Heavy Metal Concentrations in Free-Living Southern Caracaras (Caracara plancus) in the Northeast Region of Brazil

Abstract

Background: With the continuously increasing release of heavy metals in the environment, mostly from anthropogenic sources, there is a need to find ways of evaluating and managing the issuance of these contaminants and correct its damages. The birds being at the top of some food chains reflect the presence of metals in the environment, keeping this in perspective, raptors have been successfully used for heavy metals biomonitoring studies in the past. The purpose of this study was to identify and quantify cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), and chromium (Cr) in the feathers and livers of free-living southern caracaras, live and dead, from Recife, Pernambuco state, Northeast of Brazil.Material, Methods & Results: Sixty-two feathers from live and dead southern caracaras and 21 livers from dead southern caracaras were analyzed by atomic absorption spectrometry for Hg and by inductively coupled plasma optical emission spectrometry for Cd, Cr, Pb, and Cu. Concentrations of Cr and Cu elements were detected in all feather and liver samples analyzed from live and dead caracaras. There was no difference in the concentration of metals between feathers of dead and live caracaras: Pb (P = 0.3576), Cd (P = 0.0792), Cr (P = 0.5475), and Cu (P = 0.3603), but significant variation was observed for Hg (P = 0.0459). The highest concentrations of Pb (P < 0.0001) and Cr (P < 0.0001) were found in the feathers than in the liver. On the other hand, the highest concentrations of Cu were found in liver samples (P = 0.0011). No significant variation in the concentrations of Cd (P = 0.7770) and Hg (P = 0.3669) was found between feathers and liver samples.Discussion: Chromium, as well as Hg, and Cu have a high affinity for keratin, which may explain the higher concentrations of Cr in caracaras feathers in this research. Lead was detected in all liver samples analyzed. Elevated levels were also found in the feathers of dead (95.2%) and live (75.6%) caracaras. The presence of Pb may be due to external contamination by pollutants, such as fossil fuels. Higher concentrations of Hg were observed in dead caracaras feathers, this concentrations change during molting but are not affected by external contamination. Metals, such as Hg, and Cd, accumulate in organisms from different trophic levels, which may indicate that this contamination comes mainly from feed. Pearson’s coefficient here showed no correlation between metals from dead caracaras feathers and livers, although a few previous studies have shown a correlation between metal concentrations from tissues and feathers. This pattern can be attributed to the different time of exposure of feathers to metals in relation to livers. The concentrations of metals in hepatic tissues reflect the levels of elements in the diet of these birds, characterizing acutely the contamination of the ecosystem. On the other hand, feathers represent the exposure in the time of molting, when the artery supplies metals, thus representing a chronic exposure. In feathers from live birds, the Pearson’s correlation analysis showed a high to moderate correlation between metals, which may suggest that they come from a similar source, but there is no way to specify the origin since the metals surveyed could be present in the soil, water, or in the prey eaten by these animals. For the purpose of environmental analyses, it is required to determine the exact source of contamination. Considering that it is possible to confirm the presence of these heavy metals in southern caracaras, these birds may be important environmental bioindicators. The development of systematic research on animals and the environment is essential for monitoring the levels of metal pollutants and evaluating their impact in order to guide measures to protect fauna and human health.