Tracking Grevy's Zebra: Lewa and Beyond
Grevy’s zebra (Equus grevyi) are the most endangered zebra species: in the late 1970s approximately 15,000 individuals remained but it is believed that there are now only around 2000 (1700 – 2400) left in the wild.
Today, Grevy’s zebra are found in southern Ethiopia and northern Kenya, having retreated from an historic range encompassing much of the Horn of Africa. Within the vast complex of community land and conservancies, national parks and reserves, not to mention Urban areas making up the north of Kenya, the Grevy’s zebra continues to adapt in an ever more sedentary, human dominated, landscape. Approximately 13% of the remaining population takes refuge in the secure managed wilderness of Lewa Wildlife Conservancy near Isiolo.
Lewa’s small but vital population of approximately 350 is nestled at the southern limit of the Wamba area, between more widely distributed sub-populations in Laikipia and Laisamis. Movement between safe areas for the Grevy’s is fraught with risk, including large carnivores, dry savannahs, poachers and the growing pressure from expanding human populations and their livestock. Understanding these movements is essential to planning conservation measures, which will secure the species into the future.
As part of the national strategy to conserve the Grevy’s zebra, Lewa and Marwell Wildlife, in partnership with the Grevy’s zebra Technical Committee (GZTC) have been embarked on a telemetry study using radio collars to follow individual Grevy’s zebra on their travels throughout the Lewa conservation landscape for the past 6 years.
By placing GSM (Global System for Mobile Communication) radio collars on a few key individuals, the GPS (Global Positioning System) device in the collar locates the zebra to within 10m and uses the mobile phone network to beam information to the central server in Nairobi, where researchers can access it.
At the same time we use camera traps strategically placed at wildlife corridor gaps in Lewa’s boundary fence, which allow the zebra and other wildlife to pass in and out of the conservancy and it’s neighbouring lands. There are now about 30 radio collared zebra being monitored and having their collars replaced and removed in a carefully managed study.
You can follow some of these individuals on a smart-phone app called MiSavannah, available on the app stores for Google and iPhone. The app features elephant, lion and vultures as well.
On the 5th of June this year, we placed a new collar on a zebra male who is regularly seen commuting to the north of Lewa. Several times a week the male moves out of Lewa into the adjacent Leparua Community Conservancy. Having observed the male for almost three years now, we have come to know him by a feint scar he carries on his right flank, between his pelvis and ribs.
On the 5th however we were to get to know him more intimately and in a somewhat alarming way. We’d seldom seen the male in the flesh as his movement were always well concealed in dense acacia thorn scrub, so we relied on photographs taken by remote cameras at night, as he passed through the fence gap.
But on this day we were determined to get closer to him, close enough to immobilise him with a dart and fit a radio collar. We were keyed up on this occasion, as this male had long intrigued us as he disappeared to the north under cover of night and returned each day just before the dawn. Where did he spend his evenings and what was the attraction, which drew him out of Lewa’s safe haven and into the dark north?
As we observed him through binoculars that morning we noticed a “thorn” protruding from his flank. It was hard to see, but visible as he turned side on, meandering away from us through the bush. We radioed for the vet to come and immobilise him and advised that he may need to treat a minor wound and some infection.
The vet arrived and after some time managed to bring the male down with his dart. As we approached him, lying safely on his side we saw nothing untoward. But as soon as we raised him upright, on his haunches, it was clear that this was no thorn in his side. A thin, toughened spiral steel shaft protruded approximately an inch from an old wound, largely healed, and only slightly weeping.
The vet set to work immediately to extract the spike and we quickly realised that it must have a barbed tip and would not easily be released from the tight scar tissue that had encased it over many months.
After a delicate operation, lasting well into half an hour, the weapon emerged coated in clean bright red blood, but intact. Consulting the local men working with us we were informed that this was a Turkana arrowhead, commonly used in hunting large mammals. The metal tip and shaft are made from heavy gauge toughened steel wire, typically harvested from power line stanchion cables. Using a tempering fire a broad, barbed head is beaten out of a strand of the wire, and its shaft twisted to increase its tensile strength. The arrow is fried from a hard wood long bow with the head in a vertical position to maximise the chances of penetrating between the ribs of the quarry. As the animal flees, gravity and its forward motion drag the heavy shaft downward in a twisting motion that locks the had in place between the ribs ensuring it stays in it’s marque.
Our male Grevy’s zebra had survived this and lived with the impediment for a number of years already, earning him the moniker, Mshale, meaning Arrowhead, in Kiswahili. Now with his collar fitted and beaming data to us every hour well not only be able to track his progress through the dense bush-veld he loves, but be able to keep a close watch on his wound as it heals by re-locating him frequently.
We have been using telemetry (radio collars which are regularly re-located) since 2006, and hope to continue this effort for the foreseeable future. The fine scale movement data the collars collect is invaluable to the conservation of this highly endangered species.
The radio collars will enable us to better understand the ranging patterns of these remote populations. By understanding the zebra’s movements better we will be able to study the key threats to the species. For example, by finding out how often they come into contact with humans and how much conflict there is over resources like water, we can develop conservation strategies with the local communities to benefit both the wild zebras and the people that live with them. We also want to establish if there are any links between the Kenyan animals and the decreasing Ethiopian populations whose numbers are estimated at less than 100 individuals. The information gained will ultimately help provide employment opportunities as better-managed Grevy’s zebra populations have the potential to increase tourism.
The information we hope to gain will provide insights for a number of questions, including among others:
• Identifiying of conservation hotspots
• Describing seasonal use of the landscape by the Grevy’s zebra
• Daily, weekly and monthly ranging behaviour
• Explaining their access to and use of water
• Defining their ranging behaviour under different land management practises
• How their movements change in relation to predator abundance
Reasons for project
The Grevy’s zebra decline is the result of illegal hunting for meat and medicinal purposes, as well as an increasing competition with domestic livestock for resources such as grass and the already limited supply of water in these drought prone countries.
This project is a great opportunity for us to reduce the threats to the endangered Grevy’s zebra whilst at the same time strengthening local community livelihoods.
Grevy’s zebra are a key component of community-based tourism in northern Kenya and safeguarding this species will greatly enhance opportunities for community development.