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Why is it so hard to get rhinos pregnant?

If you’ve been brought to this article by a Google search or if the question that comprises this headline enticed you enough to follow it here, you clearly feel as if this is a query in need of answering.

There is this impression, not entirely unfounded, that rhino are difficult to breed. This impression is certainly pervasive and shaped in large part by the well-documented difficulties that conservationists have experienced in their attempts to bring the Northern White rhino species back from the brink of extinction.

Certainly there have been difficulties in the Northern White rhino population rehabilitation programme, and exploring those difficulties will form a part of our attempt to answer the question ‘Why is it so hard to get rhinos pregnant?’.

However, in this article we will also make clear that the impression this question is founded on isn’t comprehensively well-rounded and, in fact, the rhino populations extant today can stand as testament to the incredible bounce-back ability of these creatures. If we continue with rhino conservation efforts that is.

The Northern White rhinoceros population rehabilitation programme at Ol Pejeta

Today, there are just two Northern White rhinos alive anywhere in the world. They live at Ol Pejeta conservancy in Kenya and they are protected by a 24-hour guard and a variety of other security measures.

The two remaining Northern Whites are both females – called Fatu and Najin – and, in any case, unable to naturally reproduce because of complications discovered in a veterinarian’s exam. This means that the species is functionally extinct.

The last male Northern White rhino died in 2018. This last male, named Sudan, had lived with the other two females in Ol Pejeta since 2009. They, and another male – Suni –, had been transported to the conservancy from a zoo in the Czech Republic with the hope that their four-strong population, in a more native environment, might be the basis for a population rebound.

That did not happen. Not only do the two females have complications which means they cannot reproduce naturally, but Sudan had an unusually low sperm count. The other male, who died of natural causes in 2014, also failed to sire any offspring.

It’s not entirely clear why breeding attempts were so unsuccessful within this small population of Northern Whites. Initially, human intervention in the hoped-for population rebound seems to have been limited to creating the optimum conditions for the rhinos to procreate themselves.

This was the motivation behind bringing the four creatures to Kenya. Translocating any animal species is not without risks and moving rhinos is very hard. Northern White rhinos are slightly lighter than Southern Whites but they can still weigh up to 2,000 kilograms. This complicates both tranquilising dosage and the simple raw mechanics of the operation.

It was still deemed necessary, however. The hope was that the rhinos’ native East African habitat and interaction with other rhinos would encourage the four translocated rhino to behave more naturally and begin to reproduce. This hope was seemingly rewarded when it was observed that two of the Northern Whites, Suni and Najin, did mate in 2012.

The pregnancy did not take, however. Perhaps this was due to the complications that a vet would later discover inside Najin. Perhaps, Suni, like Sudan, had a low sperm count.

Whatever the reason, it is clear that the attempts to rebuild the populations of Northern White Rhinos from these four creatures was beset by difficulties that could not easily be catered for.

Attempts at IVF followed and sperm samples from Sudan have been stored so efforts are not over in the attempts to bring Northern Whites back from the brink. There has even been success in impregnating a rhino through IVF – a Southern White rhino was impregnated via IVF in 2018; she successfully carried her baby to term.

It is obvious, however, that these four unfortunate creatures –  through an obvious lack of fault of their own and those working to help conserve them –  were not ideal candidates for the role and responsibility of rebuilding an entire sub-species.

The different trajectories of the Northern and Southern White rhinoceros sub-species

Comprising the two African rhino species, are a variety of sub-species.

As you will by now know, there are two sub-species of the African White rhino: the Northern and the Southern. There are notable but minimal differences between the sub-species. Differences in size, weight, skull size and ears are used to tell them apart.

(According to WWF, there are four sub-species of Black rhino. You’ve got the Southern Central Black rhino, the Eastern Black, the South Western Black and the Western black. Like the differences between the White rhino sub-species, the Black rhino sub-species are very similar looking and have only slight differences between them.)

As has been stated, it is the Northern White rhino that is down to its last two individuals. It is quite probably impossible to ascertain what this population stood at at its greatest. Trying to gauge how many were alive in Africa’s wilds today isn’t even a certain science.

Best estimates, however, suggest that in 1960 there were over 2,000 Northern White rhinos in their historic rangeland. That rangeland consists of north-western Uganda, southern Chad, South Sudan, and parts of both the CAR and the DRC.

Of course, the unchecked hunting for rhino horn must have played a part in bringing the population as low as 1960’s 2,000. However, what brought the Northern Whites to their extinction in the wild was the political instability in the region during 1970s and 1980s. They were declared extinct in the wild in 2008.

Though there are no immediate concerns about the extinction of the Southern White rhino, this sub-species was the one that came closest to extinction because of the period of rampant hunting in the 1800s.

While Northern Whites were comparably healthy in the late 1800s, the Southern White was actually thought extinct. For the latter half of the 19th century, many people believed that the Southern Whites had been hunted to extinction until a small population of between 50 and 100 individuals were found in South Africa’s Kwa-Zulu Natal region.

Today, the population of Southern White rhinos is around 16,000. The majority of Southern Whites can be found in just four countries: Kenya, Zimbabwe, South Africa and Namibia. They are still under threat – their population sizes have, in fact, taken a not insignificant hit in recent years as a result of poaching for rhino horn – but this 16,000-strong population all grew out of less than 100 individuals.



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