Fixed wing aerial survey of wildlife in the Abu wildlife

54 Pages·2011·6.04 MB·English

by  Michael Chase

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FIXED-WING AERIAL SURVEY OF WILDLIFE IN THE ABU
WILDLIFE MANAGEMENT AREA (NG 26)
OKAVANGO DELTA, BOTSWANA
OCTOBER 2010
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Moremi Game Reserve

Report Prepared by

Michael Chase
PO Box 682
Kasane
Botswana
Tel: ++267 6250505
Email: [email protected]
January 2011
ACKNOWLEDGMENTS
This aerial survey of wildlife over the Abu concession (NG 26) was
commissioned and funded by Elephant Back Safaris (Pty) Ltd. The survey over part of
Habu (NG 8) was funded by the Department of Wildlife and National Parks (DWNP) and
the San Diego Zoo. I thank Mr. Mike Holding of Afriscreen Films for flying this survey.
The DWNP are acknowledged for their ongoing support of this work. I appreciate the
assistance of our aerial observers, Ms. Kelly Landen and Mr. Adrian Dandridge. I am
grateful to Kelly Landen who counted and verified wildlife numbers from the photos
taken by observers during the survey. I am grateful to Ms. Tania Jenkins from Afriscreen
Films for providing administrative assistance during this survey.

The management and staff of Seba Camp are thanked for their hospitality and
logistical support. I thank Ms. Cally Hanley and Mr. Adrian Dandridge for providing me
with the opportunity to conduct this important aerial survey over the Abu concession (NG
26). Mr. Mike Holding is acknowledged for reviewing an earlier draft version of this
report.

Cover Photo: Kelly Landen, 2010. A family group of elephants drink from a floodplain in the Abu concession.

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EXECUTIVE SUMMARY
During October 2010, a fixed-wing aerial wildlife survey was flown in the Abu
Elephant Back Safari concession (NG 26), and part of NG 8 which borders NG 26 in the
Okavango Delta. This wildlife aerial survey was commissioned by Elephant Back Safaris
(Pty Ltd). The survey area sampled totaled 2338 km2. The principal objective of this
survey was to provide relatively precise and accurate estimates of the numbers of wildlife
in the survey area. This is the second survey which has been flown over the concession.
This report provides the results of this survey, in addition to information on the spatial
distribution, abundance and trend of wildlife species in the concession.

The survey area was divided into four strata. The Abu concession was divided into
three strata, within each stratum the transects were parallel and regularly spaced 1 km
apart. We increased the sampling intensity to ~ 40 % compared to an earlier survey
(~ 20 % coverage) to improve the precision of our population estimates. Within the Habu
stratum transects were spaced 2 km apart. Overall mean search effort was 1.2 minutes per
km2.

Aerial surveys often underestimate wildlife numbers, with the degree of
underestimation higher for small or cryptic species than for large species. High resolution
digital cameras provided photos to compensate for any underestimating or missed
animals.

The locations of wildlife herds seen during the survey were entered into a GIS to
produce maps showing the spatial distribution and herd sizes of principal large herbivores
and birds in Abu.

There were an estimated 17339 cattle in the Habu tribal agricultural lands
bordering Abu, which are separated from the concession by the Southern Buffalo Fence.
This largely subsistence farming and tribal cattle grazing area has a large and valuable
zebra population (2093). Wildlife in the Habu tribal area is separated from the Okavango
Delta by the Southern Buffalo Fence. Programmes to conserve this regions wildlife and
unique habitats are urgently needed.

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The estimated population numbers for the principal large herbivores and birds in Abu
concession were:

Species Estimate No. Variance % CI Lower CL Upper CL Density
seen (km2)
Woodland Sp
Elephant 3606 1453 81527 16 3042 4169 1.95
Elephant Bulls 531 213 2364 18 435 627 0.29
Elephant Family 3075 1240 76238 18 2528 3621 1.66
Ele Carcass 3 65 25 104 31 44 85 0.04
Buffalo 3745 1523 740163 45 2043 5446 2.02
Giraffe 426 173 3980 29 310 550 0.23
Impala 2705 1094 176939 31 1873 3537 1.46
Kudu 308 125 2051 29 218 397 0.17
Tsessebe 278 111 2352 34 182 374 0.15
Warthog 131 51 427 31 90 171 0.07
Wildebeest 151 57 2407 64 57 248 0.08
Zebra 1303 524 57010 36 831 1775 0.70
Wetland Sp
Hippo 287 117 3055 38 177 396 0.15
Reedbuck 58 24 156 41 33 83 0.03
Lechwe 1995 811 47744 22 1563 2427 1.08
Bird Sp
Bateleur eagle 94 47 258 66 62 126 0.05
Ostrich 97 35 1058 66 35 161 0.05
Saddle-bill stork 154 61 449 27 112 196 0.08
Wattled crane 148 59 767 36 93 202 0.08
Fish eagle 146 59 524 31 101 191 0.08
1 Estimates for wildlife and cattle seen in Habu are provided in Tables 8 to 24.

