What happens when the last of a male species dies?

Sudan, the last male northern white rhino, is dead. Now conservationists must embrace the hi-tech methods that could save the species

Afew days back, I woke up to the news that Sudan, the world’s last male northern white rhino, had died. The 45-year-old animal was euthanised at his home in the Ol Pejeta conservancy in Kenya. He was old and he was ill. His time had come. Although this is desperately sad, the stark reality is that his passing makes no difference to those who seek to save his kind.

Despite a brief flirtation with Tinder last year, Sudan had been effectively dead from the waist down for years. His wobbly hind legs made it impossible for him to reproduce. His carers knew this, so veterinarians took the precaution of collecting and freezing away samples of his sperm, along with specimens from four other males who died before him. The hope is that these frozen semen samples can now be used to save the northern white rhino.

If we learn one thing from Sudan’s passing, it should be that it’s time for a new era of conservation, one where traditional methods such as habitat restoration and anti-poaching schemes are supplemented with emerging, hi-tech, state-of-the-art methods including IVF, stem cell science and, dare I say it, gene editing.

To save the northern white rhino, scientists need two basic ingredients: sperm, which they have, and eggs, which are in alarmingly short supply. The two remaining females — Sudan’s daughter and granddaughter — have health problems of their own and are too related to kick-start a genetically viable rhino population. So it’s here that scientists must turn to cellular alchemy.

For years, I’ve been following the work of veterinarian Thomas Hildebrandt from the Leibnitz Institute for Zoo and Wildlife Research in Berlin, Germany. Under his guidance, researchers have been taking skin cells biopsied from northern white rhinos in the past, adding in genes to turn them into stem cells and then coaxing them to become eggs. In this way, dead animals can still pass on their genes. Labgrown eggs will then be fertilised with thawed sperm samples, to create test-tube rhinos which will be carried to term by surrogates from the species’ closest living relative, the southern white rhino.

Conventional conservation methods have sadly failed the northern white rhino. This is its last hope.

Elsewhere, techniques cut from the same cloth could throw a lifeline to other desperately endangered species. In the bird world, sperm from the threatened houbara bustard have been grown inside a chicken and then used to generate live houbara chicks. In the plant kingdom, researchers have tweaked the DNA of the iconic American chestnut tree to make it resistant to an invasive fungus that was driving the species to extinction.

Genetically vibrant

Meanwhile, in the world of mammals, the most daring proposal to date comes from Revive and Restore, an American NGO that has submitted two proposals to the United States Fish and Wildlife Service, the body that oversees American nature. They concern the black-footed ferret, a feisty North American mustelid once all but wiped out by an infectious disease called sylvatic plague.

Today, the animals that exist are massively inbred, but stashed away in vats of liquid nitrogen are the cells of wild ferrets that died without breeding.

The first part of the plan is to use these cells for cloning, creating new genetically vibrant animals which will then breed naturally and introduce lost genetic variation back into the population.

But there’s no point going to all this trouble if the animals are then set free and die from disease. So the second proposal involves editing the ferrets’ DNA to make it plagueresistant. If the two proposals are accepted and they work, it will make conservation history. What is learnt from the black-footed ferret could then be applied to countless other vulnerable species in need of assistance.

We live in the midst of a global biodiversity crisis, yet despite the best intentions of the many brilliant, committed individuals who work tirelessly to stem the tide of loss, we sometimes find ourselves fighting a losing battle. Of course Sudan’s passing should be a time for reflection, but it is also a time to look to the future.

Conservation needs to move out of its comfort zone and seize developments from the worlds of genetics and cell biology. Many conservationists will not like this. Conservationists are, by and large, a very conservative group, yet the fact remains: there are intractable wildlife problems that cannot be solved using existing methods. Times are desperate. It’s time for conservationists to embrace desperate measures. Helen Pilcher is an author, science writer, presenter and comedian.

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