African lions might appear invincible, but the King of the Jungle is more vulnerable than you may think. Human activity likely drove the lions in Zimbabwe’s Savé Valley Conservancy to the brink of extinction before the introduction of new individuals helped to rescue the population.
Despite the growth in numbers, researchers suspected that the lions’ difficult past could have left them with underlying genetic weaknesses. Bettine Jansen van Vuuren, Director of the Centre for Ecological Genomics and Wildlife Conservation at the University of Johannesburg, South Africa, and Rosemary Groom, Field Projects Coordinator at the African Wildlife Conservation Fund, Zimbabwe, with colleagues, studied the genetics of this population. I interviewed Jansen van Vuuren and Groom via email to find out more about their investigation and findings.
What led you to study conservation genetics?
BJvV and RG: An increasing number of species are threatened by human activity. I was motivated by seeing firsthand how inaccurate and insufficient data can hamper conservation efforts. I find it very humbling and rewarding to be able to contribute to the field.
The African lion is an iconic species. Why is it under threat?
BJvV and RG: The African lion is mostly threatened by habitat loss and direct conflict with humans. As a top predator, the species is persecuted because it is seen as a threat to human life and to livestock. More recently, the expansion of human-occupied areas and of fenced land has eroded the lions’ habitat.
Your study focused on a population in Southern Zimbabwe, the Savé Valley Conservancy lions, which is recovering after the introduction of new individuals. Given this growth, why did you have concerns about the population’s genetics?
BJvV and RG: We knew that the founding population here comprised just a few individuals, and experienced a severe bottleneck. Unless genetically distinct lions had naturally entered the group, this meant that all the lions in the area were likely to be closely related, sharing a very small gene pool. We were therefore concerned about the possibility of the lions being inbred. A lack of genetic diversity can reduce the ability of the population to adapt to a changing environment, to produce healthy offspring, and in general to survive and to grow, so it was an important question to investigate.
To study the genetic diversity of the lions, you obtained DNA samples from 42 individuals. How did you manage this?!
BJvV: Rosemary Groom has dedicated much of her life to protecting wildlife including lions in the Savé Valley Conservancy. We were able to take advantage of her expertise to obtain the samples. No animal was tranquilized specifically in order to obtain genetic samples. Instead, we collected blood and tissue samples over several years from lions that had either died or that we had tranquilized with darts for fitting of tracking collars, snare removal or veterinary intervention.
Groom working with an immobilized lion
What did you find out about the Savé Valley population’s genetic diversity?
BJvV and RG: We were concerned, but unsurprised, to find low levels of genetic diversity in the lion population in the Savé Valley Conservancy, as compared with other wild populations. Importantly, we also found that these lions were genetically differentiated from other lion populations. It is therefore crucial that this population receives our protection to prevent the further loss of genetic diversity.
Why do you think these lions are so genetically different from nearby populations?
BJvV and RG: When their movements are unrestricted, male lions will usually disperse and join other prides, which maintains genetic diversity. But in this region, high human population densities, fences and human-animal conflict prevent this from happening, essentially trapping a small number of related individuals in a specific region. This leads to inbreeding, and the loss of diversity. In a small population, loss of genetic diversity is accelerated because as allele frequencies randomly fluctuate over time – a process known as genetic drift – the alleles are more likely to be lost from the population.
What do you hope your study might lead to, and what are the next steps for your research?
BJvV and RG: Our work highlights some red flags for the conservation and management of these lions. The next step will be to engage with the Zimbabwean Parks and Wildlife Management Authority to try and implement some of our suggestions, perhaps including the introduction of one or two unrelated males into the Savé Valley Conservancy to supplement genetic diversity. It will also be important to continue monitoring the population to ensure that genetic diversity is maintained. This work on lions also complements our work on wild dogs in the region, as we seek to understand the dynamics of top predators in the region. Ultimately, we hope to contribute to the successful conservation of various Savé Valley Conservancy species.
Research Article: Tensen L, Groom RJ, Khuzwayo J, Jansen van Vuuren B (2018) The genetic tale of a recovering lion population (Panthera leo) in the Savé Valley region (Zimbabwe): A better understanding of the history and managing the future. PLoS ONE 13(2): e0190369. https://doi.org/10.1371/journal.pone.0190369
Images Credits: Ben & Gab; Rosemary Groom