What they Game Counts? - ESA conducts game counts
and surveys through ground based surveys, aerial surveys or water based surveys.
We aim to provide safe, reliable, efficient and cost-effective procedures that
obtain unbiased estimates of populations and trends in large areas. By offering
a range of potential survey options we can develop a suitable methodology that
suits the respective needs of the customer or is adapted to the constraints
of the local environment.
Our service – ESA can go to any private concession
or game ranch to conduct a game count and survey of the population structure.
We have our own survey equipment, including ground survey vehicles and boats,
which can either be driven or transported to anywhere in southern Africa.
While also having access to a Cessna 182, which has been fitted out specifically
to undertake aerial survey work. We use the latest in modern census techniques,
including ‘red hen’ digital aerial filming of the surveyed line
to help reduce bias in population estimation.
How they help you - These data allow us to inform
you, the concessionaire, safari operator or ranch owner, of the health and
long-term viability of your wildlife species. By knowing the number and structure
of the population of wild animals in your region you will be better placed
to put in place the most effective management policies.
Aerial surveys
OR ground surveys? - We conduct
both ground based surveys and aerial surveys, both have their specific advantages
and disadvantages, and we have provided you with a detailed appraisal of
these benefits and limitations below:
The advantages of ground based surveys:
PRACTICALITY
COST EFFICEINCY
- While total time required for the survey is longer with respect to ground
surveys, cost-efficiency can be greater, due to minimal equipment and men
required.
- Total time required is dependent not just upon the size of the region,
but the habitat complexity of the surveyed region. Different survey methods
and different transect intensities are required for different habitat types,
requiring an extended period to both design and conduct the survey.
VIABILITY OF DATA GENERATED BY GROUND SURVEYS
- The most precise and accurate population estimates, i.e. those
with greater accuracy at the point estimate and with less variance in the
95% confidence interval around that point estimate, can be gained from
ground surveys.
- Evidence of direct comparisons between fixed-wing aerial and ground surveys
in areas of Africa, from Zambia through to Kenya, show aerial surveys underestimate
ungulate populations by 14% to 59%, demonstrating that ground surveys can
provide a better estimate of the population than even those conducted by
helicopter.
- Ground surveys provide information on the structure of the population,
i.e. age / sex composition and recruitment rates that can be used to help
model and predict trends in the growth / decline of the population.
- These data can not be obtained from aerial surveys and help to determine
the viability of different species and the potential off-take. Where ecosystem
managers have monitored populations to be decreasing at alarming levels,
ground surveys have been employed to obtain information on their structure
and growth rates, so that the cause of the decline can be ascertained. If
the yearling recruitment rate is declining due to any temporary anomaly,
then the population will be strong enough to withstand the constraint, as
adult females allow for future growth. If adult females are dieing then there
is more cause for concern and more proactive management may be required.
- Depending on the methodology applied, ground surveys can help to
provide detailed information on the spatial distribution and habitat preference
of each species observed.
- These data help to determine the potential effect of habitat change and
ecological change on different species.
The advantages of aerial surveys:
PRACTICALITY
- Access - Aerial surveys allow for a total coverage of the area concerned
to be observed and monitored. This is obviously beneficial in a wetland
region such as the Okavango delta, where ground access is sometimes limited.
- Time span – Aerial surveys allow for data to be gathered from across
large regions quickly.
- Ecological impact – Aerial surveys have a limited ecological impact.
Ground surveys can require off-road access and disturb animals to a greater
extent than aerial surveys.
- Guest impact – Aerial surveys will allow for each concession to
be monitored with a minimal impact for lodge guests.
COST/EFFICIENCY
- Depending on the required accuracy of the wildlife population estimate
and the viability of the data, each concession can be surveyed at an maximum
approximate flying time cost of 1hr per 125km2 of area to be surveyed.
- Plus flying time to and from the concession area.
- Transect width can be set from between 1min (2km) intervals in high wildlife
density regions to 3min (4.8km) intervals in low density regions, providing
between 27% to 15% coverage.
- This compares to 27% coverage used by Kruger Park managers as from 2004.
- Total coverage, or up to 50% coverage as is achieved in some of the most
intensive strip count aerial surveys.
- Line distance sampling reduces flight time and improves cost efficiency,
while improving point estimates and reducing variance in confidence intervals.
- Line distance sampling reduces bias in aerial survey data by assuming
that a total count of all individuals / groups is not achieved.
- However, a total count must occur on the transect line, with decreasing
incidence of observation expected with increasing distance from the transect
line.
- Stratification of concessions can improve cost effectiveness of aerial
surveys, but each strata needs to have a minimum of 20 transects and contain
between 60-80 observations. Over small concessions it may be advisable
to utilise one strata that covers the whole region.
VIABILITY OF DATA GENERATED BY AERIAL SURVEYS
- Aerial census data are renowned for their fallibility, especially when
the censured population occurs in low densities and / or within a clumped
distribution.
- Census data underestimate the size of populations due to among other
reasons, incomplete counts, which may miss 12-77% of any population.
- At best, aerial surveys underestimate the actual population by approximately
13%, and at worst by up to 59%.
- These variations occur around the point estimate, which itself is liable
to be bound by upper and lower confidence intervals of at best 20-25% and
at worst by over 100% of the actual estimate.
- The variation in the population estimate is also critically affected
by survey effort, which in Botswana varies widely between different regions.
The highest quality surveys conducted by DWNP or those conducted with the
narrowest transect widths occur along the Chobe, at 3 min (4.8km) intervals,
surveying a total of 14% of the region. This figure decreases to 7% in
for example Moremi GR and Makgadikgadi NP, but down to 4% across the majority
of the country.
- Therefore depending upon the location of your area of interest there
will potentially be a further decline in the bias and underestimate of
the actual population present.
- While new survey methods, such as line distance sampling and double counting
have reduced these bias estimates within Botswana, achieving highly accurate
population estimates on individual wildlife populations from aerial surveys
is not a reality.
- Aerial surveys serve a purpose where the goal is to achieve an understanding
of long-term trends in populations that are spread over vast and sometimes
inaccessible regions.
POTENTIAL IMPROVEMENTS TO STANDARD AERIAL SURVEYS.
- Using 2 extra observers in a fixed-wing aircraft increases the estimate
in population size by 9%, from 36% to 45%, from a population of known numbers.
These results come from a study completed in Madikwe Game Reserve, South
Africa, conducted on multiple species.
- Using a Hughes 500 helicopter achieved an estimate of 77% of known numbers
and a Jet Ranger 89% of known numbers. The benefit of using a helicopter,
being that the aircraft can stop along the transect and assess numbers within
a herd more accurately, while flying at slower ground speeds and thereby
reducing visibility bias. However, greater bias in the population estimates
was still found for waterbuck, kudu and impala, showing that helicopter surveys
were still liable to the same bias as other aerial surveys.
