The Cape Mountain Zebra stallion snorted his warning and positioned himself in front of his herd. He was fully alert and stood his ground while his herd retreated. Once they had travelled a short distance away, the three females also turned and stood motionless, watching with curiosity and shielding their foals with their bodies. We were ready for them and immediately started shooting. We were aiming for every individual in the herd. But we did not want trophies. We wanted stripes; photographic shots of every animal to add to a database for the population.
De Hoop Nature Reserve in the Western Cape is home to one of the most important populations of Cape mountain zebra. The animals have greater genetic variation than any others alive and are vital for the long-term survival of the subspecies. Cape mountain zebra were once widely distributed in the mountains of the Cape Province, but by the 1950s the subspecies was almost extinct. As a result of hunting and a greater demand for pasture for livestock, the world population had been reduced to less than 80 animals in five small areas of the Eastern and Western Cape. Fortunately, following a number of focused conservation initiatives, the population now numbers approximately 1600. Nevertheless, the Cape mountain zebra are still listed as Endangered by IUCN (The World Conservation Union).
The main objective of the IUCN Species Action Plan for the Cape mountain zebra is to ‘build up numbers to a target of 2500 as quickly as possible’. This requires that existing populations are monitored and managed efficiently to ensure that numbers are increasing. Also that once particular populations are large enough (over 100 animals), some individuals are translocated to new conservation areas. Animals are translocated for two reasons: the first is that areas of protected suitable habitat are rarely large enough to sustain high numbers of Cape mountain zebra; the second is that by geographically separating animals, conservation managers avoid having ‘all their eggs in one basket’. This helps to protect against disastrous events such as a fatal disease infecting the population.
There are three natural populations of Cape mountain zebra that remain today. These are in Mountain Zebra National Park near Cradock, Kammanassie Nature Reserve and Gamkaberg Nature Reserve, both in the Western Cape. There are an additional 30 new populations that have been founded from translocated individuals. The majority of these animals have originated from Mountain Zebra National Park; this means that over 91% of all Cape mountain zebras alive are related to animals from this one population. The De Hoop population is the only one founded from animals from two of the natural populations, namely Mountain Zebra National Park and Kammanassie Nature Reserve. Ten animals were introduced to De Hoop in the 1970s. It is the unique mixture of these animals that makes the population so important in terms of genetic variation and why it is vital that the population is managed effectively.
Despite the importance of the De Hoop Cape mountain zebra, only very limited data had been collected on the population since 1999. The result was that by 2004 conservation managers did not know the total number of animals in the reserve and could not develop efficient management strategies for the population. It was with this in mind that in 2004 a project began to re-establish long-term population monitoring of the Cape mountain zebra in De Hoop. The project is run through Durham University in the UK in collaboration with CapeNature, who are the primary custodians of the conservation land protecting Cape mountain zebras. Funding for this important project comes from the Darwin Initiative in the UK.
As Project Officer, my first task was to determine the status of the population. Training the field rangers was paramount to the success of the project and so I have taught them to carry out regular monitoring of the population and to collect specific information about each herd and every individual in the herds that they find. This includes the location of the herd and the identity of each individual. The rangers record the information using CyberTracker (www.cybertracker.co.za). Also, in order to update the population database, I had to ensure that every individual in the population was photographed.
Finding Cape mountain zebra to monitor is not easy. They are wary creatures and all too often shadows in the distance would turn out to be nothing more than a clump of bushes. Two of the De Hoop field rangers and I had been driving through De Hoop on a weekly ‘zebra patrol’ when we had spotted dark shapes on a hill in the distance. We had moved closer in anticipation, wondering whether they would be a herd of Cape mountain zebra, a herd of grazing eland or just more bushes. Then, as one animal looked up, we realised we had found a Cape mountain zebra stallion with his herd - it was not his stripes that gave him away, but the unmistakable shape of his head and large ears.
