Abstract
Improving our sparse knowledge of the mating and reproductive behaviour of white rhinoceros (Ceratotherium simum Burchell, 1817) is essential for the effective conservation of this iconic species. By combining morphological, physiological and habitat data with paternity assignments of 104 known mother–offspring pairs collected over a period of 13 years, we provide the most comprehensive analysis of the mating system in this species. We show that while the overall mating system was promiscuous, and both males and females produced more offspring when mating with several partners, half of all females with multiple offspring were monogamous. Additionally, we find that mating and reproductive success varied significantly among territorial males in two independent sets of males. In females, however, variation in the mating and the reproductive success was not larger than expected by random demographic fluctuations. Horn size, testosterone metabolite concentration, territory size, habitat openness and the volume of preferred food within the territory did not seem to influence male mating or reproductive success. Moreover, there was no sign of inbreeding avoidance: females tended to mate more frequently with closely related males, and one daughter produced a progeny with her father. The lack of inbreeding avoidance, in combination with the skew in male reproductive success, the partial monogamy in females and the territorial‐based mating system, jeopardizes the already low genetic variation in the species. Considering that the majority of populations are restricted to fenced reserves and private farms, we recommend taking preventive measures that aim to reduce inbreeding in white rhinoceros. A video abstract can be viewed here.
Highlights
The world is in a period of mass extinction (Ceballos, Ehrlich, & Dirzo, 2017) with species disappearing at an accelerating pace
These populations encounter a number of risks if they remain isolated for prolonged periods of time: first, they undergo a loss of genetic variability due to genetic drift, which decreases the fitness of individuals in the short term and leads to a lack of adaptive flexibility in the long term (Frankham, Briscoe, & Ballou, 2002; Giglio, Ivy, Jones, & Latch, 2016; Ralls, Brugger, & Ballou, 1979); second, inbreeding tends to increase due to the limited mating opportunities and reinforces the loss of genetic variability; and the lack of gene flow between several small populations of a species leads to divergence in allelic diversity, which decreases future possibilities of cross-breeding between populations (Brekke, Bennett, Santure, & Ewen, 2010)
Some wild white rhinoceros already show genetic drift occurring between populations (Moodley et al, 2018), and it is likely that this drift is even more pronounced on private game farms, which usually hold smaller populations compared to conservation areas
Summary
The world is in a period of mass extinction (Ceballos, Ehrlich, & Dirzo, 2017) with species disappearing at an accelerating pace. Some wild white rhinoceros already show genetic drift occurring between populations (Moodley et al, 2018), and it is likely that this drift is even more pronounced on private game farms, which usually hold smaller populations compared to conservation areas This emphasizes that farms and national parks need active management of their remaining populations and that existing guidelines on how to select individual animals for translocation and reintroduction. The population was managed in such a way that all territorial males were exchanged on a 10-year basis in order to prevent inbreeding This gave us the opportunity to study the influence of the different traits on the mating and reproductive success of two different groups of territorial males that were introduced sequentially—with removal of the first set of males—into the same population of females. Our study describes the mating system and mate choice behaviour of a managed population of white rhinoceros, which is representative of most isolated rhinoceros populations in Southern Africa
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