Northern white rhino: New hopes for IVF rescue
A new study raises hopes of saving one of the last animals of its kind.
A victim of poaching, the northern white rhino population has been reduced to just two females, which are both unable to breed.
DNA evidence shows the rhino is more closely related than previously thought to its southern white cousin.
Creating rhino hybrids using IVF is likely to have a positive outcome, say scientists, although this option is considered a last resort.
The white rhino split into two divided populations living in the north and south of Africa around one million years ago.
But an extensive analysis of DNA from living rhinos and museum specimens shows the northern and southern populations mixed and bred at times after this date, perhaps as recently as 14,000 years ago.
"Despite the fact that they started to diverge one million years ago, we show that they have been exchanging genes during that period, possibly as recently as the last ice age, when the African savannah expanded and reconnected the two populations," lead researcher Dr Michael Bruford of Cardiff University told BBC News.
"So, if they have been exchanging genes recently, this may imply that they could do so now."
Cross breeding using assisted reproductive technology could potentially act to rescue the northern white rhino from its current predicament, he said.
The northern white rhino was once common throughout the north of the African continent, including Uganda, South Sudan, the DRC and Chad.
Illegal hunting to meet demand for rhino horn caused a rapid decline in the wild, and the rhino sub-species was declared extinct on the wild in 2008.
Earlier this year, Sudan, the last male northern white rhino, died at the age of 45.
Two females are left - his daughter and granddaughter, who live in Ol Pejeta Conservancy in Kenya, where they are guarded around the clock. However, both have health problems of their own and cannot breed naturally.
The southern white rhino is found in southern Africa, including South Africa, Namibia, and Zimbabwe.
Numbers dropped to a few hundred individuals around a century ago, but conservation efforts led to a recovery. About 20,000 exist in protected areas and private game reserves.
What would it take to save the northern white rhino?
The survival of the northern white rhino looks bleak, and relies on last-ditch hotly-debated conservation efforts, which involve IVF and cloning.
A priceless store of frozen sperm from male northern white rhinos still exists, but conservationists are divided about how it should be used.
In July, one team took eggs from female southern rhinos - which number around 20,000 in the wild - and fertilised them with frozen sperm from a male northern white rhino, to create hybrid embryos.
The new study suggests this sort of approach might pay off, given that the two rhinos are closer genetically than once thought.
"We think it improves the chances," said Prof Bruford. "It is difficult to predict what might happen if we cross the two subspecies but given the current options for the northern white rhino it becomes a more viable option, should other approaches fail."
Other options include using frozen tissue from a wider pool of northern white rhinos to generate stem cells that have the capacity to develop into eggs and sperm.
This would avoid diluting the gene pool, but is more challenging to achieve.