Annual Game Count Olifants West Nature Reserve Balule Nature Reserve 2020
Report Compiled by Paul Allin
Annual game counts are conducted in order to obtain the most accurate representation of the species within Balule Nature Reserve. For many years the same methodology has been employed allowing for consistency in the data and the ability to detect trends over time. In 2019 only half of the regions in Balule opted to do the game count. This year all regions were counted again, however this was done using a different team and following a slightly different methodology. This report is based on the data from the aerial game count and will address the differences that appear compared to previous years.
The area of Boston was included this year in the count, and therefore the total size of the reserve increased. Without know populations in the area prior to inclusion it is hard to know the net effect of adding a new area. For this purpose it is key to look at densities per ha and biomass per ha. These data can then be compared to primary vegetation production to help understand why species increase or decrease in a given year.
Conditions during the count were good, with clear weather and the count was conducted before the first rains. The flight path is shown on the following page in figure 1 (data from the helicopter) and figure 2 (data of counted animals). Figure 2 shows which part of the reserve was flown per day, gaps can be attributed to no animals being counted in a specific location.
A predator call up was conducted across much of the reserve. Olifants West Nature Reserve (OWNR) chose not to participate in the call up due to the limited reliability in gathering accurate data and avoiding counting the same individual multiple times. Furthermore there is research to support the call-ups have a disruptive effect on the spatial distribution of predators across the landscape. For these reasons OWNR collated the predator numbers from the lodges across the region, providing detailed break-downs of the demographics and locations.
Figure 1. Flight path recorded by the helicopter.
Figure 2. Flight path based on the location and date each animal was recorded during the game count. OWNR BNR All Species # kg/ha #/ha # kg/ha #/ha African Wild Cat 0.000 0.000 1 0.000 Buffalo 0.000 0.000 266 2.589 0.005 Bushbuck 9 0.031 0.001 40 0.021 0.001 Crocodile 15 0.000 0.002 29 0.001 Duiker - Grey 6 0.013 0.001 32 0.011 0.001 Elephant 183 79.538 0.021 883 58.449 0.016 Giraffe 43 5.034 0.005 249 4.440 0.004 Hippo 89 15.119 0.010 131 3.389 0.002 Hyena - Spotted 6 0.000 0.001 10 0.000 Impala 1623 8.701 0.188 8326 6.798 0.147 Kudu 64 1.372 0.007 479 1.563 0.008 Leopard 1 1 Lion 0.000 0.000 16 0.000 Nyala 4 0.039 0.000 35 0.052 0.001 Raptor nests 6 0.000 0.001 36 0.001 Rhino - Black 3 0.348 0.000 17 0.300 0.000 Rhino - White 0.000 0.000 41 1.375 0.001 Sable 0.000 0.000 11 0.043 0.000 Sharps Grysbok 0.000 0.000 1 0.000 0.000 Steenbok 4 0.005 0.000 24 0.005 0.000 Warthog 21 0.166 0.002 124 0.149 0.002 Waterbuck 49 1.164 0.006 261 0.944 0.005 Wildebeest - Blue 0.000 0.000 101 0.416 0.002 Zebra 70 2.496 0.008 271 1.471 0.005 TOTAL 2196 114.026 0.255 11385 82.016 0.201 Table 1. Overview of all game counted during the aerial survey in OWNR and BNR.
Table 1 shows the animal numbers counted during the aerial surveys in 2020 in OWNR and BNR respectively, densities in biomass (kg/ha) and individuals (#/ha) are given to be able to compare areas with different sizes. The mean animal mass is taken from Smithers and Skinners (2005). As the aerial census in 2019 only included half of BNR trends over time are only done using these densities as extrapolation of figures is not possible due to very different vegetation types, rainfall and soils.
Within any ecosystem to ensure long-term sustainability, vegetation, herbivores and carnivores need to remain in balance. The data (number, location, and sex of each animal) that these game counts provide is analysed and compared to the veld condition and rainfall to identify imbalances within the ecosystem functioning.
Following 4 years of very dry and drought conditions last season was again slightly above average in rainfall and the veld remained stable. The late rains in April ensured an above average biomass to persist during the winter.
Figure 3 shows the slight decline in carrying capacity from 825.85 in 2019 to 784.57in 2020, with a strong correlation to the precipitation. The increase in floral biomass will have had a significant impact in general health of herbivores and one would expect an increase in populations of most species.
