and body mass on day 0), and decomposition variables (days of decomposition, liver weight, liver water content and body mass during necropsy) in common kestrels. Pearson correlation coefficients (r) are presented. The directions of the relationships are shown with positive and solid lines, or negative and dashed lines. * p < 0.05, ** p ≤ 0.01.