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); "ad" (>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 <1Status - "resident" (member of the resident family group) or "floater" (an animal not associated with the resident family group, during dispersion)Date - date in format yyyy-mm-ddDeath_cause - reson of deathLatitude - Latitude in decimal form expresses geographic coordinates as a single decimal numberLongitude - Longitude in decimal form expresses geographic coordinates as a single decimal numberkidney_sample_ID - ID of the kidney sampleBa_kidney - Concentration of Barium in the kidney sample [mg/kg dry weight]Be_kidney - Concentration of Beryllium in the kidney sample [mg/kg dry weight]Bi_kidney - Concentration of Bismuth in the kidney sample [mg/kg dry weight]Ca_kidney - Concentration of Calcium in the kidney sample [mg/kg dry weight]Cd_kidney - Concentration of Cadmium in the kidney sample [mg/kg dry weight]Co_kidney - Concentration of Cobalt in the kidney sample [mg/kg dry weight]Cr_kidney - Concentration of Chromium in the kidney sample [mg/kg dry weight]Cu_kidney - Concentration of Copper in the kidney sample [mg/kg dry weight]Hg_kidney - Concentration of Mercury in the kidney sample [mg/kg dry weight]Li_kidney - Concentration of Lithium in the kidney sample [mg/kg dry weight]Mg_kidney - Concentration of Magnesium in the kidney sample [mg/kg dry weight]Mn_kidney - Concentration of Manganese in the kidney sample [mg/kg dry weight]Mo_kidney - Concentration of Molybdenum in the kidney sample [mg/kg dry weight]Ni_kidney - Concentration of Nickel in the kidney sample [mg/kg dry weight]Pb_kidney - Concentration of Lead in the kidney sample [mg/kg dry weight]Se_kidney - Concentration of Selenium in the kidney sample [mg/kg dry weight]Sn_kidney - Concentration of Tin in the kidney sample [mg/kg dry weight]Sr_kidney - Concentration of Strontium in the kidney sample [mg/kg dry weight]Ti_kidney - Concentration of Titanium in the kidney sample [mg/kg dry weight]V_kidney - Concentration of Vanadium in the kidney sample [mg/kg dry weight]Zn_kidney - Concentration of Zinc in the kidney sample [mg/kg dry weight]liver_sample_ID - ID of the liver sampleBa_liver - Concentration of Barium in the liver sample [mg/kg dry weight]Be_liver - Concentration of Beryllium in the liver sample [mg/kg dry weight]Bi_liver - Concentration of Bismuth in the liver sample [mg/kg dry weight]Ca_liver - Concentration of Calcium in the liver sample [mg/kg dry weight]Cd_liver - Concentration of Cadmium in the liver sample [mg/kg dry weight]Co_liver - Concentration of Cobalt in the liver sample [mg/kg dry weight]Cr_liver - Concentration of Chromium in the liver sample [mg/kg dry weight]Cu_liver - Concentration of Copper in the liver sample [mg/kg dry weight]Hg_liver - Concentration of Mercury in the liver sample [mg/kg dry weight]Li_liver - Concentration of Lithium in the liver sample [mg/kg dry weight]Mg_liver - Concentration of Magnesium in the liver sample [mg/kg dry weight]Mn_liver - Concentration of Manganese in the liver sample [mg/kg dry weight]Mo_liver - Concentration of Molybdenum in the liver sample [mg/kg dry weight]Ni_liver - Concentration of Nickel in the liver sample [mg/kg dry weight]Pb_liver - Concentration of Lead in the liver sample [mg/kg dry weight]Se_liver - Concentration of Selenium in the liver sample [mg/kg dry weight]Sn_liver - Concentration of Tin in the liver sample [mg/kg dry weight]Sr_liver - Concentration of Strontium in the liver sample [mg/kg dry weight]Ti_liver - Concentration of Titanium in the liver sample [mg/kg dry weight]V_liver - Concentration of Vanadium in the liver sample [mg/kg dry weight]Zn_liver - Concentration of Zinc in the liver sample [mg/kg dry weight]