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2000
1500
1000
500
0 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Grazing Capacity (LAU in Olifants West) Rainfall (mm)
Figure 3. Grazing capacity for Olifants West vs rainfall for the past 11 years.
Herbivore demographics
Balule Herbivore demographics can be used as an indicator of the health of an ecosystem. Herbivores can be divided into four classes based on the nature of their feeding strategies: bulk feeders, grazers, browsers and mixed feeders, in line with all ARC reports. A fifth category is also added showing all mega-herbivores, as they are important drivers of ecosystem functioning and change. Each of the mega-herbivores is already included in one of the feeding classes so figure 2 and 3 do not show the mega herbivores separately The ratios between the feeding classes should be taken into consideration, so as to maintain the balance or correct an imbalance.
10.46% 0.70%
7.93%
80.91%
Bulk grazers Selective grazers Browsers Mixed feeders
Figure 4. Distribution of 2020 herbivores numbers in BNR across the feeding classes.
Appendix 1a and 1b give an overview of all the animals per feeding class per region for the 2020 count.
Figure 5 shows the same as figure 2, now animal numbers have been replaced with animal biomass as a more comparable metric between feeding classes. It is clear that there is a huge imbalance between the feeding classes and this has been shown over time in figure 6, including the guideline provided by the ARC. The ration of bulk grazers has continued to drop, mainly as a result of far fewer buffalo this year. Ideally ratio would be manipulated by management using introductions of underrepresented classes and offtakes of the overrepresented classes.
10.46% 0.70%
7.93%
80.91%
Bulk grazers Selective grazers Browsers Mixed feeders
Figure 5. Distribution of herbivores density (ton/Ha) in Balule across the feeding classes.
% of biomass/feeding class 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 2012 2013 2014* 2015 2016 2017 2018 2019 2020 Guidline
Bulk grazers Selective grazers Mixed feeders Browsers
Figure 6. Ratio of feeding classes over time in Balule. *in 2014 only mega herbivores were counted.
Megaherbivores
Megaherbivore species counted during the census are elephant (Loxodonta africana), white rhinoceros (Ceratotherium simum), black rhinoceros (Diceros bicornis), buffalo (Syncerus caffer) and hippopotamus (Hippopotamus amphibious).
A total of 690 megaherbivores were counted across the regions of Balule, up 24.32 % from 2018, Table 3. When looking at biomass, figure 4, there is an increase of 99.04%, predominately due to the high increase in elephant counted, that make up just over 82% of the mega herbivore biomass. Given the fact that both elephant and buffalo are highly mobile species, these changes will need to be compared to the mega herbivore fixed wing data and preferably also to the APNR data, neither of which were available when writing this report.
Mega herbivores Density #/ha Biomass kg/ha
2017 0.0224 59.4963 2018 0.0173 44.7588 2019 0.0137 38.3695 2020 0.0236 66.1028 Table 2. Total mega-herbivore counts per region in Balule.
Mega herbivores 70.0000 0.0250
60.0000 0.0200 50.0000
40.0000 0.0150
30.0000 0.0100 #/ha
Biomass kg/ha 20.0000 0.0050 10.0000
0.0000 0.0000 2017 2018 2019 2020
Biomass kg/ha Density #/ha
Figure 7. Total mega-herbivore biomass (kg/ha) and density (#/ha) in Balule.
The downward trend has reversed drastically, as a result of a large increase in elephant numbers. Elephant are a highly mobile species that travel significant distances in the open system and population figures should be viewed in conjuncture with the rest of the APNR. Unfortunately data are not available for the rest of the APNR. Given the life history, elephants under ideal circumstances can increase 3-5% per annum. They are not really susceptible to predators and therefore any increase beyond this can only be attributed to migration, off-takes or disease.
Looking at the long-term trends, figure 5, shows a significantly different picture to last year, this the result of the sharp increase in elephant and buffalo numbers. Long-term trends are given as numbers per ha to show population density increases rather than biomass increase.