Although the characteristic black and white stripe patterns of zebras look very distinct (and have resulted in their nickname ‘horses in pyjammas’), they provide very good camoflage. This is particularly the case in rocky mountain habitats where mountain zebras typically live and where they become almost invisible. Mountain zebras appear stripier than the Burchell’s or plains zebra, the more common species of zebra in Southern Africa. The stripes on a mountian zebra are closer together than on a Burchell’s zebra because they lack the grey ‘shadow’ stripes; they also have stripes all the way down their legs and what is known as a ‘grid iron pattern’ across their rump. The Cape mountain zebra is slightly smaller than the other subspecies, the Hartmann’s mountain zebra, which is found mainly in Namibia. The few small populations of Hartmann’s mountain zebra in South Africa pose a potential threat to the much rarer Cape mountain zebra because the two subspecies can hybridise. The same is true for horses and donkeys and it is vital than none of these animals come into contact with Cape mountain zebras. This is also important because it will help to prevent the spread of diseases such as the sarcoid virus to the vulnerable Cape mountain zebra.
Whilst the stripe pattern makes the task of spotting the De Hoop zebras more challenging in an area of 60327ha, they are very helpful in another way. Every individual has a unique stripe pattern, which, just like a fingerprint for humans, can be used to determine which zebra is which. This means that individuals can be monitored through out their lives providing information such as the number of offspring they produce and how long they live.
As soon as we had moved close enough to be able to distinguish the stripe patterns of the herd that we had spotted on the hill, the field rangers had taken out the telescope, camera and file containing photographs of all the known individuals in the population. By comparing the stripe patterns of each of the adults in the herd to those in the file, the rangers established that this herd was an unknown breeding herd, which would add to the total population number for the reserve! This is when it was time to start shooting with the camera, because it was vital that photographs of both sides of every individual were taken before they ran away. This is easier said than done; Cape mountain zebra do not often stand side-on waiting for their photograph to be taken! Fortunately, these animals were feeling cooperative and with a bit of patience we got all the photographs that we need.
By the time the rangers have finished recording the information needed about the new herd, it is time for us to head back to the office. Just before we get there, two Cape mountain zebras trot across in front of the vehicle. They are immediately recognised; the two males, which form what is known as a ‘bachelor’ herd, are often seen near the office. Bachelor herds consist mainly of animals that are not yet old enough to start breeding or have past their breeding prime. Most animals in bachelor herds are male, but there may also be some females in the herds. Individuals frequently move between bachelor herds and once they are old enough they will form a breeding herd. Breeding herds, which consist of a stallion and up to five females and their young, are much more stable than bachelor herds. Once females have joined a breeding herd they tend to stay together for life. Stallions on the other hand may lose their breeding herd to a stronger male, in which case the displaced stallion re-joins the bachelor herds.
Once the rangers have finished recording data on the two bachelors we return to the office, where they download the information collected during the day onto the main computer. All of the data and photographs of individuals seen in De Hoop over the past year and a half of monitoring have been used to update the population database. The result is that the conservation managers now know a lot more about the status of the De Hoop population. Thirteen births and eight deaths have been recorded during the past 18 months, which means that the population is now close to 100 animals. Although this tells us that there has been an increase in the population since 1999, it is not as positive as it sounds. Males now out number females and the population growth rate has slowed. This information has important implications for the management of the population. It suggests that it may be time to translocate some of the animals to new conservation areas to allow the remainder to continue breeding successfully. This will also help to protect the genetic variation of the population. The IUCN Action Plan states that a minimum of 14 animals, in favour of females, should be introduced to a new area in order to give the new population a good chance of becoming established and of increasing. This means that the De Hoop males will need to be mixed with animals from Mountain Zebra National Park (which has 350 animals), further increasing genetic variation. Any area selected for new populations must contain enough suitable habitats to support at least 100 zebras in the future.
