Tuskless Elephants

As the poaching crisis rumbles on, African elephant populations are being decimated. But something strange is also happening to the appearance of elephants. They’re losing their tusks. If you take a safari in Zambia, you’re now far more likely to see an elephant with no tusks than you did back in 1969. 10.5% of females were tuskless back then and that rose to 38.2% by 1989, whilst in the adult male population, tuskless males rose from making up 1% in the early 1970’s to 10% in 1993 [1]. The same is true in Gorongosa National Park, Mozambique and Queen Elizabeth National Park, Uganda. Tusklessness is actually a perfectly natural phenomenon in elephant populations, but it is quite uncommon (only around 3-4% of a population can be expected to be tuskless) [2]. In South Africa, this is even more extreme: 98% of female elephants living in the Addo Elephant National Park are now tuskless! So why are there more tuskless elephants?

herd-elephants-getty.jpg Africa's elephant population has decreased by an estimated 110,000, down to 415,000, since 2006 Getty

Well, this is a modern-day example of evolution in action. Poachers and big game hunters have acted as a lethal and highly effective form of selection by removing tusked elephants from the population. This artificial selection strongly favours elephants without tusks (since they are more likely to survive and reproduce) and so poachers have drastically altered the gene pool in most African populations. However, scientists are still struggling to get to grips with how tusklessness is controlled and passed on.

Tusklessness is clearly heritable, we know that much. Take the Addo Elephant National Park population that is descended from only 11 individuals that were left behind in 1931 because of big game hunting [1]. Eight of these elephants were female and four were tuskless females so the population has been built on using a very small gene pool with a very high proportion of tusklessness. There also seems to be a discrete gene that is controlling tusklessness and inherited by offspring. But why do many of these populations show major changes in females? It seems that this tusklessness gene is sex-linked, in that a tuskless mother will have a tuskless daughter but a tusked son. However, then the genetics of this get a bit more complicated. For example, sometimes males are tuskless too even though it is mostly only tusked males that breed despite poaching. So for now, a simple explanation seems to be a bit of a way off.

Monitoring tusked elephants present in Addo Elephant National Park has also found that tusks recorded in 2008 were on average half the size compared to those adorning elephants 100 years ago [1]. This reduction in tusk size has also been attributed to poachers, killing off older, breeding elephants with the largest tusks. So, will we see elephants reducing their tusk size further because of poaching? And will this be enough to save them? Sadly, these changes occurred over 100 years, which is actually extremely rapid in evolutionary terms but not fast enough to keep up with the unrelenting pace of poaching. Elephants only have years or decades before they could be lost from the African landscape – not enough time for evolution to act for a slow-breeding giant. These changes have also had no effect on the level of poaching. Poachers are so desperate for ivory, that the relative size of tusks is not that important – a tusk (~5.5kg) still represents thousands of dollars (sold at $100 per kg ($45 per pound) to dealers which then sell it for $750 per kg) [2].

However, a lack of tusks seems a fairly good deterrent for poachers – no tusks means no ivory and no money, right? Unfortunately for elephants, not having tusks is bad news. They are a very important part of their day-to-day lives as they are needed to move trees and branches and excavate for food and water. Tusks also function for self-defence, as well as fighting and displaying for mates [1]. Many conservationists consider an elephant without tusks to be a disabled elephant – almost as if we were to lose our legs or arms. But is this a price that has to be paid to ensure elephants survive the current poaching crisis? The trouble is that there are many more issues affecting elephants than just poaching. For example, how will tuskless elephants cope with climate change? If these elephants are poorer at obtaining water and food, then climate change could spell disaster if habitat and water availability is reduced.

All in all, without strong action in dismantling the ivory trade and poaching in Africa, the future for elephants looks bleak and tuskless. If you want to find out more about how you can help – take a look at the links below.