The report also compares the results of this survey to the first fixed-wing aerial
survey conducted in September 2009 (Sept09). Differences between the two fixed-wing
aerial surveys (Sept10 & Oct09) of wildlife in the Abu concession are also presented and
compared. While the surveys provide a good overview of the sizes of wildlife
populations, there is still insufficient information to say much about trends other than that
there are no population crashes. Maps, and tables illustrating the distribution, numbers
and density of wildlife species in the concession are provided.
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TABLE OF CONTENTS

Page
ACKNOWLEDGMENTS................................................................................................ii
EXECUTIVE SUMMARY.............................................................................................iii
TABLE OF CONTENTS..................................................................................................v
LIST OF TABLES...........................................................................................................vi
LIST OF FIGURES.......................................................................................................viii
FIXED-WING AERIAL WILDLIFE SURVEY OF ABU – ELEPHANT BACK SAFARI
CONCESSION (NG 26) OKAVANGO DELTA, BOTSWANA....................................1

Introduction...........................................................................................................1
Study Area............................................................................................................2
Methods................................................................................................................4
Fixed-Wing Aerial Survey............................................................4
Flight Procedures..........................................................................4
Observations.................................................................................6
Strip Width and Calibration..........................................................7
Data Analysis........................................................................................................8
Strip Transect Sampling / Fixed-Wing Aerial Survey..................8
Search Effort.................................................................................9
Results.................................................................................................................10
Sampling Effort...........................................................................10
Wildlife Estimates.......................................................................11
Observations...............................................................................13
Wildlife Distributions.................................................................16
Habu (NG8) Survey....................................................................17
Trends in Wildlife Numbers in Abu...........................................19
Discussion...........................................................................................................20
Wildlife Estimates.......................................................................20
Observations...............................................................................20
Wildlife Distribution...................................................................21
Trends in Wildlife Numbers.......................................................21
Recommendations.......................................................................22
Conclusion..........................................................................................................22
References...........................................................................................................24

Appendix 1..........................................................................................................44
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LIST OF TABLES

Table Page

Table 1. Sampling statistics for the aerial survey of wildlife in Abu concession,
Oct10................................................................................................................10
Table 2. Wildlife estimates and statistics for major wildlife species, elephant
carcasses, baobab trees and birds in Abu1, NG 26 WMA during aerial
survey, Oct10...................................................................................................12
Table 3. Numbers seen, herds observed and average herd size of animals, baobabs
and carcasses seen in each stratum..................................................................13
Table 4. Comparison of numbers of individual animals seen and numbers of
herds/groups seen by the left and right observers............................................14
Table 5. Comparison between observer estimates and photographs of the same
animals.............................................................................................................15
Table 6. Number, size and the extent of damage to baobab trees seen during the
aerial survey.....................................................................................................16
Table 7. Estimated numbers, densities and differences between estimated numbers
of animals Sept09 and Oct10, aerial surveys...................................................19
Table 8. Population estimates and statistics for elephants in Abu (NG 26) and
Habu.................................................................................................................26
Table 9. Population estimates and statistics for elephant bulls in Abu (NG 26) and
Habu.................................................................................................................27
Table 10. Population estimates and statistics for elephant family groups in Abu
(NG 26) and Habu............................................................................................28
Table 11. Estimates of elephant carcasses in Abu (NG 26) and Habu, .........................29
Table 12. Population estimates and statistics for buffalo in Abu (NG 26) and
Habu.................................................................................................................30
Table 13. Population estimates and statistics for giraffe in Abu (NG 26)......................31
Table 14. Population estimates and statistics for hippopotamus in Abu (NG 26)
and Habu..........................................................................................................32
Table 15. Population estimates and statistics for impala Abu (NG 26) and Habu.........33
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Table 16. Population estimates and statistics for kudu Abu (NG 26) and Habu............34
Table 17. Population estimates and statistics for lechwe Abu (NG 26), .......................35
Table 18. Population estimates and statistics for ostrich in Abu (NG 26) and Habu.....36
Table 19. Population estimates and statistics for reedbuck Abu (NG 26) and
Habu.................................................................................................................37
Table 20. Population estimates and statistics for tsessebe Abu (NG 26).......................38
Table 21. Population estimates and statistics for wildebeest Abu (NG 26)...................39
Table 22. Population estimates and statistics for zebra Abu (NG 26), and Habu..........40
Table 23. Population estimates and statistics for birds Abu (NG 26),............................41
Table 24. Population estimates and statistics for cattle in Habu (NG 8),.......................43