Mega-herbovore density 0.06
0.05
0.04
0.03 R² = 0.2948 0.02 Density #/ha
0.01
0 2012 2013 2014 2015 2016 2017 2018 2019 2020
Black Rhino Buffalo Elephant Hippo White Rhino Cumulative
Figure 8. Multi-year trend in mega herbivore density (#/ha) including trendline. 2019 only including data from helicopter counted regions, not extrapolated data.
Bulk grazers
Bulk grazers are grazers that display no, or a low selection in grasses they consume, generally going for quantity rather than quality of grasses. The species included are: buffalo (Syncerus caffer), hippopotamus (Hippopotamus amphibious), white rhinoceros (Ceratotherium simum), sable (Hippotragus niger), waterbuck (Kobus ellipsiprymnus) and zebra (Equus quagga). 12.0000 0.0250
10.0000 0.0200
8.0000 0.0150 6.0000 #/ha 0.0100 4.0000 Biomass kg?ha
0.0050 2.0000
0.0000 0.0000 2017 2018 2019 2020
Biomass kg/ha Density #/ha
Figure 9. Total bulk grazers biomass (kg/ha) and density (#/ha) in Balule.
This years’ count was significantly higher than the last few years. The downward trend seems to have been halted and slowly climbing. Buffalo numbers are still far below drought and pre drought numbers and this has a major impact on the total biomass of the feeding class. Increasing veld condition should encourage more buffalo to return and as with the comment in the mega herbivore paragraph, should be analysed across the broader landscape not just BNR.
0.07
0.06 0.05
0.04 R² = 0.4727 0.03 0.02
0.01 0 2012 2013 2014 2015 2016 2017 2018 2019
Buffalo Hippo Rhino Sable Waterbuck Zebra Cumulative Expon. (Cumulative)
Figure 10. Multi-year trend in bulk grazer density (#/ha) including trendline. 2014 game count only included megaherbivores, 2019 only including data from helicopter counted regions, not extrapolated data.
Selective grazers
Selective grazers are grazers that display strong selection in grasses they consume, this selection can be in a number of factors such as height or quality of grasses. The species included are: blue wildebeest (Connochaetes taurinus) and warthog (Phacochoerus aethiopicus). Selective grazers are generally more effected by low grass quality due to drought conditions.
As seen in figure 11 the density was strongly impacted during the drought and persisted to decline. This past year has seen significant increase, most notably in the blue wildebeest. This is most likely due to the fact that last year’s count did not include most of their natural habitat. When comparing it to the longer trend the density of wildebeest has been consistent since 2016. Despite last year only including half the reserve there were more warthogs counted than in 2020. This indicates that the decline that has been going on since 2015 has not been halted yet. This species is known as a boom or bust species and they were expected to respond swiftly to favourable conditions.
0.6000 0.0090 0.0080 0.5000 0.0070 0.4000 0.0060 0.0050 0.3000
0.0040 #/ha 0.2000 0.0030 Biomass kg/ha 0.0020 0.1000 0.0010 0.0000 0.0000 2017 2018 2019 2020
Biomass kg/ha Density #/ha
Figure 11. Total selective grazer biomass (kg/ha) and density (#/ha) in Balule.
0.018 0.016 0.014 0.012 0.01 0.008 R² = 0.7964 Density #/ha 0.006 0.004 0.002 0 2012 2013 2014 2015 2016 2017 2018 2019 2020
Blue Wildebeest Warthog Cumulative
Figure 12. Multi-year trend in selective grazer density (#/ha) including trendline. 2014 game count only included megaherbivores, 2019 only including data from helicopter counted regions, not extrapolated data.
Browsers
The species included in this category are: black rhinoceros (Diceros bicornis), bushbuck (Tragelaphus scriptus), duiker (Sylvicapra grimmia), giraffe (Giraffa camelopardalis), kudu (Tragelaphus strepsiceros), nyala (Tragelaphus angasii), Sharpe's grysbuck (Raphicerus sharpei) and steenbuck (Raphicerus campestris). Note that the mega-herbovores are included in the feeding class analysis as they form such a large portion of the biomass in the classes. 10.0000 0.0300
8.0000 0.0250 0.0200 6.0000 0.0150
4.0000 #/ha 0.0100
Biomass kg/ha 2.0000 0.0050 0.0000 0.0000 2017 2018 2019 2020
Biomass kg/ha Density #/ha
Figure 13. Total browser biomass (kg/ha) and density (#/ha) in Balule.
