Citizen science reveals increase in Kenya’s Grevy’s zebra population

July 15, 2018

Recently announced results from the ‘Great Grevy’s Rally’ show that there are now around 2,800 Grevy’s zebra in Kenya representing a healthy increase in numbers compared to previous surveys despite the challenging environment.

The Grevy’s zebra is one of seven remaining species of wild equids left on the planet. In the 1970s they roamed widely in the semi-arid habitats throughout the Horn of Africa, and in Kenya, there were over 15,000 individuals. By the late 1980s, their range had shrunk and numbers had dropped to around 4,000 and by the start of this century, only about 2,000 Grevy’s zebras were estimated to remain. 

With large areas to cover, counting Grevy’s zebra has always posed a challenge. As a member of Kenya’s Grevy’s Zebra Technical Committee, the Marwell team was party to discussions leading to a radical change in tactic by enlisting the public to search for Grevy’s zebras and take photographs of their stripe patterns over two consecutive days. By using ‘Sight-Resight’ statistics, scientists were then able to estimate population sizes nationally and by county. Thus, the Great Grevy’s Rally (GGR) came into being in 2016, leading to an estimate of around 2,300 Grevy’s zebra across Kenya at that time. 

Since then, Kenya has been plagued by severe droughts in its central and northern counties where Grevy’s zebra reside, so it was important for us to understand how this might have affected their populations. In January this year, 212 photographers in 143 vehicles, seven motorcycles and four light aircraft participated in the second Great Grevy’s Rally. Collectively, participants covered 25,000 km2 and took 23,000 photographs of Grevy’s zebra, with the Marwell team leading the charge across the large, remote and most northerly part of the species’ Kenyan range. 

The 2018 GGR results were shared for the first time at a black & white themed ball held last weekend in Nanyuki to mark the publication of a new 10-year Recovery and Action Plan for Grevy’s Zebra in Kenya. During the event, Dr. Patric Omondi, emissary for the Ministry of Wildlife and Tourism and the Cabinet Secretary, accepted the GGR census estimates for Grevy’s zebra as the officially recognized numbers for a threatened species. Remarkably, this is the first time that census results from a non-governmental group or consortium have been officially accepted for an endangered species in Kenya. 

Tim Woodfine, Marwell’s Director of Conservation said: “The recovery of Grevy’s zebra in Kenya is a great example of conservation success arising from a clear vision, collaboration and long term commitment. The threats to these magnificent animals still exist and efforts need to continue, but it’s heartening to see what can be achieved”. 

The next GGR is planned for 2020 when once again visiting volunteer citizen scientists will be invited to join local communities, landowners and conservationists to photograph and help monitor the status of these magnificent animals.