REPORT ON THE AERIAL GAME CENSUS OF THE NORTHERN TULI GAME RESERVE, BOTSWANA. Compiled by J. Selier Mashatu Game Reserve August 2008.

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1 REPORT ON THE AERIAL GAME CENSUS OF THE NORTHERN TULI GAME RESERVE, BOTSWANA Compiled by J. Selier Mashatu Game Reserve August 2008 Introduction No form of wildlife management whether it is the establishment of hunting or cropping 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. Reliable game counts are one of the cornerstones of effective wildlife management. It is important that counts are repeatable in order to pick up on reliable trends in population growth. Several methods of game counting exist and the method of choice is determined by the size of the area, habitat types, game species to be counted, manpower and of course cost. Within the Northern Tuli Game Reserve total aerial counts have been conducted since The objective of a total game count is to locate and count every animal in the census zone. There is thus no sample error attached to the final estimate of 1

2 numbers. There are however other sources of error and bias when conducting a total aerial count. These are (i) failing to search the whole area; (ii) failing to locate all the animals and (iii) failing to count all animals accurately. The above errors can be minimized by properly planned strip widths, controlling the height and speed of the aircraft and using experienced counters. An aerial survey of the Northern Tuli Game Reserve (NTGR) was undertaken from the 2 nd 4 th of August The purpose of the survey was to determine the population totals of the various herbivore species occurring within the reserve. Note: Predators were not counted. Thirteen previous surveys of a similar nature have been undertaken (1984; 1986; 1987; 1988; 1989; 1991; 1993; 1995; 1996; 1997; 1999; 2001; 2007). Data from these counts are invaluable to the reserve. The longer a database is running, the more valuable and useful the data becomes. This survey was part of a regional elephant (only) survey involving two other aircraft simultaneously flying sectors adjacent to the Northern Tuli Game Reserve in Botswana, South Africa and Zimbabwe. The area surveyed is bordered by the Limpopo River in the south, the Shashe River in the east, the Tuli Circle in the north the Tuli Back line veterinary fence in the west and the farm Oerwoud (Redshields) in the south west. The latter farm has only been included in the counts since Methodology Figure 1: Limpopo Valley airfield A total count of all herbivore species was conducted using a Cessna 206 fixed wing, six seater aircraft on the 4 th of August An average height of 250 ft AGL was 2

3 maintained at an average airspeed of knots. Aircraft flight lines over Notugre were predetermined and GPS coordinates of the end points of each transect were programmed into the GPS. Transects run across the full width of Notugre and surrounding areas (if applicable) in a North/South direction. To achieve 100% coverage, transects were placed on every 28 Seconds of latitude (± 800M apart). Figure 2: The Transect surveys in the Notugre giving 100% area coverage The entire area was covered in three flights of approximately three, three and two hours respectively; flying parallel transects 800 m apart. Census strips of 400 m either side of the aircraft were counted. Markers were placed on the windows to indicate 200 m and 400 m sections and calibrated for each observer individually. A pilot, navigator and four counters were used. The pilot, navigator and one of the counters had extensive experience in game counting, while the other three counters had little or no previous experience in game counting. The team for the general game count were Raymond Steyn (Pilot), Cathy Greaver (navigator); Bruce Petty (Charter), Nick Hiltermann (Tuli Lodge), Jeanetta Selier (Mashatu) and Guy Williams (Mashatu) as counters. A data capture computer program supplied by SANParks was used and accurately recorded the numbers and the distribution of the animals as they were 3

4 entered. This gave us an accurate distribution of the game that we counted. It also had an added benefit of recording the exact track that the aircraft flew so that one could verify that the transect widths were correct and flown accurately. The correction factor used is determined based on the probability of the percentage of the population sighted during the count and is based on Kruger National Park experience. A total aerial count of the elephant population within the Central Limpopo River Valley was conducted on the 2-3 rd of August. The results of this count will be presented in a separate document. Results The operation went smoothly and our objectives were achieved. Weather conditions during the general game count were good with little to no cloud cover. A wind velocity of up to 36 knots was experienced at times during the count. Whilst conducting the elephant survey in the Tuli Circle general game was counted (Table 1). The count was, however, done at 500 ft with a strip width of 1000 m. The figures reflected are thus not an accurate reflection of total numbers of game within the Circle but a rough indication of what was observed during the count. The census data for the Northern Tuli Game Reserve, including herd size distribution, is summarized in Table /90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 06/07 07/08 MJ TK Pontdrift Nitani Charter LVA Figure 3: Rainfall comparison for six stations within the Northern Tuli Game Reserve from 1989/1990 to the 2007/2008 season 4

