Sexual Maturity and Life Stage Influences Toxic Metal Accumulation in Croatian Brown Bears
The influence of reproductive and (early) life stages on toxic metal levels was investigated in the brown bear (Ursus arctos), the largest mammalian predator species in Croatia. The purpose was to examine critical clusters in a population that might be at a higher risk of adverse health effects caused by metals as environmental contaminants. Levels of cadmium, mercury and lead in muscle, liver and kidney cortex of 325 male and 139 female bears, quantified by inductively coupled plasma mass spectrometry, were analysed according to distinct bear life stages (young: cub, yearling, subadult; mature: adult). Metal levels did not differ among sexes in young animals (< 4 years), except for mercury in muscles (higher in females), and adult females had higher cadmium and mercury. A trend of renal cadmium accumulation with age in immature male animals disappeared once they reached maturity, whereas for females this trend has only slowly declined in mature compared to immature bears. In early life stage (< 1 year), bear cubs had lower cadmium, comparable mercury, and higher lead in the kidneys than the bears of the following age category (yearlings). Due to a higher proportion of renal lead transfer from the mother to the cub compared with cadmium, it may be that the high burden of cadmium found in kidneys of older females has lower toxicological concern for their cubs than the lead content. Sex, reproductive, and life stages of bears were confirmed as important in assessing toxic metal burden.
The help of local hunters and experts with the collection of samples is gratefully acknowledged. The authors thank Dr. Z. Kljaković-Gašpić for valuable comments on the manuscript, and Mr. Makso Herman and Ms. Željana Pavlaković for language editing.
This research was funded by the Ministry of Science, Education, and Sports of the Republic of Croatia (Grant No. 022-0222148-2135). The Veterinary Faculty team was supported by the European Commission under the “HUNT” project of the 7th Framework Programme for Research and Technological Development (Grant No. 212160), “LIFE DINALP BEAR” project (Grant No. LIFE13 NAT/SI/000550), and the Research Council of Norway under the project “The role of natural resources in sustainable rural livelihoods in the western Balkans. The distribution and flow of costs and benefits” (application No. ES459363). Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use made of the information. The views expressed in this publication are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission.
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Conflict of interest
The authors declare that they have no conflict of interest.
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