Metals and metalloids in wolves and wolf-dog hybrids in human-dominated landscapes of Central Europe

The concentrations of 21 elements (Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Hg, Li, Mg, Mn, Mo, Ni, Pb, Se, Sn, Sr, Ti, V, Zn) in the livers and kidneys of 58 gray wolves (Canis lupus) and 8 wolf×dog (Canis lupus familiaris) hybrids collected in Poland from 2018 to 2024.We freeze-dried liver and kidney samples prior to mineralization and subsequently homogenized them. We performed mineralization in a Speedwave microwave digestion system (Berghof, Germany), using Teflon vessels (DAP-100 type). We mineralized liver samples (0.5g ± 0.005g) in a mixture of 6 ml HNO3 (65% v/v, ultra-pure grade) and 1.5 ml H2O2 (30% v/v). We carried out the mineralization process according to the following scheme: 20 minutes at room temperature, rising to 195°C, 15 minutes at 195°C, and then cooling to room temperature. The pressure inside the vessel did not exceed 20 bar throughout the procedure. After the mineralization was completed, we cooled the vessels to room temperature, and transferred the clear solutions to 50 ml measuring flasks and filled into the indicator with deionized water (ELGA PureLab Classic).We determined the mineral composition of liver and kidney samples using an iCAP Series 6500Duo ICP-OES spectrometer (Thermo Scientific, UK). The instrument settings were as follows: RF generator power of 1150 W, RF generator frequency of 27.12 MHz, coolant gas flow rate of 16 L·min−1, carrier gas flow rate of 0.65 L·min−1, auxiliary gas flow rate of 0.4 L·min−1, maximum integration time of 15 s, pump rate of 50 rpm, viewing configuration – axial, replicate – 3, flush time of 20 s. We performed calibration using multi-element standards CCS-4, CCS-5, and CCS-6 (100 µg/mL in 7% HNO3, Inorganic Ventures, USA). The dataset contains the following columns:Sample_ID - ID of the individualSpecies - species "wolf" Canis lupus or "wolf-dog hybrid" Canis lupus-Canis lupus familiarisAge_category - "juv" (1 year old)Sex - "female" or "male"Breeder - "true" (the animal was a breeder), "false" (the animal was not a breeder)Age_years - estimated age in years, for juveniles it is indicated as