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LIST OF FIGURES

Figure Page

Figure 1. Abu WMA (concession number, NG 26) in the Okavango Delta, northern
Botswana............................................................................................................2
Figure 2. Abu fixed wing aerial survey strata determined by major land cover types1.......3
Figure 3. The distribution of all wildlife seen during the aerial survey of Abu
(NG 26), Oct10..................................................................................................................17

Figure 4. Distribution of cattle and wildlife in Abu (NG 26) and Habu (NG 8)...............18

Figure 5. Land use map and key features in and surrounding Abu (NG 26) WMA..........25

Figure 6. Distribution of elephants in Abu and Habu, Oct10............................................26

Figure 7. Distribution of elephant bulls in Abu (NG 26) and Habu, Oct10......................27

Figure 8. Distribution of elephant family groups in Abu (NG 26) and Habu, Oct10........28

Figure 9. Distribution of elephant carcasses (category 3) in Abu (NG 26) and Habu,
Oct10................................................................................................................29

Figure 10. Distribution of buffalo herds in Abu (NG 26) and Habu, Oct10.....................30

Figure 11. Distribution of giraffe in Abu (NG 26), Oct10................................................31

Figure 12. Distribution of hippopotamus in Abu (NG 26) and Habu, Oct10....................32

Figure 13. Distribution of impala Abu (NG 26) and Habu, Oct10....................................33

Figure 14. Distribution of kudu Abu (NG 26) and Habu, Oct10.......................................34

Figure 15. Distribution of lechwe Abu (NG 26), Oct10....................................................35

Figure 16. Distribution of ostrich in Abu (NG 26) and Habu, Oct10................................36

Figure 17. Distribution of reedbuck Abu (NG 26) and Habu, Oct10................................37

Figure 18. Distribution of reedbuck Abu (NG 26), Oct10.................................................38

Figure 19. Distribution of wildebeest Abu (NG 26), Oct10..............................................39

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Figure 20. Distribution of zebra in Abu (NG 26), and Habu, Oct10.................................40
Figure 21. Distribution of birds in Abu (NG 26) Oct10....................................................41
Figure 22. Distribution of cattle in Habu (NG 8), Oct10..................................................43
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FIXED-WING AERIAL WILDLIFE SURVEY OF ABU – ELEPHANT BACK SAFARI
CONCESSION (NG 26) OKAVANGO DELTA, BOTSWANA

Introduction

This survey was flown in October 2010 (Oct10) and is the second fixed-wing aerial
wildlife survey of the Abu Wildlife Management Area (WMA, concession number - NG 26) in
the Okavango Delta. The first survey was conducted in September 2009 (Sept09) (Viljoen
2009). For the Oct10 survey, the area sampled was increased to include part of NG 8, a tribal
farming area which borders NG 26. Both surveys were flown by means of a sample count.

Monitoring large herbivores is central to research and management activities in many
conservation areas. Aerial surveys were originally developed to estimate (trends in) population
sizes of individual species. However, emphasis is shifting increasingly towards conservation of
diversity and communities instead of individual species, as a growing literature shows the
importance of herbivore diversity for ecosystem functioning (Joris et al. 2008). Large
woodland mammals (elephant, buffalo, wildebeest, zebra and impala), wetland species (hippo)
and floodplain ungulates (lechwe, reedbuck, and waterbuck) were counted. Large birds (cranes,
storks, ground hornbill, fish eagle and bateleur) were also recorded during the survey.

This report presents information from the Oct10 survey but also compares data with the
first aerial survey flown in Sept09. These surveys provide valuable information and afford
resource managers with the opportunity to assess wildlife distribution, abundance and trends
between aerial surveys, and compare changes over time. These data also give the Department
of Wildlife and National Parks (DWNP) and the Abu concession important information to
better conserve and manage their wildlife populations. The survey also contributes to co-
management of wildlife between protected areas, tribal lands and adjoining ecotourism
concessions. This co-management responsibility for monitoring wildlife aims to strengthen
DWNP aerial surveys and other wildlife monitoring programmes. Higher order goals and
objectives for wildlife conservation in the Okavango Delta are best achieved through such
private sector collaboration and responsibility.

At a larger scale the surveys contribute important data to current conservation and
development initiatives such as the Okavango Delta Management Plan, Bio-Okavango and
independent wildlife research projects. The survey area is also part of the Kavango Zambezi
Transfrontier Conservation Area and Ramsar Site. The Abu concession, borders Moremi Game
Reserve (GR), and is a critical part of the Okavango Delta ecosystem, that provides linkages
and corridors for wildlife movement (Chase 2009).

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