This year the browser numbers picked up following the sharp decline in 2019. Overall however there is a downward trend since 2016. The most notable drop is in kudu numbers, which comprises of the biggest portion of biomass in this feeding class. Giraffe numbers are more stable but also declining. The smaller browsers are not only harder to find, but are also generally only found individually or in pairs. This is seen in a high annual fluctuation in numbers of these species from year to year. When looking at biomass density however these fluctuations are negligible as they represent such a small portion of the browser biomass.
0.035
0.03
0.025
0.02 R² = 0.5856 0.015
Density #/ha 0.01 0.005
0 2012 2013 2014 2015 2016 2017 2018 2019 2020
Black rhino Bushbuck Duiker Giraffe Klipspringer Kudu Nyala Sharpe's Grysbuck Steenbuck Cumulative
Figure 14. Multi-year trend in browser density (#/ha) including trendline. 2014 game count only included megaherbivores, 2019 only including data from helicopter counted regions.
Mixed feeders
Mixed feeders are by far the most numerous species in Balule, both in numbers (81.6%) and biomass (80.9%). Their success can be attributed to both the high saturation of water on the landscape and their ability to utilise both browse and graze. They follow available crude protein in vegetation and will generally swap from grazing to browsing when the quality of graze drops too far. This makes the feeding class very resilient and able to thrive in harsh conditions. The two species in this class are: elephant (Loxodonta africana) and impala (Aepyceros melampus). Impala numbers stabilised during the drought and have risen strongly following a year of average rain. Elephant numbers have risen much more strongly than would be possible from natural population growth and much of this growth must be attributed to migration. These numbers would need to be analysed with the data from the fixed-wing count as well as data from the whole of the APNR.
70.0000 0.2500 60.0000 0.2000 50.0000 40.0000 0.1500
30.0000 0.1000 #/ha 20.0000 Biomass kg/ha 0.0500 10.0000 0.0000 0.0000 2017 2018 2019 2020
Biomass kg/ha Density #/ha
Figure 15. Total mixed feeders biomass (kg/ha) and density (#/ha) in Balule.
0.25
0.2
R² = 0.1306 0.15
0.1 Density #/ha
0.05
0 2012 2013 2014 2015 2016 2017 2018 2019 2020
Elephant Impala Cumulative Figure 16. Multi-year trend in mixed feeder density (#/ha) including trendline. 2014 game count only included megaherbivores, 2019 only including data from helicopter counted regions.
Diversity Index
Biodiversity is one of the goals set out in the Balule management plan, and although there are no concrete targets the annual game count allows for an analysis of large mammalian biodiversity. The Simpson’s Index of Diversity is a tool used to estimate how likely it is that two randomly sampled individuals would belong to different species. This measure takes into account both the number of unique species (richness) and how many individuals of each species there are (abundance). It was calculated both for Balule and the associated reserves in the APNR using the formula below, where n is the total number of organisms of a particular species and N is the total number of organisms of all species. The Index of Diversity is calculated using the following formula: ∑n(n-1) D = 1 - N(N-1)
Diversity of the combined regions counted this year by helicopter was 0.46, compared to last year 0.47, showing diversity is stable. It is important to note however that the diversity from last year is only based on the count of the 6 regions counted and not the whole reserve. The diversity is still lower than that of the whole of the APNR in 2018 of 0,49, however as no data for the APNR has been available since then, it is not possible to compare BNR with the rest.
Conclusion
This report is a representation of the aerial count conducted in September 2020. The data for 2019 used in other reports was extrapolated and included input from regional wardens. These additional data were excluded in this report to ensure that a comparable methodology is used consistently. This years’ flight path deviated somewhat from previous years and the team counting was also different. As with any change in methodology this will impact the accuracy of the data, but it is not possible to determine how much without a comparative study.
Elephant and buffalo have a disproportionate effect on the trends in biomass as they are highly mobile, gregarious species. With Balule forming only a small portion of the Greater Kruger, these data are limited in use for management decisions. More telling trends are the species that are numerous but territorial, e.g. hippo and impala. Hippo numbers have fluctuated over the last 5 years and this years’ count falls within these fluctuations. Impala have declined significantly, over 20% from the high in 2018. Given the negative selection of impala in predator diets and their ability to adapt this decline is surprising.