5 Table 1: Census totals Aerial survey of the Tuli Circle (August 2008) 2008 Correction 2008 Factor Impala Wildebeest Zebra Eland Giraffe Kudu Table 2: Census totals Aerial survey of the Northern Tuli Game Reserve (August 2008). Total % Corrected Tot Ave/ STDEV Group Size distribution Counted Pop Total Obs Herd Impala Wildebeest Zebra Eland Giraffe Kudu Waterbuck Warthog Elephant* Ostrich Steenbok 8 Duiker Bushbuck Ground h/b Baboon tp Hyena Jackal Lion Bat eared fox * Elephant numbers include Mapungubwe Counting probability is based on experience in Kruger National Park. Discussion During the 2004/2005 season the reserve experienced yet another drought with rainfall figures as low as 86mm measured at Pont drift border post for the season. The past two rainy seasons have been markedly better with 301 mm and 293 mm rain measured at Pont drift border (Appendix A). Even when comparing rainfall figures within the reserve large fluctuations can be observed between different locations over the same period of time. 5

6 There has been an increase in the majority of the game species counted this year compared to the 2007 game count. Number fluctuations for each species will be dealt with individually (Appendix B all game count data). The increase in animal numbers can mainly be attributed to the better conditions on the reserve after the drought of 2004/2005. Impala Count data for the last two aerial counts show a decline in impala numbers. The sharp decline of 32% shown in the 2007 game count can be explained by the drought of 2004/2005 but this would not be a reason for a further decline of 32% during It is my opinion that the majority of the groups were located during the 2008 count, but that group sizes during the game count (2008) might have been under estimated. There were several large herds encountered and as been shown the counting error is larger with larger groups encountered. This does not rule out the fact that impala numbers have been declining over the past few years and care should be taken when determining cropping quotas. There is also a possibility that herds could be moving into the Tuli Circle as well as long the Limpopo River further into the Tuli Block. The distribution and group sizes of all groups encountered are presented in figure 3. Even though some groups were observed within the mopane veld the majority of the herds counted were distributed along river courses and drainage lines. Wildebeest Wildebeest numbers increased by 157% from the pervious count conducted in It is likely that wildebeest numbers where under estimated in 2007, but does not rule out the possibility that the numbers went down from 2001 to 2007 as a result of the drought in 2004/2005. When comparing the data from the 2001 and 2008 count, a 19.5% growth is shown in the wildebeest population over a period of seven years. The wildebeest distribution and group sizes are shown in figure 5. 6

7 Figure 4: Impala numbers and distribution during the 2008 game count 7

8 Figure 5: Wildebeest numbers and distribution during the 2008 game count 8

9 Zebra A similar trend is seen in the zebra numbers. If the data of 2007 is used the increase in zebra numbers is 116%. If, however, the count data of 2001 is used there is a 37% increase in the zebra numbers over a seven-year period. Group size and area distribution is presented in figure 6. Eland There was a sharp increase in the eland numbers from 2007 to 2008 (39%). Eland numbers are however still lower when compared to the 2001 figure counted. It is possible that the eland numbers were over estimated in 2001 but it is also possible that limited resources during the years of very low rainfall since 2001 caused a decline in the eland numbers. Movement of eland out of the reserve and into the Tuli Circle cannot be ruled out and very likely. Figure 7 shows the group size distribution as well as overall distribution of eland on the reserve. Giraffe Giraffe numbers increased by 14.4% since the 2007 count and is still lower than the total counted in 2001 (218). During the aerial survey of the Tuli Circle 36 giraffes were counted. Adding this figure to the count data of 2008 the total adds up to 243 giraffes in the area. Giraffe distribution within the reserve is shown in figure 8. Kudu Kudu numbers are up by 63% from the 2007 game count but still significantly lower than any of the counts prior to The distribution and group sizes for kudus during the 2008 count are presented in figure 9. Waterbuck Waterbuck showed a sharp decline from a 100 in 2007 to only 26 counted in the 2008 count. Sightings of waterbuck were within the Limpopo Riverine and it is possible due to the low visibility within the riverine that several waterbuck groups were missed. Waterbuck are, however very susceptible to droughts and a slow recovery from 2005 is likely. 9

