Some 38 years or longer ago conservationists already had a clear vision with the practicalities that can be encountered with Park Management and saw the necessity to perform game counts.
In "Counting Animals" Norton-Griffith emphasizes:
No form of wildlife management, whether it is the establishment of cropping or hunting quotas, the development of tourism or the demarcation of boundaries is possible without reliable information on the numbers, population dynamics and movements of the animals concerned. This account deals with many of the practical problems that are met with when designing and carrying out a wildlife census. (1)
To get reliable counting figures either for the total number of game in a park or for each species, is of paramount importance. These figures will influence future wildlife and park management plans and strategies.
Different types of counting systems can and are used. Bothma and du Toit claim in "Game Ranch Management" that all systems have strong but also weak points:
"There is no single comprehensive counting technique that is suitable for all the possible types of animals and their habitus. Factors like costs, area size, animals to be counted, type of habitat, available manpower, timing during the year could influence final results." (2)
Various census techniques are described - all varying tremendously in accuracy, time effort, manpower and expenses. Size and habitat structure of the census unit are decisive for the correct choice of method. Besides road strip counts from vehicles and walked transects, aerial surveys and water hole counts present the most common and practical techniques within the Namibian environment.
For remote and large areas as found in Namibia, the only feasible and practical method is quite often an aerial survey carried out by a helicopter or another light aircraft. It is a reliable method to estimate numbers of mainly large bodied mammals that can be easily perceived from the air and allows covering a large area in a short period of time. It is however less suitable for the estimation of small antelope species and predators due to size, camouflage and potential nocturnal activity. Often aerial surveys fail to provide accurate data on population demography such as age classes and sex ratios unless the target species exhibits sexual dimorphism in the presence or absence of horns that can be easily viewed from the air.
While a water hole conducted census is able to make this information accessible, other disadvantages arise: A water hole game count can exclusively be conducted during a certain time of the year namely when no additional water reservoirs are available and animals are forced to gather around artificially provided water-points. Water hole counts are time and labor intense, require numerous dedicated and skilled staff in order to prevent the same (herd of) animal(s) to be counted more than once or missed ("over- and/or undercount" principle). Volunteers are always of great help, but sometimes lack the basic experience that is essentially needed and often suffer from fatigue and exhaustion as game counts last normally for a continuous 72 hours period.
Our chosen method was an aerial survey with a 'Total Area Count', using a GPS incorporated navigation system to come close to an 'all-covered park area flight path', with the most likelihood of getting close to an accurate total number of species count.
Timing of a census if of utmost importance. Because aerial surveys provide the best possible results if carried out during the dry season when animals can be easily seen and are not hidden beneath a layer of green leaves, we chose the month of October with a presently poor leaf coverage (hope and confident that with rain this will change).
To get to the exact count figure is extremely difficult. Multiple factors can influence that figure as for example time of the day. It would be ideal to know the exact number, but a reliable figure - even if not absolutely correct - is more important and of use to follow historic, present and potential future trends. Thus a "repeatable precise count with a same result for the same number of animals" (carries more weight even though that count may be inaccurate due to over- or underestimation of the true numbers and that is with-in limits). (2)
The main object of this year’s game count of the different species and in total was:
1. To follow trend numbers in population size
2. To determine population dynamics
3. To evaluate sex ratios for management purposes
4. To evaluate food biomass availability of different species in a closed system
As this year’s census was the second one with-in the perimeters of the Okonjima Nature Reserve (ONR), performed in a different way compared to the first one done in 2014, comparison of figures should be taken up in a very cautious manner.
The count in 2014 was performed with the aid of a Gyrocopter, flying at a faster speed and at a higher altitude than this year’s count with a helicopter.
This year’s counting span width started at 200 meters to soon be reduced to 150 meters on each side of the counter for better accuracy and accountability.
The Okonjima Nature Reserve was divided into five sections due to various practical factors taken in consideration like ensuring flight continuity, minimize counter fatigue, minimize game crossing in-between flight paths within and between blocks, reducing the flight time resulting in flight costs reduction and the time factor, as this count could not be completed within a day.
The circles indicate an accumulation of one or more species in that specific area, where it was not possible to have an immediate count figure ready on the straight flight line, thus the helicopter had to circle that specific spot to ensure an accurate spot number.
The circles in Fig.1 show distinctly the preferred accumulation areas of one or more game species in that area / spot at any given time depending on the availability of fodder. A strong accumulation of game species in certain areas can result in overgrazing; in particular around permanent water sources. By closing chosen water points, migration into less populated / popular areas containing usable biomass (fodder) can be motivated and thus, the rate of overgrazing decreased. This goes hand in hand with drought, park management and future park strategy planning to ensure food availability and continuity of genetic diversity of the different species.
Figure 1: Five subdivisions of the reserve indicated in different colors, flight path, visual area coverage and game concentration.
Areas absent of circles indicate either very thick bush, mountains terrain with only few individuals of different species seen. The mountain areas with their slopes indicating not only their value as grazing areas (if accessible), but are also a very very valuable and sustainable seed bank supply source to the surrounding grazing areas.
Figure 2: Numbers of game species introduced in 2000 in comparison to game count numbers obtained during game count 2016 and increase in percent [%]
Figure 3: Share of different game species occurring in Okonjima Nature Reserve (ONR) as obtained during the game count 2016.
One of many very valuable positive observation trends, was the increase of the introduced species numbers into the Reserve in 2000 (Fig. 2). All these species were either low in numbers or absent from that area, but historically were present on the ONR area. It is our intention to redo a follow-up aerial game census in one years’ time incorporating and using the same technique and methodology, possibly using two helicopters to complete the count in only one day.
1. Norton-Griffiths, Mike. Counting animals. No. 1. Serengeti Ecological Monitoring Programme, African Wildlife Leadership Foundation, 1978.
2. du P, Bothma J., and J. G. du Toit. 'Game ranch management." Pretoria, South Africa: Van Schaik (2010).