Cheetahs are known for their low genetic variability. Such a genetic monomorphism is generally thought to be linked with a low reproductive performance of females and high offspring mortality. Cheetahs in captivity indeed often do not reproduce well, thus it was thought that this is also true for free-ranging cheetahs. It is partly true in ecosystems where cheetahs coexist with large carnivore species such as lions and spotted hyenas, however, in these cases the high cub mortality is mainly due to direct killing of the cubs when the larger competitors detect them in the lair. We study cheetahs on farmland in Namibia, where no lions and spotted hyenas occur, thus we can study the reproductive performance of cheetahs without their competitors. We compare our findings with cheetahs kept in large enclosures on Namibian farms or conservation facilities, as well as with cheetahs kept in European zoological gardens.

We showed with our research that all free-ranging females reproduce successfully and have high raising successes. In Namibian farmland, 79% of cubs survived to the age of independence, which is significantly and several times higher than in ecosystems containing lions and spotted hyenas. We further demonstrated with our collaboration partners using ultrasonography imaging that the low reproductive performance of captive females is due to the “asymmetric reproductive aging” (ARA), a phenomenon that occurs when females are not bred early in their life and thus cycle continuously over many years. The resulting continuous oestrogen fluctuation often leads to pathologies of the inner reproductive organs after a few years. This can prevent a successful fertilization and gestation, eventually leading to infertility. For cheetahs, it is therefore important to become pregnant early in their life to prevent the onset of ARA. In addition, cheetah females should not be kept together in the same enclosure the months before planned mating, because the cycle of the subordinate females might become suppressed by the dominant female. Also, the breeding pairs should not be kept together for extended periods when mating is anticipated to ensure sexual interest and arousal when the female is in heat.

These results indicate that the low genetic variability is not the cause for the low reproductive performance of captive cheetahs, but rather the age at first reproduction and the social composition of cheetahs kept together. Also allostatic load (“stress”) had no effect on the reproductive performance of cheetahs. For this we examined with ultrasonography the size of adrenal glands of free-ranging cheetahs and cheetahs kept in large enclosures in Namibia. The adrenal glands produce glucocorticoids which are the stress hormones. High and chronic stress leads to a high production of glucocorticoids and thus an increase of adrenal glands. Reproducing free-ranging and non-reproducing captive cheetahs in Namibia had similar sizes of adrenal glands, thus similar stress levels. We also developed and validated with our collaborators enzyme immunoassays to measure androgen (sexual hormones) and glucocorticoid metabolites in faeces of cheetahs. Measurements of faeces of females in European zoological gardens also revealed that successful breeders had similar stress levels as unsuccessful breeders (though both groups had higher levels than Namibian cheetahs), supporting our findings in Namibia that stress does not hamper reproductive performance in cheetahs.

Cheetahs are not the only species with a low genetic variability. Carnivore species do generally have lower genetic variability than other mammalian species and there are carnivore species such as honey badgers and other mustelids with even lower genetic variability than cheetahs. But cheetahs became a textbook example for conservation genetics because of their apparent challenges to breed them in captivity and their high disease susceptibility in captivity in earlier times. See also sub-projects on health status and immune system for more details.

Publications reporting on these topics

• Wachter B, Thalwitzer S, Hofer H, Lonzer J, Hildebrandt TB, Hermes R 2011: Reproductive history and absence of predators are important determinants of reproductive fitness: the cheetah controversy revisited. Conservation Letters 4: 47-54. Doi: 10.1111/j.1755-263X.2010.00142.x. 

• Ludwig C, Wachter B, Silinski-Mehr S, Ganswindt A, Bertschinger H, Hofer H, Dehnhard M 2013: Characterisation and validation of an enzyme-immunoassay for the non-invasive assessment of faecal glucocorticoid metabolites in cheetahs (Acinonyx jubatus). General and Comparative Endocrinology 180: 15-23. Doi: 10.1016/j.ygcen.2012.10.005.

• Pribbenow S, Wachter B, Ludwig C, Weigold A, Dehnhard M 2016: Validation of an enzyme-immunoassay for the non-invasive monitoring of faecal testosterone metabolites in male cheetahs (Acinonyx jubatus). General and Comparative Endocrinology 228: 40-47. Doi: 10.1016/j.ygcen.2016.01.015.

• Crosier AE, Wachter B, Schulman M, Lüders I, Koester DC, Wielebnowski N, Comizzoli P, Marker L 2018: Reproductive physiology of the cheetah and assisted reproductive techniques. In: Cheetahs: Biology and conservation. Marker L, Boast L, Schmidt-Küntzel A (eds), Academic Press, San Diego, USA. 385-402. Doi: 10.1016/B978-0-12-804088-1.00027-7.

• Ludwig C, Dehnhard M, Pribbenow S, Silinski-Mehr S, Hofer H, Wachter B 2019: Asymmetric reproductive aging in cheetah (Acinonyx jubatus) females in European zoos. Journal of Zoo and Aquarium Research 7: 87-93. Doi: 10.19227/jzar.v7i2.382.