A few months later and I am out monitoring Cape mountain zebra with the De Hoop staff again and about to shoot more individuals, again with harmless camera equipment, but this time from a very different angle. In fact at times I am not even sure what angle, as I try to focus on the animals. One moment the horizon is where I expect it to be and the next I am struggling to work out which way is up as we turn and drop closer to the herd. We are flying over the whole of De Hoop and neighbouring Denel Test Range by helicopter, hoping to count every Cape mountain zebra and as many of the other large animals as possible. Other species we are looking for include bontebok (another rare subspecies), eland and kudu. At the same time as carrying out population counts, we are taking photographs of all of the Cape mountain zebras to determine whether individuals can be identified from photographs taken from a helicopter.
Once the first mission of the Darwin Initiative project had been completed and the De Hoop Cape mountain zebra were being monitored regularly, the second phase could begin. This was to involve a lot more counting of zebras. For the past 30 years, large mammals within CapeNature reserves such as De Hoop have been counted by field rangers driving set routes through the area once each month. However, results from counts up until 1999 indicated that it was not providing accurate population numbers for Cape mountain zebras for which exact numbers were known. This suggested that counts for other species were also inaccurate. Therefore, the aim of the second phase of the project was to determine the most efficient way to count populations of large mammal in Western Cape reserves. The idea was to use four different methods to estimate the number of Cape mountain zebra in De Hoop and to compare the results to the known population number. The methods being tested were: the existing ground count by field rangers, a more rigorous ground count, an aerial count and the fourth, rather than counting actual zebras, involved counting their dung piles to estimate the number of animals. The results would provide valuable information to help develop monitoring and management strategies, not only for Cape mountain zebra, but for all large mammal species within De Hoop and other Western Cape Nature Reserves.
By the end of the helicopter census we had flown a total of 860km, had been flying for almost seven hours and had counted all except eight of the Cape mountain zebras in the area. This count, which was at the end of winter, was a great improvement on the count using the same method at the end of the summer. In March, less than half of the population was counted. The more accurate count was likely to be down to the fact that at the end of winter, more animals were using the grasslands making them easier to spot and count from the air. The aerial census at the end of winter provided much better coverage of the area than the existing monthly ground count by rangers and so more reliable population estimates for Cape mountain zebra, eland and springbok (also ostrich). Counts for bontebok were similar using these two methods. The more rigorous ground count provided fairly accurate population estimates, but required a large amount of effort; the same was true for the dung pile count. This means that these methods are not feasible for use in CapeNature reserves where manpower is limited.
An annual aerial census at the correct time of year provides a fairly accurate population count for Cape mountain zebra. However, in a reserve such as De Hoop where a more intensive monitoring programme is also feasible, a combination of these methods should be used to monitor the population. More regular monitoring not only provides an accurate population number, but also more detailed information about the population such as the number of males and females and the number and timing of births and deaths. Such information is vital for the development of effective management strategies for a population. This is particularly important for a high conservation priority species such as Cape mountain zebra.
The De Hoop field rangers have now been successfully trained to carry out efficient regular monitoring of the Cape mountain zebra and the population database has been updated with all of the animals in the reserve. This means that monitoring of the population can continue for many years to come. As a result, the status of the population will constantly be updated, enabling conservation managers to make informed management decisions. Their goal is to ensure that the De Hoop population continues to reproduce at a healthy rate and that the correct number and individuals are translocated to new conservation areas.
Due to the success of the population monitoring programme in De Hoop, staff from Gamkaberg and Kammanassie Nature Reserves are now being trained to monitor their Cape mountain zebra populations more efficiently. Again, this will enable conservation managers to identify how best to manage these natural populations so that they continue to increase in size. It is hoped that the populations will reach 100 animals so that individuals can be translocated to found populations with animals from Mountain Zebra National Park and De Hoop. It is only by ensuring that populations continue to grow so that the IUCN’s target of 2500 animals is reached (and exceeded) and by mixing animals from particular populations to improve the genetic variation that managers can secure the long-term survival of the charismatic Cape mountain zebra. This will allow people to continue ‘shooting stripes’ for many generations to come……with harmless photographic equipment of course.