# Chemical Characterization of the Marking Fluid of Breeding and Non-Breeding Male Cheetahs
## 3 Results and Discussion
### Relative Concentrations of the 12 Common VOCs  
The mean relative concentration (RC) was calculated only for the 12 VOCs identified in every male cheetah's MF. This was conducted to identify potential differences regarding the RCs of volatiles between the two breeding groups. Table 2 summarizes the mean RCs and standard deviations of the 12 (common) VOCs in the two groups. Between the two breeding groups (Figure 2), the RC of indole was significantly higher in the NB group (\(p\) = 0.03), whereas the RC of dodecanoic acid was significantly higher in the B group (\(p\) = 0.05). \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**RC (Unitless)**} \\ \hline
**VOC** & **Non-Breeding (5.5 \(\pm\) 0.8y)** & **Breeding (8.9 \(\pm\) 1.3y)** \\ \hline
**Dimethyl disulfide** & \(0.05\pm 0.03\) & \(0.05\pm 0.03\) \\ \hline
**Hexanal** & \(0.01\pm 0.00\) & \(0.01\pm 0.00\) \\ \hline
**2-methylmercaptofuran** & \(0.23\pm 0.10\) & \(0.19\pm 0.11\) \\ \hline
**3-ethylcyclopentanone** & \(0.08\pm 0.03\) & \(0.05\pm 0.03\) \\
**Benzaldehyde** & \(0.29\pm 0.62\) & \(0.72\pm 0.65\) \\ \hline
**Acetophenone** & \(0.18\pm 0.29\) & \(0.32\pm 0.25\) \\ \hline
**2-Furanmethanol** & \(0.04\pm 0.02\) & \(0.03\pm 0.02\) \\ \hline
**Phenol** & \(0.05\pm 0.01\) & \(0.04\pm 0.02\) \\ \hline
**Octanoic acid** & \(0.28\pm 0.67\) & \(0.16\pm 0.13\) \\ \hline
**Nonanoic acid** & \(0.15\pm 0.12\) & \(0.37\pm 0.34\) \\ \hline
**Indole** & \(0.06\pm 0.02\) & \(0.03\pm 0.02\) \\
**Dodecanoic acid** & \(0.04\pm 0.03\) & \(0.12\pm 0.1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean relative concentration, estimated concentration, and standard deviation of the 12 common VOCs per breeding group. Indole is known to be involved in sexuality and age differentiation in cats and house mice [7; 13; 32]. In male domestic cats (Felis _silvestris_ catus), this was found to correlate significantly with age resulting in increasing concentrations along with increasing age [33]. In this study, the RC of indole was significantly higher in the younger NB males (\(p=0.03\)); therefore, the concentration of indole in the MF could be correlated in a negative manner to age in cheetahs as well. Indole has also been identified in the MF/urine of lions, domestic cats, and tigers [5; 7; 12; 13]. On the other hand, dodecanoic acid is known to be a pheromone that helps regulate oviposition in insects [34]. Although this VOCs involvement in mammalian reproduction is unknown, it has been identified in the urine of both male and female caracals [35], as well as one male Bengal tiger [36]. Therefore, the fact that this VOC is not exclusively identified in female felines means it likely has no function in the birthing process; however, it cannot be excluded from its role in any other function in reproduction in other mammalian species. Besides indole, the only other four commonly identified VOCs already known as pheromomes relating to sexuality in various species are acetophenone (anti-attraction, attraction, responsiveness, stimulates overmarking), benzaldehyde (affects sexual behavior), dimethyl disulfide (attraction, sniffing), and phenol (estrus, sexuality) [7; 13; 37; 38]. Phenol was found to be an indication of estrus in female buffaloes, which was hypothesized to be converted to 4-methyl phenol during estrus [39]. In a study measuring the VOC and CO\({}_{2}\) content of human breath, the concentration of phenol and indole rose in some male individuals during sexual arousal, which quickly declined shortly after [40]. Phenol has also been identified in the MF/urine of lions and tigers [7; 12; 13; 36]. Dimethyl disulfide, which has been identified in the urine of male and female snow leopards [41], lions, tigers, and cheetahs [3; 7; 11; 12; 13], has also been identified in the vaginal secretions of female hamsters and has been observed to act as a male attractant [13; 42].