Predator numbers are very challenging to determine using aerial surveys, yet crocodiles should be clearly visible. The decline by 53% compared to last year is very surprising and if correct something that should be examined thoroughly. No reports of mass die-offs or other evidence that the crocodiles have disappeared off the landscape are known. Appendix 1a: game count data
A summary of all species counts as reported by each reserve for the 2020 Game Count.
Category Species AMF BPNR DOR GPNR MSK MRNR MSNR ONGR OREC ORGR OWNR PNR Paul TRF UHK YPNR Total Bulk Buffalo, Hippo, # 63 0 71 40 82 33 29 20 75 100 208 44 4 2 16 194 981 grazers Sable, Density Waterbuck, 0.032 0.000 0.034 0.013 0.010 0.008 0.010 0.006 0.019 0.018 0.024 0.015 0.006 0.006 0.008 0.039 0.017 White Rhino, #/ha Zebra Biomass 19.963 0.000 15.482 4.471 4.273 8.710 7.841 1.786 9.840 7.758 18.779 3.725 2.106 11.621 1.640 21.924 8.437 kg/ha
Selective Warthog, # 11 5 0 15 40 15 28 2 15 27 21 17 0 1 4 24 225 grazers Wildebeest Density 0.006 0.002 0.000 0.005 0.005 0.004 0.010 0.001 0.004 0.005 0.002 0.006 0.000 0.003 0.002 0.005 #/ha Biomass 0.714 0.214 0.000 0.781 0.691 0.671 1.899 0.043 0.255 0.660 0.166 1.212 0.000 0.713 0.467 0.624 0.565 kg/ha
Mixed Impala, # 496 176 480 308 621 299 591 621 573 2122 1806 301 112 0 37 666 9209 Elephant Density 0.251 0.074 0.229 0.103 0.078 0.075 0.209 0.194 0.143 0.383 0.209 0.100 0.160 0.000 0.019 0.133 0.163 #/ha Biomass 122.322 36.345 42.319 8.453 23.961 110.437 135.299 33.282 60.210 59.847 88.239 67.605 7.401 0.000 34.189 104.681 65.247 kg/ha
Browsers Black rhino, # 16 3 59 83 83 21 21 74 73 147 133 69 4 1 34 56 877 Bushbuck, Density Duiker, Giraffe, 0.008 0.001 0.028 0.028 0.010 0.005 0.007 0.023 0.018 0.027 0.015 0.023 0.006 0.003 0.017 0.011 0.015 Kilpspringer, #/ha Kudu, Nyala, Biomass Sharp's 3.594 0.584 13.494 7.958 3.235 2.706 4.288 7.259 8.234 12.895 6.842 9.974 1.057 0.565 3.912 5.459 6.392 Grysbok, kg/ha Steenbok Mega Black Rhino, # 119 21 67 15 59 133 108 24 76 86 275 51 1 2 20 281 1338 herbivores Buffalo, Density Elephant, 0.060 0.009 0.032 0.005 0.007 0.033 0.038 0.008 0.019 0.016 0.032 0.017 0.001 0.006 0.010 0.056 0.024 Hippo, White #/ha Rhino Biomass 131.578 33.312 45.660 5.956 22.459 116.327 133.238 25.267 60.957 47.401 95.004 63.750 0.788 11.621 34.750 120.029 66.103 kg/ha
Appendix 1b: Regions of Balule
Region Hectares Abbreviation % of Balule Amsterdam 1974 AMF 3.41% Doreen 2100 DOR 3.63% Grietjie Private Nature Reserve 3000 GPNR 5.19% Maseke 8000 MSK 13.83% Mohlabetsi River Nature Reserve 3982 MRNR 6.88% Mohlabetsi South Nature Reserve 2830 MSNR 4.89% Olifants North Game Reserve 3200 ONGR 5.53% Olifants River East Conservancy 4008 OREC 6.93% Olifants River Game Reserve 6739 ORGR 11.65% Olifants West Nature Reserve 8628 OWNR 14.91% Parsons Nature Reserve 3000 PNR 5.19% Paul 700 Paul 1.21% Triangle farm 327 TRF 0.57% Uhkhozi 2000 UHK 3.46% York 5000 YPNR 8.64% Boston 2364 BPNR 4.09% Total 57852 100%