10 Figure 6: Zebra numbers and distribution during the 2008 game count 10

11 Figure 7: Eland numbers and distribution during the 2008 game count 11

12 Figure 8: Giraffe numbers and distribution during the 2008 game count 12

13 Figure 9: Kudu numbers and distribution during the 2008 game count 13

14 Conclusions The majority of the species counted showed an increase when compared to the 2007 count. The decline in impala numbers is possibly a result of undercounting of the larger groups observed during the 2008 count. Kudu and waterbuck numbers are a concern and seem to be very low throughout. Fluctuations in numbers for specifically the larger migratory species might be as a result of individuals moving into the Tuli Circle. If there is a persistent high hunting pressure on these species in the Tuli Circle it can account for the large fluctuations seen in the Northern Tuli Game Reserve numbers. The Tuli Circle effectively serves as a sink with the reserve continuously filling the vacuum created by hunting within the Circle. Comments and recommendations In order for the surveys to have any meaning to the reserve and the TFCA in future it is important that we keep the survey team consistent. The more experience the counters have in counting animals the more accurate and reliable the data will become. It is therefore important that individuals decide whether they would like to be part of the counting team, but will then have to show commitment in being available for the counts. The reserve should aim at setting dates well in advance to assist members in opening up their schedules. It is further important that the counts be conducted over more or a less the same period every year to keep the data consistent. Regardless of the more recent problems with obtaining enough counters for the aerial count it is my belief that the counts are vital and the data obtained very valuable. This is a view shared by Dr Ian Whyte. With counts being conducted since 1984 the reserve has built up an amazing database on population dynamics within the area. If we can improve our counting ability (which has already improved since last year) the data will be invaluable for future management and especially in light of the SL-TFCA development. A very detailed census instruction document was drawn up by Raymond Steyn and will assist both pilots and counters in future with planning and conducting aerial counts in the reserve. The majority of the more recent counts were conducted over the July/August period. August in general is a very busy month for all the tourism operations. It is suggested that the aerial counts be scheduled as far as possible in the last two weeks of July, preferably during the last week for a three-day period. 14

15 Looking at the data from the Tuli Circle it is suggested that the Tuli Circle be included in the general game count of the Northern Tuli Game Reserve. Mapungubwe already conducts a game count later in the year. Combining the data from both the Mapungubwe counts and a combined count in NTGR and Tuli Circle will give us a far better understanding of number fluctuations within the area. Funds for counting the Circle will however have to be sourced prior to the count. The data capture program used during the game count was a great help. The program enabled us, while flying, to determine whether a specific group of animals had already been counted and on the ground it gave us the ability to plot the distribution of each species independently. We now have numbers as well as an accurate distribution of each species on the day of counting. It is suggested that the program be used each year for the general game count. Acknowledgements A word of thanks to Naledi and Raymond Steyn for accommodating participants in the aerial count, Pete le Roux for sourcing and collecting AVGAS for the aerial count, Nick Hiltermann for his organisation, Dennis Summers and his airfield team for always being ready and waiting to help with the refuelling of the planes. A special 15

16 word of thanks to Raymond Steyn for his superb flying, Cathy Greaver (SANParks) for navigating and the counters Guy Williams (Mashatu), Nick Hiltermann (Tuli) and Bruce Petty (Charter). Our thanks to Raymond Steyn for the comprehensive count instructions document for the reserve. References CESVI, Concept paper for the Zimbabwe component of the Limpopo/Shashe Trans Frontier Conservation Area. HARRISON, M.S.J Notes on the origins of the dry zone of the Limpopo Valley. South African Journal of Science 80: LE ROUX, P.G Results of the 2001 aerial game census Northern Tuli Game Reserve, Botswana. July MCKENZIE, A.A Co-operative hunting in the black-backed jackal Canis mesomelas Schreber. PhD thesis University of Pretoria, Pretoria. 16

17 Appendix A: Rainfall data from Station [ ] Pontdrift (Coordinates S and E) from 1980 to (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Season

18 Appendix B: Aerial game census data for the Northern Tuli Game Reserve from 1983 to % Pop Impala Wildebeest Zebra Eland Giraffe Kudu Waterbuck Warthog Elephant* Ostrich Steenbok Duiker Bushbuck Ground h/b Baboon tp Hyena Jackal Lion B/e fox * 2001 first year the farm Oerwoud was included in the game census. 18

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