## 3 Results and Discussion
### Hg Concentration in Fossil Animals' Hair
#### 3.1.1. Woolly Mammoth Hair and Hemolyzed Blood  
Hairs of four fossil mammoths were studied; the Hg concentrations are shown in the Figure 3a. Higher concentrations were in hair samples of [PERSON] and Yukagir mammoths from the Last Glacial and Preboreal warming, respectively, whereas the lowest Hg concentrations were in older specimens, Oymyakonsky and Malolyakhovsky mammoths (45-33 ka yr BP). There was rare opportunity to sample enough freshly thawed hair material from different parts of the body of the same animal ([PERSON] mammoth). Samples of hair taken from the neck and back leg demonstrated slightly different concentrations: 0.017 and 0.024 g/g, respectively. The difference between Hg concentrations sampled from different body areas for modern animals varied insignificantly for yak from 0.004 to 0.007 g/g (this study) and for beef cattle from 0.062 to 0.070 g/g [46]. The comparison of guard and down yak hair demonstrated a negligible difference in Hg concentrations: 0.0054 and 0.0058 g/g, respectively. Cattle hair also yielded similar Hg concentrations: 0.010 and 0.008 g/g for guard and down hairs. It was shown that the elemental composition and concentrations of most elements of beef cattle hair on different body areas does not differ notably [46]. Of course, in the ideal case, hair sampled from the same body areas should be used for the comparison of the animals. However, unfortunately, there are very few opportunities to get hair samples from the same part of body for different prehistoric animals. Therefore, comparison of prehistoric animals' hair sampled from different body surface areas is evidently acceptable due to minor differences in the concentrations as confirmed by our results (no more than 30%). There was rare chance to determine Hg concentration in hemolyzed blood of Malolyakhovsky mammoth. Mercury measurement in the whole blood provides information about recent exposure (-1-2 months) to both organic and inorganic mercury through ingestion of food and drinking water and inhalation of elemental mercury vapor in ambient air. The level of mercury in blood indicates recent exposure, but it does not reflect historical exposure or variations in exposure. Here we determined Hg concentration in mammoth hemolyzed blood \(0.69\pm 0.07\) g/L. Hg levels in mammoth blood are below background levels of mercury in the blood of people who do not consume fish \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Hg Concentration, g/g**} & \multicolumn{3}{c}{**Prehistoric Animals**} & \multicolumn{3}{c}{**Modern Animals**} & \multirow{2}{*}{**Reference Values**} \\ \cline{2-2} \cline{5-6}  & **Mammoth** & **Bison** & **Woolly Rhinoceros** & & **Yak** & **Cattle** \\ \hline number of samples & 4 & 2 & 1 & 1 & 145 & - \\ \hline hair average & 0.031 & 0.11 & 0.092 & 0.0056 & 0.0066 [46] & 1 [45] \\  & & & & & \(<\)0.5 [47] \\ \hline hair range & 0.017–0.049 & 0.035–0.177 & - & - & 0.002–0.011 [48] & 0.02–0.042 [48] \\ \hline blood \({}^{\star}\) & 0.69 \(\pm\) 0.07 & - & - & - & \(<\)0.438 (ND-15.4) [49] & \(<\)2 [45] \\ \hline \hline \end{tabular}  
* g/L; ND—not detected.  
\end{table} 
Table 4: Hg concentrations in hair of modern and prehistoric animals and reference values. Figure 3: Mercury concentration in hair of different fossil specimens: (a) mammoth; (b) bison and rhino. (<2 ug/L) [45]. It is comparable with relatively low levels of total mercury in the blood of modern animals: The median value of Hg in blood of Galician cows from NW Spain was <0.438 ug/L, with the range of <0.438 to 15.4 ug/L [49]. This is similar to Hg concentrations in blood of surveyed dogs from Alaska (0.16-12.38 ng/g) [50]. Hair to blood Hg ratio in Malolyakhovsky mammoth was 36, which is closer to the hair to blood ratio in fish-fed dogs (59 \(\pm\) 7.6), harbor seals (22-40), and polar bears (100) [51], than to the WHO value for humans (250) used for risk assessments to predict blood Hg from hair concentrations [8].