The potential role of semiochemicals in the reproductive management of cheetahs in captivity

Thesis (MScAgric)--Stellenbosch University, 2024.

ENGLISH ABSTRACT: Cheetah (Acinonyx jubatus) numbers have been reduced to less than 7,100 individuals, and the species is currently listed as vulnerable according to the IUCN. Captive breeding has been used for a long time as a method of conservation of the species. Unfortunately, cheetahs have proven difficult to breed in captivity and females are susceptible to asymmetric reproductive aging and endometrial hyperplasia, which is prevented by breeding them when they are still young adults. However, younger females show a significantly lower frequency of mating behaviour than older females, which negatively affects breeding introductions and, therefore, decreases mating success. The urine of male cheetahs plays an olfactory role in mate choice of female cheetahs, and the two most successful captive breeding methods imply the involvement of semiochemicals in cheetah courtship. Therefore, the aim of this study was to investigate the role of semiochemicals in the breeding behaviours of cheetahs to potentially develop a synthetic scent that can be used in captive cheetah breeding programs. For this purpose, three trials have been conducted. In the first experiment the marking fluid (MF) of 4 breeding (B; age: 8.9±1.3 years old) and 4 non-breeding (NB; age: 5.5±0.8 years old) male cheetahs was analysed to identify differences in the volatile organic compounds (VOCs). Of the fifty-three VOCs identified, twelve VOCs were detected in the MF of all the males. Five of the twelve VOCs (i.e. dimethyl disulfide, benzaldehyde, acetophenone, phenol, and indole) are known to be involved in attraction/sexual behaviour in mammals. Among these, the relative concentration (RC) of indole was significantly higher in the NB group (0.06 ± 0.02), and the RC of dodecanoic acid was significantly higher in the B group (0.12 ± 0.1). In the second trial, benzaldehyde, acetophenone, indole, dimethyl disulfide and phenol were used according to the average RC of these VOCs from the breeding males’ group in the previous trial. Each VOC was applied to wooden logs (with water as the control), and seven male cheetahs were exposed to the logs. There was no significant effect of any VOC on the cheetah's behavioural response, however, the males did react negatively towards benzaldehyde and dimethyl disulfide. In the third trial, a synthetic scent (SS) was created using the five pheromones identified in the MF of the males of experiment one. Eight female cheetahs of different age groups (2–4 y and 6–8 y) were enrolled in this trial. The SS did not have a significant effect on the total frequency of oestrous behaviour displayed by the females used in this study, however, the SS did significantly increase the sniff behaviour in general. Findings from this novel study indicated that VOCs can be isolated in the MF of male cheetahs, but no conclusive evidence was obtained that VOCs can be used in the development of a SS for use in captive cheetah breeding programs. Nonetheless, the results of this study does indicate that VOCs do have an effect on cheetahs and their behaviour.

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